Potentiating effect of clonidine on anxiolytic action of buspirone in rats

The anxiolytic effects of buspirone (Bus) and clonidine (Clo) were studied in the social interaction (SI) test and the elevated plus-maze (EPM) in rats. Bus 1 mg.kg-1 (ip, 15 min) and Clo 10 micrograms.kg-1 (ip, 15 min) prolonged the active interaction time (AIT) in the SI test. While neither Bus 0.3 mg.kg-1 nor Clo 3 micrograms.kg-1 was effective in this model, combination of them increased AIT. Yohimbine 30 micrograms.kg-1 (ip, 15 min before Bus) reversed such a potentiating effect. On the other hand. Bus 0.3 mg.kg-1 or/and Clo 3 micrograms.kg-1 did not affect the VI (variable interval) schedule-controlled behavior. In EPM test, neither Bus 0.5 mg.kg-1 nor Clo 30 micrograms.kg-1 increased the percentages of open-arms entries (OE%) or of the time spent in open-arms (OT%). But these 2 indices were increased by combining Bus 0.5 mg.kg-1 with Clo 30 micrograms.kg-1. The results suggested that Clo potentiated the anxiolytic effect of Bus probably by its alpha 2-adrenoceptor agonist action in SI and EPM tests.