Neural control of erection
Section snippets
Understanding penile erection: local mechanisms, peripheral neural pathways and peripheral pharmacology
Penile erection takes place when both dilation of the penile arteries and relaxation of the erectile tissue (corpus cavernosum and corpus spongiosum) occur [1]. Dilation of the penile arteries results in an increased blood flow to the penis, and erectile tissue relaxation results in an engorgement of the penis with blood. Because the erectile tissue is surrounded by the tunica albuginea, a tissue that does not distend easily, the increased blood flow to the penis increases not only the penile
The spinal network that controls erection
The spinal cord contains the three sets of motoneurons (thoracolumbar sympathetic, sacral parasympathetic and sacral pudendal) that are anatomically linked with the penis and functionally linked with erection. Recordings performed in humans and animals reveal that these spinal neural populations are closely linked; however, they are located neither in the same spinal segments (thoracolumbar and lumbosacral) nor in the same spinal areas (sacral parasympathetic nucleus and Onuf or DM and DL
Spinal pharmacology
Lumbosacral neurons, either sacral parasympathetic preganglionic ones, pudendal motoneurons or interneurons, bear a great variety of receptors and are surrounded by numerous fibers from local, peripheral and supraspinal origins that release many neurotransmitters. A rapid review of the literature suggests that a theoretical sacral parasympathetic preganglionic neuron bears the adrenergic alpha-1A-a, b, d and alpha-2A-a and b receptor subtypes, the dopaminergic D2 receptor subtype, the
Androgens and reflexive erections
In adult animals with a complete section of the spinal cord, castration strongly depresses reflexive erections [51]. In castrated rats that display few or no reflexive erections, testosterone [51], [113], [114] and dihydrotestosterone, but not estradiol [115], [116], delivered peripherally, restore reflexive erections. The implantation of testosterone directly into the lower spinal cord, or into the spinal canal, also reverses the deleterious effects of castration on reflexive erections [117].
Spinal lesions, reflexive erections and treatments for erectile dysfunction
Lesions of the spinal cord, such as those occurring during multiple sclerosis, spinal cord injury, tumor, syringomyelia, transverse myelitis, arachnoiditis, disk disease and myelodysplasia, can lead to erectile dysfunction [1]. As mentioned above, reflexive erections remain if the sacral reflex arch is spared. Although the basic mechanisms through which the spinal cord controls erection in physiological conditions are better understood today, this set of information has not yet provided any
The supraspinal control of penile erection
In humans and animals, penile erection occurs in several contexts, some of which have nothing to do with a sexually relevant context. Erections have been observed in utero in humans [131], and in rats during copulation, in response to genital stimulation, during sleep [132], in the presence of a receptive female with no possibility to engage in copulation (“noncontact erections” [133]), and in response to the injection of centrally acting drugs [134]. It is possible that several different areas
Central brain lesions in humans and penile erection
Among the neurologic disorders than can cause erectile dysfunction through alteration of central pathways are tumor, stroke, encephalitis, Parkinson's disease, dementias, the olivopontocerebellar degeneration (Shy-Drager syndrome) and epilepsy of the temporal lobe [1], [157]. In contrast, erections occur after lesions of the pyriform cortex and amygdaloid complex (the Kluver-Bucy syndrome [84]).
Perspectives for treating erectile dysfunction in humans through a central target
The link between dopaminergic pathways and central pro-erectile pathways has been indirectly evidenced in human patients suffering from the alteration of dopaminergic transmission. Some Parkinson's patients treated with apomorphine, L-DOPA or bromocriptine report the occurrence of erections and increased libido or an improved sexual interest [158], [159], [160], [161], [162], [163]. The effects of apomorphine in these patients must be evaluated on a basis different from other patients [164].
Androgens and the central control of penile erection
As castration depresses sexual behavior, it is not possible to record any erections during copulation in castrated male rats, although there are historical and clinical reports of castrated men keeping sexual activity and erections. In these men, it is possible that castration was performed when they were adults, a time after androgen-dependent systems have been organized during the neonatal period and activated during puberty. In rats, castration suppresses noncontact and apomorphine-induced
Provisory conclusions
What can we learn and what can we expect from the developments in basic and clinical research on the nervous control of penile erection? The last 20 years have seen tremendous advances in the understanding of the basic mechanisms of erection and in efficient treatments of erectile dysfunction. However, one should not forget that (i) the role of the various abdominal and pelvic nerves in the control of penile erection had been clearly stated at the end of the 19th century (see Ref. [15] as an
References (193)
- et al.
Nitric oxide and cyclic GMP formation upon electrical field stimulation cause relaxation of corpus cavernosum smooth muscle
Biochem. Biophys. Res. Commun.
(1990) - et al.
The role of cyclic adenosine monophosphate, cyclic guanosine monophosphate, endothelium and nonadrenergic, noncholinergic neurotransmission in canine penile erection
J. Urol.
(1993) - et al.
Oral drug therapy for erectile dysfunction
Urol. Clin. North Am.
(2001) - et al.
Hemodynamics of erection in the monkey
J. Urol.
(1983) - et al.
