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Presynaptic α4β2 nicotinic acetylcholine receptors increase glutamate release and serotonin neuron excitability in the dorsal raphe nucleus. J Neurosci 2013; 32:15148-57. [PMID: 23100436 DOI: 10.1523/jneurosci.0941-12.2012] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Several behavioral effects of nicotine are mediated by changes in serotonin (5-HT) release in brain areas that receive serotonergic afferents from the dorsal raphe nucleus (DRN). In vitro experiments have demonstrated that nicotine increases the firing activity in the majority of DRN 5-HT neurons and that DRN contains nicotinic acetylcholine receptors (nAChRs) located at both somata and presynaptic elements. One of the most common presynaptic effects of nicotine is to increase glutamate release. Although DRN receives profuse glutamatergic afferents, the effect of nicotine on glutamate release in the DRN has not been studied in detail. Using whole-cell recording techniques, we investigated the effects of nicotine on the glutamatergic input to 5-HT DRN neurons in rat midbrain slices. Low nicotine concentrations, in the presence of bicuculline and tetrodotoxin (TTX), increased the frequency but did not change the amplitude of glutamate-induced EPSCs, recorded from identified 5-HT neurons. Nicotine-induced increase of glutamatergic EPSC frequency persisted 10-20 min after drug withdrawal. This nicotinic effect was mimicked by exogenous administration of acetylcholine (ACh) or inhibition of ACh metabolism. In addition, the nicotine-induced increase in EPSC frequency was abolished by blockade of α4β2 nAChRs, voltage-gated calcium channels, or intracellular calcium signaling but not by α7 nAChR antagonists. These data suggest that both nicotine and endogenous ACh can increase glutamate release through activation of presynaptic α4β2 but not α7 nAChRs in the DRN. The effect involves long-term changes in synaptic function, and it is dependent on voltage-gated calcium channels and presynaptic calcium stores.
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Chang B, Daniele CA, Gallagher K, Madonia M, Mitchum RD, Barrett L, Vezina P, McGehee DS. Nicotinic excitation of serotonergic projections from dorsal raphe to the nucleus accumbens. J Neurophysiol 2011; 106:801-8. [PMID: 21593391 DOI: 10.1152/jn.00575.2010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Tobacco use is a major public health problem, and although many smokers report that they want to quit, only a small percentage succeed. Side effects associated with nicotine withdrawal, including depression, anxiety, and restlessness, certainly contribute to the low success rate. The dorsal raphe nucleus (DRN) is a serotonergic center with many functions, including control of mood and emotional state. We investigated the effect of nicotine on DRN neurons that project to the nucleus accumbens (NAc), an area involved in reward-related behaviors. Using a retrograde labeling method, we found that 75% of DRN-NAc projection neurons are serotonergic. In coronal slices that include the DRN, whole cell recordings were conducted on neurons identified by fluorescent backlabeling from NAc or randomly selected within the nucleus. Nicotine increased action potential firing rates in a subset of DRN neurons. Voltage-clamp recording revealed nicotinic acetylcholine receptor (nAChR)-mediated inward currents that contribute to the nicotine-induced excitation. Nicotinic receptors also indirectly affect excitability by modulating synaptic inputs to these neurons. Nicotine enhanced excitatory glutamatergic inputs to a subset of DRN-NAc projection neurons, while inhibitory γ-aminobutyric acid (GABA)ergic inputs were modulated either positively or negatively in a subset of these neurons. The net effect of nAChR activation is enhancement of serotonergic output from DRN to the NAc, which may contribute to the effects of nicotine on mood and affect.
