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Abstract
Desensitization is an intriguing characteristic of ligand-gated channels, whereby a decrease or loss of biological response occurs following prolonged or repetitive stimulation. Nicotinic acetylcholine receptors (nAChRs), as a member of transmitter gated ion channels family, also can be desensitized by continuous or repeated exposure to agonist. Desensitization of nicotinic receptors can occur as a result of extended nicotine exposure during smoking or prolonged acetylcholine when treatment of Alzheimer's disease (AD) with cholinesterase inhibitors, or anticholinesterase agent poisoning. Studies from our lab have shown that nAChRs desensitization is not a nonfunctional state and we proposed that desensitized nAChRs could increase sensitivity of brain muscarinic receptor to its agonists. Here, we will review the regulation of nicotinic receptor desensitization and discuss the important biological function of desensitized nicotinic receptors in light of our previous studies. These studies provide the critical information for understanding the importance of nicotinic receptors desensitization in both normal physiological processing and in various disease states.
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Affiliation(s)
- Hai Wang
- Beijing Institute of Pharmacology and Toxicology, Beijing 100850, P.R. China.
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352
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Zhou FM, Liang Y, Salas R, Zhang L, De Biasi M, Dani JA. Corelease of dopamine and serotonin from striatal dopamine terminals. Neuron 2005; 46:65-74. [PMID: 15820694 DOI: 10.1016/j.neuron.2005.02.010] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2004] [Revised: 01/04/2005] [Accepted: 02/07/2005] [Indexed: 10/25/2022]
Abstract
The striatum receives rich dopaminergic and more moderate serotonergic innervation. After vesicular release, dopamine and serotonin (5-hydroxytryptamine, 5-HT) signaling is controlled by transporter-mediated reuptake. Dopamine is taken up by dopamine transporters (DATs), which are expressed at the highest density in the striatum. Although DATs also display a low affinity for 5-HT, that neurotransmitter is normally efficiently taken up by the 5-HT transporters. We found that when extracellular 5-HT is elevated by exogenous application or by using antidepressants (e.g., fluoxetine) to inhibit the 5-HT transporters, the extremely dense striatal DATs uptake 5-HT into dopamine terminals. Immunohistochemical results and measurements using fast cyclic voltammetry showed that elevated 5-HT is taken up by DATs into striatal dopamine terminals that subsequently release 5-HT and dopamine together. These results suggest that antidepressants that block serotonin transporters or other factors that elevate extracellular 5-HT alter the temporal and spatial relationship between dopamine and 5-HT signaling in the striatum.
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Affiliation(s)
- Fu-Ming Zhou
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030, USA
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353
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Bamford NS, Robinson S, Palmiter RD, Joyce JA, Moore C, Meshul CK. Dopamine modulates release from corticostriatal terminals. J Neurosci 2005; 24:9541-52. [PMID: 15509741 PMCID: PMC6730145 DOI: 10.1523/jneurosci.2891-04.2004] [Citation(s) in RCA: 184] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Normal striatal function is dependent on the availability of synaptic dopamine to modulate neurotransmission. Within the striatum, excitatory inputs from cortical glutamatergic neurons and modulatory inputs from midbrain dopamine neurons converge onto dendritic spines of medium spiny neurons. In addition to dopamine receptors on medium spiny neurons, D2 receptors are also present on corticostriatal terminals, where they act to dampen striatal excitation. To determine the effect of dopamine depletion on corticostriatal activity, we used the styryl dye FM1-43 in combination with multiphoton confocal microscopy in slice preparations from dopamine-deficient (DD) and reserpine-treated mice. The activity-dependent release of FM1-43 out of corticostriatal terminals allows a measure of kinetics quantified by the halftime decay of fluorescence intensity. In DD, reserpine-treated, and control mice, exposure to the D2-like receptor agonist quinpirole revealed modulation of corticostriatal kinetics with depression of FM1-43 destaining. In DD and reserpine-treated mice, quinpirole decreased destaining to a greater extent, and at a lower dose, consistent with hypersensitive corticostriatal D2 receptors. Compared with controls, slices from DD mice did not react to amphetamine or to cocaine with dopamine-releasing striatal stimulation unless the animals were pretreated with l-3,4-dihydroxyphenylalanine (l-dopa). Electron microscopy and immunogold labeling for glutamate terminals within the striatum demonstrated that the observed differences in kinetics of corticostriatal terminals in DD mice were not attributable to aberrant cytoarchitecture or glutamate density. Microdialysis revealed that basal extracellular striatal glutamate was normal in DD mice. These data indicate that dopamine deficiency results in morphologically normal corticostriatal terminals with hypersensitive D2 receptors.
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354
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Nuutinen S, Ahtee L, Tuominen RK. Time and brain region specific up-regulation of low affinity neuronal nicotinic receptors during chronic nicotine administration in mice. Eur J Pharmacol 2005; 515:83-9. [PMID: 15894304 DOI: 10.1016/j.ejphar.2005.04.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2004] [Revised: 01/18/2005] [Accepted: 02/02/2005] [Indexed: 10/25/2022]
Abstract
We studied the effects of chronic oral nicotine on brain low affinity nicotine binding sites. Mice received nicotine in the drinking water for 4 or 7 weeks. Receptor binding was measured at 24 or 48 h after cessation of nicotine administration with [3H]methyllycaconitine, an antagonist in alpha7 and alpha3/alpha6beta2beta3* nicotinic receptors in striatum, midbrain, hippocampus and cortex. Chronic nicotine for 4 weeks resulted in a significant increase in the [3H]methyllycaconitine binding in the striatum and cortex, whereas after 7 weeks the increase in binding could be found in the hippocampus but not in the other brain areas studied. For comparison, high affinity nicotine binding sites (mostly alpha4beta2) were measured with [3H]epibatidine after 7-week chronic nicotine treatment. [3H]Epibatidine binding sites were increased in the hippocampus, midbrain and cortex, but not in the striatum. The up-regulation of [3H]methyllycaconitine binding was significant at 24 h but that of [3H]epibatidine binding sites was not observed until at 48 h after cessation of chronic nicotine. These results suggest that up-regulation of low affinity nicotine binding sites does occur during chronic nicotine administration. Furthermore, the low affinity and high affinity binding differ clearly as regards regions and duration suggesting that different nicotinic receptors respond differently to nicotine administration.
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Affiliation(s)
- Saara Nuutinen
- Division of Pharmacology and Toxicology, Faculty of Pharmacy, P.O. Box 56 (Viikinkaari 5 E), University of Helsinki, FIN-00014, Finland
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355
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Wilson CJ. The Mechanism of Intrinsic Amplification of Hyperpolarizations and Spontaneous Bursting in Striatal Cholinergic Interneurons. Neuron 2005; 45:575-85. [PMID: 15721243 DOI: 10.1016/j.neuron.2004.12.053] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2004] [Revised: 11/23/2004] [Accepted: 12/17/2004] [Indexed: 10/25/2022]
Abstract
Striatal cholinergic interneurons pause their ongoing firing in response to sensory stimuli that have acquired meaning as a signal for learned behavior. In slices, these cells exhibit both spontaneous activity patterns and spontaneous pauses very similar to those seen in vivo. The mechanisms responsible for ongoing firing and spontaneous pauses were studied in striatal slices using perforated patch recordings. All hyperpolarizations, whether spontaneous or generated by current injection, were amplified and shaped by two hyperpolarization-activated currents. Hyperpolarization onsets were regeneratively amplified by a potassium current (KIR) whose activation promoted further hyperpolarization. The termination of hyperpolarizations was controlled by a time-dependent nonspecific cation current (HCN). The duration and even the sizes of spontaneous and driven hyperpolarizations and pauses in spontaneous activity in cholinergic interneurons are largely autonomous properties of the neuron, rather than reflections of characteristics of the input eliciting the response.
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Affiliation(s)
- Charles J Wilson
- Department of Biology, University of Texas at San Antonio, 6900 North Loop, 1604 West, San Antonio, Texas 78249, USA.
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356
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Di Angelantonio S, Bernardi G, Mercuri NB. Methamidophos transiently inhibits neuronal nicotinic receptors of rat substantia nigra dopaminergic neurons via open channel block. Neurosci Lett 2005; 369:208-13. [PMID: 15464266 DOI: 10.1016/j.neulet.2004.07.074] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2004] [Revised: 07/16/2004] [Accepted: 07/20/2004] [Indexed: 10/26/2022]
Abstract
The use of acetylcholinesterase (AChE) inhibitors is the primary therapeutic strategy in the treatment of Alzheimer's disease. However, these drugs have been reported to have effects beyond the simple stimulation of neuronal acetylcholine receptors (AChRs) by elevated acetylcholine (ACh), interfering directly with the nAChR. Therefore, a pure pharmacological blockade of AChE is not usually obtained. In this study, the patch-clamp technique was utilized to determine the effects of methamidophos, a pesticide that is considered a selective AChE inhibitor, on nAChRs of substantia nigra dopaminergic neurons. In spite of the fact that methamidophos has been reported to be devoid of direct nicotinic actions, our main observation was that it selectively and reversibly blocked nAChR responses, without directly affecting the holding current. Methamidophos produced a downward shift in the dose response curve for nicotine; the mechanism accounting for this non-competitive antagonism was open channel block, in view of its voltage dependence. Pre-treatment with vesamicol did not prevent the reduction of nicotine-induced currents, indicating that the effect on nAChRs was independent from the activity of methamidophos as a cholinesterase inhibitor. Our results conclude that methamidophos has a complex blocking action on neuronal nAChRs that is unlinked to the inhibition of AChE. Therefore, it should not be considered a selective AChE inhibitor and part of its toxic effects could reside in an interference with the nicotinic neurotransmission.
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Affiliation(s)
- Silvia Di Angelantonio
- Laboratorio di Neurologia Sperimentale IRCCS-Fondazione Santa Lucia, Via Ardeatina 306, 00179 Roma, Italy; Dipartimento di Fisiologia Umana e Farmacologia Università La Sapienza di Roma, Roma, Italy.
