AJP - Gastrointestinal and Liver Physiology, Vol 272, Issue 5 1075-G1082, Copyright © 1997 by American Physiological Society

ARTICLES

Effects of transmural field stimulation in isolated smooth muscle of human rectum and internal anal sphincter

E. B. Glavind, A. Forman, G. Madsen and A. Tottrup
Department of Obstetrics and Gynecology, University Hospital of Aarhus, Denmark.

Smooth muscle preparations from the circular muscle layer of the most distal rectum and the proximal and distal human internal anal sphincter (IAS) mounted in organ baths to record isometric tension developed spontaneous tension. Transmural electrical field stimulation (TMS) induced frequency- and impulse duration-dependent relaxations sensitive to tetrodotoxin in the stimulation range of 0.5-40 Hz and 0.04-0.6 ms. Poststimulus contractions were most frequent and prominent in rectal preparations. Maximal relaxations were comparable in the three locations and were achieved at 10 Hz and 0.4 ms. The frequency inducing half-maximal response was lower in rectal strips compared with IAS. Phentolamine (10-(6) M) enhanced relaxations and diminished off-contractions at 40 Hz in distal IAS. N omega-nitro-L-arginine (L-NNA) concentration dependently inhibited both relaxations and off-contractions (10 Hz, 0.4 ms). The pD2 values (-log EC50) of L-NNA were lower in rectal muscle compared with those in IAS. L-Arginine (10-(4) M) inhibited the blocking effect of L-NNA. In one-half of the preparations, L-NNA reversed the relaxations to duration contractions (15-40 Hz), which were inhibited by atropine in rectal preparations and by phentolamine in IAS. In conclusion, excitatory innervation of the IAS is alpha-adrenergic and cholinergic in the rectum. A product of the L-arginine-nitric oxide pathway mediates the TMS-induced inhibition of the muscle and is also involved in poststimulus contractions.

This article has been cited by other articles:

				M. A. F. de Godoy and S. Rattan Role of phospholipase A2 (group I secreted) in the genesis of basal tone in the internal anal sphincter smooth muscle Am J Physiol Gastrointest Liver Physiol, November 1, 2007; 293(5): G979 - G986. [Abstract] [Full Text] [PDF]

				L. Hecker, K. Baar, R. G. Dennis, and K. N. Bitar Development of a three-dimensional physiological model of the internal anal sphincter bioengineered in vitro from isolated smooth muscle cells Am J Physiol Gastrointest Liver Physiol, August 1, 2005; 289(2): G188 - G196. [Abstract] [Full Text] [PDF]

				M. Yamanouchi, H. Shimatani, M. Kadowaki, S. Yoneda, T. Nakagawa, H. Fujii, and M. Takaki Integrative control of rectoanal reflex in guinea pigs through lumbar colonic nerves Am J Physiol Gastrointest Liver Physiol, July 1, 2002; 283(1): G148 - G156. [Abstract] [Full Text] [PDF]

				S. Chakder and S. Rattan Involvement of pituitary adenylate cyclase-activating peptide in opossum internal anal sphincter relaxation Am J Physiol Gastrointest Liver Physiol, October 1, 1998; 275(4): G769 - G777. [Abstract] [Full Text] [PDF]