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Yates JR. Pharmacological Treatments for Methamphetamine Use Disorder: Current Status and Future Targets. Subst Abuse Rehabil 2024; 15:125-161. [PMID: 39228432 PMCID: PMC11370775 DOI: 10.2147/sar.s431273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2024] [Accepted: 08/15/2024] [Indexed: 09/05/2024] Open
Abstract
The illicit use of the psychostimulant methamphetamine (METH) is a major concern, with overdose deaths increasing substantially since the mid-2010s. One challenge to treating METH use disorder (MUD), as with other psychostimulant use disorders, is that there are no available pharmacotherapies that can reduce cravings and help individuals achieve abstinence. The purpose of the current review is to discuss the molecular targets that have been tested in assays measuring the physiological, the cognitive, and the reinforcing effects of METH in both animals and humans. Several drugs show promise as potential pharmacotherapies for MUD when tested in animals, but fail to produce long-term changes in METH use in dependent individuals (eg, modafinil, antipsychotic medications, baclofen). However, these drugs, plus medications like atomoxetine and varenicline, may be better served as treatments to ameliorate the psychotomimetic effects of METH or to reverse METH-induced cognitive deficits. Preclinical studies show that vesicular monoamine transporter 2 inhibitors, metabotropic glutamate receptor ligands, and trace amine-associated receptor agonists are efficacious in attenuating the reinforcing effects of METH; however, clinical studies are needed to determine if these drugs effectively treat MUD. In addition to screening these compounds in individuals with MUD, potential future directions include increased emphasis on sex differences in preclinical studies and utilization of pharmacogenetic approaches to determine if genetic variances are predictive of treatment outcomes. These future directions can help lead to better interventions for treating MUD.
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Affiliation(s)
- Justin R Yates
- Department of Psychological Science, Northern Kentucky University, Highland Heights, KY, USA
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Hámor PU, Knackstedt LA, Schwendt M. The role of metabotropic glutamate receptors in neurobehavioral effects associated with methamphetamine use. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2023; 168:177-219. [PMID: 36868629 DOI: 10.1016/bs.irn.2022.10.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Metabotropic glutamate (mGlu) receptors are expressed throughout the central nervous system and act as important regulators of drug-induced neuroplasticity and behavior. Preclinical research suggests that mGlu receptors play a critical role in a spectrum of neural and behavioral consequences arising from methamphetamine (meth) exposure. However, an overview of mGlu-dependent mechanisms linked to neurochemical, synaptic, and behavioral changes produced by meth has been lacking. This chapter provides a comprehensive review of the role of mGlu receptor subtypes (mGlu1-8) in meth-induced neural effects, such as neurotoxicity, as well as meth-associated behaviors, such as psychomotor activation, reward, reinforcement, and meth-seeking. Additionally, evidence linking altered mGlu receptor function to post-meth learning and cognitive deficits is critically evaluated. The chapter also considers the role of receptor-receptor interactions involving mGlu receptors and other neurotransmitter receptors in meth-induced neural and behavioral changes. Taken together, the literature indicates that mGlu5 regulates the neurotoxic effects of meth by attenuating hyperthermia and possibly through altering meth-induced phosphorylation of the dopamine transporter. A cohesive body of work also shows that mGlu5 antagonism (and mGlu2/3 agonism) reduce meth-seeking, though some mGlu5-blocking drugs also attenuate food-seeking. Further, evidence suggests that mGlu5 plays an important role in extinction of meth-seeking behavior. In the context of a history of meth intake, mGlu5 also co-regulates aspects of episodic memory, with mGlu5 stimulation restoring impaired memory. Based on these findings, we propose several avenues for the development of novel pharmacotherapies for Methamphetamine Use Disorder based on the selective modulation mGlu receptor subtype activity.
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Affiliation(s)
- Peter U Hámor
- Department of Psychology, University of Florida, Gainesville, FL, United States; Center for Addiction Research and Education, University of Florida, Gainesville, FL, United States; Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, NY, United States
| | - Lori A Knackstedt
- Department of Psychology, University of Florida, Gainesville, FL, United States; Center for Addiction Research and Education, University of Florida, Gainesville, FL, United States
| | - Marek Schwendt
- Department of Psychology, University of Florida, Gainesville, FL, United States; Center for Addiction Research and Education, University of Florida, Gainesville, FL, United States.
