Activation of GABAA and opioid receptors reduce penile erection induced by hexarelin peptides.
The effect of muscimol, a GABA(A) receptor agonist, and of morphine, an opioid receptor agonist, on penile erection induced by the hexarelin analogue peptide EP 80661 (GAB-D-Trp(2-Me)-D-Trp(2-Me)-LysNH(2)) and on the increase in the concentration of NO(2)(-) and NO(3)(-) that occurs concomitantly in the dialysate obtained from the paraventricular nucleus (PVN) of the hypothalamus by intracerebral microdialysis, was studied in male rats. Muscimol (50, 100 and 200 ng) and morphine (0.1, 0.5, 1 and 5 microg) given into the PVN dose-dependently reduced penile erection induced by EP 80661 (1 microg) injected into the PVN. The reduction of penile erection was parallel to a decrease of the concomitant NO(2)(-) and NO(3)(-) increase that occurs in the paraventricular dialysate in these experimental conditions. Muscimol and morphine effects on EP 80661-induced penile erection and NO(2)(-) increase were prevented by the prior administration into the PVN of bicuculline (250 ng) and naloxone (5 microg), respectively. The present results show that the activation of GABA(A) receptors and of opioid receptors in the PVN reduces penile erection induced by hexarelin analogue peptides by reducing the increase in NO activity that occurs in this hypothalamic nucleus in these experimental conditions.
Succu
Salvatora
S
Bernard B. Brodie Department of Neuroscience and Center of Excellence for the Neurobiology of Addictions, University of Cagliari, Cittadella Universitaria, S.P. Monserrato-Sestu, Km 0.700, 09042 Monserrato (CA), Italy.
Mascia
Maria Stefania
MS
Melis
Tiziana
T
Melis
Maria Rosaria
MR
Deghenghi
Romano
R
Argiolas
Antonio
A
D000818:Animals; D004305:Dose-Response Relationship, Drug; D018755:GABA Agonists / Q000494:pharmacology*; D008297:Male; D017551:Microdialysis; D008845:Microinjections; D009020:Morphine / Q000494:pharmacology; D009118:Muscimol / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D009842:Oligopeptides / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D010410:Penile Erection / Q000187:drug effects*; D010455:Peptides / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000187:drug effects*; D011957:Receptors, Opioid / Q000819:agonists*
C428245:EP 80661; D018755:GABA Agonists; D009294:Narcotics; D009566:Nitrates; D009842:Oligopeptides; D010455:Peptides; D011963:Receptors, GABA-A; D011957:Receptors, Opioid; C086184:hexarelin; D009118:Muscimol; D009569:Nitric Oxide; D009020:Morphine