Effects of 6-hydroxydopamine Treatment at birth on the submaxillary gland of the rat

Abstract

Six and 18 months after neonatal administration of 6-hydroxy-dopamine or surgical sympathetic denervation the submaxillary gland of the rat showed a marked depletion of noradrenaline stores. Six months afer removal of the superior cervical ganglion the gland's endogenous noradrenaline was lowered to 0.032 +/- 0.004 mug/g while after neonatal 6-hydroxydopamine the values were 0.228 +/- 0.023 mug/g (controls 2.145 +/- 0.382 mug/g). Eighteen months after either type of sympathetic denervation the neurotransmitter was still depleted. In rats treated with 6-hydroxydopamine the sailagogue effect of injected noradrenaline was potentiated 2.7-fold while the potentiation of the effect of noradrenaline was 3.6 times after surgical denervation. The magnitude of the supersensitivity developed to isoprenaline did not differ between both types of denervation. No supersensitivity to the cholinomimetic agent, methacholine, was observed. Cocaine administration or removal of the superior cervical ganglion slightly increased the supersensivity to noradrenaline in rats treated with 6-hydroxydopamine. Eighteen months after surgical or chemical denervation, the activity of choline-acetyl-transferase in the submaxillary gland was increased by about 50%. Of the respiratory enzymes studied, sussinic dehydrogenase, fumarase and cytochrome oxidase, the activity of only the latter was markedly reduced by a chronic sympathetic denervation. From the results obtained it is concluded that neonatal treatment with 6-hydroxy-dopamine causes a permanent and almost complete sympathectomy of the submaxillary gland of the rat.