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

Summary Six and 18 months after neonatal administration of 6-hydroxydopamine or surgical sympathetic denervation the submaxillary gland of the rat showed a marked depletion of noradrenaline stores. Six months after removal of the superior cervical ganglion the gland's endogenous noradrenaline was lowered to 0.032±0.004 g/g while after neonatal 6-hydroxydopamine the values were 0.228±0.023 g/g (controls 2.145±0.382 g/g). Eightheen months after either type of sympathetic denervation the neurotransmitter was still depleted. In rats treated with 6-hydroxydopamine the sialagogue 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 supersensitivity to noradrenaline in rats treated with 6-hydroxydopamine. Eighteen months after surgical or chemical denervation, the activity of choline-acetyltransferase in the submaxillary gland was increased by about 50%. Of the respiratory enzymes studied, succinic dehydrogenase, fumarase and cytochrome oxidase, the activity of only the latter was markedly reduced by chronic sympathetic denervation. From the results obtained it is concluded that neonatal treatment with 6-hydroxydopamine causes a permanent and almost complete sympathectomy of the submaxillary gland of the rat.Supported partially by grant N⁰ 3211/73, Consejo Nacional de Investigaciones Cientificas y Técnicas.