Effects of apomorphine, physostigmine and vasoactive intestinal peptide on penile erection and yawning in diabetic rats.

The present report describes for the first time the effects of systemic administration of apomorphine and of physostigmine, as well as the effects of central and systemic administration of vasoactive intestinal peptide (VIP), on penile erection and yawning in rats with streptozotocin-induced diabetes. Systemic administration of apomorphine induced both penile erection and yawning in non-diabetic rats but not in diabetic rats, while that of physostigmine induced only yawning in non-diabetic rats, and neither yawning nor penile erection in diabetic rats. Intracerebroventricular administration of VIP induced both penile erection and yawning in non-diabetic rats, but neither was induced in diabetic rats. Application of VIP as an ointment to the surface of the glans penis induced penile erection but not yawning in both non-diabetic and diabetic rats. Thus, penile erection and yawning are less easily induced in diabetic rats than in non-diabetic rats. Grooming occurred whenever penile erection was induced, but was not associated with yawning.