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357
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Krolewski DM, Bishop C, Walker PD. Intrastriatal dopamine D1 receptor agonist-mediated motor behavior is reduced by local neurokinin 1 receptor antagonism. Synapse 2005; 57:1-7. [PMID: 15858838 DOI: 10.1002/syn.20148] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Recent evidence suggests that striatal neurokinin receptors modulate dopamine (DA)-induced motor behaviors. To further examine this, we studied the effects of intrastriatal neurokinin 1 receptor (NK1R) antagonism on motor behaviors induced by direct infusion of the full DA D1 receptor agonist SKF 82958. Adult male Sprague-Dawley rats received bilateral intrastriatal 0.8-mul infusions of the NK1R receptor antagonist LY 306,740 (0, 27, or 54 nmol/side) followed by intrastriatal infusions of SKF 82958 (0 or 24 nmol/side) into the dorsal striatum. Following each infusion, rats were placed into automated activity monitors for the quantification of horizontal activity, total distance traveled, movement bouts, and stereotypy counts. As expected, SKF 82958 increased motor activity on all behavioral measures. More importantly, whereas 27 nmol was without effect, prior infusion of 54 nmol LY 306,740 significantly reduced most aspects of behavior. The results of this study suggest that functional NK1Rs within the striatum play a permissive role in the motor behaviors induced by D1R stimulation.
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Affiliation(s)
- David M Krolewski
- Department of Anatomy and Cell Biology, Wayne State University, School of Medicine, Detroit, Michigan 48201, USA
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358
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359
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Tisch S, Silberstein P, Limousin-Dowsey P, Jahanshahi M. The basal ganglia: anatomy, physiology, and pharmacology. Psychiatr Clin North Am 2004; 27:757-99. [PMID: 15550292 DOI: 10.1016/j.psc.2004.06.004] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The basal ganglia are perceived as important nodes in cortico-subcortical networks involved in the transfer, convergence, and processing of information in motor, cognitive, and limbic domains. How this integration might occur remains a matter of some debate, particularly given the consistent finding in anatomic and physiologic studies of functional segregation in cortico-subcortical loops. More recent theories, however, have raised the notion that modality-specific information might be integrated not spatially, but rather temporally, by coincident processing in discrete neuronal populations. Basal ganglia neurotransmitters, given their diverse roles in motor performance, learning, working memory, and reward-related activity are also likely to play an important role in the integration of cerebral activity. Further work will elucidate this to a greater extent, but for now, it is clear that the basal ganglia form an important nexus in the binding of cognitive, limbic, and motor information into thought and action.
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Affiliation(s)
- Stephen Tisch
- Sobell Department of Motor Neuroscience & Movement Disorders Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom
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360
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Gale SD, Perkel DJ. Properties of dopamine release and uptake in the songbird basal ganglia. J Neurophysiol 2004; 93:1871-9. [PMID: 15548618 DOI: 10.1152/jn.01053.2004] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Vocal learning in songbirds requires a basal ganglia circuit termed the anterior forebrain pathway (AFP). The AFP is not required for song production, and its role in song learning is not well understood. Like the mammalian striatum, the striatal component of the AFP, Area X, receives dense dopaminergic innervation from the midbrain. Since dopamine (DA) clearly plays a crucial role in basal ganglia-mediated motor control and learning in mammals, it seems likely that DA signaling contributes importantly to the functions of Area X as well. In this study, we used voltammetric methods to detect subsecond changes in extracellular DA concentration to gain better understanding of the properties and regulation of DA release and uptake in Area X. We electrically stimulated Ca(2+)- and action potential-dependent release of an electroactive substance in Area X brain slices and identified the substance as DA by the voltammetric waveform, electrode selectivity, and neurochemical and pharmacological evidence. As in the mammalian striatum, DA release in Area X is depressed by autoinhibition, and the lifetime of extracellular DA is strongly constrained by monoamine transporters. These results add to the known physiological similarities of the mammalian and songbird striatum and support further use of voltammetry in songbirds to investigate the role of basal ganglia DA in motor learning.
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Affiliation(s)
- Samuel D Gale
- Graduate Program in Neurobiology and Behavior, University of Washington, Seattle, WA 98195, USA.
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361
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Lin JY, Chung KKH, de Castro D, Funk GD, Lipski J. Effects of muscarinic acetylcholine receptor activation on membrane currents and intracellular messengers in medium spiny neurones of the rat striatum. Eur J Neurosci 2004; 20:1219-30. [PMID: 15341594 DOI: 10.1111/j.1460-9568.2004.03576.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Acetylcholine, acting through muscarinic receptors, modulates the excitability of striatal medium spiny neurones. However, the underlying membrane conductances and intracellular signalling pathways have not been fully determined. Our aim was to characterize excitatory effects mediated by M1 muscarinic acetylcholine receptors in these neurones using whole-cell patch-clamp recordings in brain slices of postnatal rats. Under voltage-clamp, muscarine evoked an inward current associated with an increase in cell membrane resistance. The current, which reversed at -85 mV, was sensitive to the M1 receptor antagonist pirenzepine. Blocking the potassium conductance attenuated the response and the residual current was further reduced by ruthenium red (50 microm) and reversed at +15 mV. Simultaneous recordings from cholinergic interneurones and medium spiny neurones in conjunction with spike-triggered averaging revealed small unitary excitatory postsynaptic currents in four of 39 cell pairs tested. The muscarine-induced inward current was attenuated by a phospholipase C (PLC) inhibitor, U73122, but not by a protein kinase C inhibitor, chelerythrine, or by the intracellular calcium chelator 1,2-bis(2-aminophenoxy) ethane-N,N,N',N'-tetra-acetic acid, suggesting that the current was associated with PLC in a protein kinase C- and Ca2+ -independent manner. The phosphatidylinositol 4-kinase inhibitor wortmannin (10 microm) reduced the recovery of the inward current, indicating that the recovery process was dependent on the removal of diacylglycerol and/or inositol 1,4,5 triphosphate or resynthesis of phospholipid phosphatidylinositol 4,5-bisphophate. Ratiometric measurement of intracellular calcium after cell loading with fura-2 demonstrated a muscarine-induced increase in calcium signal that originated mainly from intracellular stores. Thus, the cholinergic excitatory effect in striatal medium spiny neurones, which is important in motor disorders associated with altered cholinergic transmission in the striatum such as Parkinson's disease, is mediated through M1 receptors and the PLC-dependent pathway.
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Affiliation(s)
- John Y Lin
- Division of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92-019, New Zealand
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362
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Zhang L, Zhou FM, Dani JA. Cholinergic drugs for Alzheimer's disease enhance in vitro dopamine release. Mol Pharmacol 2004; 66:538-44. [PMID: 15322245 DOI: 10.1124/mol.104.000299] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Alzheimer's disease is a neurodegenerative disorder associated with a decline in cognitive abilities. Patients also frequently have noncognitive symptoms, such as anxiety, depression, apathy, and psychosis, that impair daily living. The most commonly prescribed treatments for Alzheimer's disease are acetylcholinesterase inhibitors, such as donepezil and galantamine. Enhanced cholinergic functions caused by these compounds are believed to underlie improvements in learning, memory, and attention. The noncognitive aspects of dementia, however, are usually linked to serotonin and dopamine rather than acetylcholine because those neurotransmitter systems most directly influence mood, emotional balance, and psychosis. Fast-scan cyclic voltammetry applied to mouse striatal brain slices was used to measure the real-time release of dopamine arising from spontaneous activity or from single electrical stimulations. At concentrations that include their prescribed dosage ranges, donepezil (1-1000 nM) and galantamine (50-1000 nM) increase action potential-dependent dopamine release. Consistent with previous literature, the data support slightly different modes of action for donepezil and galantamine. The ability of these commonly prescribed drugs to alter catecholamine release may underlie their influence over noncognitive symptoms of dementia. Furthermore, these results suggest that acting via nicotinic receptors, these drugs may serve presently untapped therapeutic roles by altering dopamine release in other disorders involving dopaminergic systems.
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Affiliation(s)
- Lifen Zhang
- Division of Neuroscience, Baylor College of Medicine, Houston, TX 77030-3498, USA
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363
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Abstract
Smoking cessation activities and support for its implementation should be integrated into the health care system. The outcome of smoking cessation has improved with the availability of proper behavior approaches and medications. Incorporating these guidelines into daily clinical practice ensures that health care providers provide the opportunity for patients to quit smoking. The best hope of improved treatment comes from combining existing and new pharmacotherapies with effective behavioral therapy.
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Affiliation(s)
- Arunabh Talwar
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, 300 Community Drive, North Shore University Hospital, Manhasset, NY 11030, USA.
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364
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Ronesi J, Lovinger DM. Induction of striatal long-term synaptic depression by moderate frequency activation of cortical afferents in rat. J Physiol 2004; 562:245-56. [PMID: 15498813 PMCID: PMC1665477 DOI: 10.1113/jphysiol.2004.068460] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The striatum regulates motor output, and it is thought that changes in the synaptic efficacy of inputs to the striatum contribute to motor learning and habit formation. Previously, several laboratories have observed that brief high frequency stimulation (HFS) of cortical afferents innervating the dorsolateral striatum induces a long-term decrease in synaptic efficacy called long-term depression (LTD). We recently showed that HFS-induced striatal LTD requires retrograde signalling involving postsynaptic release of endocannabinoids and activation of presynaptic CB1 cannabinoid receptors. In the present study we have employed whole-cell recording in brain slices to examine a new form of LTD at corticostriatal synapses that can be induced by a 10 Hz, 5 min train. The decrease in synaptic efficacy is associated with a decrease in presynaptic release probability, as demonstrated by a decrease in frequency but not amplitude of spontaneous excitatory postsynaptic currents (sEPSCs) and an increase in the paired pulse ratio (PPR). This form of LTD is blocked by antagonists for CB1 and D2 dopamine receptors and impaired by blockers of L-type calcium channels. However, 10 Hz-induced LTD does not depend on postsynaptic depolarization, unlike HFS-induced LTD. Furthermore, this new form of LTD is not prevented by treatments known to block HFS-induced LTD, including antagonism of metabotropic glutamate receptors (mGluRs), chelation of postsynaptic calcium, or intracellular application of an anandamide membrane transport inhibitor (VDM11). From these findings it is not clear that the endocannabinoid responsible for this form of LTD acts in a retrograde fashion, and the cellular source of endocannabinoid necessary for 10 Hz-induced LTD is as yet unknown. Our results demonstrate that a prolonged moderate frequency train induces cannabinoid-dependent LTD, further supporting the idea that endocannabinoids play a prominent role in the regulation of long-lasting changes in striatal output.
