Abstract
BackgroundPenile erection is a complex reflex under spinal control and modulated by the brain. The hemodynamic events under autonomic control and the perineal muscles somatic activity are interconnected during the reflex erection at the spinal level, however if the afferent feedback on the corpus cavernosum pressure during an erection affects the somatic activity (perineal muscles contractions) and vice versa is not known. This study was aimed to test this hypothesis using a rat model.MethodsIntracavernous pressure (ICP) and bulbocavernosus (BC) muscle EMG were recorded during reflex erections elicited with dorsal penile nerve (DNP) electrical stimulation in anaesthetized acutely spinalized SD rats with surgically (bilateral cavernous nerve section, CnX, n = 8) and pharmacologically (trimetaphan infusion, TMPh, n = 8) abolished pressor response, or with surgically (bilateral section of the motor branch of the pudendal nerve, PnX, n = 7) and pharmacologically (1 mg/kg d-tubocurarine, n = 8) blocked perineal muscles contractions, or with interrupted afferent input from the penis (bilateral crush of the dorsal penile nerve, DPnX, n = 7). Control rats (n = 8) received no intervention.ResultsModerate positive correlations were found between net parameters of pressor and somatic activity during DNP-stimulation induced reflex erection in spinal rats, particularly the speed of pressor response development was positively correlated to EMG parameters. No changes of EMG activity were found in CnX rats, while the decrease of BC EMG in TMPh-treated males can be attributed to direct inhibitory action of TMPh on neuromuscular transmission. Pressor response latency was increased and ICP front slope decreased in dTK and PnX rats, indicating that perineal muscles contraction augment pressor response. DPN crush had little effect on ICP and EMG.ConclusionAfferent input on the level of intracavernous pressure and the perineal muscles activity has minimal impact on, correspondingly, the somatic and the autonomic components of the reflex erection in spinal males, once the reflex has been initiated.
Highlights
Penile erection is a complex reflex under spinal control and modulated by the brain [1, 2]
Instrumental recordings during reflex erection in the rat [10] or mouse [11] reveal tonic pressure increase mediated by the parasympathetic neurons [12], superimposed with suprasistolic pressure peaks in the corpora cavernosum [10, 13] and spongiosum [14, 15]
Apart from the crucial role the perineal muscles play in penile movements during copulation and glans erection, changes of reflex erection in paralyzed rats imply some auxiliary role of these muscles in initiation and/or maintaining the tonic pressure increase during the erection [12]
Summary
The hemodynamic events under autonomic control and the perineal muscles somatic activity are interconnected during the reflex erection at the spinal level, if the afferent feedback on the corpus cavernosum pressure during an erection affects the somatic activity (perineal muscles contractions) and vice versa is not known. Instrumental recordings during reflex erection in the rat [10] or mouse [11] reveal tonic pressure increase mediated by the parasympathetic neurons [12], superimposed with suprasistolic pressure peaks in the corpora cavernosum [10, 13] and spongiosum [14, 15]. Apart from the crucial role the perineal muscles play in penile movements during copulation and glans erection, changes of reflex erection in paralyzed rats imply some auxiliary role of these muscles in initiation and/or maintaining the tonic pressure increase during the erection [12]
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