The human vas deferens: correlation of response pattern to noradrenaline and histological structure

Specimens of human vas deferens were studied histologically and by measuring changes in response to adrenoceptor agonists. In intact tissues noradrenaline induced both lengthening and shortening responses which were identified with contractions of circular and longitudinal muscle respectively. The agonists phenylephrine or methoxamine evoked mainly shortening but little lengthening. The tissues were unresponsive to clonidine or isoprenaline. Longitudinal strips but not rings responded reliably to phenylephrine and to caffeine. The lengthening responses of intact specimens to noradrenaline were relatively insensitive to the antagonist phenoxybenzamine. In contrast both shortening and lengthening responses were inhibited by prazosin or phentolamine but not by idazoxan. A physiological function for the predominance of muscle types in different specimens is proposed. A pharmacological selectivity for the muscle types by alpha 1-selective adrenoceptor agonists and by phenoxybenzamine is discussed and the clinical implication considered.