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Machado da Silva MC, Iglesias LP, Candelario-Jalil E, Khoshbouei H, Moreira FA, de Oliveira ACP. Role of Microglia in Psychostimulant Addiction. Curr Neuropharmacol 2023; 21:235-259. [PMID: 36503452 PMCID: PMC10190137 DOI: 10.2174/1570159x21666221208142151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 10/13/2022] [Accepted: 10/14/2022] [Indexed: 12/14/2022] Open
Abstract
The use of psychostimulant drugs can modify brain function by inducing changes in the reward system, mainly due to alterations in dopaminergic and glutamatergic transmissions in the mesocorticolimbic pathway. However, the etiopathogenesis of addiction is a much more complex process. Previous data have suggested that microglia and other immune cells are involved in events associated with neuroplasticity and memory, which are phenomena that also occur in addiction. Nevertheless, how dependent is the development of addiction on the activity of these cells? Although the mechanisms are not known, some pathways may be involved. Recent data have shown psychoactive substances may act directly on immune cells, alter their functions and induce various inflammatory mediators that modulate synaptic activity. These could, in turn, be involved in the pathological alterations that occur in substance use disorder. Here, we extensively review the studies demonstrating how cocaine and amphetamines modulate microglial number, morphology, and function. We also describe the effect of these substances in the production of inflammatory mediators and a possible involvement of some molecular signaling pathways, such as the toll-like receptor 4. Although the literature in this field is scarce, this review compiles the knowledge on the neuroimmune axis that is involved in the pathogenesis of addiction, and suggests some pharmacological targets for the development of pharmacotherapy.
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Affiliation(s)
- Maria Carolina Machado da Silva
- Department of Pharmacology, Neuropharmacology Laboratory, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil;
- Department of Neuroscience, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Lia Parada Iglesias
- Department of Pharmacology, Neuropsychopharmacology Laboratory, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | | | - Habibeh Khoshbouei
- Department of Neuroscience, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Fabrício Araujo Moreira
- Department of Pharmacology, Neuropsychopharmacology Laboratory, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
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TBHQ-Overview of Multiple Mechanisms against Oxidative Stress for Attenuating Methamphetamine-Induced Neurotoxicity. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2020; 2020:8874304. [PMID: 33354283 PMCID: PMC7735854 DOI: 10.1155/2020/8874304] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 11/16/2020] [Accepted: 11/19/2020] [Indexed: 12/13/2022]
Abstract
Methamphetamine is a derivative of amphetamines, a highly addictive central stimulant with multiple systemic toxicity including the brain, heart, liver, lung, and spleen. It has adverse effects such as apoptosis and breakdown of the blood-brain barrier. Methamphetamine is a fatal and toxic chemical substance, and its lethal mechanism has been widely studied in recent years. The possible mechanism is that methamphetamine can cause cardiotoxicity and neurotoxicity mainly by inducing oxidative stress so as to generate heat, eliminate people's hunger and thirst, and maintain a state of excitement so that people can continue to exercise. According to many research, there is no doubt that methamphetamine triggers neurotoxicity by inducing reactive oxygen species (ROS) production and redox imbalance. This review summarized the mechanisms of methamphetamine-induced neurotoxicity including apoptosis and blood-brain barrier breakdown through oxidative stress and analyzed several possible antioxidative mechanisms of tert-butylhydroquinone (TBHQ) which is a kind of food additive with antioxidative effects. As a nuclear factor E2-related factor 2 (Nrf2) agonist, TBHQ may inhibit neurotoxicity caused by oxidative stress through the following three mechanisms: the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase system, the astrocytes activation, and the glutathione pathway. The mechanism about methamphetamine's toxic effects and its antioxidative therapeutic drugs would become a research hotspot in this field and has very important research significance.