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Affiliation(s)
- Ben Chang
- Department of Anesthesia & Critical Care, University of Chicago, 5841 South Maryland Ave., MC 4028, Chicago, IL 60637, USA
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Villégier AS, Belluzzi JD, Leslie FM. Serotonergic mechanism underlying tranylcypromine enhancement of nicotine self-administration. Synapse 2010; 65:479-89. [PMID: 20936688 DOI: 10.1002/syn.20864] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Accepted: 09/17/2010] [Indexed: 11/06/2022]
Abstract
Although nicotine is generally considered to be the main psychoactive component of tobacco, growing evidence highlights the importance of nonnicotine compounds in smoking reinforcement. Monoamine oxidase (MAO) inhibition is a major consequence of smoking and MAO inhibitors, such as tranylcypromine, increase nicotine reinforcement. Tranylcypromine has multiple pharmacological effects, increasing monoamine release for a few hours immediately after its administration and blocking MAO activity for several days. To assess the relative role of these two actions, adult male rats were tested in consecutive daily 3-h sessions for self-administration of nicotine (3 μg kg⁻¹) inj⁻¹, i.v.) either 20 or 1 h following administration of tranylcypromine (3 mg kg⁻¹). Both paradigms were shown to produce highly significant inhibition of MAO activity. However, whereas animals readily acquired self-administration when pretreated with tranylcypromine 1 h prior to testing, they did not with the longer pretreatment interval. Such animals did immediately acquire nicotine self-administration when the tranylcypromine pretreatment interval was switched to 1 h prior to testing on Day 4, indicating that an acute effect of the MAO inhibitor was responsible for enhanced nicotine reinforcement. Several lines of evidence implicate serotonin (5-HT) as the mediator of this enhancement: (1) Tranyclypromine-enhanced nicotine reinforcement was blocked by the 5-HT₂ receptor antagonists, ritanserin and ketanserin; (2) parachloroamphetamine (PCA), a 5-HT releaser, also enhanced nicotine self-administration in animals in which MAO activity was inhibited; (3) pretreatment with tranylcypromine increased PCA-induced 5-HT overflow in the nucleus accumbens. These findings suggest that MAO inhibition enhances serotonergic transmission, which serves a critical role in the reinforcing effects of nicotine.
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Affiliation(s)
- Anne-Sophie Villégier
- Department of Pharmacology, School of Medicine, University of California, Irvine, California 92697, USA.
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Villégier AS, Gallager B, Heston J, Belluzzi JD, Leslie FM. Age influences the effects of nicotine and monoamine oxidase inhibition on mood-related behaviors in rats. Psychopharmacology (Berl) 2010; 208:593-601. [PMID: 20069419 PMCID: PMC2813528 DOI: 10.1007/s00213-009-1760-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Accepted: 12/14/2009] [Indexed: 01/20/2023]
Abstract
RATIONALE Epidemiological studies have demonstrated a comorbidity of smoking with depression and anxiety, particularly during adolescence. However, few animal studies have considered possible synergistic interactions between nicotine and other tobacco smoke constituents, such as monoamine oxidase (MAO) inhibitors, in the regulation of mood. OBJECTIVES The aim of the study was to test the hypothesis that nicotine combined with the irreversible MAO inhibitor, tranylcypromine, will differentially affect depression- and anxiety-related behaviors in adolescent and adult rats. METHODS Nicotine (0, 0.05, 0.2 mg/kg, s.c.) and tranylcypromine (3 mg/kg, i.p.) were tested separately, or together, on male rats aged postnatal days 30 and 68, in three mood-related behavioral tests: forced swim test (FST), elevated plus maze (EPM), and open field. RESULTS Nicotine (0.2 mg/kg) in adults significantly decreased floating time in the FST and increased time spent in the open arm of the EPM, with no change in locomotor activity. Tranylcypromine pretreatment combined with nicotine (0.2 mg/kg) significantly increased locomotor activity and time spent in the center of the open field. Whereas nicotine alone had no significant effect on adolescents, it significantly increased locomotor activity and decreased floating time in the FST when combined with tranylcypromine pretreatment. CONCLUSIONS There is an age-dependent effect of nicotine, alone and in combination with MAO inhibition, on mood-related behaviors. Whereas nicotine alone induces mood improvement in adults, it has no effect on adolescents. Nicotine combined with tranylcypromine has unique, age-dependent effects. Thus, experimental studies of smoking should consider both age and other tobacco constituents, such as MAO inhibitors, as critical factors.