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Affiliation(s)
- Jennifer Ronesi
- Laboratory for Integrative Neuroscience, National Institute of Alcohol Abuse and Alcoholism, NIH, Rockville, MD 20852, USA
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365
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Tzavos A, Jih J, Ragozzino ME. Differential effects of M1 muscarinic receptor blockade and nicotinic receptor blockade in the dorsomedial striatum on response reversal learning. Behav Brain Res 2004; 154:245-53. [PMID: 15302131 PMCID: PMC3206590 DOI: 10.1016/j.bbr.2004.02.011] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2003] [Revised: 01/06/2004] [Accepted: 02/18/2004] [Indexed: 11/26/2022]
Abstract
The present studies determined whether blockade of M(1)-like muscarinic or nicotinic cholinergic receptors in the dorsomedial striatum affects acquisition or reversal learning of a response discrimination. Testing occurred in a modified cross-maze across two consecutive sessions. In the acquisition phase, a rat learned to turn to the left or to the right. In the reversal learning phase, a rat learned to turn in the opposite direction as required during acquisition. Experiment 1 investigated the effects of the M(1)-like muscarinic receptor antagonist, pirenzepine infused into the dorsomedial striatum on acquisition and reversal learning. Experiment 2 examined the effects of the nicotinic cholinergic antagonist, mecamylamine injected into the dorsomedial striatum on acquisition and reversal learning. Bilateral injections of pirenzepine at 10 microg, but not 1 microg, selectively impaired reversal learning. Analysis of the errors indicated that pirenzepine treatment did not impair the initial shift, but increased reversions back to the original response choice following the initial shift. Bilateral injections of mecamylamine, 6 or 18 microg, did not affect acquisition or reversal learning. The results suggest that activation of M(1) muscarinic cholinergic receptors, but not nicotinic cholinergic receptors, in the dorsomedial striatum is important for facilitating the flexible shifting of response patterns.
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Affiliation(s)
- Arianna Tzavos
- Laboratory of Integrative Neuroscience, Department of Psychology, University of Illinois at Chicago, 1007 West Harrison Street, Chicago, IL 60607, USA
| | - Jane Jih
- Laboratory of Integrative Neuroscience, Department of Psychology, University of Illinois at Chicago, 1007 West Harrison Street, Chicago, IL 60607, USA
| | - Michael E. Ragozzino
- Laboratory of Integrative Neuroscience, Department of Psychology, University of Illinois at Chicago, 1007 West Harrison Street, Chicago, IL 60607, USA
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366
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Abstract
Epidemiological studies show that smoking is associated with a lower incidence of Parkinson's disease (PD). This finding is important because it could provide clues about therapeutic strategies for protection against this debilitating movement disorder. Smoke contains numerous chemicals that could be responsible for the apparent protective effect. Here, a role for nicotine is considered, because this chemical stimulates brain dopaminergic systems and provides some symptomatic benefit in PD. Nicotine also has a neuroprotective action. Putative factors and signaling pathways involved in the actions of nicotine are discussed. An understanding of the molecular basis for the reduced occurrence of PD in tobacco users is crucial for the development of intervention strategies to reduce or halt disease progression.
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Affiliation(s)
- Maryka Quik
- The Parkinson's Institute, 1170 Morse Avenue, Sunnyvale, CA 94089, USA.
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367
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Edwards KR, Hershey L, Wray L, Bednarczyk EM, Lichter D, Farlow M, Johnson S. Efficacy and safety of galantamine in patients with dementia with Lewy bodies: a 12-week interim analysis. Dement Geriatr Cogn Disord 2004; 17 Suppl 1:40-8. [PMID: 14676468 DOI: 10.1159/000074681] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Observations on the neurochemistry of dementia with Lewy bodies (DLB) have suggested that cholinesterase inhibitors (ChEIs) might be beneficial in treating some clinical symptoms of DLB. A 24-week, multicenter open-label study was designed to assess the safety and efficacy of the ChEI galantamine in patients with DLB, and an interim analysis of results was performed at 12 weeks. Efficacy analyses were performed on data from 25 patients. Scores on the Neuropsychiatric Inventory (NPI-12) improved (decreased) by 7.52 points over the 12 weeks (marginally significant, p = 0.061). NPI-12 scores decreased by half in 12 of the 25 patients. Highly significant improvement was observed in scores on the NPI-4 subscale (delusions, hallucinations, apathy, and depression: p = 0.003). Scores on the Clinician's Global Impression of Change (CGIC) improved by 0.95 points (significant, p = 0.02). Improvements also were found in secondary efficacy variables, including cognitive, functional, activities of daily living, sleep and confusion assessments. Motor scores, as measured by the UPDRS motor subscale, showed mild improvement, which demonstrates that galantamine has no adverse effect on parkinsonian symptoms. Adverse events generally were transient and of mild-to-moderate intensity. Two of the 25 patients discontinued galantamine because of nausea and anorexia. One serious adverse event was recorded, but it was judged to be unrelated to the study medication.
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Affiliation(s)
- Keith R Edwards
- Alzheimer's Diagnostic and Treatment Center, Neurological Research Center, Bennington, Vt. 05201, USA.
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368
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Morris G, Nevet A, Bergman H. Anatomical funneling, sparse connectivity and redundancy reduction in the neural networks of the basal ganglia. ACTA ACUST UNITED AC 2004; 97:581-9. [PMID: 15242667 DOI: 10.1016/j.jphysparis.2004.01.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The major anatomical characteristics of the main axis of the basal ganglia are: (1) Numerical reduction in the number of neurons across layers of the feed-forward network, (2) lateral inhibitory connections within the layers, and (3) neuro-modulatory effects of dopamine and acetylcholine, both on the basal ganglia neurons and on the efficacy of information transmission along the basal ganglia axis. We recorded the simultaneous activity of neurons in the output stages of the basal ganglia as well as the activity of dopaminergic and cholinergic neurons during the performance of a probability decision-making task. We found that the functional messages of the cholinergic and dopaminergic neurons differ, and that the cholinergic message is less specific than that of the dopaminergic neurons. The output stage of the basal ganglia showed uncorrelated neuronal activity. We conclude that despite the huge numerical reduction from the cortex to the output nuclei of the basal ganglia, the activity of these nuclei represents an optimally compressed (uncorrelated) version of distinctive features of cortical information.
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Affiliation(s)
- Genela Morris
- Department of Physiology, the Interdisciplinary Center for Neural Computation and the Eric Roland Center for Neurodegenerative Diseases, Hadassah Medical School, The Hebrew University, P.O. Box 12272, Jerusalem 91120, Israel
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369
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Feng Y, Niu T, Xing H, Xu X, Chen C, Peng S, Wang L, Laird N, Xu X. A common haplotype of the nicotine acetylcholine receptor alpha 4 subunit gene is associated with vulnerability to nicotine addiction in men. Am J Hum Genet 2004; 75:112-21. [PMID: 15154117 PMCID: PMC1181994 DOI: 10.1086/422194] [Citation(s) in RCA: 157] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2004] [Accepted: 04/23/2004] [Indexed: 11/03/2022] Open
Abstract
Nicotine is the major addictive substance in cigarettes, and genes involved in sensing nicotine are logical candidates for vulnerability to nicotine addiction. We studied six single-nucleotide polymorphisms (SNPs) in the CHRNA4 gene and four SNPs in the CHRNB2 gene with respect to nicotine dependence in a collection of 901 subjects (815 siblings and 86 parents) from 222 nuclear families with multiple nicotine-addicted siblings. The subjects were assessed for addiction by both the Fagerstrom Test for Nicotine Dependence (FTND) and the Revised Tolerance Questionnaire (RTQ). Because only 5.8% of female offspring were smokers, only male subjects were included in the final analyses (621 men from 206 families). Univariate (single-marker) family-based association tests (FBATs) demonstrated that variant alleles at two SNPs, rs1044396 and rs1044397, in exon 5 of the CHRNA4 gene were significantly associated with a protective effect against nicotine addiction as either a dichotomized trait or a quantitative phenotype (i.e., age-adjusted FTND and RTQ scores), which was consistent with the results of the global haplotype FBAT. Furthermore, the haplotype-specific FBAT showed a common (22.5%) CHRNA4 haplotype, GCTATA, which was significantly associated with both a protective effect against nicotine addiction as a dichotomized trait (Z=-3.04, P<.005) and significant decreases of age-adjusted FTND (Z=-3.31, P<.005) or RTQ scores (Z=-2.73, P=.006). Our findings provide strong evidence suggesting a common CHRNA4 haplotype might be protective against vulnerability to nicotine addiction in men.