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Shorter DI, Zhang X, Domingo CB, Nielsen EM, Kosten TR, Nielsen DA. Doxazosin treatment in cocaine use disorder: pharmacogenetic response based on an alpha-1 adrenoreceptor subtype D genetic variant. THE AMERICAN JOURNAL OF DRUG AND ALCOHOL ABUSE 2020; 46:184-193. [PMID: 31914324 DOI: 10.1080/00952990.2019.1674864] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Background: The α1 antagonist doxazosin reduces cocaine use in individuals with cocaine use disorder (CUD) through a functional polymorphism of the α1 adrenoreceptor. The regulatory role of the α1 adrenoreceptor subtype D (ADRA1D) gene polymorphism in CUD is uncharacterized.Objectives: To study how the genetic variant of ADRA1D gene (T1848A, rs2236554) may affect the treatment efficacy of doxazosin in reducing cocaine use.Methods: This 12-week pilot trial included 76 participants with CUD with ADRA1D (T1848A, rs2236554) AA (N = 40) or AT/TT genotype (N = 36). Participants were randomized to doxazosin (8 mg/day, N = 47) or placebo (N = 29), and followed with thrice weekly urine toxicology and once weekly cognitive behavioral psychotherapy.Results: The AA and the AT/TT groups had comparable baseline rates of cocaine positive urines at weeks 1-2 (~ 76%). In the placebo group, an increase of cocaine positive urines in the AT/TT group was found as compared to the AA group (24% vs. 9%). In the doxazosin group, a greater decrease in cocaine positive urines was found in the AT/TT group relative to the AA group. The difference between the doxazosin and placebo groups in cocaine negative urines became evident at weeks 5-6 and peaked at weeks 9-10 (~35% difference). The AT/TT group demonstrated a significant medication and time by medication effect (p < .001), whereas the AA group did not.Conclusion: The T-allele carriers showed a greater reduction of cocaine use after treatment with doxazosin in participants with the ADRA1D gene polymorphism (T1848A), suggesting that this SNP may serve as a pharmacogenetic marker in pharmacotherapy of CUD.
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Affiliation(s)
- Daryl I Shorter
- Mental Health Care Line, Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas, USA.,Menninger Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, Houston, Texas, USA
| | - Xuefeng Zhang
- Mental Health Care Line, Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas, USA.,Menninger Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, Houston, Texas, USA
| | - Coreen B Domingo
- Mental Health Care Line, Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas, USA.,Menninger Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, Houston, Texas, USA
| | - Ellen M Nielsen
- Mental Health Care Line, Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas, USA.,Menninger Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, Houston, Texas, USA
| | - Thomas R Kosten
- Mental Health Care Line, Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas, USA.,Menninger Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, Houston, Texas, USA
| | - David A Nielsen
- Mental Health Care Line, Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas, USA.,Menninger Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, Houston, Texas, USA
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Sugama S, Takenouchi T, Hashimoto M, Ohata H, Takenaka Y, Kakinuma Y. Stress-induced microglial activation occurs through β-adrenergic receptor: noradrenaline as a key neurotransmitter in microglial activation. J Neuroinflammation 2019; 16:266. [PMID: 31847911 PMCID: PMC6916186 DOI: 10.1186/s12974-019-1632-z] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2019] [Accepted: 11/06/2019] [Indexed: 02/06/2023] Open
Abstract
Background The involvement of microglia in neuroinflammatory responses has been extensively demonstrated. Recent animal studies have shown that exposure to either acute or chronic stress induces robust microglial activation in the brain. In the present study, we investigated the underlying mechanism of brain microglial activation by acute stress. Methods We first looked at the spatial distribution of the noradrenaline (NA)-synthesizing enzyme, DBH (dopamine β-hydroxylase), in comparison with NA receptors—β1, β2, and β3 adrenergic receptors (β1-AR, β2-AR, and β3-AR)—after which we examined the effects of the β-blocker propranolol and α-blockers prazosin and yohimbine on stress-induced microglial activation. Finally, we compared stress-induced microglial activation between wild-type (WT) mice and double-knockout (DKO) mice lacking β1-AR and β2-AR. Results The results demonstrated that (1) microglial activation occurred in most studied brain regions, including the hippocampus (HC), thalamus (TM), and hypothalamus (HT); (2) within these three brain regions, the NA-synthesizing enzyme DBH was densely stained in the neuronal fibers; (3) β1-AR and β2-AR, but not β3-AR, are detected in the whole brain, and β1-AR and β2-AR are co-localized with microglial cells, as observed by laser scanning microscopy; (4) β-blocker treatment inhibited microglial activation in terms of morphology and count through the whole brain; α-blockers did not show such effect; (5) unlike WT mice, DKO mice exhibited substantial inhibition of stress-induced microglial activation in the brain. Conclusions We demonstrate that neurons/microglia may interact with NA via β1-AR and β2-AR.
