title: Regional cholinergic differences between distal and proximal colonic myenteric plexus.
abstract: We investigated differences in myogenic and neural response of proximal vs. distal guinea pig colon in longitudinal and circular muscle. Spontaneous phasic contractions were more intense in distal colon in both layers. Phasic contractile frequency was also greater in distal colon in both layers. In both longitudinal and circular muscle, acetylcholine induced greater contractions in distal than in proximal colon (maximal response: longitudinal, 7.00 +/- 1.04 X 10(4) vs. 3.50 +/- 0.49 X 10(4) N/m2; circular, 3.29 +/- 0.82 X 10(4) vs. 8.92 +/- 1.30 X 10(3) N/m2). Compared with proximal colon, electric field stimulation induced greater atropine-sensitive contractions in distal colon in both muscle layers (maximal response: longitudinal, 4.22 +/- 0.53 X 10(4) vs. 7.53 +/- 1.97 X 10(3) N/m2; circular, 2.14 +/- 0.79 X 10(3) vs. -5.28 +/- 2.04 X 10(2) N/m2). In contrast, there were no regional differences in atropine-insensitive relaxations. Veratridine (10(-5) M) stimulated greater [3H]acetylcholine release from distal longitudinal muscle-myenteric plexus than from proximal preparations (11.44 +/- 2.03 vs. 5.84 +/- 1.26% of total tissue radioactivity). These data suggest the greater contractile responses in the distal colon are because of enhanced cholinergic response to neural stimuli and increased muscle sensitivity to acetylcholine, whereas there are no differences in the inhibitory responses to neural stimuli.
authors.affiliation: Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109.
authors.forename: W L
authors.initials: WL
authors.lastname: Hasler
authors.forename: S
authors.initials: S
authors.lastname: Kurosawa
authors.forename: O Y
authors.initials: OY
authors.lastname: Chung
mesh_terms: D000109:Acetylcholine / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D002794:Choline / Q000378:metabolism; D003106:Colon / Q000187:drug effects / Q000294:innervation* / Q000502:physiology; D004558:Electric Stimulation; D006168:Guinea Pigs; D006426:Hemicholinium 3 / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation / Q000502:physiology; D009197:Myenteric Plexus / Q000187:drug effects / Q000502:physiology*; D009928:Organ Specificity; D010830:Physostigmine / Q000494:pharmacology; D014701:Veratridine / Q000494:pharmacology
chemical_list: D006426:Hemicholinium 3; D014701:Veratridine; D010830:Physostigmine; D002794:Choline; D000109:Acetylcholine