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Affiliation(s)
- Anne-Sophie Villégier
- Department of Pharmacology, School of Medicine, University of California, Irvine, CA 92697, USA.
| | - Brittney Gallager
- Department of Pharmacology, School of Medicine, University of California, Irvine, CA 92697 USA
| | - Jon Heston
- Department of Pharmacology, School of Medicine, University of California, Irvine, CA 92697 USA
| | - James D. Belluzzi
- Department of Pharmacology, School of Medicine, University of California, Irvine, CA 92697 USA
| | - Frances M. Leslie
- Department of Pharmacology, School of Medicine, University of California, Irvine, CA 92697 USA ,Department of Anatomy and Neurobiology, School of Medicine, University of California, Irvine, CA 92697 USA
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Inhibition of monoamine oxidases desensitizes 5-HT1A autoreceptors and allows nicotine to induce a neurochemical and behavioral sensitization. J Neurosci 2009; 29:987-97. [PMID: 19176807 DOI: 10.1523/jneurosci.3315-08.2009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Although nicotine is generally considered to be the main compound responsible for addictive properties of tobacco, experimental data indicate that nicotine does not exhibit all the characteristics of other substances of abuse. We recently showed that a pretreatment with mixed irreversible monoamine oxidases inhibitors (MAOIs), such as tranylcypromine, triggers a locomotor response to nicotine in mice and allows maintenance of behavioral sensitization to nicotine in rats. Moreover, we showed by microdialysis in mice that behavioral sensitization induced by compounds belonging to main groups of drugs of abuse, such as amphetamine, cocaine, morphine, or alcohol, was underlain by sensitization of noradrenergic and serotonergic neurons. Here, this neurochemical sensitization was tested after nicotine, tranylcypromine, or a mixture of both compounds. Data indicate that, whereas neither repeated nicotine nor repeated tranylcypromine alone has any effect by itself, a repeated treatment with a mixture of nicotine and tranylcypromine induces both behavioral sensitization and sensitization of noradrenergic and serotonergic neurons. The development of neurochemical and behavioral sensitizations is blocked by prazosin and SR46349B [(1Z,2E)-1-(2-fluoro-phenyl)-3-(4-hydroxyphenyl)-prop-2-en-one-O-(2-dimethylamino-ethyl)-oxime hemifumarate], two antagonists of alpha1b-adrenergic and 5-HT(2A) receptors, respectively, but not by SCH23390 [R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride], a D(1) receptor antagonist. Finally, we found that pretreatments with WAY 100635 [N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclo-hexane carboxamide trihydrochloride], a 5-HT(1A) receptor antagonist, can also induce a behavioral and neurochemical sensitization to repeated nicotine. Complementary experiments with 8-OHDPAT (8-hydroxy-dipropylamino-tetralin), a 5-HT(1A) receptor agonist, and analysis of 5-HT(1A) receptors expression in the dorsal raphe nucleus after a tranylcypromine injection indicate that MAOIs contained in tobacco desensitize 5-HT(1A) autoreceptors to trigger the strong addictive properties of tobacco.
