Blockade of nicotinic acetylcholine receptor enhances the responsiveness to bupropion in the mouse forced swim test.

The objective of the present study is to investigate the role of α4, α5, α6 or ß2 nAChR subunits in the antidepressant-like effect of bupropion. Adult male mice were treated with subcutaneous acute doses of bupropion (3 and 10 mg/kg) 30 min before the forced swim test (FST) in α4, α5, α6, or ß2 nAChR subunit knockout (KO) and wild-type (WT) mice. In addition, the effects of ß2* antagonist dihydro-ß-erythroidine (DHßE, 3 mg/kg) on antidepressant-like effects of bupropion in C57BL/6 J mice were assessed. Our results showed that baseline immobility and climbing time did not differ between KO and corresponding WT mice except for ß2 KO. Bupropion significantly decreased immobility time and increased climbing time in the α4, α6 and ß2 nAChR KO mice in comparison to WT littermates, indicating that lack of these nAChR subunits enhanced antidepressant effects of bupropion. On the contrary, the α5 nAChR subunit deletion did not alter the FST behavior in the bupropion-treated mice. Not only in the transgenic mice, bupropion also showed antidepressant-like effects in the WT mice. In addition, DHßE pretreatment before bupropion administration resulted in decreased immobility time and increased climbing time. Taken together, the present study provides evidence on the involvement of α4*, α6*, and ß2* (* indicates possible presence of other subunits) nAChRs in the antidepressant-like effects of bupropion in the FST.

Knockout of alpha 5 nicotinic acetylcholine receptors subunit alters ethanol-mediated behavioral effects and reward in mice.

Evidence suggests that there is an association between polymorphisms in the α5 nicotinic acetylcholine receptor (nAChR) subunit and risk of developing alcohol dependence in humans. The α5 nAChR subunit has also recently been shown to modulate some of the acute response to ethanol in mice. The aim of the current study was to further characterize the role of α5-containing (α5*) nAChRs in acute ethanol responsive behaviors, ethanol consumption and ethanol preference in mice. We conducted a battery of tests in male α5 knockout (KO) mice for a range of ethanol-induced behaviors including hypothermia, hypnosis, and anxiolysis. We also investigated the effects of α5* nAChR on ethanol reward using the Conditioned Place Preference (CPP) assay. Further, we tested the effects of gene deletion on drinking behaviors using the voluntary ethanol consumption in a two-bottle choice assay and Drinking in the Dark (DID, with or without stress) paradigm. We found that deletion of the α5 nAChR subunit enhanced ethanol-induced hypothermia, hypnosis, and an anxiolytic-like response in comparison to wild-type controls. The α5 KO mice showed reduced CPP for ethanol, suggesting that the rewarding properties of ethanol are decreased in mutant mice. Interestingly, Chrna5 gene deletion had no effect on basal ethanol drinking behavior, or ethanol metabolism, but did decrease ethanol intake in the DID paradigm following restraint stress. Taken together, we provide new evidence that α5 nAChRs are involved in some but not all of the behavioral effects of ethanol. Our results highlight the importance of nAChRs as a possible target for the treatment of alcohol dependence.

Assessment of the influence of histaminergic actions on cocaine-like effects of 3alpha-diphenylmethoxytropane analogs.

Previous studies demonstrated that analogs of benztropine (BZT) possess high affinity for the dopamine (DA) transporter (DAT) but generally have behavioral effects different from those of cocaine, suggesting either unique actions at the DA transporter or that another action of these drugs interferes with cocaine-like effects. Because the parent compound has histamine-antagonistic effects, the affinity of its analogs for histamine H(1), H(2), and H(3) receptors were compared with DA transporter affinity to assess whether those differences predicted the amount of cocaine-like activity. All of the compounds displaced [(3)H]mepyramine from H(1), [(125)I]iodoaminopotentidine from H(2), and [(3)H]N-alpha-methylhistamine from H(3) histamine receptors with affinities ranging from 15.7 to 37,600, 218 to >4430, and 4040 to >150,000 nM, respectively. Affinities at histamine H(1) receptors were, respectively, approximately 25- or 300-fold greater than those at H(2) or H(3) histamine receptors. Relative affinities for H(1) and DAT binding did not reliably predict the degree of cocaine-like stimulation of locomotor activity. In addition, interactions of various histaminic agents with cocaine assessed whether an action at any of the histamine sites could interfere with cocaine-like effects. None of the histaminic agents fully substituted for cocaine in rats trained to discriminate 10 mg/kg cocaine from saline nor did any of the compounds antagonize or otherwise diminish the discriminative stimulus effects of cocaine. The results suggest that affinity for histamine receptors cannot account for the diminished cocaine-like effects of the BZT analogs and suggest alternatively that these compounds have actions different from those of cocaine but likely mediated by their interaction with the DAT.