EFFECTS OF SUN-8399, A POTENT AND SELECTIVE 5-HT1A AGONIST, ON CONFLICT BEHAVIOR AND AMBULATORY ACTIVITY IN MICE - COMPARISON WITH THOSE OFBUSPIRONE, TANDOSPIRONE AND DIAZEPAM

Behavioral effects of p.o. administration of SUN 8399, a selective 5-H T1A agonist, on the operant behavior under a MULT VI 1.5 min/FR 5-puni shment schedule of food reinforcement and on the ambulatory activity w ere evaluated in mice, and the characteristics were compared with thos e of other 5-HT1A agonists, buspirone and tandospirone, and the benzod iazepine diazepam. Diazepam (3 and 10 mg/kg) significantly increased t he punished response without eliciting any significant change in the n onpunished response; i.e., showing anticonflict action. SUN 8399 (3 - 30 mg/kg) and buspirone (1 - 10 mg/kg) did not significantly change ei ther the punished or non-punished responses. Tandospirone significantl y increased the non-punished response at 10 mg/kg, but significantly d ecreased both the punished and nonpunished responses at 30 mg/kg. The single administration of SUN 8399 (10 mg/kg), buspirone (3 and 30 mg/k g) and tandospirone (10 and 30 mg/kg) significantly increased the ambu latory activity, while diazepam tended to decrease it. The ambulation- increasing effect of methamphetamine (2 mg/kg, s.c.) was reduced by bu spirone (10 and 30 mg/kg) and tandospirone (10 and 30 mg/kg), but enha nced by diazepam (3 and 10 mg/kg). Buspirone (30 mg/kg), tandospirone (10 and 30 mg/kg) and diazepam (3 and 10 mg/kg) significantly reduced the ambulation-increasing effect of scopolamine (0.5 mg/kg, s.c.). SUN 8399 (3 - 100 mg/kg) did not modify the effects of either methampheta mine or scopolamine. The present results suggest that 5-HT1A agonists scarcely show anticonflict action on the Geller-type conflict behavior in mice. However, SUN 8399 possesses different behavioral characteris tics from those of the other two 5-HT1A agonists in terms of interacti ons with methamphetamine and scopolamine.