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Accumbal α-adrenoceptors, but not β-adrenoceptors, regulate behaviour that is mediated by reserpine-sensitive storage vesicles. Behav Pharmacol 2015; 26:81-90. [PMID: 25325287 DOI: 10.1097/fbp.0000000000000098] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
It has previously been demonstrated that mesolimbic α-adrenoceptors, but not β-adrenoceptors, control the release of dopamine that is derived from reserpine-sensitive storage vesicles. The aim of the present study was to investigate whether these storage vesicles also regulate α-adrenoceptor-mediated or β-adrenoceptor-mediated changes in behaviour. Accordingly, rats were pretreated with reserpine before the α-adrenoceptor antagonist phentolamine or the β-adrenoceptor agonist isoproterenol was locally applied to the nucleus accumbens. Both phentolamine and isoproterenol increased the duration of walking, rearing and grooming and decreased the duration of sitting. Reserpine counteracted the behavioural response elicited by phentolamine but not by isoproterenol. The results of the present study demonstrate that mesolimbic α-adrenoceptors, but not β-adrenoceptors, regulate behaviour that is mediated by reserpine-sensitive storage pools. It is hypothesized that the observed α-adrenoceptor-mediated increase in locomotor activity is due to the α-adrenoceptor-mediated increase in the release of accumbal intravesicular dopamine. Our finding that α-adrenoceptors inhibit, whereas β-adrenoceptors stimulate, locomotor activity may help explain why noradrenaline or environmental stressors have previously been found to have opposing effects on the regulation of behaviour.
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Meyer F, Latour J, Cools AR, Verheij MMM. Noradrenaline-induced release of newly-synthesized accumbal dopamine: differential role of alpha- and beta-adrenoceptors. Front Cell Neurosci 2014; 8:243. [PMID: 25309315 PMCID: PMC4162431 DOI: 10.3389/fncel.2014.00243] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2014] [Accepted: 07/31/2014] [Indexed: 11/24/2022] Open
Abstract
Previous studies have shown that intra-accumbens infusion of isoproterenol (ISO), a beta-adrenoceptor-agonist, and phenylephrine (PE), an alpha-adrenoceptor-agonist, increase the release of accumbal dopamine (DA). In the present study we analyzed whether the ISO-induced release of DA is sensitive to pretreatment with the DA synthesis inhibitor alpha-methyl-para-tyrosine (AMPT). Earlier studies have shown that the PE-induced release of DA is derived from DA pools that are resistant to AMPT. In addition to PE, the alpha-adrenoceptor-antagonist phentolamine (PA) was also found to increase accumbal DA release. Therefore, we investigated whether similar to the DA-increasing effect of PE, the DA increase induced by PA is resistant to AMPT. Pretreatment with AMPT prevented the ISO-induced increase of accumbal DA. The accumbal DA increase after PA was not reduced by the DA synthesis inhibitor, independently of the amount of DA released. These results show that mesolimbic beta-, but not alpha-adrenoceptors, control the release of accumbal newly-synthesized DA pools. The DA-increasing effects of PE have previously been ascribed to stimulation of presynaptic receptors located on noradrenergic terminals, whereas the DA-increasing effects of PA and ISO have been ascribed to an action of these drugs at postsynaptic receptors on dopaminergic terminals. The fact that AMPT did not affect the accumbal DA response to PE and PA, whereas it did prevent the accumbal DA increase to ISO, supports our previously reported hypothesis that the noradrenergic neurons of the nucleus accumbens containing presynaptic alpha-adrenoceptors impinge upon the dopaminergic terminals in the nucleus accumbens containing postsynaptic adrenoceptors of the alpha but not of the beta type. The putative therapeutic effects of noradrenergic agents in the treatment of DA-related disorders are shortly discussed.
