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Comparison of the biphasic excitatory junction potential with membrane responses to adenosine triphosphate and noradrenaline in the rat anococcygeus muscle
Author(s) -
Byrne N.G.,
Large W. A.
Publication year - 1984
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1984.tb16229.x
Subject(s) - excitatory postsynaptic potential , adenosine triphosphate , adenosine , neuromuscular junction , chemistry , norepinephrine , muscle contraction , neuroscience , biophysics , medicine , biology , anatomy , biochemistry , inhibitory postsynaptic potential , dopamine
1 The effects of field stimulation and ionophoretic application of adenosine triphosphate (ATP) and noradrenaline were studied in the rat anococcygeus by means of an intracellular micro‐electrode. 2 Field stimulation at room temperature produced three types of electrical membrane response: (a) a ‘fast’ excitatory junction potential (e.j.p.) which had a latency of less than 100 ms and a time to peak of 300 ms; (b) a ‘slow’ e.j.p. which had a latency of several hundred ms and a time to peak of 1–2 s, and (c) an inhibitory junction potential (i.j.p.) which had a time to peak of about 1.5 s. All three responses were blocked by tetrodotoxin. 3 The ionophoretic application of ATP produced both monophasic and biphasic depolarizations; these responses had a latency of less than 30 ms and a time to peak of 150–300 ms. In contrast, ionophoretically‐applied noradrenaline produced a depolarization which had a mean latency of 471 ms and a time to peak of 861 ms. 4 The ‘slow’ e.j.p. and the noradrenaline‐induced depolarization were blocked by prazosin whereas the ‘fast’ e.j.p. and the ATP responses were resistant to this antagonist and also to atropine. 5 These results are further evidence that the ‘fast’ e.j.p. in some smooth muscle tissues is mediated by ATP.