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Affiliation(s)
- Yan Feng
- Program for Population Genetics, and Department of Biostatistics, Harvard School of Public Health, and Division of Preventive Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston; Center for Eco-Genetics and Reproductive Health, Health Science Center, Peking University, Beijing; and Anhui Institute of Biomedicine, Anhui Medical University, and School of Life Science, University of Science and Technology of China, Hefei, Anhui, China
| | - Tianhua Niu
- Program for Population Genetics, and Department of Biostatistics, Harvard School of Public Health, and Division of Preventive Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston; Center for Eco-Genetics and Reproductive Health, Health Science Center, Peking University, Beijing; and Anhui Institute of Biomedicine, Anhui Medical University, and School of Life Science, University of Science and Technology of China, Hefei, Anhui, China
| | - Houxun Xing
- Program for Population Genetics, and Department of Biostatistics, Harvard School of Public Health, and Division of Preventive Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston; Center for Eco-Genetics and Reproductive Health, Health Science Center, Peking University, Beijing; and Anhui Institute of Biomedicine, Anhui Medical University, and School of Life Science, University of Science and Technology of China, Hefei, Anhui, China
| | - Xin Xu
- Program for Population Genetics, and Department of Biostatistics, Harvard School of Public Health, and Division of Preventive Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston; Center for Eco-Genetics and Reproductive Health, Health Science Center, Peking University, Beijing; and Anhui Institute of Biomedicine, Anhui Medical University, and School of Life Science, University of Science and Technology of China, Hefei, Anhui, China
| | - Changzhong Chen
- Program for Population Genetics, and Department of Biostatistics, Harvard School of Public Health, and Division of Preventive Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston; Center for Eco-Genetics and Reproductive Health, Health Science Center, Peking University, Beijing; and Anhui Institute of Biomedicine, Anhui Medical University, and School of Life Science, University of Science and Technology of China, Hefei, Anhui, China
| | - Shaojie Peng
- Program for Population Genetics, and Department of Biostatistics, Harvard School of Public Health, and Division of Preventive Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston; Center for Eco-Genetics and Reproductive Health, Health Science Center, Peking University, Beijing; and Anhui Institute of Biomedicine, Anhui Medical University, and School of Life Science, University of Science and Technology of China, Hefei, Anhui, China
| | - Lihua Wang
- Program for Population Genetics, and Department of Biostatistics, Harvard School of Public Health, and Division of Preventive Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston; Center for Eco-Genetics and Reproductive Health, Health Science Center, Peking University, Beijing; and Anhui Institute of Biomedicine, Anhui Medical University, and School of Life Science, University of Science and Technology of China, Hefei, Anhui, China
| | - Nan Laird
- Program for Population Genetics, and Department of Biostatistics, Harvard School of Public Health, and Division of Preventive Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston; Center for Eco-Genetics and Reproductive Health, Health Science Center, Peking University, Beijing; and Anhui Institute of Biomedicine, Anhui Medical University, and School of Life Science, University of Science and Technology of China, Hefei, Anhui, China
| | - Xiping Xu
- Program for Population Genetics, and Department of Biostatistics, Harvard School of Public Health, and Division of Preventive Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston; Center for Eco-Genetics and Reproductive Health, Health Science Center, Peking University, Beijing; and Anhui Institute of Biomedicine, Anhui Medical University, and School of Life Science, University of Science and Technology of China, Hefei, Anhui, China
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370
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Wu J, George AA, Schroeder KM, Xu L, Marxer-Miller S, Lucero L, Lukas RJ. Electrophysiological, pharmacological, and molecular evidence for alpha7-nicotinic acetylcholine receptors in rat midbrain dopamine neurons. J Pharmacol Exp Ther 2004; 311:80-91. [PMID: 15178698 DOI: 10.1124/jpet.104.070417] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Dopamine (DA) neurons located in the mammalian midbrain have been generally implicated in reward and drug reinforcement and more specifically in nicotine dependence. However, roles played by nicotinic acetylcholine receptors, including those composed of alpha7-subunits [alpha7-nicotinic acetylcholine receptors (nAChRs)], in modulation of DA signaling and in nicotine dependence are not clearly understood. Although midbrain slice recording has been used previously to identify functional alpha7-nAChRs, these preparations are not optimally designed for extremely rapid and reproducible drug application, and rapidly desensitized, alpha7-nAChR-mediated currents may have been underestimated or not detected. Here, we use patch-clamp, whole-cell current recordings from single neurons acutely dissociated from midbrain nuclei and having features of DA neurons to characterize acetylcholine-induced, inward currents that rapidly activate and desensitize, are mimicked by the alpha7-nAChR-selective agonist, choline, blocked by the alpha7-nAChR-selective antagonists, methyllycaconitine and alpha-bungarotoxin, and are similar to those of heterologously expressed, human alpha7-nAChRs. We also use reverse transcriptase-polymerase chain reaction, in situ hybridization, and immunocytochemical staining to demonstrate nAChR alpha7 subunit gene expression as message and protein in the rat substantia nigra pars compacta and ventral tegmental area. Expression of alpha7 subunit message and of alpha7-nAChR-mediated responses is developmentally regulated, with both being absent in samples taken from rats at postnatal day 7, but later becoming present and increasing over the next 2 weeks. Collectively, this electrophysiological, pharmacological, and molecular evidence indicates that nAChR alpha7 subunits and functional alpha7-nAChRs are expressed somatodendritically by midbrain DA neurons, where they may play important physiological roles and contribute to nicotine reinforcement and dependence.
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Affiliation(s)
- Jie Wu
- Division of Neurology, Barrow Neurological Institute, 350 West Thomas Road, Phoenix, AZ 85013-4496, USA.
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371
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Papke RL, Meyer EM, Lavieri S, Bollampally SR, Papke TAS, Horenstein NA, Itoh Y, Porter Papke JK. Effects at a distance in α7 nAChR selective agonists: benzylidene substitutions that regulate potency and efficacy. Neuropharmacology 2004; 46:1023-38. [PMID: 15081799 DOI: 10.1016/j.neuropharm.2004.01.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2003] [Revised: 12/11/2003] [Accepted: 01/07/2004] [Indexed: 11/16/2022]
Abstract
Anabaseine is a marine worm toxin that is a relatively non-selective nicotinic agonist, activating both muscle-type and neuronal nicotinic acetylcholine receptors (nAChR) with varying efficacy. While anabaseine has significant activity with muscle-type and neuronal alpha 3 beta 4 and alpha 4 beta 2 receptors, benzylidene anabaseine (BA) derivatives have high selectivity for the alpha 7 receptor subtype. Two BA compounds with substituents at the 2 and 4 positions of the benzylidene ring, GTS-21 and 4OH-GTS-21, may have therapeutic potential for treating neuropathological disorders such as Alzheimer's disease due to their alpha 7 selectivity. In this study, we specifically investigated the influence of the benzylidene attachment to anabaseine on alpha 7 nicotinic receptor selectivity, as well as the effects of specific substituents at the 4- position of the benzylidene moiety. We demonstrate that benzylidene-attachment alone is sufficient to confer alpha 7 selectivity to anabaseine. Increased potency and receptor binding affinity was obtained with a 4-hydroxyl substitution. Two other 4-substituted benzylidene anabaseines, 3-(4'-methylthiobenzylidene)anabaseine (4-MeS-BA) and 3-(4-trifluoromethylbenzylidene) anabaseine (4-CF(3)-BA), offered very little agonist activity for any nicotinic receptors and instead were antagonists for both alpha 7 and neuronal alpha 3 beta 4 and alpha 4 beta 2 receptors. Since the relative amounts of agonist and antagonist activities for specific BA compounds vary with the specific drug/receptor combinations, benzylidene anabaseines provide valuable tools for nAChR drug-receptor structure-function relationships.
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Affiliation(s)
- Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267 JHMHSC, Gainesville, FL 32610-0267, USA.
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372
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Zhang H, Sulzer D. Frequency-dependent modulation of dopamine release by nicotine. Nat Neurosci 2004; 7:581-2. [PMID: 15146187 DOI: 10.1038/nn1243] [Citation(s) in RCA: 257] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2004] [Accepted: 03/10/2004] [Indexed: 11/08/2022]
Abstract
Although nicotine activation of dopamine release is implicated in addiction, it also desensitizes nicotinic acetylcholine receptors (nAChRs), leading to a prolonged depression of evoked dopamine release. Here we show that nicotine's effects depend on the firing pattern of dopamine neurons, so that while desensitization of nAChRs indeed curbs dopamine released by stimuli emulating tonic firing, it allows a rapid rise in dopamine from stimuli emulating phasic firing patterns associated with incentive/salience paradigms. Nicotine may thus enhance the contrast of dopamine signals associated with behavioral cues.
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Affiliation(s)
- Hui Zhang
- Department of Neurology, Columbia University, 650 W 168th Street, New York, New York 10032, USA
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373
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Rice ME, Cragg SJ. Nicotine amplifies reward-related dopamine signals in striatum. Nat Neurosci 2004; 7:583-4. [PMID: 15146188 DOI: 10.1038/nn1244] [Citation(s) in RCA: 411] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2003] [Accepted: 03/23/2004] [Indexed: 11/09/2022]
Abstract
Reward-seeking behaviors depend critically on dopamine signaling--dopamine neurons encode reward-related information by switching from tonic to phasic (burst-like) activity. Using guinea pig brain slices, we show that nicotine, like cocaine and amphetamine, acts directly in striatum where it enhances dopamine release during phasic but not tonic activity. This amplification provides a mechanism for nicotine facilitation of reward-related dopamine signals, including responses to other primary reinforcers that govern nicotine dependence in smokers.
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Affiliation(s)
- Margaret E Rice
- University Department of Pharmacology, Mansfield Road, Oxford OX1 3QT, UK
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374
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Abstract
Rabbit syndrome is an antipsychotic-induced rhythmic motion of the mouth/lips, resembling the chewing movements of a rabbit. The movement consists of a vertical-only motion, at about 5Hz, with no involvement of the tongue. Usually, the involuntary movements associated with rabbit syndrome appear after a long period (in most cases months or years) of antipsychotic treatment; however, a few patients with the syndrome have had treatment histories with no antipsychotic involvement. The reported prevalence of rabbit syndrome ranges from 2.3 to 4.4% of patients treated with typical antipsychotics. There have been isolated reports of rabbit syndrome in patients treated with the atypical agents risperidone and clozapine. Patients with rabbit syndrome are most often misdiagnosed as having oral tardive dyskinesia. In such cases the key for correct diagnosis is the involvement of tardive tongue movements, which does not occur in rabbit syndrome. The treatment of rabbit syndrome is empirical, reflecting poor understanding of its neuropathology. The first step is to reduce the amount of antipsychotic treatment as much as possible. However, since, in most cases, full withdrawal of antipsychotic treatment is impossible, the syndrome cannot be completely abolished without additional measures. The next stage of treatment involves specific drugs that aim to control the syndrome. Anticholinergic drugs are the best known treatment. Rabbit syndrome does not respond to treatment with levodopa or dopamine agonists. The most striking aspect of this syndrome is its specificity. Rabbit syndrome affects only the buccal region, and within this area it involves a highly stereotyped involuntary movement. This immediately focuses attention on the basal ganglia, in particular the substantia nigra pars reticulata, which is also implicated in oral dyskinesia. Continuing neurophysiological and pharmacological research of the basal ganglia holds the key to better understanding and treatment of this syndrome in the coming years.
