AJP - Gastrointestinal and Liver Physiology, Vol 251, Issue 6 804-G814, Copyright © 1986 by American Physiological Society
Physiological characteristics of ovine pyloric sphincter
Y. Ruckebusch and C. H. Malbert
A special probe was validated to record in situ pyloric sphincter activity
by changes in fiber-optic light transmission and sleeve pressure associated
with the propagation of antroduodenal contractions, the onset of the phase
of regular spiking activity (RSA) of the migrating myoelectric complex, the
RSA-like events elicited by duodenal acidification, and the pharmacological
stimulation of the gastroduodenal junction. Rapid changes in light
transmission associated with antroduodenal contractions were super-imposed
on slow variations, suggesting the existence of both phasic and tonic
components in pyloric sphincter activity. The phasic activity coincided
with isolated closures of the pyloric orifice, closures associated with
antral or duodenal bulb contractions, and with long-lasting rhythmic
closures during the development of the RSA phase. The resting tone
increased during antral and/or duodenal stimulation and by feeding
"appetizers" but decreased during antroduodenal quiescence and at the onset
of general anesthesia. It is concluded that the ovine pylorus predominantly
exists in a state of low resting tone but can act as a true sphincter with
both inherent tonic and phasic activity.
