OMEGA-CONOTOXIN PREVENTS APOMORPHINE-INDUCED AND OXYTOCIN-INDUCED PENILE ERECTION AND YAWNING IN MALE-RATS

The effect of the intracerebroventricular (ICV) administration of ω-conotoxin GVIA on penile erection and yawning induced by oxytocin or by the dopaminergic agonist apomorphine was studied in male rats. The peptide toxin, 1-10 ng given ICV 5 min before oxytocin (30 ng ICV) or apomorphine (80 μg/kg SC), but not its carboxymethylated (CM) derivative, prevented the above behavioral responses in a dose-dependent manner. Similarly, ω-conotoxin (5 ng) unilaterally injected inthe paraventricular nucleus of the hypothalamus (PVN) prevented penile erection and yawning induced by the microinjection of oxytocin (10 ng) or apomorphine (50 ng) in the PVN. ω-Conotoxin injected in the PVN, but not in the preoptic area, prevented also penile erection and yawning induced by systemic apomorphine (80 μg/kg SC). ICV ω-conotoxin was unable to prevent stereotypy induced by apomorphine (500 μg/kg SC). The present results provide further evidence that calcium plays a major role in the expression of penile erection and yawning and that apomorphine and oxytocin induce these behavioral responses by mobilizing calcium through ω-conotoxin-sensitive (N-type) calcium channels. © 1990.