A. Abysique et al., EVIDENCE FOR SUPRASPINAL NERVOUS CONTROL OF EXTERNAL ANAL-SPHINCTER MOTILITY IN THE CAT, Brain research, 795(1-2), 1998, pp. 147-156
The aim of this study was to investigate the role of noradrenergic des
cending nervous pathways in external anal sphincter motility. For this
purpose, the effects of intravenously injected adrenoceptor antagonis
t and agonist on the tonic electrical activity of this sphincter were
studied in anesthetized cats. The effects of stimulating the region of
the locus coeruleus and the effects of intravenous, intracerebroventr
icular and intrathecal injection of the above drugs on the electromyog
raphic responses of this muscle to pudendal nerve stimulation were als
o investigated. The tonic sphincteric activity and the reflex response
triggered by electrically stimulating pudendal afferent nerve fibers
were inhibited by alpha(1)-adrenoceptor antagonist nicergoline and enh
anced by alpha(1)-adrenoceptor agonist phenylephrine. Stimulation of t
he locus coeruleus area either inhibited or enhanced the reflex respon
ses. Intracerebroventricular and intrathecal injection of the alpha(1)
-adrenoceptor agonists, morphine and leu-enkephalin decreased the ampl
itude of these reflex responses. All the effects of opioids were block
ed by naloxone and by spinalization performed at the cervical and lumb
ar levels. The direct response elicited by stimulating the sphincteric
motor axons was not affected either by these drugs or by the brainste
m stimulation. These results suggests the existence of a pontine neuro
nal network controlling the motility of the external anal sphincter vi
a noradrenergic and opioid neurons. (C) 1998 Elsevier Science B.V. All
rights reserved.