Differential effects of CGS 12066B and CP-94,253 on murine social and agonistic behaviour.

Although it has been previously proposed that 5-HT1B agonism specifically attenuates rodent agonistic behaviour, more recent investigations have indicated that such influences may be ancillary to an anxiogenic effect. The present study examined the influences of two 5-HT1B agonists, CGS 12066B and CP-94,253, on murine agonistic behaviour. In a resident-intruder paradigm, CGS 12066B (0.5-5.0 mg/kg) decreased resident offensive aggression, social interest, and exploration while dose-dependently enhancing defensive behaviours across the dose range tested. CP-94,253 (2.5-10.0 mg/kg) also reduced elements of resident offensive behaviour whereas defensive behaviours were largely unchanged. Some elements of resident nonsocial and social behaviour were enhanced at 2.5 and 5.0 mg/kg but decreased at 10.0 mg/kg. The behavioural profile of CP-94,253, but not CGS 12066B, supports the proposal that 5-HT1B receptors inhibit agonistic behaviour without concomitant sedative or anxiogenic effects. Findings are discussed in relation to 5-HT1A/1B/2C receptors involved in agonistic behaviour and anxiety.