Equine pelvic flexure myoelectrical activity during fed and fasted
states.
Merritt, A. M., R. B. Panzer, G. D. Lester, J. A. Burrow.
Island Whirl Equine Colic Research Laboratory, Department of Large
Animal Clinical Sciences, College of Veterinary Medicine, University
of Florida, Box 100136 HSC, Gainesville FL 32610-0136
APStracts 2:0063G, 1995.
The pelvic flexure is the midpoint of the equine large colon that
marks the junction of dorsal and ventral components. Previous studies
of intraluminal pressure in this region indicate that it could be an
important motility control center. The present study was undertaken
to expand our knowledge of normal myoelectric activity around the
pelvic flexure region. Eight bipolar silver wire electrodes were
surgically fixed at 5 cm intervals to the colonic serosa of 5 adult
horses, starting 30 cm oral to the pelvic flexure on the left ventral
colon (LVC) and ending 15 cm aboral to the pelvic flexure on the left
dorsal colon (LDC). Recordings of myoelectric activity were done
after feed had been withheld for 20 hours or when the horses had been
allowed to eat hay up to the time of the recording session. The
activity was recorded on a polygraph, digitized, processed through a
commercial graphics software package and stored on magnetic tape for
later analyses. Action potential activity was basically separated
into long spike bursts (LSB) that were >/=4 seconds duration and
short spike bursts (SSB) that were <4 seconds duration and
quantified by a software program developed exclusively for the equine
large intestine. Readily identifiable myoelectric patterns included:
1) intense repetitive bursts of LSB's, occurring sporadically and
lasting 3-6 minutes, that migrated rapidly (3 cm/sec) aborally over
all electrode sites, designated as colonic migrating motility
complexes (CMMC); 2) distinct, consistently recurring, spike clusters
made up of LSB and SSB activity, occurring at 10-15 minute intervals
and lasting 4-8 minutes each, that slowly (0.5-1.0 cm/min) migrated
aborally; 3) a small amount of myolectrical activity between the
spike clusters comprised primarily of SSB's; 4) distinct LSB's,
occurring randomly, that rapidly propagated orally, aborally and
occasionally bi-directionally across all electrode sites independant
of spike cluster occurance. When interrupted by a CMMC, the involved
spike clusters disappeared in the immediate post-CMMC period and then
resumed at the previous intervals. LSB, but not total (LSB + SSB)
spike, activity was significantly (P< 0.05) greater at the pelvic
flexure and on the LDC in the fed vs. the fasted state.
Received 26 January 1994; accepted in final form 13 March 1995.
APS Manuscript Number G32-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 19 April 1995.