Comparison of antipsychotic activity and discriminative stimulus effects of the novel acylprolyltyrosine containing compound, GZR-123, and sulpiride.

The present experiment has been performed to determine the pharmacological profile of a newly synthesized systematically active prolyltyrosine containing compound, caproyl-L-Pro-L-Tyr methyl ester (GZR-123), and to compare it with that of the standard atypical benzamide neuroleptic, sulpiride. GZR-123 demonstrated antagonistic activity on apomorphine-induced climbing and on L-DOPA-dependent extrapolatory behavior in dose ranging between 0.4-4.0 mg/kg i.p.. It did not provoke a cataleptogenic effect or lethality, even at doses much higher than those causing antidopamine effects (more than 500 mg/kg). The effective doses of sulpiride in the above-listed antidopamine tests were shown to be 17.5 and 16.0 mg/kg i.p. correspondingly. Although these doses of sulpiride did not demonstrate cataleptogenic effects, an increase of the dose level to 120 mg/kg induced pronounced catalepsy. Both GZR-123 (6 mg/kg) and sulpiride (40 and 60 mg/kg) were investigated by training rats to discriminate each of them from saline in a two-lever, water-reinforcement operant procedure. Both GZR-123 and sulpiride demonstrated weak discriminability in this task. GZR-123 increased drug-associated lever selection when administered in doses of 2 and 6 mg/kg, for sulpirirde these doses were demonstrated to be 25-60 mg/kg. In contrast to GZR-123, which did not provoke a sedative effect, sulpiride in higher discriminable doses caused sedation, which stems probably from the motivational, but not from the motor deficit.