The group III mGlu receptor agonist ACPT-I exerts anxiolytic-like but not antidepressant-like effects, mediated by the serotonergic and GABA-ergic systems

Our earlier studies have demonstrated that (1S,3R,4S)-1-aminocyclo-pentane-1,3,4-tricarboxylic acid ACPT-I, a group III mGlu receptor agonist, produced anxiolytic-like and antidepressant-like actions after central administration. Here we describe the anxiolytic-like effects of ACPT-I after intraperitoneal administration in the stress-induced hyperthermia (SIH), elevated plus-maze (PMT) tests in mice and in the Vogel test in rats. However, the compound did not produce antidepressant-like effects in the tail suspension test (TST) or in the forced swim test (FST) in mice. The potential anxiolytic effect of ACPT-I (20 mg/kg) in the SIH test was inhibited by the benzodiazepine receptor antagonist flumazenil (given i.p., 10 mg/kg), and by a 5-HT1A receptor antagonist N-{2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl}-N-(2-pyridynyl) cyclohexane-carboxamide (WAY100635) (0.1 mg/kg s.c.). At the same time, ritanserin (0.5 mg/kg i.p.), the 5-HT2A/C receptor antagonist, did not change the anxiolytic-like effects of ACPT-I. The results of these studies indicate that the GABA-ergic and serotonergic systems are involved in the potential anxiolytic action of ACPT-I.