Autonomic control of penile erection in the dog.

Abstract

1. In anaesthetized dogs, resting mean penile artery pressure (p.a.p.) and corpus cavernosum pressure (c.c.p.) were 70‐100% and 10‐15% of mean systemic blood pressure, respectively. 2. Stimulation of the pelvic nerve at 10 Hz produced an immediate drop in p.a.p. and c.c.p., followed 10‐30 s later by a rise in c.c.p. to the level of p.a.p. This level was 60‐90% of systemic pressure, and was maintained throughout stimulation. 3. The threshold for a rise in c.c.p. was 3‐5 Hz. Atropine (1 mg/kg), phentolamine (200 micrograms kg‐1) and propranolol (200 micrograms kg‐1) had no effect on the response to pelvic nerve stimulation. 4. C.c.p., p.a.p. and their changes in response to pelvic nerve stimulation were not significantly altered by either stimulation or section of the hypogastric nerves. 5. Cutting the sympathetic chain on both sides at L5, or administration of phentolamine, had no effect on resting c.c.p. or p.a.p. However, subsequent responses to pelvic nerve stimulation were enhanced. 6. When the pelvic nerve was stimulated during excitation of the sympathetic chain, there was still an initial drop in p.a.p. and c.c.p. but the subsequent increase in c.c.p. was delayed or abolished. These effects were mimicked by close arterial injection of phenylephrine and blocked by alpha‐adrenergic antagonists. 7. This study suggests that erections in response to pelvic nerve stimulation result from an initial increase in volume of the corpus spongiosum, followed 20 s later by a stiffening of the corpus cavernosum as its pressure increases. Only the latter process is inhibited by activity of the sympathetic fibres.

Acetylcholine as a Possible Neurotransmitter in Penile Erection

“…Penile tumescence was visually monitored by at least two investigators and recorded. The flow through the cavernous arteries was measured in four monkeys (7)(8)(9)(10) by duplex ultrasound. 17 Pulse and blood pressure were monitored closely with the aid of a Doppler probe (Parks Medical Electronics) on the radial artery and a pediatric blood pressure cuff ( fig.…”

Nitric oxide as a mediator of cocaine‐induced penile erection in the rat

“…In human subjects and rats, it is generally believed that penile erection is mediated by opposing inputs from the parasympathetic and sympathetic nervous system to penile vascular smooth muscles via the action of acetylcholine and noradrenaline (Carati et al, 1987;de Groat & Steers, 1988;Lue & Tanagho, 1988). Whereas adrenergic neurotransmission mediates contraction of corporal smooth muscles and causes detumescence, cholinergic neurotransmission promotes smooth muscle relaxation and penile erection.…”

The sympathetic role as an antagonist of erection

“…As shown in previous horseradish peroxidase studies in dogs [9], the cavernous nerve fibers are connected to central ganglion cells in the spinal cord at the level of T12-L3 (sympathetic centers) and S1-$3 (parasympathetic centers Previous reports on the effects of sympathetic nerve stimulation on penile erection are contradictory [1,4,14,15]. This study was undertaken to clarify intracavernous pressures changes during erection and detumescence induced by neurostimulation of the sympathetic and parasympathetic system.…”

“…Previous reports on the effects of sympathetic nerve stimulation on penile erection are contradictory [1,4,14,15]. This study was undertaken to clarify intracavernous pressures changes during erection and detumescence induced by neurostimulation of the sympathetic and parasympathetic system.…”