Effects of Hypogastric Nerve and Sympathetic Chain Stimulation on the Pelvic Nerve Induced Penile Erection in the Dog

Abstract

The effects of electrical stimulation of hypogastric nerve and sympathetic chain on ‘electroerection’ (penile erection induced by electrical stimulation of the pelvic nerve) were studied in dogs to clarify the physiological roles that these neural inputs may play in producing and/or maintaining penile erection. As an objective parameter of hemodynamics of the penile circulation, the pressure in the corpus cavernosum of the penis was measured. Hypogastric nerve electrostimulation was performed in 24 dogs who had received pelvic nerve stimulation and, therefore, had ‘electroerection’. Ten dogs responded to this procedure with an augmentation of ‘electroerection’, 10 with an attenuation of ‘electroerection’, and 4 with no appreciable changes. 4 out of the 10 animals who exhibited an attenuation response were then given an α₁-adrenergic blocker (prazosin hydrochloride) prior to the electrical stimulation to evaluate the specificity of the effects of the hypogastric nerve stimulation. In 3 of the 4 dogs the attenuation effect was abolished by this treatment and instead an augmentation effect became evident. Sympathetic chain electrostimulation was performed in 6 dogs with ‘electroerection’. When applied to the L_4–5 interganglionic segment, it produced a biphasic response which consisted of an initial increase followed by a decrease of the intracorporeal pressure. In contrast, stimulation of the L_2–3 interganglionic segment produced a monophasic response consisting of only augmentation of the intracorporeal pressure. These data suggested that there might be two groups of fibers in the hypogastric nerve and sympathetic chain which are functioning antagonistically, and that the anti-erectile neural inputs are mediated primarily by the α₁-adrenergic system. To examine the sites of penile vasculature where the innervating hypogastric nerve exerts its effects, electrical pelvic/hypogastric nerve stimulations were performed in dogs in whom the inflow blood circulation to the corpora cavernosa was disrupted by arterial ligation and replaced by a constant saline infusion. It appears that the stimulatory input via the hypogastric nerve caused an increased blood flow into the cavernous space due to vasodilation of the inflow blood vessels, and the inhibitory effect occurred mainly due to relaxation of the draining blood vessels with a resultant increase of the blood outflow from the cavernous space.

Priapism in Dogs

“…However, an inhibitory effect may also occur due to relaxation of the outflow blood vessels, causing increased blood outflow from the cavernous space. 13 The hypogastric nerve is responsible for ejaculation and prostatic secretion. 12 Sympathetic chain fibers inhibit erection.…”

Priapism Associated with Lumbar Stenosis in a Dog

“…It would also be possible that relaxation of the erect penis would be impaired (Aoki et al. ). The dog from this case presented urinary bladder distension possibly due to detrusor areflexia and delayed bowel transit, which are also symptoms that have been associated with disturbed parasympathetic functions on bladder and bowel control (Benevento and Sipski ; Kent ) and gradual locomotory problems (Baba et al.…”

Resolution of Recurrent Ischemic Priapism After Celiac Plexus Block: Case Report Evidence for its Neurogenic Origin?

“…The autonomic innervation of the penis influencing penile erection is well understood to receive sympathetic input from thoracolumbar segments of the spinal cord (T10‐L1), which condenses into the superior hypogastric plexus in the retroperitoneum before relaying bilateral pelvic projections that coalesce with sacral parasympathetic projections at the level of the pelvic plexus and cavernous nerves [5]. This sympathetic input may be proerectile, and electrophysiologic studies have shown that stimulation of sympathetic pathways at suprasacral levels exerts vasodilatory effects in the penis [6–8]. Priapism has been described to occur in association with degenerative lumbar spinal stenosis and spondylolisthesis [9,10], as well as lumbar epidural anesthesia [11], supporting the concept that disturbed autonomic neuronal function at thoracolumbar spinal cord levels likely constitutes a mechanism of priapism.…”

“…Fibers within the plexus arise from preganglionic splanchnic nerves, parasympathetic preganglionic nerves from phrenic and vagus nerves, and sympathetic postganglionic fibers [15]. While nociceptive input from abdominal and pelvie viscera is carried by afferent nerves that are part of the spinal nerves coursing through the celiac plexus, this neuronal distribution accompanies sympathetic nerves, which are consistent with the sympathetic nerve supply of the penis [6–8]. Thus, the neurolytic mechanism of the nociception of the celiac plexus block conceivably also may interrupt deranged sympathetic neuronal discharges that elicit penile erection.…”