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Affiliation(s)
- Miguel Schwartz
- Department of Neurology, Bnai Zion Medical Center, Haifa, Israel.
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375
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Smith JE, Co C, Yin X, Sizemore GM, Liguori A, Johnson WE, Martin TJ. Involvement of cholinergic neuronal systems in intravenous cocaine self-administration. Neurosci Biobehav Rev 2004; 27:841-50. [PMID: 15019433 DOI: 10.1016/j.neubiorev.2003.11.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recent studies suggest the participation of cholinergic neurons in the brain processes underlying reinforcement. The involvement of cholinergic neurons in cocaine self-administration has been recently demonstrated in studies using muscarinic and nicotinic agonists and antagonists, microdialysis, assessment of choline acetyltransferase activity and acetylcholine (ACh) turnover rates. The present experiment was initiated to identify subsets of cholinergic neurons involved in the brain processes that underlie cocaine self-administration by lesioning discrete populations with a selective neurotoxin. Rats were trained to self-administer cocaine and the cholinergic neurotoxin 192-IgG-saporin or vehicle was then bilaterally administered into the posterior nucleus accumbens (NAcc)-ventral pallidum (VP). The 192-IgG-saporin induced lesions resulted in a pattern of drug-intake consistent with either a shift in the dose intake relationship to the left or downward compared to sham-treated controls. A second experiment used a self-administration threshold procedure that demonstrated this lesion shifted the dose intake relationship to the left compared to the sham-vehicle treated rats. The magnitude and extent of the lesion was assessed by measuring the expression of p75 (the target for 192-IgG-saporin) and choline acetyltransferase (ChAT) in the NAcc, VP, caudate nucleus-putamen (CP) and vertical limb of the medial septal nucleus-diagonal band (MS-DB) of these rats using real time reverse transcriptase-polymerase chain reaction. Significant reductions in gene expression for p75 (a selective marker for basal forebrain cholinergic neurons) and ChAT were seen in the MS-DB and VP while only small decreases were seen in the NAcc and CP of the 192-IgG-saporin treated rats. These data indicate that the overall influence of cholinergic neurons in the MS-DB and VP are inhibitory to the processes underlying cocaine self-administration and suggest that agonists directed toward subclasses of cholinergic receptors may have efficacy as pharmacotherapeutic adjuncts for the treatment of cocaine abuse.
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Affiliation(s)
- James E Smith
- Department of Physiology and Pharmacology, Center for the Neurobiological Investigation of Drug Abuse, Wake Forest University School of Medicine, Wake Forest University, Winston-Salem, NC 27157-1083, USA.
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376
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Hernández LF, Segovia G, Mora F. Effects of activation of NMDA and AMPA glutamate receptors on the extracellular concentrations of dopamine, acetylcholine, and GABA in striatum of the awake rat: a microdialysis study. Neurochem Res 2004; 28:1819-27. [PMID: 14649723 DOI: 10.1023/a:1026115607216] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The effects of activation of the AMPA and NMDA ionotropic glutamate receptors on the extracellular concentration of dopamine, acetylcholine, (ACh) and GABA in striatum of the awake rat was investigated. Also the levels of DOPAC, HVA, and choline (Ch) were included in this study. Seven to eight days after stereotaxical implantation of a guide-cannulae assembly, microdialysis experiments were performed. The dopamine and ACh content of samples were measured by HPLC coupled to electrochemical detection. GABA was measured using fluorometric detection. Perfusion of AMPA (1, 20, 100 microM) produced a dose-related increase of dopamine and a dose-related decrease of DOPAC and HVA. AMPA 100 microM decreased extracellular concentrations of ACh and increased the extracellular concentration of Ch and GABA. Perfusion of NMDA 500 microM increased the concentration of dopamine and decreased DOPAC and HVA. Also, NMDA 100 microM decreased DOPAC. NMDA 500 microM decreased the extracellular concentrations of ACh and increased the concentrations of Ch and GABA. Perfusion of the AMPA/kainate-antagonist DNQX (100 microM) blocked the effects of AMPA (100 microM) on dopamine, DOPAC, HVA, ACh, and GABA concentrations. Perfusion of the NMDA-antagonist CPP (100 microM) blocked the effects of NMDA 500 microM on dopamine, DOPAC, HVA, ACh, Ch, and GABA concentrations. These results suggest an interaction between glutamate-dopamine-ACh-GABA in striatum of the awake rat.
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Affiliation(s)
- L F Hernández
- Department of Physiology, Faculty of Medicine, University Complutense, Madrid, Spain
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377
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Marenco S, Carson RE, Berman KF, Herscovitch P, Weinberger DR. Nicotine-induced dopamine release in primates measured with [11C]raclopride PET. Neuropsychopharmacology 2004; 29:259-68. [PMID: 14666115 DOI: 10.1038/sj.npp.1300287] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Nicotine-induced dopamine (DA) release constitutes a pharmacological probe of the DA system that has potential use in patients with schizophrenia, who have abnormally elevated DA release after amphetamine administration and possibly abnormalities in nicotinic signaling. We performed positron emission tomography studies in five rhesus monkeys that received i.v. nicotine doses ranging from 0.01 to 0.06 mg/kg. [(11)C]raclopride was administered with either a bolus plus constant infusion or with paired bolus injections. The dynamics of D-2-binding potential (BP) after nicotine administration were studied and compared to amphetamine. Nicotine caused a significant albeit small reduction (5%, p<0.03) in BP, regardless of methodology of tracer administration. This effect disappeared 2.5 h after nicotine administration. Amphetamine caused much larger and prolonged displacement of [(11)C]raclopride as compared to nicotine. There was no correlation between changes in BP and nicotine dose or plasma level. Regional differences in the nicotine effect within the basal ganglia were not found. Our data are consistent with the increase in DA detected with microdialysis in animals after acute nicotine administration, however, a larger effect size would be desirable to attempt studies comparing human smokers with and without schizophrenia.
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378
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Di Angelantonio S, Bernardi G, Mercuri NB. Donepezil modulates nicotinic receptors of substantia nigra dopaminergic neurones. Br J Pharmacol 2004; 141:644-52. [PMID: 14744806 PMCID: PMC1574242 DOI: 10.1038/sj.bjp.0705660] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. The effects of donepezil, one of the most common cholinesterase inhibitors used for treatment of Alzheimer's disease, were studied on nicotinic receptors (nAChRs)-mediated postsynaptic currents, in dopaminergic neurons of the substantia nigra pars compacta, using the patch-clamp recording technique in slice preparations. 2. Donepezil (10-100 microM) selectively and reversibly depressed nicotine currents, induced by brief puffer pulses, through a glass micropipette positioned above the slice. 3. The peak amplitude fading of the responses generated by repeated test applications of low doses of nicotine was accelerated by donepezil, while it slowed the recovery of nicotine currents after a large, desensitising, dose of the same agonist. 4. Donepezil depressed even maximal responses to nicotine, revealing a noncompetitive mechanism of action; moreover, the inhibition of nAChRs was voltage and time independent. 5. Pretreatment with vesamicol or methamidophos did not prevent the reduction of nicotine-induced currents. The data indicated direct effect on nAChR, independent from the activity of donepezil as cholinesterase inhibitor.
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Affiliation(s)
- Silvia Di Angelantonio
- Laboratorio di Neurologia Sperimentale, IRCCS-Fondazione Santa Lucia, Via Ardeatina 306, Rome 00179, Italy.
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379
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Wilcock G, Howe I, Coles H, Lilienfeld S, Truyen L, Zhu Y, Bullock R, Kershaw P. A long-term comparison of galantamine and donepezil in the treatment of Alzheimer's disease. Drugs Aging 2004; 20:777-89. [PMID: 12875613 DOI: 10.2165/00002512-200320100-00006] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
OBJECTIVE To compare the long-term efficacy and safety of galantamine 24 mg/day and donepezil 10 mg/day in patients with Alzheimer's disease. PATIENTS AND STUDY DESIGN This was a rater-blinded, randomised, parallel-group multicentre study (18 outpatient clinics) in the UK. 182 patients (69 male, 113 female) with Alzheimer's disease were randomised to galantamine (n = 94) or donepezil (n = 88) for 52 weeks. MAIN OUTCOME MEASURES The effects of galantamine and donepezil on function using the Bristol Activities of Daily Living Scale (BrADL); cognition using the Mini-Mental State Examination (MMSE) and Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog/11); behaviour using the Neuropsychiatric Inventory (NPI); caregiver burden using the Screen for Caregiver Burden; and safety were assessed. RESULTS BrADL total scores showed no significant difference between treatment groups in mean change from baseline to week 52. In the total population, in terms of cognition, galantamine patients' scores on the MMSE at week 52 did not differ significantly from baseline (-0.52 +/- 0.39, p < 0.5 vs baseline), whereas donepezil patients' scores deteriorated significantly from baseline (-1.58 +/- 0.42, p < 0.0005 vs baseline). The between-group difference in MMSE change, which showed a trend for superiority of galantamine, did not reach statistical significance (p < or = 0.1). In the ADAS-cog/11 analysis, between-group differences for the total population were not significant, whereas galantamine-treated patients with MMSE scores of 12-18 demonstrated an increase (worsening) in the ADAS-cog/11 score of 1.61 +/- 0.80 versus baseline, compared with an increase of 4.08 +/- 0.84 for patients treated with donepezil, with a significant between-group difference in favour of galantamine (p < or = 0.05). More caregivers of patients receiving galantamine reported reductions in burden compared with donepezil. Changes from baseline in NPI were similar for both treatments. Both treatments were well tolerated; most adverse events were transient and of mild-to-moderate intensity, and were consistent with the findings of previous clinical trials. CONCLUSIONS Significant advantages were found in the treatment response to galantamine (versus donepezil) on cognition as measured by response rates on the MMSE and ADAS-cog/11.
