Noradrenergic supersensitivity in the rat vas deferens during barbital withdrawal.

Three days' withdrawal from long-term barbital administration results in a shift to the left and increase in the maximum response of the concentration--effect curve to norepinephrine in the isolated rat vas deferens. The maximum response to carbachol and potassium was also increased without a leftward displacement of the concentration--effect curves. This specific increase in sensitivity to norpinephrine could indicate an adaptive alteration of the adrenoreceptors of the rat vas deferens (receptor supersentivity) as has been proposed for supersensitivity in the central nervous system during withdrawal from neuroleptics and barbiturates.