Comparative electrophysiological investigations with Hydergine and other psychogeriatric agents on corticol and...

The action of systemically administered Hydergine on the spontaneous neuronal firing of neurons located in various brain areas of the anaesthetized rat was investigated using conventional extracellular single cell recording techniques. Whereas locus coeruleus neurons were activated by both acute and repetitive injections of the drug, spontaneously active neurons of the medial septal nucleus, pyramidal cells of the hippocampus and unidentified neurons of the cingulate cortex were not affected. The possible functional consequences of the drug's activating action on locus coeruleus noradrenergic neurons are discussed. In view of the finding that noradrenaline affects the signal-to-noise ratio in various brain areas and given the widespread innervation pattern of noradrenergic fibers arising from locus coeruleus, Hydergine through its action on this brain area may potentially affect many brain regions.