Effects of neuropeptide Y (NPY) on submucosal neurons of the guinea-pig descending colon were investigated electrophysiologically by means of intracellular electrophysiological recordings. NPY (100 nM) induced a marked and prolonged hyperpolarization, accompanied by a decrease in input resistance in most (90%) neurons. This NPY-induced hyperpolarization was diminished and augmented by membrane hyperpolarization and depolarization, respectively. The NPY-hyperpolarization was not affected by exposure to either calcium-free solu solutions or the α2-adrenoceptor antagonist, idazoxan (1 μM). When more than one peptide was applied to a neuron, NPY, PYY and Pro34-NPY were equipotent, whilst NPY13-36 was less potent. It was concluded that NPY hyperpolarized submucosal neurons of the guinea-pig descending colon, possibly via a direct action on postsynaptic Y1-receptor and increasing potassium conductance.
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