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Affiliation(s)
- Shuei Sugama
- Department of Physiology, Nippon Medical School, 1-1-5 Sendagi Bunkyo-ku, Tokyo, 113-8602, Japan.
| | - Takato Takenouchi
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, 1-2 Ohwashi, Tsukuba, Ibaraki, 305-8634, Japan
| | - Makoto Hashimoto
- Division of Sensory and Motor Systems, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo, 156-0057, Japan
| | - Hisayuki Ohata
- Department of Physiology, Nippon Medical School, 1-1-5 Sendagi Bunkyo-ku, Tokyo, 113-8602, Japan
| | - Yasuhiro Takenaka
- Department of Physiology, Nippon Medical School, 1-1-5 Sendagi Bunkyo-ku, Tokyo, 113-8602, Japan
| | - Yoshihiko Kakinuma
- Department of Physiology, Nippon Medical School, 1-1-5 Sendagi Bunkyo-ku, Tokyo, 113-8602, Japan
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Korpi ER, den Hollander B, Farooq U, Vashchinkina E, Rajkumar R, Nutt DJ, Hyytiä P, Dawe GS. Mechanisms of Action and Persistent Neuroplasticity by Drugs of Abuse. Pharmacol Rev 2015; 67:872-1004. [DOI: 10.1124/pr.115.010967] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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Tomita M, Katsuyama H, Watanabe Y, Shibaike Y, Yoshinari H, Tee JW, Iwachidou N, Miyamoto O. c-Fos immunoreactivity of neural cells in intoxication due to high-dose methamphetamine. J Toxicol Sci 2014; 38:671-8. [PMID: 24025783 DOI: 10.2131/jts.38.671] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Methamphetamine (METH) is a powerful and toxic psychostimulant that is abused worldwide. Although many studies of its toxic functions have been done on animals and humans, the mechanism is still poorly understood. In addition, the doses of METH examined have often been low. Here, we investigated the effects of intoxication due to administration of 20 mg/kg METH on neuronal activity. The mice showed hyperthermia and stereotyped behavior during 60 min after injection. We examined plasma stress hormone levels, which indicated that exposure to METH stimulated the hypothalamic-pituitary-adrenal (HPA) axis and caused release of stress hormones soon after injection. The maximum levels of adrenocorticotropic hormone and corticosterone occurred 10 and 60 min, respectively, after injection. We examined c-Fos protein in 16 different brain regions at 60 min post injection to identify potential brain regions subject to the stimulant effect. Nine regions, including the anterior hypothalamic area, medial preoptic area, lateral hypothalamic area, paraventricular thalamic nucleus, lateral anterior hypothalamic nucleus, lateral septum, striatum, nucleus accumbens, and amygdala, showed a significant increase in c-Fos expression, while the other seven regions did not. These results indicate that responsive neurons in the regions containing c-Fos immunoreactivity (Fos-IR) may undergo cellular reaction to high-dose METH administration. The present study provides support for a relationship among hyperthermia, the HPA axis and neuronal activities in limited brain regions on exposure to 20 mg/kg METH.
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Chang SL, Connaghan KP, Wei Y, Li MD. NeuroHIV and use of addictive substances. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2014; 118:403-40. [PMID: 25175871 DOI: 10.1016/b978-0-12-801284-0.00013-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In the past three decades, substance abuse has been identified as a key comorbidity of human immunodeficiency virus-1 (HIV-1) infection. Many studies have found that the use and abuse of addictive substances hastens the progression of HIV-1 infection and HIV-associated neurocognitive disorders. Advances in highly active antiretroviral therapy (HAART) in the mid-1990s have been successful in limiting the HIV-1 viral load and maintaining a relatively healthy immune response, allowing the life expectancy of patients infected with HIV to approach that of the general population. However, even with HAART, HIV-1 viral proteins are still expressed and eradication of the virus, particularly in the brain, the key reservoir organ, does not occur. In the post-HAART era, the clinical challenge in the treatment of HIV infection is inflammation of the central nervous system (CNS) and its subsequent neurological disorders. To date, various explicit and implicit connections have been identified between the neuronal circuitry involved in immune responses and brain regions affected by and implicated in substance abuse. This chapter discusses past and current medical uses of prototypical substances of abuse, including morphine, alcohol, cocaine, methamphetamine, marijuana, and nicotine, and the evidence that systemic infections, particularly HIV-1 infection, cause neurological dysfunction as a result of inflammation in the CNS, which can increase the risk of substance abuse.
