Hypertensive men have a higher prevalence of erectile dysfunction (ED) than the general population. Experimental evidence of ED in hypertensive animals is scarce. This study evaluates the erectile function of spontaneously hypertensive rats (SHR) and age-matched normotensive Wistar-Kyoto rats (WKY) in vivo by the increase in intracavernosal pressure after electrical stimulation of the cavernous nerve (CN) and by isometric tension studies on corporal strips. Frequency-dependent erectile responses to CN stimulations were reduced in SHR. Phenylephrine induced lower corporal contractions in SHR although pD2 values were similar to WKY. Endothelium-dependent relaxations to ACh were impaired significantly in SHR, and indomethacin improved these relaxations in both WKY and SHR, the latter thus reaching values similar to WKY. Corporal relaxations to sodium nitroprusside were enhanced in SHR. Thus a dysfunctional alpha-adrenergic contraction of the corporal smooth muscle, an increased cyclooxygenase-dependent constrictor tone, and/or a defect in endothelium-dependent reactivity are associated with the altered erectile mechanisms in SHR. Drugs targeting endothelial dysfunction may delay the occurrence of ED as a complication of hypertension.
To better understand the similarities and differences in the neural control of penile erection occurring in different contexts, we recorded intracavernous pressure (ICP) in conscious rats using a miniaturized telemetric device. ICP changes during reflexive, noncontact, and apomorphine-induced erections were characterized by a plateau increase surmounted by peaks. Plateaus were also elicited by cavernous nerve stimulation in anesthetized rats, suggesting that the cavernous nerve represents the final common proerectile autonomic pathway in these contexts and that it responds similarly to information originating in the periphery or in supraspinal nuclei. During reflexive, noncontact, and apomorphine-induced erections, activation of spinal autonomic nuclei, considered the spinal generators of erection, would take place first, representing a prerequisite for the occurrence of peaks. Suprasystolic peaks would result from the addition of pudendal motoneuron activity. In contrast, only peaks were recorded during copulation. In this context, the convergence of peripheral and supraspinal information apparently elicits the best temporal arrangement of autonomic and somatic outflows, reflecting a highly organized and integrated spinal activity.
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