The potentiating effects of 4-aminopyridine on adrenergic transmission in the rabbit vas deferens. |
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Authors: | A Johns D S Golko P A Lauzon D M Paton |
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Affiliation: | Department of Pharmacology, University of Oklahoma College of Medicine, Oklahoma City, Oklahoma 73190, U.S.A. |
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Abstract: | The effects of 4-aminipyridine on adrenergic transmission in rabbit vas deferens were investigated. 10(-5)-10(-3) M 4-aminopyridine markedly potentiated the sustained, secondary contractile response to transmural stimulation and significantly increased the amount of (+/-)-|3H]-metaraminol released at 5 Hz, but had little effect on responses to exogenous (-)-noradrenaline. 10(-5)-10(-4) M 4-aminopyridine did not significantly alter the accumulation or efflux of (-)-[3H]-noradrenaline in rabbit heart. It is suggested that 4-aminopyridine potentiated responses of rabbit vas deferens to transmural stimulation mainly by increasing transmitter release, possibly as a result of prolongation of the action potential. Responses to transmural stimulation were also potentiated by by 2- and 3-aminopyridine and by 3,4-diaminopyridine but not by pyridine, aniline, 4-dimethylaminopyridine, 4-aminoethylpyridine or 2-aminopyrimidine. |
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Keywords: | Sympathetic-cholinergic system Electrodermal responses Yohimbine Hypothalamic stimulation Clonidine |
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