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David SP, Johnstone EC, Murphy MF, Aveyard P, Guo B, Lerman C, Munafò MR. Genetic variation in the serotonin pathway and smoking cessation with nicotine replacement therapy: new data from the Patch in Practice trial and pooled analyses. Drug Alcohol Depend 2008; 98:77-85. [PMID: 18562131 PMCID: PMC4439462 DOI: 10.1016/j.drugalcdep.2008.04.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2008] [Revised: 04/20/2008] [Accepted: 04/23/2008] [Indexed: 11/24/2022]
Abstract
The serotonin pathway has been implicated in nicotine dependence and may influence smoking cessation. Therefore, 792 cigarette smokers from the Patch in Practice trial were genotyped for the tryptophan hydroxylase (TPH1 A779C), serotonin transporter (SLC6A45-HTTLPR), and 5-HT1A (HTR1A C-1019G) polymorphisms. Cox regression analysis did not demonstrate significant effects of any of the three genotypes on relapse to smoking: TPH1 (Reference AA; AC: hazard ratio (HR) 0.99, 95% confidence interval (CI) 0.78, 1.24, p=0.90; CC: HR 0.93, 95% CI 0.73, 1.18, p=0.55); 5-HTTLPR (Reference LL; SL: HR 1.01, 95% CI 0.85, 1.20, p=0.90; SS: HR 1.13, 95% CI 0.91, 1.39, p=0.27); HTR1A (Reference CC; CG: HR 1.04, 95% CI 0.86, 1.25, p=0.70; GG: HR 1.01, 95% CI 0.82, 1.24, p=0.93). Moreover, pooled analyses of data from all three extant pharmacogenetic NRT trials (N=1398) found no significant effect of 5-HTTLPR genotype on continuous abstinence at 12-week (Reference LL; SL: odds ratio (OR)=1.25, 95% CI 0.89, 1.74, p=0.19; SS: OR=1.31, 95% CI 0.86, 1.98, p=0.21) or 26-week follow-up (Reference LL; SL: OR=0.93, 95% CI 0.64, 1.33, p=0.68; SS: OR=1.00, 95% CI 0.63, 1.58, p=1.00). These data do not support a statistically or clinically significant moderating effect of these specific 5-HT pathway genetic variants on smoking cessation. However, the possibility remains that other variants in these or other 5-HT genes may influence NRT efficacy for smoking cessation in treatment seeking smokers.
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Affiliation(s)
- Sean P. David
- Department of Family Medicine, Center for Primary Care & Prevention, The Warren Alpert Medical School of Brown University, 111 Brewster Street, Pawtucket, RI 02806, USA,Corresponding author at: Brown University Center for Primary Care & Prevention, 111 Brewster Street, Pawtucket, RI 02860, USA. Tel.: +1 401 729 2071; fax: +1 401 729 2494. (S.P. David)
| | - Elaine C. Johnstone
- Department of Clinical Pharmacology, University of Oxford, Old Road Campus Research Building, Old Road Campus, Oxford OX3 7DQ, UK
| | - Michael F.G. Murphy
- Department of Paediatrics, Childhood Cancer Research Group, University of Oxford, 57 Woodstock Road, Oxford OX2 6HJ, UK
| | - Paul Aveyard
- Department of Primary Care and General Practice, University of Birmingham, Edgbaston B15 2TT, UK
| | - Boliang Guo
- Department of Public Health and Epidemiology, University of Birmingham, Birmingham B15 2TT, UK
| | - Caryn Lerman
- Department of Psychiatry, Tobacco Use Research Center, University of Pennsylvania, 3535 Market Street, Philadelphia, PA 19194, USA
| | - Marcus R. Munafò
- Department of Experimental Psychology, University of Bristol, 12a Priory Road, Bristol BS8 1TU, UK
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Acute nicotine reduces and repeated nicotine increases spontaneous activity in male and female Lewis rats. Pharmacol Biochem Behav 2008; 91:150-4. [PMID: 18644403 DOI: 10.1016/j.pbb.2008.06.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2008] [Revised: 06/13/2008] [Accepted: 06/27/2008] [Indexed: 11/22/2022]
Abstract
The Lewis (LEW) strain of rat appears more sensitive to nicotine than other strains in self-administration, conditioned place preference, and drug discrimination behavioral studies. The present study sought to further evaluate the behavioral effects of chronic nicotine treatment in the LEW strain by assessing spontaneous activity, which has consistently revealed sensitization to chronic nicotine administration in Sprague Dawley (SD) rats. High active and low active male and female LEW rats (N=8 per group) were treated twice daily with either nicotine (0.4 mg/kg, sc) or vehicle for 14 consecutive days. Regardless of baseline activity level or sex, spontaneous activity was significantly decreased, compared to saline-treated rats, after a single nicotine injection. However, spontaneous activity increased in both low- and high-activity rats (both sexes) over the two weeks of nicotine administration to levels that were significantly higher than saline-treated rats. Based on these findings, acute and chronic nicotine administration had greater suppressive and enhancing effects on spontaneous activity in LEW rats compared to other strains of rats previously studied. These results further clarify the behavioral sensitivity of the LEW strain of rat to nicotine exposure and lend credence to the role of genetics in the individual susceptibility to nicotine dependence.
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