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Two Signal Transduction Mechanisms of Substance P‐induced Depolarization in Locus Coeruleus Neurons
Author(s) -
Koyano K.,
Velimirovic B. M.,
Grigg J. J.,
Nakajima S.,
Nakajima Y.
Publication year - 1993
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.1993.tb00973.x
Subject(s) - locus coeruleus , biophysics , depolarization , conductance , chemistry , tetrodotoxin , substance p , patch clamp , intracellular , membrane potential , reversal potential , endocrinology , medicine , neuroscience , biology , biochemistry , receptor , central nervous system , neuropeptide , physics , condensed matter physics
Effects of substance P on cultured neurons of the locus coeruleus of the rat were studied using the whole‐cell patch clamp technique. In some cells substance P produced a decrease in a K conductance which showed an inwardly rectifying property. In other cells substance P produced an initial inward current which was accompanied by a conductance increase. The rest of the cells showed responses which were mixtures of the above two responses. The measurement of the reversal potential of the initial inward current after suppressing the voltage‐gated Ca and K conductances suggests that it is caused by an increase in a non‐selective ionic conductance. In cells loaded with 260 μM GTPγS, application of substance P produced an irreversible reduction of the K conductance, while the initial inward current could still be recorded, suggesting that the former is mediated by a G protein, whereas the latter may be activated by a different signal transduction mechanism. The initial inward current was not eliminated by external application of high concentrations of tetrodotoxin, d ‐tubocurarine or amiloride. Nor was it affected by the intracellular application of cyclic GMP or cyclic AMP.