5-HT1A receptor agonists buspirone and gepirone attenuate apomorphine-induced aggressive behaviour in adult male Wistar rats.

We have studied the effects of acute serotonin (5-HT) 5-HT1A receptor agonist buspirone (0.5, 1.0, 2.5 and 5.0 mg/kg, s.c.), gepirone (5.0 and 10 mg/kg, s.c.), and 8-OH-DPAT (0.1, 0.25, and 0.5 mg/kg, i.p.) treatment on the apomorphine-induced aggressive behaviour in adult male Wistar rats. Buspirone in doses of 2.5 and 5.0 mg/kg completely blocked, gepirone (10 mg/kg) significantly attenuated the aggressiveness, and 8-OH-DPAT abolished aggressive behaviour only in the lowest dose used (0.1 mg/kg) which effect disappeared in higher doses. The antiaggressive effect of buspirone (2.5 mg/kg) and gepirone (10 mg/kg) was not reversed by a 5-HT1A receptor antagonist WAY 100635 (0.3 mg/kg). All 5-HT1A receptor agonists tested dose-dependently decreased the exploratory behaviour of experimentally naive rats, while buspirone (2.5 mg/kg) and gepirone (10 mg/kg) had only a weak effect on the locomotor activity and stereotyped behaviour in the apomorphine-pre-sensitised rats. In conclusion, our experiments demonstrate the 5-HTIA receptors may be involved in the mediation of the apomorphine-induced aggressive behaviour in adult male Wistar rats. However, the prominent antiaggressive effect of buspirone, and to a lesser extent--gepirone, seems to be mediated by some other mechanisms, evidently via the dopamine D2 receptors.