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Affiliation(s)
- Gordon Wilcock
- Department of Care of the Elderly, University of Bristol, Frenchay Hospital, Bristol, UK
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380
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Pidoplichko VI, Noguchi J, Areola OO, Liang Y, Peterson J, Zhang T, Dani JA. Nicotinic cholinergic synaptic mechanisms in the ventral tegmental area contribute to nicotine addiction. Learn Mem 2004; 11:60-9. [PMID: 14747518 PMCID: PMC321315 DOI: 10.1101/lm.70004] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2003] [Accepted: 11/21/2003] [Indexed: 01/28/2023]
Abstract
Tobacco use is a major health problem that is estimated to cause 4 million deaths a year worldwide. Nicotine is the main addictive component of tobacco. It acts as an agonist to activate and desensitize nicotinic acetylcholine receptors (nAChRs). A component of nicotine's addictive power is attributable to actions on the mesolimbic dopaminergic system, which serves a fundamental role in the acquisition of behaviors that are inappropriately reinforced by addictive drugs. Here we show that nicotine, in the same concentration and time ranges as obtained from tobacco, has three main actions that regulate the activity of midbrain dopamine (DA) neurons. Nicotine first activates and then desensitizes nAChRs on the DA neurons. This process directly excites the DA neurons for a short period of time before the nAChRs desensitize. Nicotine also enhances glutamatergic excitation and decreases GABAergic inhibition onto DA neurons. These events increase the probability for synaptic plasticity, such as long-term potentiation. The short-lived direct excitation of the DA neurons coupled with the enhanced glutamatergic afferent activity provides the presynaptic and postsynaptic coincidence necessary to initiate synaptic potentiation. In total, these synaptic events lead to a relatively long-lasting heightened activity of midbrain DA neurons. Consistent with other summarized studies, this work indicates that the synaptic changes normally associated with learning and memory can be influenced and commandeered during the nicotine addiction process.
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381
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Champtiaux N, Changeux JP. Knockout and knockin mice to investigate the role of nicotinic receptors in the central nervous system. PROGRESS IN BRAIN RESEARCH 2004; 145:235-51. [PMID: 14650919 DOI: 10.1016/s0079-6123(03)45016-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The recent use of genetically engineered knockout (Ko) and knockin (Kin) animals for neurotransmitter receptor genes, in particular, nicotinic acetylcholine receptors (nAChRs) in the brain, has provided a powerful alternative to the classical pharmacological approach. These animal models are not only useful in order to reexamine and refine the results derived from pharmacological studies, but they do also provide a unique opportunity to determine the subunit composition of the nicotinic receptors which modulate various brain functions. Ultimately, this knowledge will be valuable in the process of designing new drugs that will mimic the effects of nicotine on several important pathologies or on smoking cessation therapies. In this review, we present recent data obtained from the studies of mutant animals that contributed to our understanding of the role and composition of nAChRs in the central nervous system (CNS). The advantages and pitfalls of Ko animal models will also be discussed.
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Affiliation(s)
- Nicolas Champtiaux
- Laboratoire de Neurobiologie Moléculaire, Centre National de la Recherche scientifique, Unité de Recherche Associée 2182 Récepteurs et Cognition, Institut Pasteur, 75724 Paris, France
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382
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Pratt WE, Kelley AE. Nucleus Accumbens Acetylcholine Regulates Appetitive Learning and Motivation for Food via Activation of Muscarinic Receptors. Behav Neurosci 2004; 118:730-9. [PMID: 15301600 DOI: 10.1037/0735-7044.118.4.730] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
These experiments tested whether nucleus accumbens muscarinic or nicotinic acetylcholine receptor activation is required for rats to learn to lever press for sucrose. Muscarinic blockade with scopolamine (1.0 microg/side or 10.0 microg/side), but not nicotinic antagonism with mecamylamine (10.0 microg/side), inhibited learning and performance when applied to the core or shell. Further experiments showed that acute accumbens scopolamine treatment increased locomotor activity and reduced sucrose consumption. However, microanalyses of behavioral events in the instrumental chamber revealed that reductions of lever press performance during muscarinic blockade were not due to gross motor dysfunction. Accumbens core scopolamine was subsequently shown to reduce the amount of work rats would expend under a progressive ratio paradigm. These novel results implicate nucleus accumbens muscarinic receptors in the modulation of appetitive learning, performance, and motivation for food.
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Affiliation(s)
- Wayne E Pratt
- Wisconsin Psychiatric Institute and Clinics, Department of Psychiatry, University of Wisconsin-Madison Medical School, Madison, WI 53719, USA.
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383
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Glutamate spillover in the striatum depresses dopaminergic transmission by activating group I metabotropic glutamate receptors. J Neurosci 2003. [PMID: 14627643 DOI: 10.1523/jneurosci.23-33-10585.2003] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cortical glutamate and substantia nigra dopamine (DA) afferents converge onto the dendritic spines of medium spiny neurons (MSNs) in the striatum where they act to modulate motor and cognitive functions. The released DA spills over from its synapse and is thought to regulate glutamatergic input by acting on distal DA receptors located on corticostriatal axon terminals. By monitoring evoked DA release directly using fast-scan cyclic voltammetry, we report a reciprocal modulation by glutamate spillover on evoked striatal DA release, induced by either glutamate uptake blockade or high-frequency stimulation of corticostriatal tracts. We demonstrate that this modulation is attributable to the activation of group I metabotropic glutamate receptors. Thus, under conditions in which glutamate escapes the confines of its synapse, it can elicit the presynaptic suppression of dopaminergic neurotransmission.
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384
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Hayslett RL, Tizabi Y. Effects of donepezil on DOI-induced head twitch response in mice: implications for tourette syndrome. Pharmacol Biochem Behav 2003; 76:409-15. [PMID: 14643839 DOI: 10.1016/j.pbb.2003.08.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Tourette syndrome (TS) is a neurological disorder characterized by persistent motor and phonic tics. Administration of the selective 5-HT(2A/2C) agonist 1-(2, 5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) induces head twitches in mice that have been proposed to model tics seen in TS. Previous studies have demonstrated that nicotine markedly attenuates DOI-induced head twitch response (HTR). This and the reports that nicotine may have clinical efficacy in reducing symptoms of TS suggest possible involvement of the nicotinic cholinergic system in this disorder. Donepezil is an acetylcholinesterase inhibitor approved for use in mild to moderate Alzheimer's disease. The purpose of this study was to investigate whether donepezil might also reduce DOI-induced HTR, and whether its combination with nicotine might result in an additive or synergistic effect. Moreover, to elucidate the possible role of nicotinic receptors in this paradigm, the effects of mecamylamine, a nicotinic antagonist, was also evaluated. Acute and chronic administration of donepezil (0.1 mg/kg) or nicotine (0.5 mg/kg base), significantly reduced DOI-induced HTR. No additive or synergistic effects of donepezil and nicotine were observed. Acute mecamylamine administration (0.5-5.0 mg/kg) dose-dependently inhibited DOI-induced HTR. None of the mecamylamine doses blocked the inhibitory effects of donepezil or nicotine on DOI-induced HTR. These results suggest that donepezil may have therapeutic potential in treating motor tic symptoms of TS. Moreover, the action of donepezil and nicotine may be mediated through the same mechanism.
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Affiliation(s)
- Renee L Hayslett
- Department of Pharmacology, College of Medicine, Howard University, 520 W Street N.W., Washington, DC 20059, USA
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385
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Lovinger DM, Partridge JG, Tang KC. Plastic Control of Striatal Glutamatergic Transmission by Ensemble Actions of Several Neurotransmitters and Targets for Drugs of Abuse. Ann N Y Acad Sci 2003; 1003:226-40. [PMID: 14684449 DOI: 10.1196/annals.1300.014] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Long-lasting alterations in the efficacy of glutamatergic synapses, such as long-term potentiation (LTP) and long-term depression (LTD), are prominent models for mechanisms of information storage in the brain. It has been suggested that exposure to drugs of abuse produces synaptic plasticity at glutamatergic synapses that shares many features with LTP and LTD, and that these synaptic changes may play roles in addiction. We have examined the involvement of particular neurotransmitters in synaptic plasticity at glutamatergic synapses within the striatum, a brain region with prominent roles in initiation and sequencing of actions, as well as habit formation. Our studies indicate that multiple neurotransmitters interact to produce striatal synaptic plasticity, and that the relative strength and patterning of the afferent inputs that release the various neurotransmitters determines whether LTP or LTD is activated. Drugs of abuse interact with glutamatergic synaptic plasticity in multiple ways, including alterations in dopamine release and more direct effects on glutamate release and glutamate receptors. We hypothesize that these effects contribute to addiction by facilitating the formation of new, drug-centered habits, and by disruption of more adaptive behaviors.
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Affiliation(s)
- David M Lovinger
- Laboratory for Integrative Neuroscience, Division of Intramural Clinical and Basic Research, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland 20852, USA.
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386
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Fagen ZM, Mansvelder HD, Keath JR, McGehee DS. Short- and Long-Term Modulation of Synaptic Inputs to Brain Reward Areas by Nicotine. Ann N Y Acad Sci 2003; 1003:185-95. [PMID: 14684446 DOI: 10.1196/annals.1300.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Dopamine signaling in brain reward areas is a key element in the development of drug abuse and dependence. Recent anatomical and electrophysiological research has begun to elucidate both complexity and specificity in synaptic connections between ventral tegmental neurons and their inputs. Specifically, the activity of dopamine neurons in the ventral tegmental area relies on the combination of both excitatory and inhibitory inputs. Controlling endogenous neurotransmission to dopamine neurons is one mechanism by which drugs of abuse affect both transient and long-term changes in synaptic activity. Here, we review recent findings concerning glutamatergic, GABAergic, and cholinergic inputs to dopamine neurons, and their roles in the reinforcement associated with drug abuse. Importantly, several studies support that a single drug exposure can lead to changes in synaptic strength that are associated with learning and memory. Ultimately, these cellular changes could underlie the long-lasting effects of drugs. Furthermore, nicotinic acetylcholine receptors in the ventral tegmental area emerge as a possible common target for the behavioral and cellular actions not only of nicotine, but also of several other drugs of abuse. Finally, we explore age-related differences in nicotine sensitivity in order to understand both human epidemiological data, and laboratory animal behavioral findings that suggest adolescents are more susceptible to developing nicotine dependence.
