Role of calcium in the expression of ACTH-Induced stretching, yawning and penile erection

Abstract

The effect of ω-conotoxin GVIA, a potent and selective inhibitor of N-type calcium channels and of the organic calcium channel inhibitors nimodipine, verapamil and flunarizine, on stretching, yawning and penile erection induced by ACTH 1–24 was studied in male rats. ω-Conotoxin (1–10 ng ICV 15 min before ACTH, 10 μg ICV), but not carboxymethylated ω-conotoxin, induced a dose-dependent prevention of all ACTH effects. In contrast, organic calcium channel inhibitors (20 mg/kg IP 30–60 min before ACTH) failed to modify ACTH-induced stretching and yawning but induced a 25% decrease in the number of penile erection episodes induced by the peptide, and prevented, like ICV ω-conotoxin, oxytocin- and apomorphine-induced yawning and penile erection. When injected in the paraventricular nucleus of the hypothalamus, ω-conotoxin prevented the above behavioral responses induced by apomorphine and oxytocin but not by ACTH 1–24. The present results suggest that ACTH induces stretching, yawning and penile erection by mobilizing calcium through central ω-conotoxin-sensitive calcium channels in brain sites different from those sensitive to oxytocin and apomorphine.