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Affiliation(s)
- Francisca Meyer
- Department of Molecular Animal Physiology, Donders Institute for Brain, Cognition and Behaviour, Nijmegen Center for Molecular Life Sciences, Radboud University Nijmegen Nijmegen, Netherlands
| | - Judith Latour
- Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen Medical Centre Nijmegen, Netherlands
| | - Alexander R Cools
- Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen Medical Centre Nijmegen, Netherlands
| | - Michel M M Verheij
- Department of Molecular Animal Physiology, Donders Institute for Brain, Cognition and Behaviour, Nijmegen Center for Molecular Life Sciences, Radboud University Nijmegen Nijmegen, Netherlands ; Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen Medical Centre Nijmegen, Netherlands
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Kochenborger L, Zanatta D, Berretta LM, Lopes APF, Wunderlich BL, Januário AC, Neto JM, Terenzi MG, Paschoalini MA, Faria MS. Modulation of fear/anxiety responses, but not food intake, following α-adrenoceptor agonist microinjections in the nucleus accumbens shell of free-feeding rats. Neuropharmacology 2011; 62:427-35. [PMID: 21871465 DOI: 10.1016/j.neuropharm.2011.08.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 08/10/2011] [Accepted: 08/11/2011] [Indexed: 10/17/2022]
Abstract
This study investigated the effect of α-adrenoceptor agonists microinjected into the shell region of the accumbens nucleus (AcbSh) on feeding and anxiety-related behaviors in free-feeding rats. Male Wistar rats with a chronically implanted cannula into the AcbSh were unilaterally microinjected with either clonidine (CLON, α(2)-adrenoceptor agonist) or phenylephrine (PHEN, α(1)-adrenoceptor agonist) at the doses of 6 and 20 nmol and submitted to the elevated plus-maze (EPM), a pre-clinical test of anxiety. Immediately after the EPM test, the animals underwent food intake evaluation for 30 min. The data showed that rats microinjected with CLON (20 nmol/0.2 μl) into the AcbSh exhibited increased %Open arm time, which is compatible with an anxiolytic-like effect. The CLON-induced anxiolysis was corroborated by increased head-dipping and decreased stretched-attend posture, two ethologically derived behaviors which are fear/anxiety-motivated. The animal's locomotor activity was not changed by 20 nmol CLON microinjection into the AcbSh. However, neither dose of PHEN microinjected into the AcbSh was able to alter either the spatial-temporal or ethological variables representative of fear/anxiety and locomotion. Food intake was not altered by any dose of CLON and PHEN microinjected into the AcbSh, but the 20 nmol CLON microinjection induced increased motor activity in the feeding test. The data suggests that noradrenergic projections to the AcbSh may underlie fear/anxiety modulation through α(2)-adrenoceptor in the AcbSh, while feeding behavior was unaffected by noradrenergic modulation in the AcbSh of free-feeding rats. This article is part of a Special Issue entitled 'Anxiety and Depression'.
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Affiliation(s)
- Larissa Kochenborger
- Department of Physiological Sciences, Centre of Biological Sciences, Federal University of Santa Catarina (UFSC), 88040-900 Florianópolis, SC, Brazil.
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Verheij MMM, Cools AR. Mesolimbic alpha-, but not beta-adrenoceptors control the accumbal release of dopamine that is derived from reserpine-sensitive storage vesicles. Neuroscience 2009; 162:1163-73. [PMID: 19464350 DOI: 10.1016/j.neuroscience.2009.05.034] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2008] [Revised: 05/16/2009] [Accepted: 05/18/2009] [Indexed: 10/20/2022]
Abstract
Mesolimbic beta-, but not alpha-adrenoceptors control the accumbal release of dopamine that is derived from alpha-methyl-para-tyrosine-sensitive pools of newly synthesized neurotransmitter. The aim of this study was to investigate which of these adrenoceptors control the accumbal release of dopamine that is derived from reserpine-sensitive pools of previously stored neurotransmitter. Rats, that were divided in low-responders and high-responders to novelty, were pretreated with 1 mg/kg of reserpine before the alpha-adrenergic-agent phentolamine or the beta-adrenergic-agent isoproterenol was locally applied into the nucleus accumbens. The original finding that phentolamine and isoproterenol increased accumbal dopamine levels in low-responders and high-responders was replicated. Reserpine reduced the phentolamine-induced increase of accumbal dopamine in both types of rat. However, phentolamine could still increase accumbal dopamine levels in reserpine-treated high-responders, but not anymore in reserpine-treated low-responders. Reserpine did not reduce the isoproterenol-induced increase of accumbal dopamine in any type of rat. This study demonstrates that mesolimbic alpha-, but not beta-adrenoceptors control the accumbal release of dopamine that is derived from reserpine-sensitive storage vesicles. In addition, these data confirm our previous finding that dopamine can still be released from storage vesicles of reserpinized high-responders, but not of reserpinized low-responders. The collected data underline our notion that alpha- and beta-adrenergic drugs may have therapeutic effects in patients suffering from diseases in which accumbal dopamine is involved.
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Affiliation(s)
- M M M Verheij
- Radboud University Nijmegen Medical Center, Department of Cognitive Neuroscience, Division of Psychoneuropharmacology, 6525 EZ, Nijmegen, The Netherlands.
