Glycine Receptors Involved in Acamprosate's Modulation of Accumbal Dopatnine Levels: An In Vivo Microdialysis Study

Background: Glycine receptors (GlyRs) in the nucleus accumbens (nAc) and nicotinic acetylcholine receptors (nAChRs) in the ventral tegmental area (VTA) have been suggested to be involved in the positive reinforcing and dopamine elevating effects of ethanol. Recent studies have also shown that ethanol high-preferring rats substantially decrease their ethanol intake when treated with a glycine transporter I inhibitor (ORG 25935). Acamprosate, a drug used for relapse prevention in treatment of alcohol dependence, has also been demonstrated to elevate extracellular dopamine levels in the nAc. However, the underlying mechanism of action of acamprosate is not fully understood. Here we investigated whether acamprosate interferes with a neuronal circuitry that previously has been demonstrated to be involved in the dopamine elevating effects of ethanol and taurine. Methods: In vivo microdialysis in freely moving rats was Used to assess accumbal dopamine levels before and during local (nAc) or systemic administration of acamprosate. Results: Perfusion of 0.5 mM acamprosate in the nAc significantly increased dopamine levels. Pretreatment either with 10 mu M strychnine in the nAc or 100 mu M mecamylamine in the VTA, completely antagonized the acamprosate-induced elevation of accumbal dopamine levels. Also, systemic acamprosate administration elevated accumbal dopamine output, 111 effect that was abolished by local (nAc) pretreatment with 10 mu M strychnine. Conclusions: These results suggest that both systemic and local application of acamprosate elevate extracellular dopamine levels in the nAc by activating accumbal GlyRs. and, secondarily, tegmental nAChRs.