AJP - Gastrointestinal and Liver Physiology, Vol 245, Issue 4 582-G588, Copyright © 1983 by American Physiological Society
Neurohumoral control of colonic motility in the rabbit
W. J. Snape Jr and S. Shiff
Colonic motility was examined in the proximal (taeniated) and distal
(nontaeniated) colon of New Zealand White rabbits. Colonic myoelectric and
contractile activities were recorded by bipolar electrodes and extraluminal
strain gauges sewn on the antimesenteric serosal surface of the proximal
and distal colon. Slow-wave frequency consistently was slower in the
proximal colon (13.2 +/- 0.9) compared with the distal colon (15.8 +/- 1.2)
(P less than 0.05). During the control period 81.8 +/- 5.2% of slow waves
have superimposed spike potentials in the proximal colon. The distal colon
had similar amounts of spike activity. The distal colon had increased
base-line contractility (P less than 0.02). Atropine inhibited spike and
contractile activity on both sides of the colon, but the distal colon still
had more contractile activity than the proximal colon (P less than 0.02).
The alpha-adrenergic agonist phenylephrine and antagonist phentolamine had
no effect on colonic motility. Isoproterenol inhibited colonic smooth
muscle spike and contractile activity. This effect was blocked by
propranolol. Administration of trimethaphan camsylate caused an increase in
spike and contractile activity only in the distal colon. The effect of
trimethaphan on the distal colon was inhibited by atropine. These studies
show that 1) tonic cholinergic stimulation exists both in the proximal and
in the distal colon, 2) circulating catecholamines have minimal effect on
base-line colonic motility, and 3) tonic nonadrenergic inhibition of the
distal colon modulates the tonic cholinergic stimulation.
