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Schuler A, Yoon CH, Caffarini E, Heine A, Meester A, Murray D, Harding A. Alpha2 Agonist Use in Critically Ill Adults: A Focus on Sedation and Withdrawal Prevention. J Pharm Pract 2024:8971900241263171. [PMID: 38907529 DOI: 10.1177/08971900241263171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/24/2024]
Abstract
The management of sedation in critically ill adults poses a unique challenge to clinicians. Dexmedetomidine, an α2 agonist, has a unique mechanism and favorable pharmacokinetics, making it an attractive intravenous option for sedation and delirium in the intensive care unit. However, patients may be at risk for withdrawal with prolonged use, adding to the complexity of sedation and agitation management in this patient population. Enteral α2 agents have the benefit of cost savings and ease of administration, thus playing a role in the ability to decrease intravenous sedative use and prevent dexmedetomidine withdrawal. Clonidine and guanfacine are the two most common enteral α2 agents utilized for this purpose, however, there is a paucity of evidence regarding the comparative benefit between the two agents. The decision to use one vs the other agent should be determined based on their differing pharmacology, pharmacokinetics, and side effect profile. The most effective dosing strategy for these agents is also unknown. Ultimately, more robust literature is required to determine enteral α2 agonists place in therapy. This narrative review evaluates the currently available literature on the use of α2 agonists in critically ill adults with an emphasis on sedation, delirium, and withdrawal.
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Affiliation(s)
- Ashley Schuler
- Department of Pharmacy, Ohio Health Riverside Methodist Hospital, Columbus, OH, USA
| | - Connie H Yoon
- Department of Pharmacy, Ohio Health Riverside Methodist Hospital, Columbus, OH, USA
| | - Erica Caffarini
- Department of Pharmacy, Ohio Health Riverside Methodist Hospital, Columbus, OH, USA
| | - Alexander Heine
- Department of Pharmacy, Ohio Health Riverside Methodist Hospital, Columbus, OH, USA
| | - Alyssa Meester
- Department of Pharmacy, Ohio Health Riverside Methodist Hospital, Columbus, OH, USA
| | - Danielle Murray
- Department of Pharmacy, Ohio Health Riverside Methodist Hospital, Columbus, OH, USA
| | - Angela Harding
- Department of Pharmacy, Ohio Health Riverside Methodist Hospital, Columbus, OH, USA
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Chernoff CS, Hynes TJ, Schumacher JD, Ramaiah S, Avramidis DK, Mortazavi L, Floresco SB, Winstanley CA. Noradrenergic regulation of cue-guided decision making and impulsivity is doubly dissociable across frontal brain regions. Psychopharmacology (Berl) 2024; 241:767-783. [PMID: 38001266 DOI: 10.1007/s00213-023-06508-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Accepted: 11/14/2023] [Indexed: 11/26/2023]
Abstract
RATIONALE Win-paired stimuli can promote risk taking in experimental gambling paradigms in both rats and humans. We previously demonstrated that atomoxetine, a noradrenaline reuptake inhibitor, and guanfacine, a selective α2A adrenergic receptor agonist, reduced risk taking on the cued rat gambling task (crGT), a rodent assay of risky choice in which wins are accompanied by salient cues. Both compounds also decreased impulsive premature responding. OBJECTIVE The key neural loci mediating these effects were unknown. The lateral orbitofrontal cortex (lOFC) and the medial prefrontal cortex (mPFC), which are highly implicated in risk assessment, action selection, and impulse control, receive dense noradrenergic innervation. We therefore infused atomoxetine and guanfacine directly into either the lOFC or prelimbic (PrL) mPFC prior to task performance. RESULTS When infused into the lOFC, atomoxetine improved decision making score and adaptive lose-shift behaviour in males, but not in females, without altering motor impulsivity. Conversely, intra-PrL atomoxetine improved impulse control in risk preferring animals of both sexes, but did not alter decision making. Guanfacine administered into the PrL, but not lOFC, also altered motor impulsivity in all subjects, though in the opposite direction to atomoxetine. CONCLUSIONS These data highlight a double dissociation between the behavioural effects of noradrenergic signaling across frontal regions with respect to risky choice and impulsive action. Given that the influence of noradrenergic manipulations on motor impulsivity could depend on baseline risk preference, these data also suggest that the noradrenaline system may function differently in subjects that are susceptible to the risk-promoting lure of win-associated cues.
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Affiliation(s)
- Chloe S Chernoff
- Graduate Program in Neuroscience, Faculty of Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada.
- Department of Psychology, Downing Site, University of Cambridge, Cambridge, UK.
| | - Tristan J Hynes
- Graduate Program in Neuroscience, Faculty of Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
- Department of Psychology, Downing Site, University of Cambridge, Cambridge, UK
| | - Jackson D Schumacher
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
| | - Shrishti Ramaiah
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
- Department of Psychological and Brain Sciences, University of Massachusetts Amherst, Amherst, MA, USA
| | - Dimitrios K Avramidis
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
- Department of Psychology, University of Concordia, Montreal, QC, Canada
| | - Leili Mortazavi
- Department of Psychology, Stanford University, Stanford, CA, USA
| | - Stan B Floresco
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
| | - Catharine A Winstanley
- Graduate Program in Neuroscience, Faculty of Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada.
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada.
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Arnsten AFT, Ishizawa Y, Xie Z. Scientific rationale for the use of α2A-adrenoceptor agonists in treating neuroinflammatory cognitive disorders. Mol Psychiatry 2023; 28:4540-4552. [PMID: 37029295 PMCID: PMC10080530 DOI: 10.1038/s41380-023-02057-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2022] [Revised: 03/22/2023] [Accepted: 03/24/2023] [Indexed: 04/09/2023]
Abstract
Neuroinflammatory disorders preferentially impair the higher cognitive and executive functions of the prefrontal cortex (PFC). This includes such challenging disorders as delirium, perioperative neurocognitive disorder, and the sustained cognitive deficits from "long-COVID" or traumatic brain injury. There are no FDA-approved treatments for these symptoms; thus, understanding their etiology is important for generating therapeutic strategies. The current review describes the molecular rationale for why PFC circuits are especially vulnerable to inflammation, and how α2A-adrenoceptor (α2A-AR) actions throughout the nervous and immune systems can benefit the circuits in PFC needed for higher cognition. The layer III circuits in the dorsolateral PFC (dlPFC) that generate and sustain the mental representations needed for higher cognition have unusual neurotransmission and neuromodulation. They are wholly dependent on NMDAR neurotransmission, with little AMPAR contribution, and thus are especially vulnerable to kynurenic acid inflammatory signaling which blocks NMDAR. Layer III dlPFC spines also have unusual neuromodulation, with cAMP magnification of calcium signaling in spines, which opens nearby potassium channels to rapidly weaken connectivity and reduce neuronal firing. This process must be tightly regulated, e.g. by mGluR3 or α2A-AR on spines, to prevent loss of firing. However, the production of GCPII inflammatory signaling reduces mGluR3 actions and markedly diminishes dlPFC network firing. Both basic and clinical studies show that α2A-AR agonists such as guanfacine can restore dlPFC network firing and cognitive function, through direct actions in the dlPFC, but also by reducing the activity of stress-related circuits, e.g. in the locus coeruleus and amygdala, and by having anti-inflammatory actions in the immune system. This information is particularly timely, as guanfacine is currently the focus of large clinical trials for the treatment of delirium, and in open label studies for the treatment of cognitive deficits from long-COVID.
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Affiliation(s)
- Amy F T Arnsten
- Department Neuroscience, Yale University School of Medicine, New Haven, CT, 056510, USA.
| | - Yumiko Ishizawa
- Department Anesthesiology, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114, USA
| | - Zhongcong Xie
- Department Anesthesiology, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114, USA
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Hassani SA, Womelsdorf T. Noradrenergic alpha-2a Receptor Stimulation Enhances Prediction Error Signaling in Anterior Cingulate Cortex and Striatum. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.25.564052. [PMID: 37961384 PMCID: PMC10634832 DOI: 10.1101/2023.10.25.564052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
The noradrenergic system is implicated to support behavioral flexibility by increasing exploration during periods of uncertainty and by enhancing working memory for goal-relevant stimuli. Possible sources mediating these pro-cognitive effects are α2A adrenoceptors (α2AR) in prefrontal cortex or the anterior cingulate cortex facilitating fronto-striatal learning processes. We tested this hypothesis by selectively stimulating α2ARs using Guanfacine during feature-based attentional set shifting in nonhuman primates. We found that α2A stimulation improved learning from errors and facilitates updating the target feature of an attentional set. Neural recordings in the anterior cingulate cortex (ACC), the dorsolateral prefrontal cortex (dlPFC), and the striatum showed that α2A stimulation selectively enhanced the neural representation of negative reward prediction errors in neurons of the ACC and of positive prediction errors in the striatum, but not in dlPFC. This modulation was accompanied by enhanced encoding of the feature and location of the attended target across the fronto-striatal network. Enhanced learning was paralleled by enhanced encoding of outcomes in putative fast-spiking interneurons in the ACC, dlPFC, and striatum but not in broad spiking cells, pointing to an interneuron mediated mechanism of α2AR action. These results illustrate that α2A receptors causally support the noradrenergic enhancement of updating attention sets through an enhancement of prediction error signaling in the ACC and the striatum.
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Affiliation(s)
- Seyed A. Hassani
- Department of Psychology, Vanderbilt University, Nashville, TN 37240
- Vanderbilt Brain Institute, Nashville, TN 37240
- National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD 20824
| | - Thilo Womelsdorf
- Department of Psychology, Vanderbilt University, Nashville, TN 37240
- Vanderbilt Brain Institute, Nashville, TN 37240
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37240
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Czoty PW, Nader MA. Effects of the α-2 Adrenergic Receptor Agonists Lofexidine and Guanfacine on Food-Cocaine Choice in Socially Housed Cynomolgus Monkeys. J Pharmacol Exp Ther 2020; 375:193-201. [PMID: 32636208 DOI: 10.1124/jpet.120.266007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Accepted: 07/02/2020] [Indexed: 11/22/2022] Open
Abstract
Although norepinephrine (NE) does not appear to play a prominent role in mediating the abuse-related effects of cocaine, studies have indicated that NE α-2 receptor agonists can attenuate reinstatement of extinguished cocaine self-administration in rats and monkeys and can decrease cocaine craving in humans. In the present studies, we examined the effects of two α-2 receptor agonists, lofexidine and guanfacine, on choice between food and cocaine (0.0-0.1 mg/kg per injection) in cynomolgus monkeys. Male and female subjects were housed in stable same-sex social groups of four; social rank did not influence the effects of lofexidine and guanfacine. When administered acutely, lofexidine (0.03-3.0 mg/kg, i.v.) significantly decreased cocaine choice in females (n = 7) but not males (n = 8). However, in males, the same lofexidine doses produced dose-dependent decreases in core body temperature (n = 7), and acute guanfacine (0.003-1.0 mg/kg, i.v.) significantly decreased cocaine choice (n = 11). When lofexidine was administered for five consecutive days to a subset of the monkeys in whom lofexidine acutely decreased cocaine choice, tolerance to this effect developed to varying degrees of completeness in three of three males and two of four females. Taken together, these data suggest that α-2 receptor agonists can produce small decreases in the reinforcing strength of cocaine relative to food and that, even when efficacy is observed after acute administration, tolerance to the decreases in cocaine choice are apparent and more likely in males compared with females. SIGNIFICANCE STATEMENT: Cocaine use disorder remains a significant public health problem with no US Food and Drug Administration-approved treatments. Although cocaine elevates dopamine, serotonin, and norepinephrine (NE), the latter target has received less research. The present study noted modest effects of NE agonists on the relative reinforcing strength of cocaine with greater efficacy in female compared with male monkeys.
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Affiliation(s)
- Paul W Czoty
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Michael A Nader
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina
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Abstract
Children/adolescents with attention-deficit/hyperactivity disorder (ADHD) may have a poor or inadequate response to psychostimulants or be unable to tolerate their side-effects; furthermore, stimulants may be inappropriate because of co-existing conditions. Only one non-stimulant ADHD pharmacotherapy, the noradrenaline transporter inhibitor atomoxetine, is currently approved for use in Europe. We review recent advances in understanding of the pathophysiology of ADHD with a focus on the roles of catecholamine receptors in context of the α2A-adrenergic receptor agonist guanfacine extended release (GXR), a new non-stimulant treatment option in Europe. Neuroimaging studies of children/adolescents with ADHD show impaired brain maturation, and structural and functional anomalies in brain regions and networks. Neurobiological studies in ADHD and medication response patterns support involvement of monoaminergic neurotransmitters (primarily dopamine and noradrenaline). Guanfacine is a selective α2A-adrenergic receptor agonist that has been shown to improve prefrontal cortical cognitive function, including working memory. The hypothesized mode of action of guanfacine centres on direct stimulation of post-synaptic α2A-adrenergic receptors to enhance noradrenaline neurotransmission. Preclinical data suggest that guanfacine also influences dendritic spine growth and maturation. Clinical trials have demonstrated the efficacy of GXR in ADHD, and it is approved as monotherapy or adjunctive therapy to stimulants in Canada and the USA (for children and adolescents). GXR was approved recently in Europe for the treatment of ADHD in children and adolescents for whom stimulants are not suitable, not tolerated or have been shown to be ineffective. GXR may provide particular benefit for children/adolescents who have specific co-morbidities such as chronic tic disorders or oppositional defiant disorder (or oppositional symptoms) that have failed to respond to first-line treatment options.
