The potentiating effects of 4-aminopyridine on adrenergic transmission in the rabbit vas deferens.
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.
D000818:Animals; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D008680:Metaraminol / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects; D009638:Norepinephrine / Q000378:metabolism / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology*; D011817:Rabbits; D013268:Stimulation, Chemical; D013564:Sympathetic Nervous System / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects*; D013997:Time Factors; D014649:Vas Deferens / Q000187:drug effects / Q000294:innervation* / Q000502:physiology
D011725:Pyridines; D008680:Metaraminol; D009638:Norepinephrine