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Verheij MMM, Cools AR. Accumbal noradrenaline that contributes to the alpha-adrenoceptor-mediated release of dopamine from reserpine-sensitive storage vesicles in the nucleus accumbens is derived from alpha-methyl-para-tyrosine-sensitive pools. J Neural Transm (Vienna) 2009; 116:389-94. [PMID: 19221691 DOI: 10.1007/s00702-009-0190-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2008] [Accepted: 01/24/2009] [Indexed: 12/19/2022]
Abstract
Alpha-adrenoceptors in the nucleus accumbens are known to inhibit accumbal dopamine release from reserpine-sensitive pools. The aim of this study was to test our previously reported hypothesis that accumbal noradrenaline that controls the dopamine release from these storage vesicles is derived from alpha-methyl-para-tyrosine-sensitive pools. The sensitivity of accumbal alpha-adrenoceptors to noradrenergic agents depends on the amount of noradrenaline that is available in the synapse. In case the synaptic noradrenaline levels decrease, the conformation of alpha-adrenoceptors changes into a state that makes these receptors more sensitive to its agonists. The effects of alpha-methyl-para-tyrosine, respectively reserpine, on the alpha-adrenoceptor-agonist-induced changes of accumbal dopamine release were investigated. Alpha-methyl-para-tyrosine, but not reserpine, made accumbal postsynaptic alpha-adrenoceptors more sensitive to phenylephrine. These results indicate that noradrenaline that inhibits the release of dopamine from reserpine-sensitive storage vesicles, via stimulation of accumbal postsynaptic alpha-adrenoceptors, is derived from alpha-methyl-para-tyrosine-sensitive pools. The clinical impact of these data is discussed.
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Affiliation(s)
- M M M Verheij
- Department of Cognitive Neuroscience, Division of Psychoneuropharmacology (PNF), Radboud University (RU) Nijmegen, Medical Centre, 6525 EZ, Nijmegen, The Netherlands.
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Verheij MMM, Cools AR. Twenty years of dopamine research: individual differences in the response of accumbal dopamine to environmental and pharmacological challenges. Eur J Pharmacol 2008; 585:228-44. [PMID: 18423601 DOI: 10.1016/j.ejphar.2008.02.084] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Revised: 02/07/2008] [Accepted: 02/13/2008] [Indexed: 11/30/2022]
Abstract
Individual differences in the dopaminergic system of the nucleus accumbens of rats have extensively been reported. These individual differences have frequently been used to explain individual differences in response to environmental and pharmacological challenges. Remarkably, only little attention is paid to the factors that underlie these individual differences. This review gives an overview of the studies that have been performed in our institute during the last 20 years to investigate individual differences in accumbal dopamine release. Data are summarised demonstrating that individual differences in accumbal dopamine release are due to individual differences in: the functional reactivity of the noradrenergic system, the accumbal concentration of vesicular monoamine transporters and tyrosine hydroxylase as well as in the quantal size of the presynaptic pools of dopamine. Our data are embedded in the available literature to create a model that illustrates the putative hardware giving rise to the individual-specific release of accumbal dopamine. An important role is contributed to individual differences in the reactivity of the: hypothalamic-pituitary-adrenal axes, the reactivity of second messenger systems as well in the aminergic reactivity of the accumbens shell and core. The consequences of the individual-specific make-up and reactivity of the nucleus accumbens on the regulation of behaviour and the response to drugs of abuse will also be discussed. Apart from agents that interact with dopaminergic receptors, re-uptake or breakdown, noradrenergic agents as well as agents that interact with vesicular monoamine transporters or tyrosine hydroxylase are suggested to have therapeutic effects in subjects that are suffering from diseases in which the dopaminergic system is disturbed.
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Affiliation(s)
- Michel M M Verheij
- Department of Cognitive Neuroscience (CNS), Division of Psychoneuropharmacology (PNF), Radboud University Nijmegen Medical Centre, 6525 EZ, Nijmegen, The Netherlands.
