Single pulse stimulation of guinea-pig vas deferens and the presynaptic receptor hypothesis.
1 The effect of phenoxybenzamine on the efflux of [3H]-noradrenaline and the mechanical response to single pulse excitation of superfused guinea-pig vas deferens was determined to examine the validity of the currently accepted hypothesis of a presynaptic negative feedback system on adrenergic nerve terminals. 2 The adrenoceptor antagonist enhanced both the outflow of tritium and the mechanical response to single pulse stimulation. The efflux of labelled material and the responses to 4 pulses were also enhanced, as expected. 3 Blockade of neuronal and extraneuronal uptake did not by itself increase nerve-induced outflow or the mechanical response nor dated within the framework of a hypothesis that proposes that the enhancement of response and tritium efflux by phenoxybenzamine results from blockade of a feedback system whereby noradrenaline released by previous impulses inhibits its own subsequent release.
D000818:Animals; D003042:Cocaine / Q000494:pharmacology; D004558:Electric Stimulation; D006168:Guinea Pigs; D006854:Hydrocortisone / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D010643:Phenoxybenzamine / Q000494:pharmacology*; D014649:Vas Deferens / Q000187:drug effects / Q000502:physiology*
D010643:Phenoxybenzamine; D003042:Cocaine; D006854:Hydrocortisone; D009638:Norepinephrine