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Black BT, Soden SE, Kearns GL, Jones BL. Clinical and Pharmacologic Considerations for Guanfacine Use in Very Young Children. J Child Adolesc Psychopharmacol 2016; 26:498-504. [PMID: 26894823 DOI: 10.1089/cap.2014.0159] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Guanfacine, in the immediate release form, remains a commonly used medication for the treatment of clinically significant hyperactivity, impulsivity, or disruptive behaviors. This article reviews the available literature regarding guanfacine use in very young children (<6 years of age), and explores some of the factors that may uniquely impact the clinical pharmacology of guanfacine in very young children and that deserve consideration when it is used in this patient population. METHODS The authors performed electronic literature searches in PubMed through October 2015 using the terms attention-deficit/hyperactivity disorder, guanfacine, and alpha agonists. We also performed an informal review of the literature and used selected articles from relevant reference lists. The result was a broad, qualitative review of the literature, with a focus on specific factors regarding guanfacine use in very young children. RESULTS Despite the fact that guanfacine is commonly used in very young children, there is a paucity of published studies that looked specifically at its use in this population. In reviewing the pharmacology of guanfacine, there are specific factors that may play a unique role in its disposition in very young children. CONCLUSIONS Guanfacine is an important medication option in very young children; however, there is a significant pharmacologic "information gap," and further research is needed to help establish appropriate, safe, and effective dosing of guanfacine in this population.
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Affiliation(s)
- Benjamin T Black
- 1 Division of Developmental & Behavioral Sciences, Children's Mercy Hospital , Kansas City, Missouri
| | - Sarah E Soden
- 1 Division of Developmental & Behavioral Sciences, Children's Mercy Hospital , Kansas City, Missouri
| | - Gregory L Kearns
- 1 Division of Developmental & Behavioral Sciences, Children's Mercy Hospital , Kansas City, Missouri.,2 Arkansas Children's Hospital Research Institute , Arkansas Children's Hospital, Little Rock, Arkansas
| | - Bridgette L Jones
- 3 Division of Clinical Pharmacology, Toxicology, and Therapeutic Innovation, Children's Mercy Hospital , Kansas City, Missouri
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Huss M, Sikirica V, Hervas A, Newcorn JH, Harpin V, Robertson B. Guanfacine extended release for children and adolescents with attention-deficit/hyperactivity disorder: efficacy following prior methylphenidate treatment. Neuropsychiatr Dis Treat 2016; 112:1085-101. [PMID: 27226715 PMCID: PMC4863687 DOI: 10.2147/ndt.s94158] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Guanfacine extended release (GXR) and atomoxetine (ATX) are nonstimulant treatments for attention-deficit/hyperactivity disorder (ADHD). As nonstimulant treatments are often used after stimulants in ADHD, GXR was assessed relative to prior stimulant treatment in a randomized controlled trial (RCT), in which ATX was included as a reference arm, and in the open-label phase of a randomized-withdrawal study (RWS). Participants were 6-17 years old with ADHD Rating Scale version IV (ADHD-RS-IV) scores ≥32 and Clinical Global Impressions - Severity scores ≥4. RCT participants received dose-optimized GXR (1-7 mg/day), ATX (10-100 mg/day), or placebo for 10-13 weeks. RWS participants received dose-optimized GXR (1-7 mg/day) for 13 weeks. Participants' last stimulant medication prior to enrolment, and reasons for stopping this medication, were collected at baseline. Change from baseline ADHD-RS-IV score and the proportion of responders were assessed by prior stimulant exposure. Of 163 RCT and 296 RWS participants who had previously received stimulant treatment, 142 and 224, respectively, had received methylphenidate (MPH); due to the low number of participants and the heterogeneity of non-MPH treatments, we only report data for prior MPH treatment. The most frequent reasons for stopping MPH were lack of effectiveness or side effects. Placebo-adjusted ADHD-RS-IV changes from baseline were significant in participants receiving GXR (prior MPH, -9.8, P<0.001, effect size [ES] 0.85; stimulant-naïve, -7.6, P<0.001, ES 0.65). In ATX-treated participants, significant placebo-adjusted differences were seen in stimulant-naïve (-5.0, P=0.022, ES 0.43) but not prior MPH-treated (-1.8, P>0.05, ES 0.15) participants. More participants met responder criteria with GXR versus placebo, regardless of prior treatment. GXR response was unaffected by prior stimulant treatment; ATX produced improvement only in stimulant-naïve participants relative to placebo. These findings may be relevant to clinical decision-making regarding sequencing of ADHD treatments.
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Affiliation(s)
- Michael Huss
- Child and Adolescent Psychiatry, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Vanja Sikirica
- Global Health Economics, Outcomes Research and Epidemiology, Shire, Wayne, PA, USA
| | - Amaia Hervas
- Child and Adolescent Mental Health Unit, University Hospital Mútua de Terressa, Barcelona, Spain; Developmental Disorders Unit (UETD), Hospital San Juan de Dios, Barcelona, Spain
| | - Jeffrey H Newcorn
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Valerie Harpin
- Ryegate Children's Centre, Sheffield Children's NHS Foundation Trust, Sheffield, UK
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Sun GC, Ho WY, Chen BR, Cheng PW, Cheng WH, Hsu MC, Yeh TC, Hsiao M, Lu PJ, Tseng CJ. GPCR dimerization in brainstem nuclei contributes to the development of hypertension. Br J Pharmacol 2015; 172:2507-18. [PMID: 25573074 PMCID: PMC4409903 DOI: 10.1111/bph.13074] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 11/20/2014] [Accepted: 12/29/2014] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE μ-Opioid receptors, pro-opiomelanocortin and pro-enkephalin are highly expressed in the nucleus tractus solitarii (NTS) and μ receptor agonists given to the NTS dose-dependently increased BP. However, the molecular mechanisms of this process remain unclear. In vitro, μ receptors heterodimerize with α2A -adrenoceptors. We hypothesized that α2A -adrenoceptor agonists would lose their depressor effects when their receptors heterodimerize in the NTS with μ receptors. EXPERIMENTAL APPROACH We microinjected μ-opioid agonists and antagonists into the NTS of rats and measured changes in BP. Formation of μ receptor/α2A -adrenoceptor heterodimers was assessed with immunofluorescence and co-immunoprecipitation methods, along with proximity ligation assays. KEY RESULTS Immunofluorescence staining revealed colocalization of α2A -adrenoceptors and μ receptors in NTS neurons. Co-immunoprecipitation revealed interactions between α2A -adrenoceptors and μ receptors. In situ proximity ligation assays confirmed the presence of μ receptor/α2A -adrenoceptor heterodimers in the NTS. Higher levels of endogenous endomorphin-1 and μ receptor/α2A -adrenoceptor heterodimers were found in the NTS of hypertensive rats, than in normotensive rats. Microinjection of the μ receptor agonist [D-Ala(2) , MePhe(4) , Gly(5) -ol]-enkephalin (DAMGO), but not that of the α2A -adrenoceptor agonist guanfacine, into the NTS of normotensive rats increased μ receptor/α2A -adrenoceptor heterodimer formation and BP elevation. The NO-dependent BP-lowering effect of α2A -adrenoceptor agonists was blunted following increased formation of μ receptor/α2A -adrenoceptor heterodimers in the NTS of hypertensive rats and DAMGO-treated normotensive rats. CONCLUSIONS AND IMPLICATIONS Increases in endogenous μ receptor agonists in the NTS induced μ receptor/α2A -adrenoceptor heterodimer formation and reduced the NO-dependent depressor effect of α2A -adrenoceptor agonists. This process could contribute to the pathogenesis of hypertension.
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MESH Headings
- Adrenergic alpha-2 Receptor Agonists/administration & dosage
- Adrenergic alpha-2 Receptor Agonists/pharmacology
- Analgesics, Opioid/administration & dosage
- Analgesics, Opioid/pharmacology
- Animals
- Blood Pressure/drug effects
- Brain Stem/drug effects
- Brain Stem/metabolism
- Dimerization
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/administration & dosage
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
- Hypertension/chemically induced
- Hypertension/metabolism
- Male
- Microinjections
- Narcotic Antagonists/administration & dosage
- Narcotic Antagonists/pharmacology
- Oligopeptides/metabolism
- Protein Multimerization
- Rats
- Rats, Inbred SHR
- Receptors, Adrenergic, alpha-2/metabolism
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/antagonists & inhibitors
- Receptors, Opioid, mu/metabolism
- Solitary Nucleus/drug effects
- Solitary Nucleus/metabolism
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Affiliation(s)
- Gwo-Ching Sun
- Institute of Clinical Medicine, National Cheng-Kung UniversityTainan, Taiwan
- Department of Anesthesiology, Kaohsiung Medical University Hospital, Kaohsiung Medical UniversityKaohsiung, Taiwan
- Department of Medical Education and Research, Kaohsiung Veterans General HospitalKaohsiung, Taiwan
| | - Wen-Yu Ho
- Division of General Internal Medicine, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical UniversityKaohsiung, Taiwan
- Department of Internal Medicine, Faculty of Medicine, College of Medicine, Kaohsiung Medical UniversityKaohsiung, Taiwan
- Department of Pharmacology, National Defense Medical CenterTaipei, Taiwan
| | - Bo-Rung Chen
- Department of Medical Education and Research, Kaohsiung Veterans General HospitalKaohsiung, Taiwan
| | - Pei-Wen Cheng
- Department of Medical Education and Research, Kaohsiung Veterans General HospitalKaohsiung, Taiwan
- Department of Pharmacology, National Defense Medical CenterTaipei, Taiwan
| | - Wen-Han Cheng
- Department of Medical Education and Research, Kaohsiung Veterans General HospitalKaohsiung, Taiwan
- Institute of Clinical Medicine, National Yang-Ming UniversityTaipei, Taiwan
| | - Mei-Chi Hsu
- Department of Nursing, I-Shou UniversityKaohsiung, Taiwan
| | - Tung-Chen Yeh
- Division of Cardiology, Department of Internal Medicine, Kaohsiung Veterans General HospitalKaohsiung, Taiwan
| | - Michael Hsiao
- Genomics Research Center, Academia SinicaTaipei, Taiwan
| | - Pei-Jung Lu
- Institute of Clinical Medicine, National Cheng-Kung UniversityTainan, Taiwan
| | - Ching-Jiunn Tseng
- Department of Medical Education and Research, Kaohsiung Veterans General HospitalKaohsiung, Taiwan
- Department of Pharmacology, National Defense Medical CenterTaipei, Taiwan
- Institute of Clinical Medicine, National Yang-Ming UniversityTaipei, Taiwan
- Department of Medical Research, China Medical University Hospital, China Medical UniversityTaichung, Taiwan
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Sallee FR. The Role of Alpha2-Adrenergic Agonists in Attention-Deficit/Hyperactivity Disorder. Postgrad Med 2015; 122:78-87. [DOI: 10.3810/pgm.2010.09.2204] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Floyd R. Sallee
- Department of Psychiatry, University of Cincinnati, Cincinnati, OH
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11
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McKee SA, Potenza MN, Kober H, Sofuoglu M, Arnsten AFT, Picciotto MR, Weinberger AH, Ashare R, Sinha R. A translational investigation targeting stress-reactivity and prefrontal cognitive control with guanfacine for smoking cessation. J Psychopharmacol 2015; 29:300-11. [PMID: 25516371 PMCID: PMC4376109 DOI: 10.1177/0269881114562091] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Stress and prefrontal cognitive dysfunction have key roles in driving smoking; however, there are no therapeutics for smoking cessation that attenuate the effects of stress on smoking and enhance cognition. Central noradrenergic pathways are involved in stress-induced reinstatement to nicotine and in the prefrontal executive control of adaptive behaviors. We used a novel translational approach employing a validated laboratory analogue of stress-precipitated smoking, functional magnetic resonance imaging (fMRI), and a proof-of-concept treatment period to evaluate whether the noradrenergic α2a agonist guanfacine (3 mg/day) versus placebo (0 mg/day) reduced stress-precipitated smoking in the laboratory, altered cortico-striatal activation during the Stroop cognitive-control task, and reduced smoking following a quit attempt. In nicotine-deprived smokers (n=33), stress versus a neutral condition significantly decreased the latency to smoke, and increased tobacco craving, ad-libitum smoking, and systolic blood pressure in placebo-treated subjects, and these effects were absent or reduced in guanfacine-treated subjects. Following stress, placebo-treated subjects demonstrated decreased cortisol levels whereas guanfacine-treated subjects demonstrated increased levels. Guanfacine, compared with placebo, altered prefrontal activity during a cognitive-control task, and reduced cigarette use but did not increase complete abstinence during treatment. These preliminary laboratory, neuroimaging, and clinical outcome data were consistent and complementary and support further development of guanfacine for smoking cessation.
