title: Morphine reduces penile erection induced by the cannabinoid receptor antagonist SR 141617A in male rats: role of paraventricular glutamic acid and nitric oxide.
abstract: The effect of the opiate morphine, on penile erection induced by the cannabinoid CB1 receptor antagonist SR 141716A injected into the paraventricular nucleus of the hypothalamus and on the increase in the concentration of glutamic acid and of NO(2)(-) and NO(3)(-), which occurs concomitantly in the paraventricular dialysate obtained by intracerebral microdialysis, was studied in male rats. Morphine (0.5, 1 and 5 microg), given into the paraventricular nucleus, reduced dose-dependently penile erection induced by SR 141716A (2 microg) injected into the paraventricular nucleus. The reduction of penile erection was parallel to a decrease of the concomitant glutamic acid and NO(2)(-) and NO(3)(-) increase that occurs in the paraventricular dialysate in these experimental conditions. Morphine effects on SR 141716A-induced penile erection, glutamic acid and NO(2)(-) increase were prevented by the prior administration of naloxone, an opioid receptor antagonist (5 microg) given into the paraventricular nucleus. The present results show that the activation of opioid receptors in the paraventricular nucleus impairs penile erection induced by SR 141716A, by reducing the increase in glutamic acid and in NO activity that occurs in this hypothalamic nucleus in these experimental conditions.
authors.affiliation: Bernard B. Brodie Department of Neuroscience and Centre of Excellence for the Neurobiology of Addictions, University of Cagliari, SP Monserrato-Sestu, Italy.
authors.forename: Salvatora
authors.initials: S
authors.lastname: Succu
authors.forename: Maria Stefania
authors.initials: MS
authors.lastname: Mascia
authors.forename: Tiziana
authors.initials: T
authors.lastname: Melis
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Sanna
authors.forename: Antonio
authors.initials: A
authors.lastname: Boi
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Melis
authors.forename: Antonio
authors.initials: A
authors.lastname: Argiolas
mesh_terms: D000818:Animals; D002186:Cannabinoids / Q000037:antagonists & inhibitors*; D018698:Glutamic Acid / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009569:Nitric Oxide / Q000502:physiology*; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000502:physiology*; D010410:Penile Erection / Q000187:drug effects / Q000502:physiology*; D010880:Piperidines / Q000494:pharmacology*; D011720:Pyrazoles / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D000077285:Rimonabant
chemical_list: D002186:Cannabinoids; D010880:Piperidines; D011720:Pyrazoles; D009569:Nitric Oxide; D018698:Glutamic Acid; D009020:Morphine; D000077285:Rimonabant