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Affiliation(s)
- Zara M Fagen
- Committee on Neurobiology, University of Chicago, Chicago, Illinois 60637, USA
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387
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Mansvelder HD, De Rover M, McGehee DS, Brussaard AB. Cholinergic modulation of dopaminergic reward areas: upstream and downstream targets of nicotine addiction. Eur J Pharmacol 2003; 480:117-23. [PMID: 14623355 DOI: 10.1016/j.ejphar.2003.08.099] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nicotine reinforces smoking behaviour by activating nicotinic acetylcholine receptors in the midbrain dopaminergic reward centres. Upstream of the dopaminergic neurons nicotine induces long-term potentiation of the excitatory input to dopamine cells in the ventral tegmental area, and depresses inhibitory inputs. Both effects of nicotine were shown to last much longer than the nicotine exposure and together will activate the dopaminergic ventral tegmental area projection toward the nucleus accumbens. However, downstream of dopamine, effects of nicotine are also likely to occur. Cholinergic interneurons within the nucleus accumbens are important in the tonic control of the gamma-amino buteric acid (GABA) nucleus accumbens output neurons, which project back to the ventral tegmental area. The nicotinic acetylcholine receptors that mediate this control are likely to desensitise upon preexposure to the nicotine concentrations found in the blood of smokers. Thus, synaptic mechanisms both upstream and downstream of dopamine release are potentially important factors contributing to the etiology of nicotine addiction.
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Affiliation(s)
- Huibert D Mansvelder
- Department of Experimental Neurophysiology, Institute for Neurosciences and Centre for Neurogenomics and Cognitive Research, Vrije Universiteit Amsterdam, de Boelelaan 1087, 1081 HV, Amsterdam, The Netherlands
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388
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Middleton LS, Cass WA, Dwoskin LP. Nicotinic receptor modulation of dopamine transporter function in rat striatum and medial prefrontal cortex. J Pharmacol Exp Ther 2003; 308:367-77. [PMID: 14563785 DOI: 10.1124/jpet.103.055335] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nicotine activates nicotinic acetylcholine receptors (nAChRs) on dopamine (DA) terminals to evoke DA release, which subsequently is taken back up into the terminal via the DA transporter (DAT). nAChRs may modulate DAT function thereby contributing to the regulation of synaptic DA concentrations. The present study determined the dose-response for nicotine (0.1-0.8 mg/kg, s.c.) to modulate DA clearance in striatum and medial prefrontal cortex (mPFC) using in vivo voltammetry in urethane anesthetized rats and determined if this effect was mediated by nAChRs. Exogenous DA (200 microM) was pressure-ejected at 5-min intervals until reproducible baseline signals were obtained. Subsequently, nicotine or saline was administered, and DA pressure ejection continued at 5-min intervals for 60 min. In both striatum and mPFC, signal amplitude decreased by approximately 20% across the 60-min session in saline-injected rats. A monophasic dose-response curve was found in striatum, with a maximal 50% decrease in signal amplitude after 0.8 mg/kg. In contrast, a U-shaped dose-response curve was found in mPFC, with a maximal 50% decrease in signal amplitude after 0.4 mg/kg. Onset of nicotine response occurred 10 to 15 min after injection in both brain regions; however, the amount of time before maximal response was 45 and 30 min in striatum and mPFC, respectively. Mecamylamine (1.5 mg/kg) completely inhibited the nicotine-induced (0.8 and 0.4 mg/kg) decrease in signal amplitude in striatum and mPFC, respectively, indicating mediation by nAChRs. Thus, nicotine enhances DA clearance in striatum and mPFC in a mecamylamine-sensitive manner, indicating that nAChRs modulate DAT function in these brain regions.
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Affiliation(s)
- Lisa S Middleton
- College of Pharmacy, University of Kentucky, Lexington, Kentucky 40536, USA
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389
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Paradiso KG, Steinbach JH. Nicotine is highly effective at producing desensitization of rat alpha4beta2 neuronal nicotinic receptors. J Physiol 2003; 553:857-71. [PMID: 14555718 PMCID: PMC2343639 DOI: 10.1113/jphysiol.2003.053447] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
We examined desensitization by acetylcholine (ACh) and nicotine at the rat alpha4beta2 neuronal nicotinic receptor stably expressed in HEK cells. For both agonists, the decay in response due to desensitization ('onset') was best fitted by the sum of two exponentials with the fast component dominant at concentrations > 1 microM. The time constants for onset were similar for both agonists, and showed little concentration dependence over the range of 0.1-100 microM. Recovery from desensitization also showed two exponential components. In contrast to the similarity in onset, nicotine produced longer lasting desensitization, resulting from an increase in the proportion of receptors in the slowly recovering population and from an increase in the time constant for the slow recovery process. The proportion of receptors in the slowly recovering population increased as the duration of the desensitizing pulse increased. Desensitization was also induced by low concentrations of agonist, with no apparent macroscopic response. A 100 s application of 10 nM nicotine desensitized 70 % of the peak response, while 100 s of 10 nM ACh desensitized only 15 %. At higher concentrations of agonist, which result in a macroscopic response, desensitization in the absence of activation also can occur. Nicotine is a very potent and efficacious desensitizing agent at this neuronal nicotinic receptor.
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Affiliation(s)
- K G Paradiso
- Department of Anesthesiology, Washington University, St Louis, MO 63110, USA
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390
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Abstract
The development of electrochemical recordings with small carbon-fiber electrodes has significantly advanced the understanding of the regulation of catecholamine transmission in various brain areas. Recordings in vivo or in slice preparations monitor diffusion of catecholamine following stimulated synaptic release into the surrounding tissue. This synaptic 'overflow' is defined by the amount of release, by the activity of reuptake, and by the diffusion parameters in brain tissue. Such studies have elucidated the complex regulation of catecholamine release and uptake, and how psychostimulants and anti-psychotic drugs interfere with it. Moreover, recordings with carbon-fiber electrodes from cultured neurons have provided analysis of catecholamine release and its plasticity at the quantal level.
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Affiliation(s)
- Yvonne Schmitz
- Department of Neurology, Columbia Univeristy, New York, NY 10032, USA.
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391
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Leonard S. Consequences of low levels of nicotinic acetylcholine receptors in schizophrenia for drug development. Drug Dev Res 2003. [DOI: 10.1002/ddr.10292] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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392
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Subunit composition of functional nicotinic receptors in dopaminergic neurons investigated with knock-out mice. J Neurosci 2003. [PMID: 12944511 DOI: 10.1523/jneurosci.23-21-07820.2003] [Citation(s) in RCA: 366] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) expressed by dopaminergic (DA) neurons have long been considered as potential therapeutic targets for the treatment of several neuropsychiatric diseases, including nicotine and cocaine addiction or Parkinson's disease. However, DA neurons express mRNAs coding for most, if not all, neuronal nAChR subunits, and the subunit composition of functional nAChRs has been difficult to establish. Immunoprecipitation experiments performed on mouse striatal extracts allowed us to identify three main types of heteromeric nAChRs (alpha4beta2*, alpha6beta2*, and alpha4alpha6beta2*) in DA terminal fields. The functional relevance of these subtypes was then examined by studying nicotine-induced DA release in striatal synaptosomes and recording ACh-elicited currents in DA neurons fromalpha4, alpha6, alpha4alpha6, and beta2 knock-out mice. Our results establish that alpha6beta2* nAChRs are functional and sensitive to alpha-conotoxin MII inhibition. These receptors are mainly located on DA terminals and consistently do not contribute to DA release induced by systemic nicotine administration, as evidenced by in vivo microdialysis. In contrast, (nonalpha6)alpha4beta2* nAChRs represent the majority of functional heteromeric nAChRs on DA neuronal soma. Thus, whereas a combination of alpha6beta2* and alpha4beta2* nAChRs may mediate the endogenous cholinergic modulation of DA release at the terminal level, somato-dendritic (nonalpha6)alpha4beta2* nAChRs most likely contribute to nicotine reinforcement.
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393
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Quik M, Bordia T, Okihara M, Fan H, Marks MJ, McIntosh JM, Whiteaker P. L-DOPA treatment modulates nicotinic receptors in monkey striatum. Mol Pharmacol 2003; 64:619-28. [PMID: 12920198 DOI: 10.1124/mol.64.3.619] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nicotinic acetylcholine receptor (nAChR) activation is well known to stimulate dopamine release in the striatum. This phenomenon may be physiologically significant in the control of motor function, as well as in pathological conditions such as Parkinson's disease. An understanding of the mechanisms that influence nAChR expression and function is therefore important. Because the dopamine precursor l-DOPA is the most commonly used therapeutic agent for Parkinson's disease, we investigated the effects of l-DOPA treatment on striatal nAChR expression in unlesioned and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned monkeys. In unlesioned animals, l-DOPA (15 mg/kg) administered twice daily for 2 weeks decreased both 125I-epibatidine and [125I]iodo-3-[2(S)-azetidinylmethoxy]pyridine (A-85380) binding sites in the caudate and putamen, but did not affect 125I-alpha-CtxMII sites. alpha-CtxMII inhibition of striatal 125I-epibatidine and [125I]A-85380 binding with alpha-CtxMII suggest that there are both high- (Ki < 0.2 nM) and low-affinity (Ki > 100 nM) alpha-CtxMII-sensitive sites, as well as alpha-CtxMII-resistant sites, and that l-DOPA treatment influences only the low-affinity alpha-CtxMII-sensitive subtype. The l-DOPA effect was selective for striatal nAChRs with no change in cortical sites. Monkeys with severe nigrostriatal damage did not exhibit l-DOPA-induced declines in striatal nAChRs, suggesting that l-DOPA primarily affects nAChRs associated with dopaminergic terminals. In summary, these data show that l-DOPA treatment decreases nAChR expression, in contrast with the well established up-regulation of these sites by chronic nicotine exposure. Furthermore, they demonstrate preferential l-DOPA regulation of a novel low-affinity alpha-CtxMII-sensitive site. These declines in nAChRs with l-DOPA may be relevant to both the therapeutic and side effect profiles of l-DOPA therapy in Parkinson's disease.
