Sodium acamprosate and calcium exert additive effects on nucleus accumbens dopamine in the rat

Acamprosate (Campral® - calcium-bis[N-acetylhomotaurinate]) is one of few available pharmacotherapies for individuals suffering from alcohol use disorder. Previously, we suggested that acamprosate reduces ethanol intake by increasing dopamine in the nucleus accumbens (nAc), thereby partly substituting for alcohol's dopamine releasing effect. An experimental study suggested the calcium moiety of acamprosate to be the active component of the drug and to mediate the relapse preventing effect. The aim of the present study was to, by means of reversed in vivo microdialysis, elucidate if the dopamine elevating properties of acamprosate are mediated by N-acetylhomotaurine or by the calcium moiety. Male rats were equipped with a microdialysis probe in the nAc and received acute local treatment with regular acamprosate (CaAcamp 0.5 mM), calcium chloride (CaCl₂ 0.5 mM), sodium acamprosate (NaAcamp 0.5-1 mM), the glycine receptor (GlyR) antagonist strychnine (Stry 20 μM), or vehicle. In all experiments, extracellular levels of dopamine and taurine were examined. We found that local perfusion with both CaAcamp and CaCl₂ increased dopamine levels in a GlyR-dependent manner. NaAcamp did not influence dopamine levels, but concomitant administration with CaCl₂ resulted in an additive dopamine output compared to the drugs administrated alone. We also found CaAcamp and the combination of CaCl₂ and NaAcamp to increase accumbal taurine levels, suggesting that CaAcamp may act indirectly on GlyRs via taurine release. The present results indicate that both N-acetylhomotaurine and the calcium moiety of acamprosate have dopamine elevating properties within the nAc and that, in this respect, these substances are beneficial in combination.