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Totterdell S. The anatomy of co-morbid neuropsychiatric disorders based on cortico-limbic synaptic interactions. Neurotox Res 2007; 10:65-85. [PMID: 17062369 DOI: 10.1007/bf03033236] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Many brain disorders appear to involve dysfunctions of aminergic systems. Alterations in dopamine activity may underpin both schizophrenia and the establishment and maintenance of drug dependence while disruption of serotonergic signalling may be crucial in both depression and schizophrenia. The co-existence of nicotine and alcohol abuse with depression and schizophrenia is well-documented as is the particular vulnerability of adolescents. At the same time, a common group of brain structures is increasingly implicated in neuropathological studies. For example, depression may involve a lack of serotonin signalling, particularly in the prefrontal cortex, while in schizophrenia there is evidence for reduced dopamine signalling in the same brain region, co-existing with hyperactivity in the mesolimbic dopamine pathway. Increased dopamine release from the mesolimbic dopamine pathway is also a common factor of drugs of abuse. Furthermore, the control of motivational behaviour and dopamine release is apparently modified by hippocampal and amygdala activity, both brain regions showing pathological changes in schizophrenia and depression. Our work has focused on the intricate synaptic interactions of aminergic terminals and cortical and subcortical neurons in order to unravel the anatomical basis for these disorders and their treatments. We show convergence of dopamine and cortical inputs onto single neurons in the nucleus accumbens, and between different cortical inputs to individual neurons, providing a basis for the gating mechanisms attributed to these interactions. We have also examined local and extrinsic connections in the prefrontal cortex and the basis for regulation of both cortical neurons and midbrain dopamine neurons by serotonin from the raph é nucleus. Together with data concerning subcellular receptor distributions, this information provides a detailed synaptic framework for interpreting behavioural, pharmacological and physiological data and enhances our understanding of possible circuitry underlying comorbidity of disorders such as schizophrenia and depression with drug abuse, information invaluable in the introduction of enhanced therapies.
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Affiliation(s)
- S Totterdell
- Department of Pharmacology, Oxford University, Mansfield Road, Oxford, OX1 3QT, UK.
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Ihalainen JA, Tanila H. In vivo regulation of dopamine and noradrenaline release by alpha2A-adrenoceptors in the mouse nucleus accumbens. J Neurochem 2004; 91:49-56. [PMID: 15379886 DOI: 10.1111/j.1471-4159.2004.02691.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The present study investigated the role of alpha2A-adrenoceptor (alpha2A-AR) subtype in the regulation of noradrenaline (NA) and dopamine (DA) release in the nucleus accumbens (NAc). The effect of locally infused and systemically injected alpha2-AR agonist, dexmedetomidine (DMT), and alpha2-AR antagonist, atipamezole, on NA and DA release was investigated in alpha2A-AR knockout and control mice by using in vivo microdialysis. In addition, we compared the drug effects on DA and NA release in the NAc to their effect on locomotor activity. Baseline NA and DA concentrations did not differ between genotypes. Local infusion of DMT decreased, in a concentration-dependent manner, NA, but not DA, levels in the control mice. However, systemic injection of DMT decreased both NA and DA levels in the control mice. In both cases DMT had no effects on transmitter release in alpha2A-AR knockout mice. Our results suggest that alpha2-ARs regulate the release of NA, but not DA, at the terminal level in the NAc. However, alpha2-ARs regulate DA release in the NAc indirectly by their effect on DA neurones in the ventral tegmental area via an unknown mechanism. In both cases the regulation is mediated by alpha2A-adrenoceptor subtype. Also the modulation of locomotor activity by alpha2-AR agonist and antagonist seems to be mediated via alpha2A-adrenoceptors.
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Affiliation(s)
- Jouni A Ihalainen
- Department of Neuroscience and Neurology, University of Kuopio, Finland.
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Yavich L, Sirviö J, Haapalinna A, Ylinen A, Männistö PT. Atipamezole, an alpha2-adrenoceptor antagonist, augments the effects of L-DOPA on evoked dopamine release in rat striatum. Eur J Pharmacol 2003; 462:83-9. [PMID: 12591099 DOI: 10.1016/s0014-2999(03)01324-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The effects of atipamezole, an alpha(2)-adrenoceptor antagonist, L-3,4-dihydroxyphenylalanine (L-DOPA) and the combination of these drugs on dopamine overflow were studied in dopaminergic presynaptic terminals of rat caudate and nucleus accumbens. Dopamine overflow evoked by 100 pulses of electrical stimulation of the medial forebrain bundle at a low (20 Hz) and high (50 Hz) frequency was measured by in vivo voltammetry. L-DOPA (15 mg/kg) increased dopamine overflow in the caudate nucleus, but this dose had no effects in the nucleus accumbens. Atipamezole (300 microg/kg) had no effects on its own on dopamine overflow, but it did increase the size of the readily releasable storage pool and the effects of L-DOPA treatment in both structures. The combination of the drugs increased dopamine overflow to a larger extent at high compared to low stimulation frequencies. We conclude that the rat caudate nucleus is more sensitive than the nucleus accumbens to the effects of L-DOPA, and the effects of L-DOPA treatment might be effectively enhanced by antagonism of alpha(2)-adrenoceptors.