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Affiliation(s)
- Sherry A. McKee
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT,Cancer Prevention and Control Research Program, Yale Cancer Center, New Haven, CT,Corresponding Author: Sherry A. McKee, Ph.D., Dept. of Psychiatry, Yale University School of Medicine, 2 Church St South, Suite 109, New Haven, CT., 06519 USA phone: 203-737-3529, fax 203-737-4243,
| | - Marc N. Potenza
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT,Department of Neurobiology, Yale University School of Medicine, New Haven, CT,Yale Child Study Center, Yale University School of Medicine, New Haven, CT
| | - Hedy Kober
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT
| | - Mehmet Sofuoglu
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT,VA Connecticut Healthcare System, West Haven, CT
| | - Amy F. T. Arnsten
- Department of Neurobiology, Yale University School of Medicine, New Haven, CT
| | | | - Andrea H. Weinberger
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT,Cancer Prevention and Control Research Program, Yale Cancer Center, New Haven, CT
| | - Rebecca Ashare
- Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
| | - Rajita Sinha
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT
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Bello NT. Clinical utility of guanfacine extended release in the treatment of ADHD in children and adolescents. Patient Prefer Adherence 2015; 9:877-85. [PMID: 26170637 PMCID: PMC4494608 DOI: 10.2147/ppa.s73167] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Attention deficit hyperactivity disorder (ADHD) is the most common psychiatric illness in children and adolescents. Several stimulant medications, such as methylphenidate and amphetamine derivatives, are available to treat ADHD in pediatric patients. Nonstimulant medications are more preferred by some parents, other caregivers, and patients because they lack the abuse potential of stimulant medications. In the US, one available nonstimulant option is guanfacine extended release (XR). As a selective α2A adrenergic receptor, guanfacine acts on the central noradrenergic pathways and cortical noradrenergic targets to improve working memory and attention. The XR formulation of guanfacine, compared with the immediate-release formulation, is more effective for the long-term management of ADHD and is associated with fewer adverse effects. Available data also indicate that guanfacine XR is superior to atomoxetine and is as effective as the nonselective α2 adrenergic receptor agonist, clonidine XR. The most common adverse effects associated with guanfacine XR are somnolence, fatigue, bradycardia, and hypotension. Somnolence is the most often cited reason for discontinuation. Guanfacine XR is also labeled for use as an adjuvant to stimulant treatment for ADHD. A similar profile of adverse effects as reported with monotherapy is reported when guanfacine XR is "added on" to stimulant therapy with somnolence as the most commonly reported adverse event. This review discusses the clinical efficacy and patient preference of guanfacine XR based on available published data on the safety, relative effectiveness, and tolerance of this medication to treat ADHD.
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Affiliation(s)
- Nicholas T Bello
- Department of Animal Sciences, Rutgers, The State University of New Jersey, New Brunswick, NJ, USA
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Hervas A, Huss M, Johnson M, McNicholas F, van Stralen J, Sreckovic S, Lyne A, Bloomfield R, Sikirica V, Robertson B. Efficacy and safety of extended-release guanfacine hydrochloride in children and adolescents with attention-deficit/hyperactivity disorder: a randomized, controlled, phase III trial. Eur Neuropsychopharmacol 2014; 24:1861-72. [PMID: 25453486 DOI: 10.1016/j.euroneuro.2014.09.014] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 08/20/2014] [Accepted: 09/21/2014] [Indexed: 11/18/2022]
Abstract
Guanfacine extended-release (GXR), a selective α2A-adrenergic agonist, is a non-stimulant treatment for attention-deficit/hyperactivity disorder (ADHD). This study assessed the efficacy (symptoms and function) and safety of dose-optimized GXR compared with placebo in children and adolescents with ADHD. An atomoxetine (ATX) arm was included to provide reference data against placebo. Patients (6-17 years) were randomized at baseline to dose-optimized GXR (0.05-0.12mg/kg/day - 6-12 years: 1-4mg/day; 13-17 years: 1-7mg/day), ATX (10-100mg/day) or placebo for 4 or 7 weeks. The primary efficacy measure was change from baseline in ADHD Rating Scale version IV (ADHD-RS-IV). Key secondary measures were Clinical Global Impression-Improvement (CGI-I) and the Weiss Functional Impairment Rating Scale-Parent Report (WFIRS-P; learning and school, and family domains). Safety assessments included treatment-emergent adverse events (TEAEs), electrocardiograms and vital signs. A total of 272 (80.5%) patients from Europe, the USA and Canada completed the study. Significant differences were observed in least squares mean change from baseline in ADHD-RS-IV total score (placebo-adjusted differences) (GXR: [-8.9, p<0.001]; ATX: [-3.8, p<0.05]), the difference from placebo in the percentage of patients showing improvement (1 ['very much improved'] or 2 ['much improved']) for CGI-I (GXR: [23.7, p<0.001]; ATX: [12.1, p<0.05]), WFIRS-P learning and school domain (GXR: [-0.22, p<0.01]; ATX: [-0.16, p<0.05]) and WFIRS-P family domain (GXR: [-0.21, p<0.01]; ATX: [-0.09, p=0.242]). Most common TEAEs for GXR were somnolence, headache and fatigue; 70.1% of GXR subjects reported mild-to-moderate TEAEs. GXR was effective and well tolerated in children and adolescents with ADHD.
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Affiliation(s)
- Amaia Hervas
- Child and Adolescent Mental Health Unit, University Hospital Mútua de Terrassa, UETD, Hospital Sant Joan de Deu, Barcelona, Spain.
| | - Michael Huss
- Child and Adolescent Psychiatry, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Mats Johnson
- The Gillberg Neuropsychiatry Centre at the Sahlgrenska Academy, University of Gothenburg, Sweden
| | - Fiona McNicholas
- Department of Child and Adolescent Psychiatry, Our Lady׳s Children׳s Hospital, Dublin, Ireland
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Abela AR, Chudasama Y. Noradrenergic α2A-receptor stimulation in the ventral hippocampus reduces impulsive decision-making. Psychopharmacology (Berl) 2014; 231:521-31. [PMID: 24062084 DOI: 10.1007/s00213-013-3262-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 08/19/2013] [Indexed: 10/26/2022]
Abstract
RATIONALE Guanfacine, an α2A-adrenergic receptor agonist, is currently in use for treatment of a variety of psychiatric disorders that are associated with impulsive decision-making (e.g., attention-deficit hyperactivity disorder; ADHD). In animals and humans, the behavioral effects of adrenergic agents are presumed to involve neuromodulation of the prefrontal cortex, consistent with the demonstrated actions of dopaminergic agents. However, recent experimental work has shown that the ventral hippocampus (vHC) contributes to decision-making and impulse control, raising the possibility that the hippocampus may be an important site of action for these drugs. OBJECTIVE The purpose of this study was to examine the effect of local vHC infusions of guanfacine and other neuropharmacological agents on behavioral decisions that involve a trade-off between reward size and delay. METHODS Different cohorts of rats were implanted with bilateral guide cannulae targeting the vHC. We examined the animals' behavior in a touchscreen version of a delay discounting task following intra-vHC infusions of: (a) guanfacine (α2A-adrenergic receptor agonist), (b) SCH 23390 (dopamine D1 receptor antagonist), and (c) muscimol/baclofen (GABAA/B agonists). RESULTS Guanfacine led to a dose-dependent reduction in impulsive decision-making, increasing the animals' tolerance for delay in exchange for a larger reward. By contrast, infusion of SCH 23390 had no behavioral effects. Consistent with previous lesion studies, reversible pharmacological inactivation with muscimol/baclofen increased impulsive decision-making. CONCLUSIONS These data provide the first evidence that guanfacine, a commonly used treatment for ADHD, may derive its clinical benefits through hippocampal stimulation, via α2A-adrenergic receptors.
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Affiliation(s)
- Andrew R Abela
- Department of Psychology, McGill University, Montreal, QC, H3A 1B1, Canada
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Faraone SV, McBurnett K, Sallee FR, Steeber J, López FA. Guanfacine Extended Release: A Novel Treatment for Attention-Deficit/Hyperactivity Disorder in Children and Adolescents. Clin Ther 2013; 35:1778-93. [DOI: 10.1016/j.clinthera.2013.09.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Revised: 08/07/2013] [Accepted: 09/06/2013] [Indexed: 10/26/2022]
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Sallee F, Connor DF, Newcorn JH. A review of the rationale and clinical utilization of α2-adrenoceptor agonists for the treatment of attention-deficit/hyperactivity and related disorders. J Child Adolesc Psychopharmacol 2013; 23:308-19. [PMID: 23782125 DOI: 10.1089/cap.2013.0028] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
OBJECTIVE Interest in the potential role for the α2-adrenoceptor agonists clonidine and guanfacine as treatments for attention-deficit/hyperactivity disorder (ADHD) has driven additional clinical studies as well as development of new formulations of these agents. This article reviews the published data that supported United States Food and Drug Administration approval and subsequent clinical use of α2-adrenoceptor agonists in the treatment of ADHD, and identifies promising directions for future research. METHODS Electronic searches were performed in PubMed through October 2012 using the base terms ADHD or attention deficit hyperactivity disorder and alpha agonists, as well as the following limits: humans, clinical trial, meta-analysis, practice guideline, randomized controlled trial, review, English. The electronic searches were complemented with reference lists from the articles retrieved by informal search of the literature, producing a qualitative review of published, pertinent drug-class preclinical and clinical data. Articles were selected for greater exposition based on hierarchy of evidence (e.g., randomized controlled trials), relevance, and quality of individual studies, as well as generalizability to clinical practice. RESULTS Results of clinical studies of immediate-release and extended-release formulations of α2-adrenoceptor agonists and basic science investigations of cognitive effects of these drugs are discussed. Studies of both clonidine and guanfacine extended-release formulations as monotherapy and adjunctive therapy with psychostimulants for the treatment of ADHD are also reviewed. CONCLUSIONS Large, randomized, placebo-controlled clinical trials support the efficacy and safety of α2-adrenoceptor agonists as monotherapy and adjunctive therapy with psychostimulants for the symptomatic treatment of ADHD. Future research could reveal whether there are cognitive benefits associated with this drug class and thus further define the role of α2-adrenoceptor agonists in the treatment of ADHD.
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Affiliation(s)
- Floyd Sallee
- Department of Psychiatry, University of Cincinnati, Cincinnati, OH 45219, USA.
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Bukstein OG, Head J. Guanfacine ER for the treatment of adolescent attention-deficit/hyperactivity disorder. Expert Opin Pharmacother 2012; 13:2207-13. [PMID: 22957772 DOI: 10.1517/14656566.2012.721778] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION Guanfacine extended release (GXR) is an alpha 1A noradrenergic agonist that has been approved by the FDA for the treatment of Attention-Deficit/Hyperactivity Disorder (ADHD) as a monotherapy, and as an adjunctive therapy to stimulants for the treatment of ADHD in children and adolescents age 6 - 17. AREAS COVERED PubMed, the Ovid Medline database, and the PsycInfo database were searched using the term 'guanfacine'. Results were then limited to criteria such as English and human, from 1990 through December 2011. The resulting yield from the comprehensive literature search was 4391 articles. The titles and abstracts of all articles were reviewed. Studies were selected for full-text review based upon their place in the hierarchy of evidence (e.g., randomized controlled trials), relevance and quality of individual studies, and generalizability to clinical practice. The search was augmented by further search of article reference lists. A total of 15 articles were selected for full-text examination. EXPERT OPINION Due to the absence of positive evidence for the efficacy of GXR for monotherapy in adolescents, clinicians should be guarded in the use of GXR for monotherapy in adolescents with ADHD. The use of GXR has considerable promise as an adjunct to stimulants for other behavioral conditions associated with ADHD.
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18
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Buffalari DM, Baldwin CK, See RE. Treatment of cocaine withdrawal anxiety with guanfacine: relationships to cocaine intake and reinstatement of cocaine seeking in rats. Psychopharmacology (Berl) 2012; 223:179-90. [PMID: 22526535 DOI: 10.1007/s00213-012-2705-1] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Accepted: 03/26/2012] [Indexed: 01/01/2023]
Abstract
RATIONALE Successful treatment of cocaine addiction is severely impeded by the propensity of users to relapse. Withdrawal severity may serve as a key predictor of susceptibility to relapse. Therefore, the identification and treatment of cocaine withdrawal symptoms such as anxiety may improve addiction treatment outcome. OBJECTIVES The current study examined the role of anxiety-like behavior during cocaine withdrawal and anxiolytic treatment in reinstatement of cocaine seeking in an animal model of relapse. METHODS Male rats experienced daily IV cocaine self-administration. One group of animals received the norepinephrine α-2 agonist, guanfacine, or vehicle prior to anxiety testing 48 h after the last self-administration session. In the second group of rats, relationships between cocaine intake, anxiety-like behavior after withdrawal of cocaine, and reinstatement responding were investigated. The third and fourth groups of animals received guanfacine, yohimbine (norepinephrine α-2 antagonist), or vehicle once per day for 3 days 48 h after cessation of cocaine self-administration, followed by extinction and subsequent reinstatement induced by cocaine injections, cocaine-paired cues, and yohimbine administration. RESULTS Cocaine-withdrawn rats at 48 h demonstrated higher levels of anxiety-like behavior as measured on a defensive burying task when compared to yoked saline controls, an effect reversed by guanfacine treatment. Cocaine intake was positively correlated with measures of anxiety-like behavior during early withdrawal, and this anxiety-like behavior was significantly correlated with subsequent cocaine-primed reinstatement. Yohimbine treatment during early withdrawal increased reinstatement to conditioned cues, while guanfacine treatment reduced reinstatement to yohimbine. CONCLUSIONS These studies suggest an important role for noradrenergic mediation of anxiety-like behavior that emerges after withdrawal of cocaine and potential risk of relapse as modeled by reinstatement, and suggest that treatment of anxiety symptoms during early abstinence may reduce the risk of relapse.
