Effects of chronic bretylium treatment on the sympathetic neuron and the smooth musculature of the rat.

The effects of chronic i.p. injection of high doses of bretylium on sympathetic nerves on the smooth musculature of the vas deferens of adult and newborn rats were examined using fluorescence histochemistry, light and electron microscopy and organ bath physiological techniques. Bretylium treatment caused mitochondrial swelling, loss of cristae and the formation of electron-dense inclusions in the mitochondria of sympathetic neurons. However, neuron degeneration was not observed and fluorescent histochemical appearance of adrenergic neurons was normal. A small transient supersensitivity of the isolated vas deferens of bretylium-treated rats to noradrenaline, but not to acetylcholine, occurred. There was, however, considerable increase in the maximal contractile response to both noradrenaline and acetylcholine. In high calcium concentrations acetylcholine-induced contractions of vasa deferentia from bretylium-treated rats were significantly greater than control; there was no difference in magnitude of noradrenaline-induced contractions.