Influence of clonidine on the ACTH-induced behavioral syndrome

In male rats, clonidine in a dose range of 1-3000 micrograms/kg i.p. antagonized the stretching-yawning syndrome induced by the intraventricular injection of ACTH-(1-24) (3 micrograms/rat) dose-dependently. On the other hand, the effect of clonidine on ACTH-induced penile erections was potentiation at low doses (5 and 10 micrograms/kg) and inhibition at the highest doses (1000 and 3000 micrograms/kg), the intermediate doses (50 and 100 micrograms/kg) being without effect. There was no relationship between these behavioral effects and the effect on arterial blood pressure.