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Affiliation(s)
- Deanne M Buffalari
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
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Childress AC. Guanfacine extended release as adjunctive therapy to psychostimulants in children and adolescents with attention-deficit/hyperactivity disorder. Adv Ther 2012; 29:385-400. [PMID: 22610723 DOI: 10.1007/s12325-012-0020-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Indexed: 12/31/2022]
Abstract
Attention-deficit/hyperactivity disorder (ADHD) is a common neurobehavioral disorder associated with a wide range of impairments. Psychostimulants are generally first-line pharmacotherapy, but symptom improvement is suboptimal in some patients. In these patients, clinicians frequently use a combination of psychostimulants and nonscheduled medications to manage ADHD, although published evidence supporting this practice was relatively scarce until recently.Guanfacine extended release (GXR), a selective alpha2A-adrenoceptor agonist, is approved as a monotherapy and adjunctive therapy to psychostimulant medications for ADHD in patients 6-17 years of age. Drug-drug interaction studies have demonstrated that the adjunctive administration of GXR with a long-acting methylphenidate preparation or lisdexamfetamine dimesylate did not change exposure to the active components of either medication in a clinically meaningful way compared with either treatment alone.Data supporting the potential efficacy of GXR adjunctive to psychostimulants were preliminarily observed in a 9-week, open-label, dose-escalation study and subsequent extension study (≤ 24 months) in subjects aged 6-17 years with suboptimal control of ADHD symptoms on psychostimulant monotherapy. In a subsequent 9-week, randomized, double-blind, placebocontrolled study of subjects aged 6-17 years with suboptimal response to a long-acting, extendedrelease, oral psychostimulant, adjunctive GXR (administered in the morning or evening) was associated with significantly greater symptom reduction than placebo and psychostimulant (ADHD Rating Scale IV [ADHD-RS-IV] total score, placebo-adjusted least squares mean reductions: GXR AM, -4.5, P = 0.002; GXR PM, -5.3, P < 0.001, based on Dunnett's test). Across multiple studies, the safety and tolerability profile of GXR administered adjunctively to psychostimulants has been consistent with the known profiles of each medication. Additional studies should further explore the role of adjunctive GXR in clinical practice to help identify those patients most likely to benefit from such therapy.
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Affiliation(s)
- Ann C Childress
- Center for Psychiatry and Behavioral Medicine, 7351 Prairie Falcon Road, Suite 160, Las Vegas, NV 89128, USA.
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20
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Gamo NJ, Arnsten AFT. Molecular modulation of prefrontal cortex: rational development of treatments for psychiatric disorders. Behav Neurosci 2011; 125:282-96. [PMID: 21480691 DOI: 10.1037/a0023165] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Dysfunction of the prefrontal cortex (PFC) is a central feature of many psychiatric disorders, such as attention deficit hyperactivity disorder (ADHD), posttraumatic stress disorder (PTSD), schizophrenia, and bipolar disorder. Thus, understanding molecular influences on PFC function through basic research in animals is essential to rational drug development. In this review, we discuss the molecular signaling events initiated by norepinephrine and dopamine that strengthen working memory function mediated by the dorsolateral PFC under optimal conditions, and weaken working memory function during uncontrollable stress. We also discuss how these intracellular mechanisms can be compromised in psychiatric disorders, and how novel treatments based on these findings may restore a molecular environment conducive to PFC regulation of behavior, thought and emotion. Examples of successful translation from animals to humans include guanfacine for the treatment of ADHD and related PFC disorders, and prazosin for the treatment of PTSD.
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Affiliation(s)
- Nao J Gamo
- Department of Neurobiology, Yale University School of Medicine, New Haven, CT 06520-8001, USA.
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Arnsten AFT, Pliszka SR. Catecholamine influences on prefrontal cortical function: relevance to treatment of attention deficit/hyperactivity disorder and related disorders. Pharmacol Biochem Behav 2011; 99:211-6. [PMID: 21295057 PMCID: PMC3129015 DOI: 10.1016/j.pbb.2011.01.020] [Citation(s) in RCA: 239] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Revised: 01/04/2011] [Accepted: 01/24/2011] [Indexed: 02/06/2023]
Abstract
The primary symptoms of attention deficit/hyperactivity disorder (ADHD) include poor impulse control and impaired regulation of attention. Research has shown that the prefrontal cortex (PFC) is essential for the "top-down" regulation of attention, behavior, and emotion, and that this brain region is underactive in many patients with ADHD. The PFC is known to be especially sensitive to its neurochemical environment; relatively small changes in the levels of norepinephrine and dopamine can produce significant changes in its function. Therefore, alterations in the pathways mediating catecholamine transmission can impair PFC function, while medications that optimize catecholamine actions can improve PFC regulation of attention, behavior, and emotion. This article reviews studies in animals showing that norepinephrine and dopamine enhance PFC function through actions at postsynaptic α(2A)-adrenoceptors and dopamine D1-receptors, respectively. Stimulant medications and atomoxetine appear to enhance PFC function through increasing endogenous adrenergic and dopaminergic stimulation of α(2A)-receptors and D1-receptors. In contrast, guanfacine mimics the enhancing effects of norepinephrine at postsynaptic α(2A)-receptors in the PFC, strengthening network connectivity. Stronger PFC regulation of attention, behavior, and emotion likely contributes to the therapeutic effects of these medications for the treatment of ADHD.
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Affiliation(s)
- Amy F T Arnsten
- Department of Neurobiology, Yale University School of Medicine, New Haven, CT 06510, USA.
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Ostopovici-Halip L, Curpăn R, Mracec M, Bologa CG. Structural determinants of the alpha2 adrenoceptor subtype selectivity. J Mol Graph Model 2011; 29:1030-8. [PMID: 21602069 PMCID: PMC3307019 DOI: 10.1016/j.jmgm.2011.04.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Revised: 04/26/2011] [Accepted: 04/27/2011] [Indexed: 11/18/2022]
Abstract
Alpha2-adrenergic receptor (α2-AR) subtypes, acting mainly on the central nervous and cardiovascular systems, represent important targets for drug design, confirmed by the high number of studies published so far. Presently, only a few α2-AR subtype selective compounds are known. Using homology modeling and ligand docking, the present study analyzes the similarities and differences between binding sites, and between extracellular loops of the three subtypes of α2-ARs. Several α2-AR subtype selective ligands were docked into the active sites of the three α2-AR subtypes, key interactions between ligands and receptors were mapped, and the predicted results were compared with the available experimental data. Binding site analysis reveals a strong identity between important amino acid residues in each receptor, the very few differences being the key toward modulating selectivity of α2-AR ligands. The observed differences between binding site residues provide an excellent starting point for virtual screening of chemical databases, in order to identify potentially selective ligands for α2-ARs.
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Affiliation(s)
- Liliana Ostopovici-Halip
- Computational Chemistry Department, Institute of Chemistry Timisoara, M. Viteazu 24, 300223, Romania.
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Bari A, Mar AC, Theobald DE, Elands SA, Oganya KCNA, Eagle DM, Robbins TW. Prefrontal and monoaminergic contributions to stop-signal task performance in rats. J Neurosci 2011; 31:9254-63. [PMID: 21697375 PMCID: PMC3145112 DOI: 10.1523/jneurosci.1543-11.2011] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2011] [Accepted: 04/13/2011] [Indexed: 11/21/2022] Open
Abstract
Defining the neural and neurochemical substrates of response inhibition is of crucial importance for the study and treatment of pathologies characterized by impulsivity such as attention-deficit/hyperactivity disorder and addiction. The stop-signal task (SST) is one of the most popular paradigms used to study the speed and efficacy of inhibitory processes in humans and other animals. Here we investigated the effect of temporarily inactivating different prefrontal subregions in the rat by means of muscimol microinfusions on SST performance. We found that dorsomedial prefrontal cortical areas are important for inhibiting an already initiated response. We also investigated the possible neural substrates of the selective noradrenaline reuptake inhibitor atomoxetine via its local microinfusion into different subregions of the rat prefrontal cortex. Our results show that both orbitofrontal and dorsal prelimbic cortices mediate the beneficial effects of atomoxetine on SST performance. To assess the neurochemical specificity of these effects, we infused the α2-adrenergic agonist guanfacine and the D(1)/D(2) antagonist α-flupenthixol in dorsal prelimbic cortex to interfere with noradrenergic and dopaminergic neurotransmission, respectively. Guanfacine, which modulates noradrenergic neurotransmission, selectively impaired stopping, whereas blocking dopaminergic receptors by α-flupenthixol infusion prolonged go reaction time only, confirming the important role of noradrenergic neurotransmission in response inhibition. These results show that, similar to humans, distinct networks play important roles during SST performance in the rat and that they are differentially modulated by noradrenergic and dopaminergic neurotransmission. This study advances our understanding of the neuroanatomical and neurochemical determinants of impulsivity, which are relevant for a range of psychiatric disorders.
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Affiliation(s)
- Andrea Bari
- Department of Experimental Psychology and Behavioural and Clinical Neuroscience Institute, University of Cambridge, Cambridge CB2 3EB, United Kingdom.
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Cognitive enhancers for the treatment of ADHD. Pharmacol Biochem Behav 2011; 99:262-74. [PMID: 21596055 DOI: 10.1016/j.pbb.2011.05.002] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 04/26/2011] [Accepted: 05/03/2011] [Indexed: 12/11/2022]
Abstract
Attention-deficit hyperactivity disorder (ADHD) is associated with multiple cognition-related phenotypic features in both children and adults. This review aims to clarify the role of cognition in ADHD and how prevailing treatments, which are often highly effective at reducing the clinical symptoms of the disorder, fare in modulating ADHD-related cognitive processes. First, we consider how the broad construct of cognition can be conceptualized in the context of ADHD. Second, we review the available evidence for how a range of both pharmacological and non-pharmacological interventions have fared with respect to enhancing cognition in individuals affected by this pervasive disorder. Findings from the literature suggest that the effects across a broad range of pharmacological and non-pharmacological interventions on the characteristic symptoms of ADHD can be distinguished from their effects on cognitive impairments. As such the direct clinical relevance of cognition enhancing effects of different interventions is somewhat limited. Recommendations for future research are discussed, including the identification of cognition-related endophenotypes, the refinement of the ADHD clinical phenotype, and studying the difference between acute and chronic treatment regimens.
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Kollins SH, López FA, Vince BD, Turnbow JM, Farrand K, Lyne A, Wigal SB, Roth T. Psychomotor functioning and alertness with guanfacine extended release in subjects with attention-deficit/hyperactivity disorder. J Child Adolesc Psychopharmacol 2011; 21:111-20. [PMID: 21476931 DOI: 10.1089/cap.2010.0064] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVES To determine whether treatment with guanfacine extended release (GXR) in subjects with attention-deficit/hyperactivity disorder (ADHD) disrupted psychomotor functioning and alertness, or impacted daytime sleepiness. METHOD This was a randomized, double-blind, placebo-controlled, multicenter, phase 2, dose-optimization, noninferiority, laboratory classroom study of GXR (1, 2, and 3 mg/day) in 182 subjects aged 6 to 17 years with ADHD. Psychomotor functioning and alertness were assessed through several measures, including the Choice Reaction Time (CRT) test from the Cambridge Neuropsychological Test Automated Battery. Sedative effects were examined via spontaneously reported adverse events of sedation, somnolence, and hypersomnia as well as fatigue and lethargy, and with two validated subject- and observer-rated sleepiness scales. Standard efficacy measures for ADHD also were included. Cardiovascular and laboratory parameters were assessed. RESULTS There were no significant differences between the GXR and placebo groups on measures of psychomotor functioning or alertness from the CRT at endpoint (least-square mean difference: 2.5 [95% confidence interval (CI): -22.9, 28.0], p = 0.8 for CRT; 2.5 [95% CI: -21.5, 26.4], p = 0.84 for correct responses; 15.5 [95% CI: -45.1, 14.1], p = 0.30 for movement time; and -8.2 [95% CI: -54.1, 37.6] p = 0.72 for total time). Most sedative adverse events were mild to moderate, occurred during dose titration, decreased with dose maintenance, and resolved during the study period. One subject in the GXR group discontinued due to fatigue and somnolence. GXR was not associated with increased daytime sleepiness. GXR treatment was associated with significant improvement in ADHD symptoms (6.3 [95% CI: 2.7, 9.8], p = 0.001 for ADHD Rating Scale IV total scores at endpoint). CONCLUSIONS At doses that resulted in significant improvement in ADHD symptoms, impairment on cognitive tasks was not observed. Daytime sleepiness did not differ with GXR compared with placebo. Results suggest that the beneficial effects of GXR on ADHD symptoms are independent of sedation.
