Effects of acamprosate on neuronal receptors and ion channels expressed in Xenopus oocytes

Background: Acamprosate (calcium acetylhomotaurinate) has proven to be a moderately effective pharmacological adjunct for the treatment of alcoholism. However, the central nervous system mechanism by which acamprosate reduces alcohol relapse remains unclear. Here we survey a number of metabotropic receptors, ligand-gated ion channels, and voltage-gated ion channels, to determine if acamprosate has actions at these sites in the central nervous system. Methods: Xenopus oocytes were injected with cDNAs or cRNAs encoding metabotropic glutamate receptors 1 and 5, M1 muscarinic receptors, glycine alpha 1 homomeric and alpha 1 beta 1 heteromeric receptors, gamma-aminobutyric acid A (GABA(A) alpha 4 beta 3 delta, alpha 4 beta 3 gamma 2s, and alpha 1 beta 2 gamma 2s) receptors, vanilloid receptor 1, and various combinations of alpha and beta subunits of voltage-gated Na+ channels. Electrophysiological responses were measured using two-electrode voltage clamp parameters after activation with agonists or voltage steps (for the voltage-gated channels). Acamprosate (0.1 to 100 mu M) was pre-applied for 1 minute, followed by co-application with agonist. Acamprosate was also applied with ethanol to determine if it altered ethanol responses at some of these receptors and channels. Results: None of the receptors or ion channels responded to acamprosate alone. Acamprosate also failed to alter the activation of receptors or channels by agonists or after activation of voltage-gated channels. There was no effect of acamprosate on ethanol responses at GABA(A) alpha 1 beta 2 gamma 2s receptors or Na+ channels. Conclusions: Acamprosate does not significantly modulate the function of these receptors and ion channels at clinically relevant concentrations. Thus, the clinical effectiveness of acamprosate in the treatment of alcoholism is not likely due to direct effects on these receptors or ion channels.