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Role of calcium in the expression of ACTH-induced stretching, yawning and penile erection
A Argiolas1, M R Melis, R Stancampiano
1B. B. Brodie Department of Neurosciences, University of Cagliari, Italy.
Abstract:
The effect of omega-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. omega-Conotoxin (1-10 ng ICV 15 min before ACTH, 10 micrograms ICV), but not carboxymethylated omega-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 omega-conotoxin, oxytocin- and apomorphine-induced yawning and penile erection. When injected in the paraventricular nucleus of the hypothalamus, omega-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 omega-conotoxin-sensitive calcium channels in brain sites different from those sensitive to oxytocin and apomorphine.
Insights
Adrenocorticotropic hormone (ACTH) triggers stretching, yawning, and penile erection via central N-type calcium channels. Omega-conotoxin GVIA blocked these ACTH effects, indicating a role for these specific calcium channels.
Area of Science:
- Neuroscience
- Pharmacology
- Endocrinology
Background:
- Adrenocorticotropic hormone (ACTH) is known to induce behavioral responses including stretching, yawning, and penile erection.
- The precise mechanisms underlying ACTH-induced behaviors, particularly the role of calcium channels, remain incompletely understood.
Purpose of the Study:
- To investigate the involvement of N-type calcium channels in ACTH-induced stretching, yawning, and penile erection in male rats.
- To compare the effects of omega-conotoxin GVIA with organic calcium channel inhibitors on these behaviors.
Main Methods:
- Male rats were administered ACTH 1-24 to induce specific behaviors.
- The effects of intracerebroventricular (ICV) omega-conotoxin GVIA and intraperitoneal (IP) organic calcium channel inhibitors (nimodipine, verapamil, flunarizine) were assessed.
- Behavioral responses were quantified, and drug effects were analyzed in relation to ACTH, oxytocin, and apomorphine administration.
Main Results:
- Omega-conotoxin GVIA dose-dependently prevented all ACTH-induced effects (stretching, yawning, penile erection).
- Organic calcium channel inhibitors partially inhibited penile erection but did not affect stretching or yawning induced by ACTH.
- Both omega-conotoxin GVIA and organic calcium channel inhibitors blocked oxytocin- and apomorphine-induced yawning and penile erection.
Conclusions:
- ACTH stimulates stretching, yawning, and penile erection through central omega-conotoxin-sensitive calcium channels.
- These channels are distinct from those targeted by oxytocin and apomorphine in mediating these behaviors.
- The findings highlight a specific role for N-type calcium channels in mediating certain ACTH-driven physiological responses.