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Affiliation(s)
- Scott H Kollins
- Duke ADHD Program, Duke University Medical Center, Durham, North Carolina 27705, USA.
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Abstract
Pharmacologic management of attention-deficit/hyperactivity disorder (ADHD) has expanded beyond stimulant medications to include alpha-2 adrenergic agonists. These agents exert their actions through presynaptic stimulation and likely involve facilitation of dopamine and noradrenaline neurotransmission, both of which are thought to play critical roles in the pathophysiology of ADHD. Furthermore, frontostriatal dysfunction giving rise to neuropsychological weaknesses has been well-established in patients with ADHD and may explain how alpha-2 agents exert their beneficial effects. In the following review, we consider relevant neurobiological underpinnings of ADHD with respect to why alpha-2 agents may be effective in treating this condition. We also review new formulations of alpha-2 agonists, emerging data on their use in ADHD, and implications for clinical practice. Integrating knowledge of pathophysiologic mechanisms and mechanisms of drug action may inform our medication choices and facilitate treatment of ADHD and related disorders.
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Arnsten AFT. The use of α-2A adrenergic agonists for the treatment of attention-deficit/hyperactivity disorder. Expert Rev Neurother 2010; 10:1595-605. [PMID: 20925474 PMCID: PMC3143019 DOI: 10.1586/ern.10.133] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Neuropsychiatric disorders involve dysfunction of the prefrontal cortex (PFC), a highly evolved brain region that mediates executive functioning. The dorsolateral PFC is specialized for regulating attention and behavior, while the ventromedial PFC is specialized for regulating emotion. These abilities arise from PFC pyramidal cell networks that excite each other to maintain goals and rules 'in mind'. Imaging studies have shown reduced PFC gray matter, weaker PFC connections and altered PFC function in patients with attention-deficit/hyperactivity disorder. Thus, medications that strengthen PFC network connections may be particularly useful for the treatment of attention-deficit/hyperactivity disorder and related disorders. Recent data show that compounds such as guanfacine can enhance PFC function by stimulating postsynaptic α-2A receptors on the dendritic spines of PFC pyramidal cells where networks interconnect. Stimulation of these receptors inhibits cAMP signaling, thus closing potassium channels and strengthening physiological connections. These actions may benefit patients with weak PFC function.
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Affiliation(s)
- Amy F T Arnsten
- Department of Neurobiology, Yale Medical School, 333 Cedar St, New Haven, CT 06510, USA.
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Connor DF, Findling RL, Kollins SH, Sallee F, López FA, Lyne A, Tremblay G. Effects of guanfacine extended release on oppositional symptoms in children aged 6-12 years with attention-deficit hyperactivity disorder and oppositional symptoms: a randomized, double-blind, placebo-controlled trial. CNS Drugs 2010; 24:755-68. [PMID: 20806988 DOI: 10.2165/11537790-000000000-00000] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
OBJECTIVE To evaluate the efficacy and safety of guanfacine extended release (XR, Intuniv; Shire Development Inc., Wayne, PA, USA) in the treatment of oppositional symptoms in children aged 6-12 years with a diagnosis of attention-deficit hyperactivity disorder (ADHD) and the presence of oppositional symptoms. SUBJECTS AND METHODS In this randomized, double-blind, placebo-controlled, multicentre, flexible-dose, dose-optimization study, children aged 6-12 years were randomized to receive guanfacine XR (1-4 mg/day) or placebo for 9 weeks. Screening and washout periods were followed by a 5-week dose-optimization period, a 3-week dose-maintenance period and a 1-week tapering period. The primary efficacy measure was change from baseline to endpoint in the oppositional subscale of the Conners' Parent Rating Scale-Revised: Long Form (CPRS-R:L) score. Change in ADHD Rating Scale IV (ADHD-RS-IV) total score was a secondary efficacy measure. Safety assessments included adverse events (AEs), vital signs, ECG readings and laboratory studies. RESULTS A total of 217 children were enrolled: 138 were randomized to receive guanfacine XR and 79 to receive placebo. Least-squares mean reductions from baseline to endpoint in CPRS-R:L oppositional subscale scores were 10.9 in the guanfacine XR group compared with 6.8 in the placebo group (p < 0.001; effect size = 0.59). A significantly greater reduction in ADHD-RS-IV total score from baseline to endpoint was also seen in the guanfacine-treated group compared with the placebo group (23.8 vs 11.5, respectively; p < 0.001; effect size = 0.92). A post hoc correlation analysis between percentage reduction from baseline to endpoint in CPRS-R:L oppositional subscale and ADHD-RS-IV total scores indicated that the decreases in oppositional symptoms and ADHD symptoms were highly correlated (r = 0.74). The most commonly reported, treatment-emergent AEs (TEAEs) in the guanfacine XR group were somnolence (50.7%), headache (22.1%), sedation (13.2%), upper abdominal pain (11.8%) and fatigue (11.0%) and most were mild or moderate in severity. TEAEs of sedation, somnolence or hypersomnia were experienced by 62.5% of subjects in the guanfacine XR group. These events were most common during the dose-titration period but most (63.5%) resolved prior to the taper period. TEAEs of fatigue, lethargy and asthenia were reported in 11.0%, 3.7% and 0.0% of subjects in the guanfacine XR group, respectively. Most subjects receiving guanfacine XR demonstrated modest changes in blood pressure, pulse rate and ECG readings that were not considered clinically significant. CONCLUSIONS In this population of children aged 6-12 years with ADHD and the presence of oppositional symptoms, significant reductions in CPRS-R:L oppositional subscale and ADHD-RS-IV total scores were observed with guanfacine XR treatment compared with placebo. Treatment with guanfacine XR at optimized doses was associated with mostly mild or moderate TEAEs. The findings of this study support the efficacy of guanfacine XR in the treatment of children with ADHD and the presence of oppositional symptoms. CLINICAL TRIAL REGISTRATION NUMBER NCT00367835.
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Affiliation(s)
- Daniel F Connor
- Department of Psychiatry, University of Connecticut School of Medicine, Farmington, Connecticut 06030-1410,USA.
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Faraone SV, Glatt SJ. Effects of extended-release guanfacine on ADHD symptoms and sedation-related adverse events in children with ADHD. J Atten Disord 2010; 13:532-8. [PMID: 19395648 DOI: 10.1177/1087054709332472] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
OBJECTIVE Guanfacine extended release (GXR) is a selective alpha(2A)-adrenoceptor agonist that is shown to be an effective nonstimulant treatment for the symptoms of attention-deficit/hyperactivity disorder. This report documents the time course and predictors of symptom efficacy and sedation-related adverse events (AEs) that emerge during GXR treatment throughout 3 randomized, placebo-controlled, double-blind trials of the drug. METHOD Analysis of data from 3 GXR clinical trials. RESULTS Few variables related to the study participants or their treatment regimen affects the emergence or magnitude of sedation-related AEs. The best predictor of sedation is treatment duration, with the likelihood of sedation-related AEs decreasing with increasing time on medication. Sedation-related AEs are not predicted by the actual dose a participant receives, the magnitude of any dose changes, or the relationship between dose received and the magnitude of dose changes. Rates of discontinuation because of sedation-related side effects average 6.3% for GXR-treated participants and 0.5% for placebo-treated participants across the three trials. CONCLUSION These results suggest that acclimation to GXR may minimize the risk for, and magnitude of, sedation-related AEs. (J. of Att. Dis. 2010; 13(5) 532-538).
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Affiliation(s)
- Stephen V Faraone
- SUNY Upstate Medical University, Department of Psychiatry and Behavioral Sciences, 750 East AdamsStreet, Syracuse, NY, USA.
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Dambrova M, Zvejniece L, Skapare E, Vilskersts R, Svalbe B, Baumane L, Muceniece R, Liepinsh E. The anti-inflammatory and antinociceptive effects of NF-kappaB inhibitory guanidine derivative ME10092. Int Immunopharmacol 2010; 10:455-60. [PMID: 20074673 DOI: 10.1016/j.intimp.2010.01.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Revised: 12/15/2009] [Accepted: 01/06/2010] [Indexed: 12/22/2022]
Abstract
The guanidine compound ME10092 (1-(3,4-dimethoxy-2-chlorobenzylideneamino)-guanidine) is known to possess anti-radical and anti-ischemic activity but its molecular targets have not been identified. This study investigated whether ME10092 regulates the nuclear factor kappa B (NF-kappaB)-mediated signal transduction in vivo. The effect of ME10092 treatment (1-100 pmol/mouse) on nuclear translocation of NF-kappaB, activation of expression of inflammatory mediators and production of nitric oxide were measured in the lipopolysaccharide (LPS)-induced brain inflammation model in mice in vivo. The antinociceptive activity of ME10092 was tested in the formalin-induced paw licking test. ME10092 dose-dependently inhibited LPS-induced nuclear translocation of NF-kappaB, transcription of tumour necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Electron paramagnetic resonance measurements showed that ME10092 inhibited the LPS-induced increase in nitric oxide content in mouse brain tissue in a dose-dependent manner. In the formalin-induced paw licking test, ME10092 (at the dose of 3mg/kg, p.o. twice daily for eight days) significantly reduced nociceptive response. In conclusion, above results indicate that ME10092 inhibits NF-kappaB activation and suppresses the up-regulation of inflammatory mediators in experimental models in vivo.
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Arnsten AFT. Toward a new understanding of attention-deficit hyperactivity disorder pathophysiology: an important role for prefrontal cortex dysfunction. CNS Drugs 2009; 23 Suppl 1:33-41. [PMID: 19621976 DOI: 10.2165/00023210-200923000-00005] [Citation(s) in RCA: 257] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Recent advances in neurobiology have aided our understanding of attention-deficit hyperactivity disorder (ADHD). The higher-order association cortices in the temporal and parietal lobes and prefrontal cortex (PFC) interconnect to mediate aspects of attention. The parietal association cortices are important for orienting attentional resources in time/space, while the temporal association cortices analyse visual features critical for identifying objects/places. These posterior cortices are engaged by the salience of a stimulus (its physical characteristics such as movement and colour). Conversely, the PFC is critical for regulating attention based on relevance (i.e. its meaning). The PFC is important for screening distractions, sustaining attention and shifting/dividing attention in a task-appropriate manner. The PFC is critical for regulating behaviour/emotion, especially for inhibiting inappropriate emotions, impulses and habits. The PFC is needed for allocating/planning to achieve goals and organizing behaviour/thought. These regulatory abilities are often referred to as executive functions. In humans, the right hemisphere of the PFC is important for regulating distractions, inappropriate behaviour and emotional responses. Imaging studies of patients with ADHD indicate that these regions are underactive with weakened connections to other parts of the brain. The PFC regulates attention and behaviour through networks of interconnected pyramidal cells. These networks excite each other to store goals/rules to guide actions and are highly dependent on their neurochemical environment, as small changes in the catecholamines noradrenaline (NA) or dopamine (DA) can have marked effects on PFC function. NA and DA are released in the PFC according to our arousal state; too little (during fatigue or boredom) or too much (during stress) impairs PFC function. Optimal amounts are released when we are alert/interested. The beneficial effects of NA occur at postsynaptic alpha(2A)-receptors on the dendritic spines of PFC pyramidal cells. Stimulation of these receptors initiates a series of chemical events inside the cell. These chemical signals lead to the closing of special ion channels, thus strengthening the connectivity of network inputs to the cell. Conversely, the beneficial effects of moderate amounts of DA occur at D(1) receptors, which act by weakening irrelevant inputs to the cells on another set of spines. Genetic linkage studies of ADHD suggest that these catecholamine pathways may be altered in some families with ADHD, e.g. alterations in the enzyme that synthesizes NA (DA beta-hydroxylase) are associated with weakened PFC abilities. Pharmacological studies in animals indicate catecholamine actions in the PFC are highly relevant to ADHD. Blocking NA alpha(2A)-receptors in the PFC with yohimbine produces a profile similar to ADHD: locomotor hyperactivity, impulsivity and poor working memory. Conversely, drugs that enhance alpha(2)-receptor stimulation improve PFC function. Guanfacine directly stimulates postsynaptic alpha(2A)-receptors in the PFC and improves functioning, while methylphenidate and atomoxetine increase endogenous NA and DA levels and indirectly improve PFC function via alpha(2A)- and D(1) receptor actions. Methylphenidate and atomoxetine have more potent actions in the PFC than in subcortical structures, which may explain why proper administration of stimulant medications does not lead to abuse. Further understanding of the neurobiology of attention and impulse control will allow us to better tailor treatments for specific patient needs.
