The present study investigates the effects induced by sildenafil (1 mg/kg, p.o.) and the dopamine agonist, SND 919 (0.1 mg/kg, i.p.) on copulatory behaviour of male rats, categorized, on the basis of seven consecutive mating pre-tests, as sluggish and normal ejaculators (SE and NE, respectively). The data obtained show that sildenafil modifies both sexual arousal and ejaculatory mechanisms of copulation. It appears that, although it induced a facilitatory effect on ejaculation of all rats, similarly to SND 919, the lowering of ejaculatory threshold was achieved by means of a reduction of mount frequency and intromission frequency in SE and NE groups, respectively. Differently from SND 919, sildenafil increased sexual arousal, diminishing post ejaculatory interval in SE animals and inter-intromission interval in both SE and NE rats. As the dopamine antagonist, (-)eticlopride (0.02 mg/kg, s.c.), significantly inhibited sildenafil-induced enhancement of sexual arousal in SE rats, it is suggested that the drug acts both peripherally and centrally.
Influence of sildenafil on copulatory behaviour in sluggish or normal ejaculator male rats: a central dopamine mediated effect? / Giuliani, Daniela; Ottani, Alessandra; Ferrari, Francesca. - In: NEUROPHARMACOLOGY. - ISSN 0028-3908. - STAMPA. - 42:4(2002), pp. 562-567. [10.1016/S0028-3908(01)00195-2]