Spatial localization and properties of pacemaker potentials in the canine rectoanal region.
The present study investigated the spatial organization of electrical activity in the canine rectoanal region and its relationship to motility patterns. Contraction and resting membrane potential (E(m)) were measured from strips of circular muscle isolated 0.5-8 cm from the anal verge. Rapid frequency [25 cycles/min (cpm)] E(m) oscillations (MPOs, 12 mV amplitude) were present across the thickness of the internal anal sphincter (IAS; 0.5 cm) and E(m) was constant (-52 mV). Between the IAS and the proximal rectum an 18 mV gradient in E(m) developed across the muscle thickness with the submucosal edge at -70 mV and MPOs were replaced with slow waves (20 mV amplitude, 6 cpm). Slow waves were of greatest amplitude at the submucosal edge. Nifedipine (1 micro M) abolished MPOs but not slow waves. Contractile frequency changes were commensurate with the changes in pacemaker frequency. Our results suggest that changing motility patterns in the rectoanal region are associated with differences in the characteristics of pacemaker potentials as well as differences in the sites from which these potentials emanate.
Mutafova-Yambolieva
V N
VN
Department of Physiology and Cell Biology, University of Nevada, Reno, Nevada 89557, USA.
O'Driscoll
K
K
Farrelly
A
A
Ward
S M
SM
Keef
K D
KD
D001003:Anal Canal / Q000033:anatomy & histology / Q000294:innervation*; D000818:Animals; D001683:Biological Clocks / Q000187:drug effects; D004285:Dogs; D004553:Electric Conductivity; D005260:Female; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000294:innervation; D009543:Nifedipine / Q000494:pharmacology; D012007:Rectum / Q000033:anatomy & histology / Q000294:innervation*; D014665:Vasodilator Agents / Q000494:pharmacology
D014665:Vasodilator Agents; D009543:Nifedipine