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Affiliation(s)
- Amy F T Arnsten
- Department of Neurobiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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Sudo RT, Calasans-Maia JA, Galdino SL, Lima MCA, Zapata-Sudo G, Hernandes MZ, Pitta IR. Interaction of morphine with a new alpha2-adrenoceptor agonist in mice. THE JOURNAL OF PAIN 2009; 11:71-8. [PMID: 19853523 DOI: 10.1016/j.jpain.2009.08.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2009] [Revised: 07/08/2009] [Accepted: 08/04/2009] [Indexed: 10/20/2022]
Abstract
UNLABELLED Finding new chemicals or adjuvants with analgesic effects in the central nervous system is clinically relevant due to the limited number of drugs with these properties. Here, we present PT-31, which is chemically related to 3-benzyl-imidazolidine, with an analgesic profile that results from alpha(2)-adrenoceptor activation. Intraperitoneal administration of PT-31 dose-dependently produced antinociception in the hot plate test, and interacted synergistically with morphine. This effect was completely reversed by yohimbine, a non-selective antagonist of alpha(2)-adrenoceptors, and by BRL 44408, a selective alpha(2A)-adrenoceptor antagonist. The combination of morphine and PT-31 produced greater antinociceptive activity than either alone, and isobolographic analysis revealed a synergistic interaction between these compounds. Docking results confirm the high affinity of the PT-31 ligand at the alpha(2A)-adrenoceptor. PERSPECTIVE This study introduces a new analgesic compound (PT-31) that acts via alpha(2A)-adrenoceptor activation. A significant increase in analgesia was observed when co-administered with morphine. PT-31 is an interesting new substance for pain therapy.
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Affiliation(s)
- Roberto T Sudo
- Programa de Desenvolvimento de Fármacos, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Brazil.
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Spencer TJ, Greenbaum M, Ginsberg LD, Murphy WR. Safety and effectiveness of coadministration of guanfacine extended release and psychostimulants in children and adolescents with attention-deficit/hyperactivity disorder. J Child Adolesc Psychopharmacol 2009; 19:501-10. [PMID: 19877974 PMCID: PMC2861960 DOI: 10.1089/cap.2008.0152] [Citation(s) in RCA: 229] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE The aim of this study was to evaluate the safety and effectiveness of guanfacine extended release (GXR) administered concomitantly with psychostimulants in children and adolescents with attention-deficit/hyperactivity disorder (ADHD) and suboptimal response to a psychostimulant alone. DESIGN AND METHODS This was a multicenter, open-label, 9-week, dose-escalation study of 75 subjects with ADHD treated with methylphenidate (MPH) or amphetamine (AMP) alone for at least 1 month, yet with suboptimal control of ADHD symptoms. Sixty-three subjects (84.0%) completed the study. Patients received GXR in addition to their psychostimulant. Starting with 1 mg/day, GXR was increased weekly to the highest tolerated dose (1, 2, 3, or 4 mg/day), which was maintained through week 6. GXR was then titrated downward in 1-mg weekly decrements from week 7 through week 9. Psychostimulant treatment regimens were continued until at least week 7. MAIN OUTCOME MEASURES Safety assessments included adverse events (AEs), vital signs, physical examination, clinical laboratory tests, the Pediatric Daytime Sleepiness Scale, and the Pittsburgh Side Effects Rating Scale. Efficacy was assessed using the ADHD Rating Scale IV (ADHD-RS-IV), the Conners' Parent Rating Scale-Revised Short Form, Clinical Global Impressions, Parent Global Assessment, and Child Health Questionnaire-Parent Form. RESULTS The most common treatment-related AEs were upper abdominal pain (25.3%), fatigue (24.0%), irritability (22.7%), headache (20.0%), and somnolence (18.7%). Most AEs were mild to moderate in severity. Investigator-rated AEs due to blood pressure decreases, heart rate, or electrocardiogram findings were infrequent. Mean changes from baseline (psychostimulant monotherapy just prior to receiving GXR) to end point in ADHD-RS-IV total score were statistically significant overall: -16.1 (p < 0.0001). Significant improvement in both subscales of the ADHD-RS-IV was observed. Improvement of symptoms was observed in a majority of subjects. CONCLUSION Coadministration of GXR and MPH or AMP was generally safe and associated with statistically significant and clinically meaningful ADHD symptom improvement in children and adolescents.
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Affiliation(s)
- Thomas J. Spencer
- Clinical and Research Program, Pediatric Psychopharmacology, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts
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Heal DJ, Cheetham SC, Smith SL. The neuropharmacology of ADHD drugs in vivo: insights on efficacy and safety. Neuropharmacology 2009; 57:608-18. [PMID: 19761781 DOI: 10.1016/j.neuropharm.2009.08.020] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Revised: 07/15/2009] [Accepted: 08/11/2009] [Indexed: 11/19/2022]
Abstract
Results from in vivo techniques, especially intracerebral microdialysis in freely-moving rats, have provided insights into potential mechanisms responsible for the efficacy and safety of catecholaminergic drugs for ADHD treatment. The drugs reviewed come from distinct pharmacological classes: psychostimulant releasing agents, eg d-amphetamine; psychostimulant reuptake inhibitors, eg dl-threo-methylphenidate (dl-MPH), and non-stimulant reuptake inhibitors, eg atomoxetine. Psychostimulants, which currently deliver the best efficacy in treating ADHD, exhibit the following characteristics on extraneuronal catecholamine concentrations in rodent brain in vivo: 1) They enhance the efflux and function of both noradrenaline and dopamine in the central nervous system. 2) The increase of dopamine efflux that they produce is not limited to cortical regions. 3) They have a rapid onset of action with no ceiling on drug effect. d-Amphetamine has a mechanism independent of neuronal firing rate, displacing intraneuronal stores of catecholamines, delaying their reuptake and inhibiting catabolism by monoamine oxidase. dl-MPH has an enigmatic, extraneuronal action that is neuronal firing rate-dependent and reuptake transporter-mediated, yet paradoxically, almost as powerful as that of d-amphetamine. In safety terms, these powerful catecholaminergic effects also make the psychostimulants liable for abuse. Since efficacy and safety derive from the same pharmacological mechanisms, it has not yet been possible to separate these two components. However, the development of once-daily psychostimulant formulations and a prodrug, lisdexamfetamine, has improved patient compliance and markedly reduced scope for their diversion/abuse. This review will discuss the in vivo pharmacological profiles of approved catecholaminergic drugs for treatment of ADHD and implications for their clinical efficacy and abuse liability.
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Affiliation(s)
- D J Heal
- RenaSci Consultancy Ltd, BioCity, Nottingham NG1 1GF, UK.
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Shields AD, Wang Q, Winder DG. alpha2A-adrenergic receptors heterosynaptically regulate glutamatergic transmission in the bed nucleus of the stria terminalis. Neuroscience 2009; 163:339-51. [PMID: 19527774 DOI: 10.1016/j.neuroscience.2009.06.022] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Revised: 06/06/2009] [Accepted: 06/09/2009] [Indexed: 10/20/2022]
Abstract
Stress is a major driving force in reinstatement of drug-seeking behavior. The bed nucleus of the stria terminalis (BNST) has been identified as a key brain region in this behavior, and receives a dense input of the stress-neurotransmitter norepinephrine through the ventral noradrenergic bundle. Activation of alpha(2)-adrenergic receptors (alpha(2)-ARs) in the BNST blocks stress-induced reinstatement of drug-seeking, indicating a potentially important role for these receptors. Currently, it is unclear how alpha(2)-AR agonists elicit this behavioral action, or through which alpha(2)-AR subtype. Activation of alpha(2)-ARs decreases glutamatergic transmission in the BNST, an effect which is nearly absent in the alpha(2A)-AR knockout mouse. Here, we take advantage of a knock-in mouse in which a hemagglutinin-tagged alpha(2A)-AR was inserted into the endogenous locus, along with the alpha(2A)-AR selective agonist guanfacine, to further study the role of the alpha(2A)-AR subtype in modulation of neurotransmission in the BNST. Using immunohistochemistry, we find that alpha(2A)-ARs are highly expressed in the BNST, and that this expression is more similar in distribution to the vesicular glutamate transporters than to either norepinephrine transporter or tyrosine hydroxylase positive terminals. Using whole cell patch-clamp recordings, we show that guanfacine causes a depression of evoked excitatory and, to a more limited extent, inhibitory fast synaptic transmission. In total, these data support a prominent heterosynaptic role for alpha(2A)-ARs in modulating fast synaptic transmission in the BNST.
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Affiliation(s)
- A D Shields
- Department of Molecular Physiology and Biophysics, 23rd and Pierce Avenue South, Vanderbilt University School of Medicine, Nashville, TN 37232-0615, USA
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Sallee FR, Lyne A, Wigal T, McGough JJ. Long-term safety and efficacy of guanfacine extended release in children and adolescents with attention-deficit/hyperactivity disorder. J Child Adolesc Psychopharmacol 2009; 19:215-26. [PMID: 19519256 DOI: 10.1089/cap.2008.0080] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Short-term, controlled studies of extended-release guanfacine (GXR), a selective alpha(2A)-adrenoreceptor agonist, demonstrate efficacy in treating attention-deficit/hyperactivity disorder (ADHD) symptoms as monotherapy. This 2-year open-label study was conducted to further assess the long-term safety and efficacy of GXR. METHODS Study participants, aged 6-17 years with ADHD, had previously been exposed to GXR therapy alone or in combination with psychostimulants in one of two antecedent trials. In this study, doses were titrated to 1, 2, 3, or 4 mg/day of GXR alone or in combination with a psychostimulant. Safety and efficacy data collected at clinic visits over 24 months provided further evidence of the overall safety and efficacy of GXR for treating ADHD. RESULTS The majority of adverse events (AEs) were mild to moderate, and few patients discontinued the study because of an AE. Efficacy measures demonstrated significant improvement beginning in the first month and lasting through the end of the 24-month treatment period. Throughout the entire 2-year study, 202 subjects (77.1%) discontinued and 60 (22.9%) completed the study. CONCLUSIONS Overall, these data support that GXR monotherapy is generally safe and effective for treating ADHD.
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Affiliation(s)
- Floyd R Sallee
- Department of Psychiatry, University of Cincinnati, Cincinnati, Ohio 45219, USA.
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Arnsten AF. The Emerging Neurobiology of Attention Deficit Hyperactivity Disorder: The Key Role of the Prefrontal Association Cortex. J Pediatr 2009; 154:I-S43. [PMID: 20596295 PMCID: PMC2894421 DOI: 10.1016/j.jpeds.2009.01.018] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Attention deficit/hyperactivity disorder (ADHD) is characterized by symptoms of inattention, impulsivity, and locomotor hyperactivity. Recent advances in neurobiology, imaging, and genetics have led to a greater understanding of the etiology and treatment of ADHD. Studies have found that ADHD is associated with weaker function and structure of prefrontal cortex (PFC) circuits, especially in the right hemisphere. The prefrontal association cortex plays a crucial role in regulating attention, behavior, and emotion, with the right hemisphere specialized for behavioral inhibition. The PFC is highly dependent on the correct neurochemical environment for proper function: noradrenergic stimulation of postsynaptic alpha-2A adrenoceptors and dopaminergic stimulation of D1 receptors is necessary for optimal prefrontal function. ADHD is associated with genetic changes that weaken catecholamine signaling and, in some patients, with slowed PFC maturation. Effective pharmacologic treatments for ADHD all enhance catecholamine signaling in the PFC and strengthen its regulation of attention and behavior. Recent animal studies show that therapeutic doses of stimulant medications preferentially increase norepinephrine and, to a lesser extent, dopamine, in the PFC. These doses reduce locomotor activity and improve PFC regulation of attention and behavior through enhanced catecholamine stimulation of alpha-2A and D1 receptors. These findings in animals are consistent with improved PFC function in normal human subjects and, more prominently, in patients with ADHD. Thus, a highly cohesive story is emerging regarding the etiology and treatment of ADHD.
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Affiliation(s)
- Amy F.T. Arnsten
- Department of Neurobiology, Yale University School of Medicine, New Haven, CT 06510, , PHONE: 203-785-4431, FAX: 203-785-5263
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Guanfacine extended release in children and adolescents with attention-deficit/hyperactivity disorder: a placebo-controlled trial. J Am Acad Child Adolesc Psychiatry 2009; 48:155-65. [PMID: 19106767 DOI: 10.1097/chi.0b013e318191769e] [Citation(s) in RCA: 152] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE This study compared the efficacy of guanfacine extended release (GXR), a selective alpha(2A)-adrenoceptor agonist, with placebo in children and adolescents with attention-deficit/hyperactivity disorder (ADHD). METHOD This double-blind, 9-week, dose-ranging, parallel-design, multicenter trial randomized 6- to 17-year-olds with ADHD to once-daily oral GXR in 1-, 2-, 3-, and 4-mg doses or placebo. Primary outcome was change in total ADHD Rating Scale-IV score from baseline to endpoint. Secondary outcomes included changes in scores of hyperactive/impulsive and inattentive subscales; clinician and parent ratings; duration of clinical effect; and safety measures. RESULTS Statistically significant reductions in ADHD Rating Scale-IV scores were observed from baseline to endpoint at all doses of GXR, with effect sizes ranging from 0.43 to 0.62. In subjects receiving GXR, mean heart rate and systolic and diastolic blood pressure decreased as the dose of GXR increased and then returned toward baseline during the dose-maintenance and dose-tapering phases of the trial. Most frequent treatment-emergent adverse events (> or = 5%) were somnolence, headache, fatigue, sedation, dizziness, irritability, upper abdominal pain, and nausea. Somnolence, sedation, and fatigue adverse events emerged within the first 2 weeks of dosing and generally resolved by study end. CONCLUSIONS : Guanfacine extended-release was effective in reducing symptoms of ADHD. Adverse events were mild to moderate, did not interfere with improvements in attention, and rarely led to discontinuation.
