Tachykinin Activation of Muscarinic Inhibition in Canine Small Intestine is Substance P in Nature
Substance P, when injected intra-arterially into the small intestine of the anesthetized dog during phasic activity, produces a dose dependant inhibition of the phasic activity. This inhibitory response was abolished by elimination of field stimulated activity by intra-arterial tetrodotoxin, but reduced by atropine treatment (on activity induced by intra-arterial motilin). This suggested that Substance P acted by releasing several inhibitory transmitters, one of which was probably acetylcholine acting on inhibitory autoreceptors on cholinergic nerves . The identity of the other transmitter/ transmitters is unknown.
KeywordsCholinergic Nerve Krebs Ringer Bicarbonate Atropine Treatment Potency Sequence Muscarinic Inhibition
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