No abstract

An animal model using the spinal rat was characterized. Electrical stimulation of the dorsal nerve of the penis elicited reflex tonic erections of the penile body and reflex bulbospongiosus muscle activity, flips and ejaculations. The tonic erections of the penile body are independent from contractions of the bulbospongiosus muscle and appear to be the result of a neurovascular process. Our observations suggest that reflex bulbospongiosus muscle activity, flips and ejaculations are a single complex reflex response, which we define as reflex ejaculatory response. Two parameters predicted the occurrence and type of reflex response. The visualization of bulbospongiosus muscle activity during surgical isolation of the dorsal nerve of the penis was sufficient to anticipate the elicitability of reflex ejaculatory responses. The latter, together with a systemic systolic pressure > or = 73 mmHg., warranted the elicitability of reflex tonic erections. The similarities found in the physiology of rat tonic penile body erections and of human erections make this model promising for further elucidation of sexual function. Moreover, the present model may prove useful for the investigation of neurogenic erectile dysfunction, and of neurogenic ejaculatory disorders.

In the present study we investigated the in vitro relaxant response of erectile tissue obtained from rabbits of different ages (3, 7 and 24 months) in order to detect the progression with age of cavernosal activity in response to substances acting via endothelium-dependent or -independent mechanisms. Noradrenaline induced a concentration-dependent contraction (0.1 microM-3 mM), with an increase in the contractility in the 24-month-old group. Acetylcholine produced a concentration-dependent relaxant effect in the three age groups, with a reduction of the maximal relaxant effect in older animals. ATP (10 microM-1 mM) and adenosine (10 microM-1 mM) induced a concentration-dependent relaxant effect that was higher in the older group. The presence of the NO2-synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME) (0.1 mM) or of the P2-purinoceptor antagonist suramin did not affect ATP relaxation. Relaxation induced by sodium nitrite and nifedipine was reduced in older animals. In conclusion, aging selectively alters the in vitro responsiveness of rabbit erectile tissue. Purinergic system remains more active despite a decrease in the maximal endothelial cholinergic activity and the direct smooth muscle relaxant component.

No abstract