Biochemical evidence of adrenergic interaction with cholinergic function in the central nervous system of the rat. 1. Effect of norepinephrine.

Abstract

The effect of centrally administered norepinephrine (NE) into the lateral ventricle on choline acetylase activity (ChAc), endogenous levels of NE, dopamine (DA) and serotonin (5HT) was studied in different regions of the rat brain. In normal rats, the highest activity of choline acetylase was found in the cerebral cortex, followed by the brain stem, the diencephalon, the hypothalamus and least in the cerebellum. Chronic administration of NE significantly increased the choline acetylase activity in all regions studied, whereas both the acute and the in vitro studies showed no significant change except in the brain stem. Serotonin level was increased in the cerebellum, but decreased in the diencephalon and the brain stem. There was no significant alteration in the level of NE in all areas studied except in the hypothalamus where there was an increase in the mean concentration. Tissue level of DA showed a significant increase in the cerebral cortex and the hypothalamus. Behaviourally, there was a significant increase in food intake on the first day of treatment with no significant change in water intake. The data suggests that NE may be involved in the regulation of acetylcholine synthesis. The significance of interaction between different monoamines and acetylcholine may be important in the study of drug tolerance phenomena.