A comparison of the responses of the isolated vas deferens of the rat to field stimulation and to noradrenaline added cumulatively and non-cumulatively

The maxima, slopes and positions of cumulative and non-cumulative dose-response curves for noradrenaline were determined on the isolated vas deferens of the rat. Cumulative log dose-response curves were flatter and reached a lower maximum than the non-cumulative curves. However transformation of the responses to fractions of the maximal responses produced curves with identical slopes and only slight differences in positions. Field stimulation led to larger and more rapidly attained maximal responses than did the addition of exogenous noradrenaline. Responses to field stimulation applied at the plateau of the cumulative dose-response curves were similar to those occurring in the control situation. It is suggested that the effectiveness of noradrenaline in producing contraction of the vas deferens may be related to the rate at which its concentration rises at the effector cells.