Haemodynamics of pelvic nerve induced penile erection in the dog: possible mediation by vasoactive intestinal polypeptide.
- 1 May 1984
- journal article
- research article
- Published by Wiley in The Journal of Physiology
- Vol. 350 (1), 209-224
- https://doi.org/10.1113/jphysiol.1984.sp015197
Abstract
The haemodynamics of erection were elucidated in the anaesthetized dog by analysing in quantitative terms the changes of penile arterial inflow, venous outflow and tissue volume during graded pelvic nerve stimulation. The study also provides information on possible neurotransmitter mechanisms of the erectile response. Erection evoked by pelvic nerve stimulation appeared to result from two main circulatory events: first, there was a prompt dilatation of the penile 'resistance vessels', causing a greatly increased arterial inflow which in the early phase bypassed the cavernous bodies and, hence, increased venous outflow to the same extent. Secondly, the erectile response proper began after a distinct delay (approximately equal to 20 s). This was apparently caused by sudden opening of low resistance 'shunt vessels' diverting part of the arterial inflow into the cavernous bodies, leading to rapid filling. During the filling phase arterial inflow greatly exceeded venous outflow, and returned to the venous outflow level again in the steady state of full erection. The initial dilator response seemed to ensure rapid erection by establishing a high pressure head from the arterial microvessels to the cavernous spaces. The threshold frequency for the penile vasodilator response to pelvic nerve stimulation was 1-2 Hz and was always higher for the erectile volume response, viz. 2-4 Hz. Maximal effects for both were obtained at 16 Hz, causing on the average a 25-fold increase in peak arterial inflow, a 17-fold increase in venous outflow and a 107% increase in penile volume. Muscarinic blockade by atropine caused no significant decrease in the blood flow response induced by pelvic nerve stimulation, but clearly curtailed the erectile response. This indicates that the dilatation of the penile 'resistance vessels' is mainly non-cholinergic in nature, whereas a cholinergic mechanism seems to contribute to the erectile volume response proper. Pelvic nerve stimulation caused a substantial output of vasoactive intestinal polypeptide (VIP) from the penis which was correlated in onset and duration to the vasodilator response. Intra-arterial (I.A.) infusion of VIP elicited moderate erection and a penile vasodilator response which resembled the neural response. Similar effects were evoked by I.A. infusion of substance P, but the output of this peptide from the penis during stimulation was poorly correlated to the vascular events. These in vivo observations indicate that VIP might be the neurotransmitter responsible for the non-cholinergic pelvic nerve induced penile vasodilatation.This publication has 19 references indexed in Scilit:
- Principal mechanisms controlling penile retraction and protrusion in rabbitsActa Physiologica Scandinavica, 1979
- Measurement of fasting and postprandial plasma VIP in man.Gut, 1978
- Peptidergic (substance P) nerves in the genito-urinary tractNeuroscience, 1978
- Occurrence of nerves containing vasoactive intestinal polypeptide immunoreactivity in the male genital tractLife Sciences, 1977
- Evidence for a Rate-Sensitive Regulatory Mechanism in Myogenic Microvascular ControlActa Physiologica Scandinavica, 1977
- Microvascular pressure distribution in skeletal muscle and the effect of vasodilationAmerican Journal of Physiology-Legacy Content, 1975
- Method for Gravimetric Registration of Changes in Tissue VolumeActa Physiologica Scandinavica, 1974
- Contraction and relaxation of the retractor penis muscle and the penile artery of the bull.1974
- Autonomic nervous control of reproduction: circulatory and other factors.1972
- Hemodynamic mechanisms of erection in the canine penisAmerican Journal of Physiology-Legacy Content, 1967