In view of the involvement of noradrenaline (NA) in the regulation of adrenocortical secretion, its role in the rise of plasma corticosterone following neural stimuli was evaluated in rats. The injection of the cathecholamine neurotoxin 6-hydroxidopamine (6-OHDA) into the ventral noradrenergic bundle in the brain stem, which projects to the hypothalamus, caused an average depletion of NA of 72% and 78% in the mediobasal hypothalamus and the paraventricular nuclei respectively, when compared to the rats injected with vehicle. In the animals injected with 6-OHDA, the basal level of corticosterone in plasma and the response to stress induced with ether were not affected. However, the adrenocortical discharge was very significantly inhibited following photic, acoustic and sciatic nerve stimulation. The present experiments support the results of previous studies on the stimulatory effect of NA on adrenocortical secretion.
- neural stimuli