Calcitonin gene-related peptide action on intestinal circular muscle.
Isolated segments of the guinea pig small intestine were used to examine the effect of calcitonin gene-related peptide (CGRP) on the motor activity of the circular muscle. CGRP (0.3-30 nM) initiated phasic contractions of the circular muscle due to stimulation of cholinergic neurons. Peristalsis, however, was inhibited by CGRP. A further analysis of this effect showed that CGRP had no inhibitory influence on the main, cholinergic, pathway of the ascending enteric reflex (AER) contraction, whereas the hexamethonium- and atropine-resistant pathways of the AER were blocked. The inhibition of the atropine-resistant AER resulted from an action of CGRP on nerves and, since it was antagonized by apamin, might be explained by a CGRP-induced activation of enteric inhibitory neurons. The direct relaxant action of CGRP on the longitudinal muscle was not affected by apamin. These findings indicate a heterogeneity and topical selectivity in the motor actions of CGRP on the gut and suggest that this peptide, when released from nerve endings within the intestine, plays a specific role in the regulation of intestinal motility.
Holzer
P
P
Department of Experimental and Clinical Pharmacology, University of Graz, Austria.
Barthó
L
L
Matusák
O
O
Bauer
V
V
D000818:Animals; D001030:Apamin / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D002116:Calcitonin / Q000494:pharmacology*; D015740:Calcitonin Gene-Related Peptide; D002217:Carbachol / Q000494:pharmacology; D005260:Female; D005769:Gastrointestinal Motility / Q000187:drug effects*; D006168:Guinea Pigs; D018738:Hexamethonium; D006584:Hexamethonium Compounds / Q000494:pharmacology; D007082:Ileum / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D007583:Jejunum / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D007700:Kinetics; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D009479:Neuropeptides / Q000494:pharmacology*; D010528:Peristalsis / Q000187:drug effects*; D012018:Reflex; D013779:Tetrodotoxin / Q000494:pharmacology
D006584:Hexamethonium Compounds; D009479:Neuropeptides; D001030:Apamin; D018738:Hexamethonium; D013779:Tetrodotoxin; D001285:Atropine; D002217:Carbachol; D002116:Calcitonin; D015740:Calcitonin Gene-Related Peptide