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Busnardo C, Tavares RF, Corrêa FMA. Mechanisms involved in the pressor response to noradrenaline microinjection into the supraoptic nucleus of unanesthetized rats. Auton Neurosci 2008; 145:63-70. [PMID: 19059010 DOI: 10.1016/j.autneu.2008.11.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2008] [Revised: 11/07/2008] [Accepted: 11/10/2008] [Indexed: 01/29/2023]
Abstract
We report on the cardiovascular effects of noradrenaline (NA) microinjection into the hypothalamic supraoptic nucleus (SON) as well as the central and peripheral mechanisms involved in their mediation. Microinjections of NA 1, 3, 10, 30 or 45 nmol/100 nL into the SON caused dose-related pressor and bradycardiac response in unanesthetized rats. The response to NA 10 nmol was blocked by SON pretreatment with 15 nmol of the alpha(2)-adrenoceptor antagonist RX821002 and not affected by pretreatment with equimolar dose of the selective alpha(1)-adrenoceptor antagonist WB4101, suggesting that local alpha(2)-adrenoceptors mediate these responses. Pretreatment of the SON with the nonselective beta-adrenoceptor antagonist propranolol 15 nmol did not affect the pressor response to NA microinjection of into the SON. Moreover, the microinjection of the 100 nmol of the selective alpha(1)-adrenoceptor agonist methoxamine (MET) into the SON did not cause cardiovascular response while the microinjection of the selective alpha(2)-adrenoceptor agonists BHT920 (BHT, 100 nmol) or clonidine (CLO, 5 nmol) caused pressor and bradycardiac responses, similar to that observed after the microinjection of NA. The pressor response to NA was potentiated by intravenous pretreatment with the ganglion blocker pentolinium and was blocked by intravenous pretreatment with the V(1)-vasopressin receptor antagonist dTyr(CH2)5(Me)AVP, suggesting an involvement of circulating vasopressin in this response. In conclusion, our results suggest that pressor responses caused by microinjections of NA into the SON involve activation of local alpha(2)-adrenoceptor receptors and are mediated by vasopressin release into circulation.
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Affiliation(s)
- Cristiane Busnardo
- Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, 14090-090, Brazil
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Long-term, open-label extension study of guanfacine extended release in children and adolescents with ADHD. CNS Spectr 2008; 13:1047-55. [PMID: 19179940 DOI: 10.1017/s1092852900017107] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION Guanfacine is a noradrenergic agonist that is believed to improve symptoms of attention-deficit/hyperactivity disorder (ADHD) through selective actions at alpha2A-adrenoceptors in the prefrontal cortex. A recent double-blind, multicenter trial supports the efficacy and safety of guanfacine extended release (GXR) for pediatric ADHD. This long-term, open-label extension was conducted to study the safety profile and effectiveness of GXR for up to 2 years. METHODS Subjects were 240 children 6-17 years of age with a diagnosis of ADHD who participated in the preceding randomized trial. GXR was initiated at 2 mg/day and titrated as needed in 1-mg increments to a maximum of 4 mg/day to achieve optimal clinical response. RESULTS The most common adverse events were somnolence (30.4%), headache (26.3%), fatigue (14.2%), and sedation (13.3%). Somnolence, sedation, and fatigue were usually transient. Cardiovascular-related adverse events were uncommon, although small reductions in mean blood pressure and pulse rate were evident at monthly visits. ADHD Rating Scale, Version IV, total and subscale scores improved significantly from baseline to endpoint for all dose groups (P<.001 for all comparisons, intent-to-treat population). CONCLUSION Long-term treatment with GXR was generally safe for up to 24 months of treatment, and effectiveness was maintained over this treatment period.
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Biederman J, Melmed RD, Patel A, McBurnett K, Konow J, Lyne A, Scherer N. A randomized, double-blind, placebo-controlled study of guanfacine extended release in children and adolescents with attention-deficit/hyperactivity disorder. Pediatrics 2008; 121:e73-84. [PMID: 18166547 DOI: 10.1542/peds.2006-3695] [Citation(s) in RCA: 209] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVE With this study we assessed the efficacy and safety of an extended-release formulation of guanfacine compared with placebo for the treatment of children and adolescents with attention-deficit/hyperactivity disorder. METHODS In this multicenter, double-blind, placebo-controlled, fixed-dosage escalation study, patients aged 6 to 17 years were randomly assigned to 1 of 3 treatment groups of guanfacine extended release (2, 3, or 4 mg/day) or placebo for 8 weeks. The primary outcome measurement was the Attention-Deficit/Hyperactivity Disorder Rating Scale IV total score. Secondary measurements included Clinical Global Impression of Improvement, Parent's Global Assessment, Conners' Parent Rating Scale-Revised: Short Form, and Conners' Teacher Rating Scale-Revised: Short Form. RESULTS A total of 345 patients were randomly assigned to placebo (n = 86) or guanfacine extended release 2 mg (n = 87), 3 mg (n = 86), or 4 mg (n = 86) treatment groups. Least-squares mean changes from baseline to the end point in Attention-Deficit/Hyperactivity Disorder Rating Scale IV total scores were significant in all groups of children taking guanfacine extended release: -16.18 in the 2-mg group, -16.43 in the 3-mg group, and -18.87 in the 4-mg group, compared with -8.48 in the placebo group. All groups of children taking guanfacine extended release showed significant improvement on hyperactivity/impulsivity and inattentiveness subscales of the Attention-Deficit/Hyperactivity Disorder Rating Scale IV, Clinical Global Impression of Improvement, Parent's Global Assessment, Conners' Parent Rating Scale-Revised: Short Form, and Conners' Teacher Rating Scale-Revised: Short Form assessments compared with placebo. The most commonly reported treatment-emergent adverse events were headache, somnolence, fatigue, upper abdominal pain, and sedation. Small to modest changes in blood pressure, pulse rate, and electrocardiogram parameters were observed but were not clinically meaningful. CONCLUSIONS Guanfacine extended release met the primary and secondary efficacy end points. It was well tolerated and effective compared with placebo.
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Affiliation(s)
- Joseph Biederman
- Pediatric Psychopharmacology Department, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
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Arnsten AF, Scahill L, Findling RL. alpha2-Adrenergic receptor agonists for the treatment of attention-deficit/hyperactivity disorder: emerging concepts from new data. J Child Adolesc Psychopharmacol 2007; 17:393-406. [PMID: 17822336 DOI: 10.1089/cap.2006.0098] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Recent developments in the field of neuroscience have illuminated the understanding of the neural circuits impaired in attention-deficit/hyperactivity disorder (ADHD) and the mechanism of action of treatments used to treat this condition. There is an exciting confluence between emerging studies in basic neurobiology and the genetic, neuroimaging, and neuropsychological analyses of ADHD. The following provides a brief review of this field, explaining how compounds like guanfacine and the traditional stimulant medications can reduce the core symptoms of ADHD by optimizing the neurochemical environment in the prefrontal cortex (PFC). Knowledge of these basic mechanisms may inform our medication choices and facilitate treatment of ADHD and related disorders.
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Affiliation(s)
- Amy F Arnsten
- Director of Graduate Studies, Deparment of Neurobiology, Yale Medical School, New Haven, Connecticut 06520-8001, USA.
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Jurgens CWD, Hammad HM, Lichter JA, Boese SJ, Nelson BW, Goldenstein BL, Davis KL, Xu K, Hillman KL, Porter JE, Doze VA. Alpha2A adrenergic receptor activation inhibits epileptiform activity in the rat hippocampal CA3 region. Mol Pharmacol 2007; 71:1572-81. [PMID: 17341653 DOI: 10.1124/mol.106.031773] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Norepinephrine has potent antiepileptic properties, the pharmacology of which is unclear. Under conditions in which GABAergic inhibition is blocked, norepinephrine reduces hippocampal cornu ammonis 3 (CA3) epileptiform activity through alpha(2) adrenergic receptor (AR) activation on pyramidal cells. In this study, we investigated which alpha(2)AR subtype(s) mediates this effect. First, alpha(2)AR genomic expression patterns of 25 rat CA3 pyramidal cells were determined using real-time single-cell reverse transcription-polymerase chain reaction, demonstrating that 12 cells expressed alpha(2A)AR transcript; 3 of the 12 cells additionally expressed mRNA for alpha(2C)AR subtype and no cells possessing alpha(2B)AR mRNA. Hippocampal CA3 epileptiform activity was then examined using field potential recordings in brain slices. The selective alphaAR agonist 6-fluoronorepinephrine caused a reduction of CA3 epileptiform activity, as measured by decreased frequency of spontaneous epileptiform bursts. In the presence of betaAR blockade, concentration-response curves for AR agonists suggest that an alpha(2)AR mediates this response, as the rank order of potency was 5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine (UK-14304) >or= epinephrine >6-fluoronorepinephrine > norepinephrine >>> phenylephrine. Finally, equilibrium dissociation constants (K(b)) of selective alphaAR antagonists were functionally determined to confirm the specific alpha(2)AR subtype inhibiting CA3 epileptiform activity. Apparent K(b) values calculated for atipamezole (1.7 nM), MK-912 (4.8 nM), BRL-44408 (15 nM), yohimbine (63 nM), ARC-239 (540 nM), prazosin (4900 nM), and terazosin (5000 nM) correlated best with affinities previously determined for the alpha(2A)AR subtype (r = 0.99, slope = 1.0). These results suggest that, under conditions of impaired GABAergic inhibition, activation of alpha(2A)ARs is primarily responsible for the antiepileptic actions of norepinephrine in the rat hippocampal CA3 region.
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Affiliation(s)
- Chris W D Jurgens
- Department of Pharmacology, Physiology and Therapeutics, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND 58202-9037, USA
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Ontsouka EC, Blum JW, Steiner A, Meylan M. mRNA expression and binding sites for alpha2-adrenergic receptor subtypes in muscle layers of the ileum and spiral colon of dairy cows. Am J Vet Res 2007; 67:1883-9. [PMID: 17078750 DOI: 10.2460/ajvr.67.11.1883] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To measure maximum binding capacity (B(max)) and levels of mRNA expression for alpha(2)-adrenergic receptor (AR) subtypes in ileal and colonic muscle layers of healthy dairy cows. SAMPLE POPULATION Ileal and colonic muscle specimens from 6 freshly slaughtered cows. PROCEDURES Ileal and colonic muscle layers were obtained by scraping the mucosa and submucosa from full-thickness tissue specimens. Level of mRNA expression for alpha(2)-AR subtypes was measured by real-time reverse transcriptase-PCR analysis and expressed relative to the mean mRNA expression of glyceraldehyde phosphate dehydrogenase, ubiquitin, and 18S ribosomal RNA. Binding studies were performed with tritiated RX821002 ((3)H-RX821002) and subtype-selective ligands as competitors. RESULTS mRNA expression for alpha(2AD)-, alpha(2B)-, and alpha(2C)-AR subtypes was similar in ileal and colonic muscle layers. The mRNA expression for alpha(2AD)-AR was significantly greater than that for alpha(2B)- and alpha(2C)-AR subtypes, representing 92%, 6%, and 2%, respectively, of the total mRNA. Binding competition of (3)H-RX821002 with BRL44408, imiloxan, and MK-912 was best fitted by a 1-site model. The B(max) of alpha(2AD)- and alpha(2C)-AR sub-types was greater than that of alpha(2B)-AR. The B(max) and level of mRNA expression were only correlated (r = 0.8) for alpha(2AD)-AR. Ratio of B(max) to mRNA expression for alpha(2C)-AR was similar to that for alpha(2B)-AR, but significantly greater than for alpha(2AD)-AR. CONCLUSIONS AND CLINICAL RELEVANCE Subtypes of alpha(2)-AR in bovine intestinal muscle layers are represented by a mixture of alpha(2AD)- and alpha(2C)-ARs and of alpha(2B)-AR at a lower density. Information provided here may help in clarification of the role of AR subtypes in alpha(2)-adrenergic mechanisms regulating bovine intestinal motility.
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Affiliation(s)
- Edgar C Ontsouka
- Clinic for Ruminants, Vetsuisse Faculty of Berne, and the Division of Nutrition and Physiology, Institute of Animal Genetics, Nutrition, and Housing, Vetsuisse Faculty, University of Berne, CH-3012 Berne, Switzerland
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Ontsouka EC, Zbinden Y, Hammon HM, Blum JW. Ontogenesis of mRNA levels and binding sites of hepatic alpha-adrenoceptors in young cattle. Domest Anim Endocrinol 2006; 30:170-84. [PMID: 16182505 DOI: 10.1016/j.domaniend.2005.07.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2005] [Revised: 07/07/2005] [Accepted: 07/13/2005] [Indexed: 11/20/2022]
Abstract
Catecholamines affect hepatic glucose production through (alpha- and beta2-) adrenoceptors (AR). We studied mRNA abundance and binding of hepatic alpha-AR in pre-term (P0) calves and in full-term calves at day 0 (F0), day 5 (F5) and day 159 (F159) to test the hypothesis that gene expression and numbers of hepatic alpha-AR in calves are influenced by age and associated with beta2-AR and selected traits of glucose metabolism. mRNA levels of alpha1- and alpha2-AR were measured by real time RT-PCR. alpha1- and alpha2-AR numbers (maximal binding, Bmax) were determined by saturation binding of (3H)-prazosin and (3H)-RX821002, respectively. alpha1- and alpha2-AR subtypes were evaluated by competitive binding. alpha1A-AR mRNA levels were lower in P0 than in F0, F5 and F159 and alpha(2AD)-AR mRNA levels were lower in F159 than in P0, F0 and F5, while alpha2C-AR mRNA levels increased from P0 and F0 to F5 and F159. Bmax of alpha1-AR increased from P0 to F5, then decreased in F159. Bmax of alpha2-AR decreased from F0 to F159. Bmax of alpha1-AR was positively associated with mRNA levels of alpha1A-AR (r = 0.7), Bmax of beta2-AR (r = 0.5) and negatively with hepatic glycogen content (r = -0.6). Bmax of alpha2-AR was negatively associated with Bmax of beta2-AR (r = -0.4). In conclusion, mRNA levels and binding sites of alpha1- and alpha2-AR in calves exhibited developmental changes and were negatively associated with hepatic glycogen content.
