Different effects of omega-conotoxin on penile erection, yawning and paraventricular nitric oxide in male rats

Eur J Pharmacol. 1998 Oct 16;359(1):19-26. doi: 10.1016/s0014-2999(98)00626-8.


A dose of apomorphine or oxytocin that induces penile erection and yawning increases nitric oxide production in the paraventricular nucleus of the hypothalamus, as determined by the increase in NO2- and NO3- concentration induced by these substances in the paraventricular dialysate obtained from male rats. All the above responses were prevented by a dose of omega-conotoxin-GVIA as low as 5 ng. This potent inhibitor of N-type Ca2+ channels was injected into the paraventricular nucleus 15 min before apomorphine (50 ng) or oxytocin (10 ng). In contrast, omega-conotoxin was ineffective when the above responses were induced by N-methyl-D-aspartic acid (50 ng). The peptide toxin (5 ng) was also ineffective on the penile erection and yawning induced by the nitric oxide donors sodium nitroprusside (50 microg) or hydroxylamine (50 microg), injected into the paraventricular nucleus. The present results suggest that omega-conotoxin-sensitive Ca2+ channels are involved in the activation of nitric oxide synthase, penile erection and yawning induced by apomorphine and oxytocin, but not by N-methyl-D-aspartic acid, at the paraventricular level.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apomorphine / pharmacology
  • Calcium / metabolism
  • Calcium Channel Blockers / pharmacology*
  • Dizocilpine Maleate / pharmacology
  • Dopamine Agonists / pharmacology
  • Dopamine Antagonists / pharmacology
  • Excitatory Amino Acid Antagonists / pharmacology
  • Haloperidol / pharmacology
  • Male
  • Nitrates / metabolism
  • Nitric Oxide / metabolism*
  • Oxytocin / pharmacology
  • Paraventricular Hypothalamic Nucleus / drug effects*
  • Paraventricular Hypothalamic Nucleus / metabolism
  • Penile Erection / drug effects*
  • Peptides / pharmacology*
  • Rats
  • Rats, Sprague-Dawley
  • Vasotocin / pharmacology
  • Yawning / drug effects*
  • omega-Conotoxin GVIA


  • Calcium Channel Blockers
  • Dopamine Agonists
  • Dopamine Antagonists
  • Excitatory Amino Acid Antagonists
  • Nitrates
  • Peptides
  • Nitric Oxide
  • Oxytocin
  • Dizocilpine Maleate
  • omega-Conotoxin GVIA
  • Haloperidol
  • Apomorphine
  • Calcium
  • Vasotocin