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Affiliation(s)
- Leonid Yavich
- Department of Pharmacology and Toxicology, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio, Finland.
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Mota A, Guimarães S. Interaction between alpha2-autoreceptors and receptors mediating the effects of angiotensin II and bradykinin in the heart of newborn rats. Eur J Pharmacol 2002; 453:265-70. [PMID: 12398914 DOI: 10.1016/s0014-2999(02)02425-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The interaction between alpha2-autoreceptors and receptors for angiotensin II and bradykinin was studied in the heart of newborn rats. The tissues were labelled with [3H]noradrenaline and then superfused with cocaine-containing medium and stimulated electrically. Angiotensin II (10-300 nM) and bradykinin (3-100 nM) enhanced the evoked overflow of tritium, the maximum increase reaching 63.2% and 87.1%, respectively. Blockade of alpha2-adrenoceptors by 100 nM yohimbine reduced, and that by 1 microM abolished, the effect of both angiotensin II and bradykinin. On the contrary, chelerythrine and staurosporine--blockers of protein kinase C--as well as forskolin, an activator of adenylyl cyclase and a blocker of phosphodiesterase, markedly enhanced the facilitatory effect of angiotensin II and bradykinin. We conclude that: (1) alpha2-autoreceptors are present in the heart of newborn rats which interact with prejunctional receptors for angiotensin II and bradykinin also present in the rat heart at that age; (2) the facilitatory influence of chelerythrine and staurosporine on the one hand and that of forskolin on the other hand suggests a link between protein kinase C and cyclicAMP pathways.
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Affiliation(s)
- Alberto Mota
- Instituto de Farmacologia e Terapêutica, Faculdade de Medicina, Universidade do Porto, Alameda Prof. Hernâni Monteiro, 4200-319, Porto, Portugal.
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Whittington RA, Virag L, Morishima HO, Vulliemoz Y. Dexmedetomidine decreases extracellular dopamine concentrations in the rat nucleus accumbens. Brain Res 2001; 919:132-8. [PMID: 11689170 DOI: 10.1016/s0006-8993(01)03012-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The effects of dexmedetomidine, a highly selective alpha(2)-adrenoceptor agonist, on extracellular dopamine (DA) concentrations in the nucleus accumbens of awake rats were collected via in vivo cerebral microdialysis and measured using HPLC with electrochemical detection. The administration of dexmedetomidine (DEX) at a low dose (2 microg/kg bolus i.v. over 2 min followed by a continuous infusion of 0.1 microg/kg per min) and a high dose (20 microg/kg bolus i.v. over 2 min followed by a continuous infusion of 1 microg/kg per min), significantly decreased extracellular dopamine concentrations in the nucleus accumbens. The observed decrease was dose-dependent, occurring sooner and to a greater magnitude in the rats receiving a high dose of DEX. This inhibitory modulation of accumbal dopamine was receptor-specific, as the decrease in extracellular DA produced by DEX was no longer evident following pre-treatment and co-infusion with the highly selective alpha(2)-adrenoceptor antagonist, atipamezole (ATZ). Thus, these data suggest that adrenoceptor agonists and antagonists may modulate dopaminergic neurotransmission via mechanisms that are specific to the alpha(2)-adrenoceptor.
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Affiliation(s)
- R A Whittington
- Department of Anesthesiology, College of Physicians and Surgeons, Columbia University, 622 West 168th Street PH 5, New York, NY 10032, USA.
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Bezard E, Brefel C, Tison F, Peyro-Saint-Paul H, Ladure P, Rascol O, Gross CE. Effect of the alpha 2 adrenoreceptor antagonist, idazoxan, on motor disabilities in MPTP-treated monkey. Prog Neuropsychopharmacol Biol Psychiatry 1999; 23:1237-46. [PMID: 10581645 DOI: 10.1016/s0278-5846(99)00067-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
1. The motor effect of the alpha 2 adrenoreceptor antagonist, idazoxan, was compared to that of L-dopa in MPTP-treated monkeys. 2. Idazoxan 2.0 mg/kg improved parkinsonian motor abnormalities which was comparable to the effects of a minimal effective dose of L-dopa. 3. At 2.0 and 5.0 mg/kg, the parkinsonian rigidity was the item most frequently alleviated by idazoxan (respectively 63.6% and 68.2%). 4. These findings provide support for the therapeutic utility of alpha 2 antagonists in the treatment of Parkinson's disease.
