Calcitonin gene-related peptide and capsaicin inhibit the circular muscle of the guinea-pig ileum.
Calcitonin gene-related peptide (CGRP) is known to excite, through the release of acetylcholine, the circular muscle (CM) of the guinea-pig ileum in vitro. In the present experiments, the effect of rat CGRP was investigated on the CM of tetrodotoxin-treated, spontaneously active ileum preparations. CGRP (1-10 nM) caused concentration-dependent inhibition of both the amplitude and frequency of spontaneous CM contractions. Capsaicin (a sensory stimulant known to release CGRP from primary afferents) also inhibited CM activity. The effect of 1 microM capsaicin underwent rapid desensitization, indicating specific action on afferent structures, whereas a high concentration of the drug (33 microM) inhibited CM activity most probably on the smooth muscle itself.
Barthó
L
L
Department of Pharmacology, University Medical School Pécs, Hungary.
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology*; D002211:Capsaicin / Q000494:pharmacology*; D005260:Female; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D013779:Tetrodotoxin / Q000494:pharmacology
D013779:Tetrodotoxin; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin