[3H]‐adenine nucleotide and [3H]‐noradrenaline release evoked by electrical field stimulation, perivascular nerve stimulation and nicotine from the taenia of the guinea‐pig caecum

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Abstract
1 The release of [3H]-noradrenaline and adenine nucleotide evoked by electrical field stimulation (20–60 V, 30 Hz), perivascular nerve stimulation (20–80 V, 60 Hz) and nicotine (10, 100 μm) was studied in the taenia of the guinea-pig caecum under various conditions. 2 Electrical stimulation at high intensity (60 V) caused the release of [3H]-adenine nucleotide; however, the inhibitory action of electrical stimulation was proportional to [3H]-noradrenaline release. 3 The intensity of the inhibitory effect of stimulation of the perivascular nerves was directly related to [3H]-noradrenaline release and not associated with the release of [3H]-nucleotide. 4 Cold storage for more than 8 days, cooling (19° C) or tetrodotoxin treatment (1 μg/ml) abolished the inhibitory responses to electrical stimulation and to nicotine. After these treatments, nicotine and electrical stimulation elicited only contractions; the release of [3H]-noradrenaline, but not that of [3H]-adenine nucleotide, was inhibited. 5 The dissociation of the inhibitory effects of electrical stimulation and nicotine from [3H]-nucleotide release does not support the hypothesis that ATP or a related nucleotide is the humoral transmitter of the non-adrenergic inhibition in the taenia of the guinea-pig caecum.