Hemodynamics of canine corpora cavernosa during erection
Urology
(1984) - et al.
Neural control of penile erection in the rat
J. Auton. Nerv. Syst.
(1995) - et al.
Anti-erectile role of the sympathetic nervous system in rats
J. Urol.
(1993) - et al.
Observations on the neurophysiology of sexual function in the male cat
J. Urol.
(1938) - et al.
The rat as a model for the study of penile erection
J. Urol.
(1989) - et al.
Intraoperative electrostimulation of the cavernous nerve: technique, results and limitations
J. Urol.
(1995)
Central nervous system innervation of the penis as revealed by the transneuronal transport of pseudorabies virus
Neuroscience
Spinal pacemaker controlling sexual reflexes in male rats
Brain Res.
Spinal block reveals roles for brain and spinal cord in the mediation of reflexive penile erections in rats
Brain Res.
Penile mechanisms and the role of the striated penile muscles in penile reflexes
Physiol. Behav.
Electromyographic analysis of male rat perineal muscles during copulation and reflexive erections
Physiol. Behav.
The role of the bulbocavernosus in penile reflex behaviour in rats
Brain Res.
Maintenance of erection of penile glans, but not penile body, after transection of rat cavernous nerves
J. Urol.
The pudendo-pudendal reflex in male and female rats
J. Auton. Nerv. Syst.
Electrical stimulation of the dorsal nerve of the penis evokes reflex tonic erections of the penile body and reflex ejaculatory responses in the spinal rat
J. Urol.
Reflex contractions of the ischiocavernosus muscles allowing electrical and pressure stimulations
J. Urol.
Bulbocavernosus reflex in normal men and in patients with neurogenic bladder and/or impotence
J. Neurol. Sci.
Contralateral termination of pudendal nerve fibers in the gracile nucleus of the rat
Neurosci. Lett.
Sensory modulation of the medial preoptic area neuronal activity by dorsal penile nerve stimulation in rats
J. Urol.
Afferents originating from the dorsal penile nerve excite oxytocin cells in the hypothalamic paraventricular nucleus of the rat
Brain Res.
Central neural regulation of penile erection
Neurosci. Biobehav. Rev.
Forebrain influences on brainstem and spinal mechanisms of copulatory behaviour: a current perspective on Frank Beach's contribution
Neurosci. Biobehav. Rev.
Supra-spinal influences on the penile reflexes of the male rat: a comparison of the effects of copulation, spinal transection and cortical spreading depression
Horm. Behav.
Lesions of the nucleus paragigantocellularis alter ex copula penile reflexes
Brain Res.
Serotonergic neurotoxic lesions facilitate male sexual reflexes
Pharmacol. Biochem. Behav.
Effects of intrathecal administration of 8-OH-DPAT on genital reflexes and mating behaviour in male rats
Physiol. Behav.
Stimulation of spinal serotonergic receptors facilitates seminal emission and suppresses penile erectile reflexes
Brain Res.
Effects of intrathecal and systemic administration of buspirone on genital reflexes and mating behaviour in male rats
Pharmacol. Biochem. Behav.
Effects of a potent dopamine receptor agonist, RDS-127, on penile reflexes and seminal emission in intact and spinally transected rats
Physiol. Behav.
Quinelorane (LY163502), a D2 dopamine receptor agonist, facilitates seminal emission, but inhibits penile erection in the rat
Pharmacol. Biochem. Behav.
Differential effects of intrathecal thyrotropin-releasing hormone (TRH) on perineal reflexes in male rats
Physiol. Behav.
GABAergic regulation of penile reflexes and copulation in rats
Physiol. Behav.
Alpha2-adrenoceptor antagonists and male sexual behaviour: II. Erectile and ejaculatory reflexes
Physiol. Behav.
Anatomy, physiology and pathophysiology of erectile function
Pharmacology of penile erection
Pharmacol. Rev.
K+ channels and gap junctions in the modulation of corporal smooth muscle tone
Drugs News Perspect.
Pituitary adenylate cyclase-activating polypeptide, helospectin, and vasoactive intestinal polypeptide in human corpus cavernosum
Br. J. Pharmacol.
A nitric oxide-like factor mediates nonadrenergic-noncholinergic neurogenic relaxation of penile corpus cavernosum smooth muscle
J. Clin. Invest.
Nitric oxide: a physiologic mediator of penile erection
Science
Sildenafil: an orally active type 5 cyclic GMP-specific phosphodiesterase inhibitor for the treatment of penile erectile dysfunction
Int. J. Impot. Res.
Molecular mechanisms and pharmacokinetics of phosphodiesterase-5 antagonists
Curr. Urol. Rep.
The autonomic innervation of the genito-urinary system
Physiol. Rev.
Autonomic nervous control of reproduction: circulatory and other factors
Pharmacol. Rev.
Organization of lumbar spinal outflow to distal colon and pelvic organs
Physiol. Rev.
The innervation of the pelvic and adjoining viscera
J. Physiol. (London)
Principal mechanisms controlling penile retraction and protrusion in rabbits
Acta Physiol. Scand.
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