Acamprosate does not antagonise the discriminative stimulus properties of amphetamine and morphine in rats

Acamprosate (calcium acetylhomotaurinate) is a GABA derivative that prevent s drinking relapses in a significant number of alcoholics. Since little is known about the interaction of acamprosate with other addictive drugs, we s tudied the effects of this agent (as sodium salt) in two groups of rats tra ined to discriminate, respectively, morphine (1.7 mg kg(-1) i.p.) or amphet amine (0.5 mg kg(-1) i.p.) from solvent in a two-lever fixed ratio 30 opera nt behaviour reinforced by water access. Accordingly to the finding that ac amprosate inhibits the action of excitatory aminoacids, its effects were co mpared with those of dizocilpine (MK-801), an NMDA antagonist. Results show that acamprosate (170 and 320 mg kg(-1) i.p.) produced a slight, and not s ignificant, shift to the left of generalization curves of both morphine and amphetamine without affecting response rates. In contrast, MK-801 potentia ted response rate effects of both morphine and amphetamine without affectin g their generalization curves. As far as discriminative stimuli participate in the relapsing process of addiction, our results do not predict a role o f acamprosate in the prevention of amphetamine or morphine abuse relapsing. (C) 1999 Academic Press.