Supersensitivity to noradrenaline in preparations of rat cauda epididymis after vasectomy.

Preparations of cauda epididymides were taken from rats unilaterally vasectomised by medial transection of the vas deferens. Responses of preparations from the operated side to field stimulation (10 pulses, 70 V, 1 ms, 0.1-20 Hz) declined in parallel with decreases in catecholamine fluorescence. There were leftward shifts in the mean cumulative concentration-response curves to noradrenaline on vasectomised cauda epididymides of 5-, 10-, and 12-fold at days 2, 7 and 28, respectively compared to unoperated cauda epididymides following vasectomy. Nisoxetine (0.1 mumol/l) enhanced the potency of noradrenaline upon unoperated but not upon vasectomised segments. There were leftward shifts of 7- and 8-fold in the mean cumulative concentration-response curves to acetylcholine in vasectomised cauda epididymides at days 2 and 7, respectively, following surgery. Responses to methoxamine and carbachol were unaffected by vasectomy. Thus neurotransmission to the smooth muscle of the rat cauda epididymis resembles that to the vas deferens, in that vasectomy results in the development of prejunctional supersensitivity to noradrenaline and acetylcholine.