Evidence for a Muscarinic Inhibitory Brake Activated by Peptides in the Canine Small Intestine
Acetylcholine (ACH) injected intraarterially (ia) contracts the canine gut by a tetrodotoxin-(TTX) and hexamethonium-insensitive, atropine-sensitive mechanism. Field stimulation (40V, 0.5ms, 1–5Hz) produces phasic and tonic contractions which are slightly reduced by hexamethonium, almost eliminated by atropine (1) and blocked by TTX. Thus the major endogenous stimulant released by field stimulation is ACH which stimulates activity via a muscarinic receptor on the smooth muscle. Phasic and tonic contractions can be elicited after atropine by ia motilin and appear to represent release of a non-muscarinic transmitter to the smooth muscle (2).
KeywordsMuscarinic Receptor Gastrointestinal Motility Myenteric Plexus Field Stimulation Excitatory Response
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