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Affiliation(s)
- Sulie L Chang
- Institute of NeuroImmune Pharmacology, Seton Hall University, South Orange, New Jersey, USA; Department of Biological Sciences, Seton Hall University, South Orange, New Jersey, USA.
| | - Kaitlyn P Connaghan
- Institute of NeuroImmune Pharmacology, Seton Hall University, South Orange, New Jersey, USA
| | - Yufeng Wei
- Institute of NeuroImmune Pharmacology, Seton Hall University, South Orange, New Jersey, USA
| | - Ming D Li
- Department of Psychiatry and Neurobehavioral Sciences, University of Virginia, Charlottesville, Virginia, USA
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Prevalence and management of lower urinary tract symptoms in methamphetamine abusers: an under-recognized clinical identity. J Urol 2013; 191:722-6. [PMID: 23968967 DOI: 10.1016/j.juro.2013.08.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/12/2013] [Indexed: 11/22/2022]
Abstract
PURPOSE We investigate the prevalence of lower urinary tract symptoms in a cohort of methamphetamine abusers, and assess the therapeutic efficacy of α-blockers and anticholinergics. MATERIALS AND METHODS From May 2011 to March 2013, 78 male methamphetamine abusers diagnosed with methamphetamine addiction were identified at the National Forensic Hospital, Korea. The I-PSS (International Prostate Symptom Score) with consultation was used to investigate the prevalence of lower urinary tract symptoms, defined as total I-PSS 8 or greater and quality of life index score of 2 or greater. These values for methamphetamine abusers were compared to those of 71 age matched controls. α-Blockers and anticholinergics were administered to methamphetamine abusers with lower urinary tract symptoms according to predominant voiding and storage symptoms based on voiding-to-storage subscore ratios. For methamphetamine abusers with no response, defined as a reduction of 4 or less in total I-PSS, an alternative drug or combination was administered. Efficacy was assessed based on a 4-week interval. RESULTS The median periods of methamphetamine abuse and abstinence were 18.1 years and 5.7 months, respectively. Methamphetamine abusers showed a higher prevalence of lower urinary tract symptoms compared to controls (77% vs 15%, p <0.001), with higher I-PSS and quality of life index score (13.3 vs 5.6 and 2.9 vs 0.9, respectively; p <0.001). Anticholinergics showed the greatest effect on I-PSS reduction with overall response rates for α-blockers, anticholinergics and combinations of 13%, 61% and 14%, respectively. Seven (12%) methamphetamine abusers did not respond to any therapy. CONCLUSIONS Lower urinary tract symptoms were highly prevalent among methamphetamine abusers. Our results imply that pathological dopaminergic mechanisms have a role in methamphetamine associated lower urinary tract symptoms. Moreover, first line anticholinergics and prompt combination with α-blockers conferred the most therapeutic benefit to nonresponders.
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Kikuchi-Utsumi K, Ishizaka M, Matsumura N, Nakaki T. Alpha(1A)-adrenergic control of piloerection and palpebral fissure width in rats. Auton Neurosci 2013; 179:148-50. [PMID: 23701912 DOI: 10.1016/j.autneu.2013.04.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 04/22/2013] [Accepted: 04/25/2013] [Indexed: 11/26/2022]
Abstract
We determined the receptor subtypes of α1-adrenoceptor, which is involved in autonomic functions induced by methamphetamine (METH) in rats. An intraperitoneal injection of METH provoked the autonomic responses piloerection, eyelid retraction, and ejaculation. Pretreatment with prazosin, a nonselective α1-adrenoceptor antagonist, completely abolished the above METH-induced responses. Prazosin also provoked eyelid ptosis in saline controls. The effects of prazosin were mimicked only by a selective α1A-adrenoceptor antagonist, silodosin, not by selective α1B or α1D antagonists. These results suggest that α1A-adrenoceptor participates in the regulation of piloerection, palpebral fissure width, and ejaculation in rats.
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