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Affiliation(s)
- Maryka Quik
- The Parkinson's Institute, 1170 Morse Ave., Sunnyvale, CA 94089-1605, USA.
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394
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Abstract
Nicotine is the crucial component in tobacco that underlies smoking behavior; however, the effects of nicotine can vary in both human and animal studies. Recent data from knockout mouse studies, neurotransmitter release studies and electrophysiological experiments support the hypothesis that conflicting behavioral effects elicited by nicotine can result from the activation of different subtypes of nicotinic acetylcholine receptors and the stimulation of antagonistic neuronal pathways. Thus, small differences in the activation state, connectivity or sensitivity of neuronal pathways among individuals might result in large differences in behavioral responses to nicotine. An understanding of the molecular and cellular processes that oppose nicotine reinforcement will be crucial for the development of new interventions to initiate smoking cessation or to prevent the transition from occasional smoking to dependence.
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Affiliation(s)
- Marina R Picciotto
- Department of Psychiatry, Yale University School of Medicine, 34 Park Street-3rd Floor Research, New Haven, CT 06508, USA.
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395
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Differential desensitization and distribution of nicotinic acetylcholine receptor subtypes in midbrain dopamine areas. J Neurosci 2003. [PMID: 12716925 DOI: 10.1523/jneurosci.23-08-03176.2003] [Citation(s) in RCA: 247] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Although many psychopharmacological factors contribute to nicotine addiction, midbrain dopaminergic systems have received much attention because of their roles in reinforcement and associative learning. It is generally thought that the mesocorticolimbic dopaminergic system is important for the acquisition of behaviors that are reinforced by the salient drives of the environment or by the inappropriate stimuli of addictive drugs. Nicotine, as obtained from tobacco, can activate nicotinic acetylcholine receptors (nAChRs) and excite midbrain neurons of the mesocorticolimbic system. Using midbrain slices from rats, wild-type mice, and genetically engineered mice, we have found differences in the nAChR currents from the ventral tegmental area (VTA) and the substantia nigra compacta (SNc). Nicotinic AChRs containing the alpha7 subunit (alpha7* nAChRs) have a low expression density. Electrophysiological analysis of nAChR currents, autoradiography of [125I]-alpha-bungarotoxin binding, and in situ hybridization revealed that alpha7* nAChRs are more highly expressed in the VTA than the SNc. In contrast, beta2* nAChRs are move evenly distributed at a higher density in both the VTA and SNc. At the concentration of nicotine obtained by tobacco smokers, the slow components of current (mainly mediated by beta2* nAChRs) become essentially desensitized. However, the minority alpha7* component of the current in the VTA/SNc is not significantly desensitized by nicotine in the range < or =100 nm. These results suggest that nicotine, as obtained from tobacco, can have multiple effects on the midbrain areas by differentially influencing dopamine neurons of the VTA and SNc and differentially desensitizing alpha7* and non-alpha7 nAChRs.
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396
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Quik M, Sum JD, Whiteaker P, McCallum SE, Marks MJ, Musachio J, McIntosh JM, Collins AC, Grady SR. Differential declines in striatal nicotinic receptor subtype function after nigrostriatal damage in mice. Mol Pharmacol 2003; 63:1169-79. [PMID: 12695545 DOI: 10.1124/mol.63.5.1169] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nigrostriatal damage leads to a reduction in striatal nicotinic acetylcholine receptors (nAChRs) in rodents, monkeys, and patients with Parkinson's disease. The present studies were undertaken to investigate whether these nAChR declines are associated with alterations in striatal nAChR function and, if so, to identify the receptor subtypes involved. To induce nigrostriatal damage, mice were injected with the selective dopaminergic toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We measured [(125)I]3 beta-(4-iodophenyl)tropane-2 beta-carboxylic acid isopropyl ester (RTI-121, dopamine transporter), (125)I-alpha-conotoxin MII (putative alpha 6-containing sites in the central nervous system), (125)I-epibatidine (multiple sites), 5-[(125)I]iodo-3-[2(S)-azetidinylmethoxy]pyridine-2HCl ([(125)I]A85380; beta2-containing sites), and (125)I-alpha-bungarotoxin (alpha 7-containing sites) binding in brains from control and MPTP-treated mice, as well as nAChR function by [(3)H]dopamine release, [(3)H]GABA release, and [(86)Rb(+)] efflux. After MPTP treatment, declines were observed in striatal dopamine transporter levels, both binding and functional measures of striatal alpha-conotoxin MII-sensitive nAChRs, and selected measures of striatal alpha-conotoxin MII-resistant nAChRs. In contrast, (125)I-alpha-bungarotoxin binding sites were not altered after nigrostriatal damage. The changes in striatal nAChRs were selective, with no declines in cortex, thalamus, or septum. Those striatal binding and functional measures of nAChRs that decreased with MPTP treatment correlated with dopamine transporter declines, an observation suggesting that the binding and functional changes in nAChRs are limited to dopaminergic terminals. The present results are the first to demonstrate differential alterations in nAChR subtype function after nigrostriatal damage, with a close correspondence between changes in receptor binding sites and function. These data suggest that the declines in nAChR sites observed in Parkinson's disease brains may be of functional significance.
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Affiliation(s)
- Maryka Quik
- The Parkinson's Institute, Sunnyvale, California 94089-1605, USA.
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397
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Chi H, de Wit H. Mecamylamine attenuates the subjective stimulant-like effects of alcohol in social drinkers. Alcohol Clin Exp Res 2003; 27:780-6. [PMID: 12766622 DOI: 10.1097/01.alc.0000065435.12068.24] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Recent studies have implicated central nicotinic cholinergic receptor systems in the reinforcing properties of alcohol. In laboratory animals, mecamylamine, a central nicotinic receptor antagonist, reduces the consumption of and preference for alcohol. This study investigated the effect of mecamylamine on the subjective responses to alcohol in humans. It was hypothesized that mecamylamine (7.5 and 15 mg) would attenuate the stimulant-like subjective effects of alcohol (0.8 g/kg) and decrease the self-reported desire to consume additional alcohol beverages. METHODS Fourteen male and 13 female nonsmokers participated in 6 laboratory sessions. During each session, subjects received, in randomized order under double-blinded conditions, a capsule containing mecamylamine (7.5 or 15 mg) or placebo followed by a beverage containing alcohol (0.8 g/kg) or placebo. Physiologic and subjective-effect measures were taken at 30-min intervals for 2 hr after beverage consumption. RESULTS Mecamylamine attenuated the stimulant and euphoric effects of alcohol and reduced the self-reported desire to consume additional alcohol beverages. This effect was most pronounced in men, even though women exhibited greater physiologic reactions to mecamylamine. CONCLUSIONS These findings suggest that nicotinic cholinergic receptors are involved in mediating some of the stimulant-like effects of alcohol.
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Affiliation(s)
- Henry Chi
- Department of Psychiatry, University of Chicago, 5841 S. Maryland Avenue, Chicago, IL 60637, USA
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398
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Gerdeman GL, Partridge JG, Lupica CR, Lovinger DM. It could be habit forming: drugs of abuse and striatal synaptic plasticity. Trends Neurosci 2003; 26:184-92. [PMID: 12689769 DOI: 10.1016/s0166-2236(03)00065-1] [Citation(s) in RCA: 341] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Drug addiction can take control of the brain and behavior, activating behavioral patterns that are directed excessively and compulsively toward drug usage. Such patterns often involve the development of repetitive and nearly automatic behaviors that we call habits. The striatum, a subcortical brain region important for proper motor function as well as for the formation of behavioral habits, is a major target for drugs of abuse. Here, we review recent studies of long-term synaptic plasticity in the striatum, emphasizing that drugs of abuse can exert pronounced influences on these processes, both in the striatum and in the dopaminergic midbrain. Synaptic plasticity in the ventral striatum appears to play a prominent role in early stages of drug use, whereas dopamine- and endocannabinoid-dependent synaptic plasticity in the dorsal striatum could contribute to the formation of persistent drug-related habits when casual drug use progresses towards compulsive drug use and addiction.
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Affiliation(s)
- Gregory L Gerdeman
- Department of Pharmacology, University of Arizona Health Sciences Center, Tucson, AZ 85724, USA.
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399
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400
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Zhou FM, Wilson C, Dani JA. Muscarinic and nicotinic cholinergic mechanisms in the mesostriatal dopamine systems. Neuroscientist 2003; 9:23-36. [PMID: 12580337 DOI: 10.1177/1073858402239588] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The striatum and its dense dopaminergic innervation originating in the midbrain, primarily from the substantia nigra pars compacta and the ventral tegmental area, compose the mesostriatal dopamine (DA) systems. The nigrostriatal system is involved mainly in motor coordination and in disorders such as Tourette's syndrome, Huntington's disease, and Parkinson's disease. The dopaminergic projections from the ventral tegmental area to the striatum participate more in the processes that shape behaviors leading to reward, and addictive drugs act upon this mesolimbic system. The midbrain DA areas receive cholinergic innervation from the pedunculopontine tegmentum and the laterodorsal pontine tegmentum, whereas the striatum receives dense cholinergic innervation from local interneurons. The various neurons of the mesostriatal systems express multiple types of muscarinic and nicotinic acetylcholine receptors as well as DA receptors. Especially in the striatum, the dense mingling of dopaminergic and cholinergic constituents enables potent interactions. Evidence indicates that cholinergic and dopaminergic systems work together to produce the coordinated functioning of the striatum. Loss of that cooperative activity contributes to the dysfunction underlying Parkinson's disease.
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Affiliation(s)
- Fu-Ming Zhou
- Division of Neuroscience, Baylor College of Medicine, Houston, Texas 77030-3498, USA
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