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Affiliation(s)
- E Bezard
- Laboratoire de Neurophysiologie, CNRS UMR 5543, Université de Bordeaux II, France
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Tanila H, Mustonen K, Sallinen J, Scheinin M, Riekkinen P. Role of alpha2C-adrenoceptor subtype in spatial working memory as revealed by mice with targeted disruption of the alpha2C-adrenoceptor gene. Eur J Neurosci 1999; 11:599-603. [PMID: 10051760 DOI: 10.1046/j.1460-9568.1999.00464.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The role of the alpha2C-adrenoceptor subtype in mediating the beneficial effect of alpha2-adrenoceptor agonists on spatial working memory was studied in adult mice with targeted inactivation of the alpha2C-receptor gene (KO) and their wild-type controls (WT). A delayed alternation task was run in a T-maze with mixed delays varying from 20 s to 120 s. Dexmedetomidine, a specific but subtype nonselective alpha2-adrenoceptor agonist, dose-dependently decreased the total number of errors. The effect was strongest at the dose of 5 microg/kg (s.c.), and was observed similarly in KO and WT mice. KO mice performed inferior to WT mice due to a higher number of perseverative errors. Dexmedetomidine slowed initiation of the motor response in the start phase at lower doses in WT mice than in KO mice but no such difference was observed in the return phase of the task, suggesting involvement of alpha2C-adrenoceptors in the cognitive aspect of response preparation or in response sequence initiation. According to these findings, enhancement of spatial working memory is best achieved with alpha2-adrenoceptor agonists which have neither agonistic nor antagonistic effects at the alpha2C-adrenoceptor subtype.
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MESH Headings
- Adrenergic alpha-Agonists/pharmacology
- Animals
- Behavior, Animal/physiology
- Brain Chemistry/physiology
- Dopamine/physiology
- Female
- Imidazoles/pharmacology
- Maze Learning/drug effects
- Maze Learning/physiology
- Medetomidine
- Memory, Short-Term/drug effects
- Memory, Short-Term/physiology
- Mice
- Mice, Inbred C57BL
- Mice, Inbred DBA
- Mice, Knockout
- Reaction Time/physiology
- Receptors, Adrenergic, alpha-2/genetics
- Receptors, Adrenergic, alpha-2/metabolism
- Space Perception/drug effects
- Space Perception/physiology
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Affiliation(s)
- H Tanila
- Department of Neuroscience and Neurology, University and University Hospital of Kuopio, Finland.
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Abstract
We evaluated the cognitive effects of two moderate doses (30 mg/kg x 3 every 12 h and 20 mg/kg x 6 every 8 h, i.p.) of 1-methyl-4-phenyl-l,2,3,6-tetrahydropyridine (MPTP) in mice. The dose of 30 mg/kg x 3 caused about 60% depletion of striatal dopamine but did not reduce the levels of its metabolites. Mice treated with MPTP did not differ from controls in their motor behavior in the open field. Mice treated with MPTP were comparable to controls in T-maze delayed alternation with fixed delays but were impaired when trials with mixed 20 s and 120 s delays were presented, indicative of a spatial working memory impairment. Dexmedetomidine at 10 microg/kg (s.c.) slightly improved delayed alternation performance in all groups but also slowed initiation of the motor response. Mice treated with MPTP at the dose of 30 mg/kg x 3 were less sensitive to this adverse effect of dexmedetomidine. The impairment in spatial working memory after MPTP exposure in mice parallels the findings in monkeys, but the deficit is much less severe.
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Affiliation(s)
- H Tanila
- Department of Neuroscience and Neurology, University of Kuopio, Finland.
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el-Kadi AO, Sharif SI. The role of dopamine in the expression of morphine withdrawal. GENERAL PHARMACOLOGY 1998; 30:499-505. [PMID: 9522166 DOI: 10.1016/s0306-3623(97)00286-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
1. Both L-dopa and low doses of apomorphine potentiated withdrawal symptoms such as jumping, "wet dog" shakes and burrows. L-dopa reduced hypothermia and potentiated body weight loss, whereas apomorphine produced opposite effects. 2. Higher doses of apomorphine attenuated jumping and burrows but had no effect on "wet dog" shakes. On the other hand, and with the exception of sulpiride, all other dopamine (DA) antagonists produced effects opposite those of the agonists with regard to jumping, "wet dog" shakes and burrows. 3. In addition, DA antagonists reduced hypothermia and body weight loss. The effects of DA agonists and antagonists were investigated in mice injected with 6-hydroxydopamine (6-OHDA) intracerebrally to examine whether DA-mediated effects are somehow linked to noradrenergic pathways. 4. Mice pretreated with 6-OHDA developed a higher degree of naloxone-induced withdrawal jumping than did untreated mice. 6-OHDA reversed the effects of apomorphine on "wet dog" shakes and burrows while abolishing those of L-dopa on all withdrawal symptoms, the only exception being jumping, which remained unchanged. 5. 6-OHDA also reversed the effects of sulpiride on all withdrawal symptoms while reversing the effects of pimozide on jumping, and it abolished its effect on hypothermia. 6. These findings provide evidence suggesting that the effects of DA agonists and antagonists are dependent at least partly on intact noradrenergic pathways.
