Activation of gamma-aminobutyric acid(A) receptors in the paraventricular nucleus of the hypothalamus reduces apomorphine-, N-methyl-d-aspartic acid-and oxytocin-induced penile erection and yawning in male rats

The effect of muscimol and baclofen injected into the paraventricular nucle us of the hypothalamus on penile erection and yawning induced by apomorphin e, oxytocin and N-methyl-D-aspartic acid (NMDA) was studied in male rats. M uscimol (20-200 ng), but not baclofen (200 ng), injected into the paraventr icular nucleus of the hypothalamus 10 min before apomorphine (50 ng), oxyto cin (10 ng) or NMDA (50 ng) reduced penile erection and yawning induced by the above compounds given into the paraventricular nucleus. Bicuculline (25 0 ng) injected into the paraventricular nucleus 5 min before muscimol (100 ng) prevented the inhibitory effect of muscimol on penile erection and yawn ing induced by apomorphine, oxytocin and NMDA, The present results show tha t gamma-aminobutyric acid (GABA) inhibits penile erection and yawning by ac ting on GABA(A) receptors in the paraventricular nucleus of the hypothalamu s. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.