Non-adrenergic Inhibition of the Electrical Activity of the Antrum Muscle Fibers of the Guinea-Pig Stomach

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Abstract
Changes in the electrical activity of antrum muscle fibers of the guinea pig stomach caused by ATP and related compounds were compared with those caused by catecholamines. The antrum preparation exhibited spontaneous electrical activity which was suppressed or inhibited by treatment with catecholamines (adrenaline, noradrenaline and isoprenaline). The inhibitory actions of catecholamines were observed in the presence of tetrodotoxin or .alpha.-blockers (phentolamine or phenoxybenzamine), while the effects were antagonized by .beta.-blockers (propranolol or DCI [dichloroisoproterenol hydrochloride]). At higher concentrations than that of catecholamines, ATP or related mucleotides produced an inhibitory effect on spike activity and the generation of slow waves. The inhibitory actions of ATP and related substances were observed in the presence of .alpha.- or .beta.-adrenergic blockers. The inhibition was present after treatment with tetrodotoxin. The inhibitory action of ATP and related compounds is due to a direct action on the antrum muscle and is not mediated by .alpha.- or .beta.-adrenoceptors.

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