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Affiliation(s)
- A O el-Kadi
- Department of Pharmacology, Faculty of Medicine, Al-Arab Medical University, Benghazi, Libya
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16
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Lu L, Ordway GA. Alpha2C-adrenoceptors mediate inhibition of forskolin-stimulated cAMP production in rat striatum. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1997; 52:228-34. [PMID: 9495543 DOI: 10.1016/s0169-328x(97)00257-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The potential role of alpha2-adrenoceptors in modulating the activity of adenylyl cyclase in the rat striatum was examined. The selective alpha2-adrenoceptor agonist, UK14,304, produced a concentration-dependent inhibition of forskolin-stimulated accumulation of cAMP in striatal slices. The effect of UK14,304 was reversed by pre-incubation of striatal slices with the selective alpha2-adrenoceptor antagonist, RX821002. To determine whether alpha2C-adrenoceptors contribute to the alpha2-adrenoceptor-induced inhibition of forskolin-stimulated cAMP accumulation, an antisense oligodeoxynucleotide directed against alpha2C-adrenoceptor mRNA (alpha(2C)AS) or a random sequence (RS) was infused directly into the striatum. The ability of alpha(2C)AS to reduce the expression of alpha2C-adrenoceptors has been previously demonstrated. Alpha2C(AS) infusions did not reduce the ability of UK14,304 to inhibit forskolin-stimulated cAMP accumulation. Instead, alpha(2C)AS significantly enhanced forskolin-stimulated cAMP accumulation on the infusion side compared to the contralateral striatum. In contrast to the effects of alpha(2C)AS, infusions of RS had no effects on forskolin-stimulated cAMP accumulation or on the ability of UK14,304 to inhibit this effect. Incubation of striatal slices from untreated rats with RX821002 could mimic the ability of alpha(2C)AS infusion to enhance forskolin-stimulated cAMP accumulation, and did so in a concentration-dependent manner. Alpha2-adrenoceptors are negatively coupled to adenylyl cyclase in the rat striatum and alpha2C-adrenoceptors appear to be under tonic activation by an endogenous ligand in striatal slices.
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MESH Headings
- Adenylyl Cyclases/metabolism
- Adrenergic alpha-Agonists/pharmacology
- Animals
- Brimonidine Tartrate
- Colforsin/pharmacology
- Corpus Striatum/drug effects
- Corpus Striatum/metabolism
- Cyclic AMP/metabolism
- Functional Laterality
- In Vitro Techniques
- Kinetics
- Male
- Oligonucleotides, Antisense/pharmacology
- Quinoxalines/pharmacology
- RNA, Messenger/antagonists & inhibitors
- Rats
- Rats, Sprague-Dawley
- Receptors, Adrenergic, alpha-2/biosynthesis
- Receptors, Adrenergic, alpha-2/drug effects
- Receptors, Adrenergic, alpha-2/physiology
- Transcription, Genetic/drug effects
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Affiliation(s)
- L Lu
- Department of Psychiatry & Behavior and Pharmacology & Toxicology, University of Mississippi Medical Center, Jackson 39216, USA
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17
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Yavich L, Lappalainen R, Sirviö J, Haapalinna A, MacDonald E. Alpha2-adrenergic control of dopamine overflow and metabolism in mouse striatum. Eur J Pharmacol 1997; 339:113-9. [PMID: 9473124 DOI: 10.1016/s0014-2999(97)01375-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The effects of the alpha2-adrenoceptor drugs, medetomidine and atipamezole, on dopamine overflow evoked by low (6 Hz-10 s) and high (50 Hz-4 s) frequency electrical stimulation of the median forebrain bundle were studied in striatum of BALB/C mice anaesthetized with chloral hydrate with fast in vivo voltammetry techniques. The effects of these drugs on the basal concentrations of dopamine metabolites were also investigated by means of differential pulse voltammetry. Medetomidine dose dependently decreased dopamine overflow in nucleus accumbens in the dose range 5-100 microg/kg, s.c. This effect was seen only at low frequency stimulation and reached 85% at a dose of 100 microg/kg. Medetomidine also decreased the basal concentration of striatal homovanillic acid. This effect did not exceed 35%. Atipamezole antagonized the inhibitory effects of medetomidine on the dopamine overflow. but showed no effect itself. We suggest that alpha2-adrenoceptors in dopaminergic terminal fields in the mouse striatum are involved in the regulation of dopamine release at physiological stimulation frequencies.
