Inhibitory action of capsaicin on cholinergic responses induced by GABAA agonists in the guinea-pig ileum.
Pretreatment of the guinea-pig ileum with capsaicin resulted consistently in depression of the neurogenic cholinergic contractions induced by the GABAA receptor agonists 3-aminopropane sulphonic acid (3-APS) and muscimol. Since capsaicin acts mainly by releasing and depleting substance P from its stores in intestinal nerves, it is likely that substance P plays a role in the response caused by GABAA-mimetic compounds, On the whole, our results suggest that excitatory responses to 3-APS and muscimol result from both direct and indirect activation of intrinsic intestinal cholinergic neurons innervating smooth muscle cells.
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002211:Capsaicin / Q000494:pharmacology*; D002799:Cholinergic Fibers / Q000187:drug effects*; D005260:Female; D006168:Guinea Pigs; D007082:Ileum / Q000294:innervation; D066298:In Vitro Techniques; D008297:Male; D009118:Muscimol / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D011963:Receptors, GABA-A / Q000187:drug effects*
D011963:Receptors, GABA-A; D009118:Muscimol; D002211:Capsaicin; D001640:Bicuculline