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MESH Headings
- Adrenergic alpha-Antagonists/pharmacology
- Animals
- Animals, Newborn
- Binding, Competitive
- Blood Glucose/metabolism
- Cattle/blood
- Cattle/genetics
- Cattle/metabolism
- Female
- Glycogen/blood
- Idazoxan/analogs & derivatives
- Idazoxan/pharmacology
- Liver/drug effects
- Liver/metabolism
- Phosphoenolpyruvate/metabolism
- Prazosin/pharmacology
- Pregnancy
- Pyruvate Carboxylase/metabolism
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, Adrenergic, alpha/biosynthesis
- Receptors, Adrenergic, alpha/genetics
- Receptors, Adrenergic, alpha/metabolism
- Receptors, Adrenergic, beta/biosynthesis
- Receptors, Adrenergic, beta/genetics
- Receptors, Adrenergic, beta/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
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Affiliation(s)
- E C Ontsouka
- Division of Nutrition and Physiology, Institute of Animal Genetics, Nutrition and Housing, Vetsuisse Faculty, University of Bern, CH-3012 Bern, Switzerland
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Dambrova M, Liepinsh E, Kirjanova O, Petrovska R, Pugovich O, Baumane L, Uhlen S, Kalvinsh I, Oliver D, Wikberg JES. Investigations on the pharmacology of the cardioprotective guanidine ME10092. J Cardiovasc Pharmacol 2005; 44:178-86. [PMID: 15243298 DOI: 10.1097/00005344-200408000-00006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The guanidine compound ME10092 (1-(3,4-dimethoxy-2-chlorobenzylideneamino)-guanidine), which possesses a strong cardioprotective effect to ischemia-reperfusion, was assessed for different pharmacological actions that may underlie its cardioprotective effect. In the living rat ME10092 decreased the blood pressure and heart rate in a dose-dependent manner. We found ME10092 to bind to alpha 1- and alpha 2-adrenoreceptors with moderate affinity (Ki values 1-4 microM), and to block adrenaline-elicited contractile responses in isolated guinea pig aortas. Our results indicate that ME10092 possesses a certain anti-oxidant profile. Thus, in a competitive manner and with low affinity it inhibited the bovine milk xanthine oxidase enzyme, as well as NAD(P)H oxidase driven oxyradical formation in membrane fractions isolated from the rat brain. By using electron paramagnetic resonance we here show that, after its systemic administration, ME10092 modulates the nitric oxide (NO) content in several tissues of the rat in a time-dependent manner. However, in vitro ME10092 inhibited the activities of nitric oxide synthases nNOS and eNOS, but not that of iNOS. Our data give evidence that the cardioprotective effect of ME10092 could be mediated through pharmacological mechanisms that include some modulation of NO production, as well as possible inhibition of radical formation during ischemia-reperfusion.
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MESH Headings
- Animals
- Aorta/cytology
- Aorta/drug effects
- Blood Pressure/drug effects
- Brain/drug effects
- Brain/metabolism
- COS Cells
- Cardiotonic Agents/pharmacology
- Chlorocebus aethiops
- Dose-Response Relationship, Drug
- Drug Evaluation, Preclinical/methods
- Guanidines/pharmacology
- Guanidines/therapeutic use
- Guinea Pigs
- Heart Rate/drug effects
- Humans
- Ileum/cytology
- Ileum/drug effects
- Injections, Intravenous
- Liver/chemistry
- Liver/drug effects
- Liver/metabolism
- Male
- Muscle Contraction/drug effects
- Muscle Contraction/physiology
- Muscle, Smooth/drug effects
- Muscle, Smooth/physiology
- Myocardial Ischemia/complications
- Myocardial Ischemia/drug therapy
- NAD/metabolism
- NADPH Oxidases/metabolism
- Nerve Tissue Proteins/antagonists & inhibitors
- Nerve Tissue Proteins/drug effects
- Nerve Tissue Proteins/metabolism
- Nitric Oxide/antagonists & inhibitors
- Nitric Oxide/metabolism
- Nitric Oxide Synthase/antagonists & inhibitors
- Nitric Oxide Synthase/drug effects
- Nitric Oxide Synthase/metabolism
- Nitric Oxide Synthase Type I
- Nitric Oxide Synthase Type II
- Nitric Oxide Synthase Type III
- Rats
- Rats, Wistar
- Receptors, Adrenergic, alpha/classification
- Receptors, Adrenergic, alpha/drug effects
- Reperfusion Injury/complications
- Reperfusion Injury/drug therapy
- Xanthine Oxidase/chemistry
- Xanthine Oxidase/metabolism
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Gentili F, Ghelfi F, Giannella M, Piergentili A, Pigini M, Quaglia W, Vesprini C, Crassous PA, Paris H, Carrieri A. α2-Adrenoreceptors Profile Modulation. 2. Biphenyline Analogues as Tools for Selective Activation of the α2C-Subtype. J Med Chem 2004; 47:6160-73. [PMID: 15566287 DOI: 10.1021/jm0408215] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A series of derivatives structurally related to biphenyline (3) was designed with the aim to modulate selectivity toward the alpha(2)-AR subtypes. The results obtained demonstrated that the presence of a correctly oriented function with positive electronic effect (+sigma) in portion X of the ligands is an important factor for significant alpha(2C)-subtype selectivity (imidazolines 5, 13, 16, and 19). Homology modeling and docking studies support experimental data and highlight the crucial role for the hydrogen bond between the pyridine nitrogen in position 3 of 5 and the NH-indole ring of Trp6.48, which is favorably oriented in the alpha(2C)-subtype, only.
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Affiliation(s)
- Francesco Gentili
- Dipartimento di Scienze Chimiche, Università degli Studi di Camerino, Via S. Agostino 1, 62032 Camerino, Italy
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Cayla C, Heinonen P, Viikari L, Schaak S, Snapir A, Bouloumié A, Karvonen MK, Pesonen U, Scheinin M, Paris H. Cloning, characterisation and identification of several polymorphisms in the promoter region of the human alpha2B-adrenergic receptor gene. Biochem Pharmacol 2004; 67:469-78. [PMID: 15037199 DOI: 10.1016/j.bcp.2003.09.029] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2003] [Accepted: 09/26/2003] [Indexed: 10/26/2022]
Abstract
Screening of a foetal brain genomic DNA library allowed to isolate a 10-kb fragment of the gene encoding the human alpha2B-adrenergic receptor, that contained 5.5 kb of the 5'-flanking region, the open reading frame and 2.9 kb of the 3'-flanking region. The 1-kb fragment upstream from the start codon was rich in GC, lacked consensus TATA or CAAT box, but contained several Sp1-binding sites. Other potential cis-regulatory elements found in the 5'-flanking region included AP2, USF, Stat-6, NFkappaB and Olf-1. A single canonical polyadenylation signal (AATAAA) was found at position +3252/+3257 and the polyadenylation site was 3274 nucleotides downstream from ATG. Transfection experiments with chimeric luciferase constructs containing various truncated fragments of the 5'-region showed that the fragment -3160/+3 exhibited promoter activity in all tested cell lines and permitted the definition of a minimal 200-bp promoter (-603/-411) containing three putative Sp1-binding sites and two initiator elements. Transcriptional activity of this region was inhibited by the addition of mithramycin, a specific inhibitor of Sp1 binding to GC-rich sequences. The search for sequence variants within a fragment covering 1.7 kb of 5'-flanking region and the coding region allowed us to identify five novel single nucleotide polymorphisms. Interestingly, the G/C substitution at position -98 relative to the start codon was common and in complete linkage with a previously identified insertion/deletion polymorphism in the coding region which was showed to affect alpha2B-adrenergic receptor function. Based on transfection data and computer-assisted sequence analysis, the -98 G/C single nucleotide polymorphism was located within a portion of the 5'-UTR (-127/+3) affecting luciferase activity and it created additional putative binding site for Sp1. However, G/C substitution had no significant incidence on promoter activity in BHK-21 or HeLa cells.
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Affiliation(s)
- Cécile Cayla
- INSERM U388, Institut Louis Bugnard, CHU Rangueil, 31403 Toulouse, France
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Szot P, Lester M, Laughlin ML, Palmiter RD, Liles LC, Weinshenker D. The anticonvulsant and proconvulsant effects of α2-adrenoreceptor agonists are mediated by distinct populations of α2a-adrenoreceptors. Neuroscience 2004; 126:795-803. [PMID: 15183527 DOI: 10.1016/j.neuroscience.2004.04.030] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/22/2004] [Indexed: 11/23/2022]
Abstract
The alpha2-adrenoreceptor (AR) is the most investigated noradrenergic receptor with regard to modulation of seizure activity. However, because of the complexity of multiple alpha2-AR subtypes and their distribution, the exact role of this receptor in modulating seizure activity is not clear. alpha2A- and alpha2C-ARs function as both autoreceptors (presynaptic) on noradrenergic neurons, where they regulate norepinephrine (NE) release, and as postsynaptic receptors on neurons that receive noradrenergic innervation, where they regulate the release of other neurotransmitters (heteroreceptor). The nonselective alpha2-AR agonist clonidine produced a proconvulsant effect on seizure susceptibility, while the selective alpha2A-AR agonist guanfacine was anticonvulsant. The effects of both alpha2-AR agonists were absent in alpha2a knockout mice, suggesting that the alpha2A-AR mediates the proconvulsant and anticonvulsant effect of alpha2-AR agonists on seizure susceptibility. To determine whether the alpha2-AR agonists were acting on inhibitory presynaptic autoreceptors to decrease NE release or on postsynaptic receptors on NE target neurons, the effects of clonidine and guanfacine were determined in dopamine beta-hydroxylase knockout (Dbh -/-) mice that lack NE. The anticonvulsant effect of guanfacine persisted in Dbh -/- mice, suggesting that guanfacine may act preferentially on alpha2A-postsynaptic receptors that regulate the action of NE on target neurons. In contrast, the proconvulsant effect of clonidine was lost in Dbh -/- mice, suggesting that clonidine may act on presynaptic autoreceptors to decrease NE release. We hypothesize that the alpha2A-presynaptic autoreceptor is responsible for the proconvulsant effect of alpha2-AR agonists, while the alpha2A-postsynaptic receptor is responsible for the anticonvulsant effect of alpha2-AR agonists. These data help to clarify the inconsistent effects of alpha2-AR agonists on seizure activity.
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Affiliation(s)
- P Szot
- Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, WA 98108, USA.
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Mutation of the alpha2A-adrenoceptor impairs working memory performance and annuls cognitive enhancement by guanfacine. J Neurosci 2002. [PMID: 12351753 DOI: 10.1523/jneurosci.22-19-08771.2002] [Citation(s) in RCA: 147] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Norepinephrine strengthens the working memory, behavioral inhibition, and attentional functions of the prefrontal cortex through actions at postsynaptic alpha2-adrenoceptors (alpha2-AR). The alpha2-AR agonist guanfacine enhances prefrontal cortical functions in rats, monkeys, and human beings and ameliorates prefrontal cortical deficits in patients with attention deficit hyperactivity disorder. The present study examined the subtype of alpha2-AR underlying these beneficial effects. Because there are no selective alpha2A-AR, alpha2B-AR, or alpha2C-AR agonists or antagonists, genetically altered mice were used to identify the molecular target of the action of guanfacine. Mice with a point mutation of the alpha2A-AR, which serves as a functional knock-out, were compared with wild-type animals and with previously published studies of alpha2C-AR knock-out mice (Tanila et al., 1999). Mice were adapted to handling on a T maze and trained on either a spatial delayed alternation task that is sensitive to prefrontal cortical damage or a spatial discrimination control task with similar motor and motivational demands but no dependence on prefrontal cortex. The effects of guanfacine on performance of the delayed alternation task were assessed in additional groups of wild-type versus alpha2A-AR mutant mice. We observed that functional loss of the alpha2A-AR subtype, unlike knock-out of the alpha2C-AR subtype, weakened performance of the prefrontal cortical task without affecting learning and resulted in loss of the beneficial response to guanfacine. These data demonstrate the importance of alpha2A-AR subtype stimulation for the cognitive functions of the prefrontal cortex and identify the molecular substrate for guanfacine and novel therapeutic interventions.
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