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Affiliation(s)
- L Yavich
- Department of Pharmacology and Toxicology, University of Kuopio, Finland.
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18
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Schmidt ME, Matochik JA, Risinger RC, Schouten JL, Zametkin AJ, Cohen RM, Potter WZ. Regional brain glucose metabolism after acute alpha 2-blockade by idazoxan. Clin Pharmacol Ther 1995; 57:684-95. [PMID: 7781269 DOI: 10.1016/0009-9236(95)90232-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
BACKGROUND Several classes of antidepressant drugs act on alpha 2-adrenergic receptors. Studies of patients with disorders responsive to treatment with these drugs report group differences in ex vivo measures of alpha 2-binding and in vivo responses mediated by alpha 2-receptors. Measurement of regional brain metabolic response to an alpha 2-antagonist may be a useful method for further definition of the role alpha 2-receptor regulation plays in the treatment of neuropsychiatric disorders. METHODS Regional brain glucose metabolism was measured before and after infusion with 200 micrograms/kg idazoxan with use of 18F-fluoro-2-deoxyglucose positron emission tomography in 13 healthy men. Arterial drug concentration, behavioral responses, and cardiovascular responses were also measured. RESULTS The absolute and normalized glucose metabolic rate significantly increased in primary visual cortex. Significant increases and decreases occurred in normalized metabolic rates in prefrontal cortical regions. Measurement of metabolic effects occurred during the peak cardiovascular response. CONCLUSIONS Our findings are consistent with regionally specific effects of alpha 2-blockade. This method may be useful for the study of alpha 2-receptor function in humans.
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Affiliation(s)
- M E Schmidt
- Section on Clinical Pharmacology, National Institute of Mental Health, Bethesda, MD 20892, USA
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19
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de Villiers AS, Russell VA, Sagvolden T, Searson A, Jaffer A, Taljaard JJ. Alpha 2-adrenoceptor mediated inhibition of [3H]dopamine release from nucleus accumbens slices and monoamine levels in a rat model for attention-deficit hyperactivity disorder. Neurochem Res 1995; 20:427-33. [PMID: 7651580 DOI: 10.1007/bf00973098] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The spontaneously hypertensive rat (SHR) has been proposed as an animal model for attention-deficit hyperactivity disorder (ADHD). The behavioural problems have been suggested to be secondary to altered reinforcement mechanisms in which nucleus accumbens dopaminergic activity plays an important role. Interaction between the noradrenergic and dopaminergic system in the nucleus accumbens has been implicated in the locomotor hyperactivity and impaired discriminative performance of SHR. The present study therefore investigated whether there was any change in the alpha 2-adrenoceptor mediated inhibition of dopamine release from nucleus accumbens slices of SHR in comparison with their normotensive Wistar-Kyoto (WKY) controls. The electrically stimulated release of [3H]dopamine (DA) from nucleus accumbens slices was decreased to a similar extent by UK14,304, an alpha 2-adrenoceptor agonist, in SHR and WKY. Basal norepinephrine (NE) levels were increased in locus coeruleus (LC) and A2 noradrenergic nuclei, but not in the A1 nucleus of SHR, while basal serotonin (5-HT) levels were increased in all these pons-medulla nuclei. These results suggest that a primarily dysfunctional LC and A2 nucleus does not have a secondary effect on dopaminergic transmission in the nucleus accumbens via alpha 2-adrenoceptor mediated inhibition of DA release. Basal monoamine levels in several brain areas of SHR were significantly different from that of WKY. DA, and 5-HT turnover were decreased in SHR versus WKY suggesting hypofunctional dopaminergic and serotonergic systems in some brain areas of SHR.
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Affiliation(s)
- A S de Villiers
- Department of Chemical Pathology, University of Stellenbosch, Tygerberg Hospital, Republic of South Africa
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