Effect of excitatory amino acid, dopamine, and oxytocin receptor antagonists on noncontact penile erections and paraventricular nitric oxide production in male rats

In male rats, noncontact erections occur concomitantly with an increase in NO2- and NO3- in the paraventricular nucleus of the hypothalamus (PVN). In the present study, both responses were reduced by the blockade of PVN excit atory amino acid receptors by dizocilpine, (+)-MK-801(1 and 5 mu g), but no t by 6-cyano-7-nitro-quinoxaline-2,3-dione (5 mu g) or (+/-)-2-amino-4-phos phono-butanoic acid (5 mu g). Also ineffective when injected into the PVN w ere the dopamine antagonists SCH 23390 (5 mu g), S(+)-raclopride (10 mu g), and cis-flupenthixol (10 mu g), and the oxytocin antagonist d(CH2)(5)Tyr(M e)(2)-Orn(8)-vasotocin (1 mu g). However, when the last was given into the lateral ventricles, it reduced noncontact erections without modifying NO2- and NO3- increases. These results suggest that excitatory amino acid transm ission increases in the PVN during noncontact erections. This may contribut e to increased NO production in the PVN, and it may activate oxytocin neuro ns mediating this sexual response.