The effect of acamprosate on the development of morphine-induced behavioral sensitization in rats.

Recently we have shown that the alcohol anti-craving drug acamprosate (calcium acetylhomotaurinate), a functional N-methyl-D-aspartate (NMDA) receptor antagonist which is used therapeutically to prevent relapse in weaned alcoholics, was also effective in suppressing (1) conditioned place aversion induced by morphine withdrawal, and (2) expression of morphine-induced behavioral sensitization. Here, we addressed the question of whether the development of behavioral sensitization, induced by daily injections of morphine (10 mg/kg) over a period of 10 days, could also be suppressed by repeated pretreatment with acamprosate (200 mg/kg). Repeated intermittent injections of morphine produced sensitization of locomotor activity and sniffing behavior. Acamprosate did not block the development of morphine-induced behavioral sensitization. This lack of effect on the development of this phenomenon is inconsistent with the view that NMDA receptor antagonists block the development of sensitization. We suggest that this may derive from the relatively low NMDA receptor-specific antagonism of acamprosate as compared to other NMDA receptor antagonists used in this model. In conclusion, the effect of acamprosate on morphine-induced behavioral sensitization seems to be restricted to the expression of this phenomenon.