Motility regulating effects of galanin on smooth muscle of porcine ileum.
We studied the effect of synthetic porcine galanin on circular and longitudinal oriented strips of pig ileal muscle. Galanin 10(-11)-10(-6) M had no effect on resting tension in the two layers. In circular muscle precontracted with carbachol 10(-6) M, galanin dose-dependently inhibited the amplitude of contractions to a maximum of 33 +/- 8% at 10(-6) M. In longitudinal muscle the amplitude of contractions induced by carbachol 10(-7) M or transmural field stimulation increased after addition of galanin 10(-9)-10(-7) M to a maximum of 21 +/- 6%, while at higher concentrations inhibition occurred. Maximal inhibition was 36 +/- 14% at galanin 10(-6) M. Tetrodotoxin did not influence the effects of galanin in the preparations. The results indicate that in the homologous species galanin inhibits the circular muscle layer, possibly by a direct action on the smooth muscle. In the longitudinal muscle the effect of galanin is apparently excitatory. The inhibition observed with high concentration of galanin could be due to tachyphylaxis and desensitization. Alternatively, an additional population of low affinity, inhibitory receptors may exist.
Haring
H
H
Department of Surgical Gastroenterology C. Rigshospitalet, University of Copenhagen, Denmark.
Tøttrup
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D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D004558:Electric Stimulation; D005260:Female; D019004:Galanin; D007082:Ileum / Q000187:drug effects*; D008297:Male; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000187:drug effects*; D009479:Neuropeptides / Q000494:pharmacology*; D010455:Peptides / Q000494:pharmacology*; D013552:Swine
D009479:Neuropeptides; D010455:Peptides; D019004:Galanin; D002217:Carbachol