Electrical activity of hypothalamus during activation of pituitary-adrenocortical system.

Multiunit activity in anterior (AHA), medial (MHA) and lateral (LHA) areas of hypothalamus during activation of the pituitary-adrenocortical system was measured in chronic experiments on rabbits. Immobilization causing blood-corticosteroid levels to rise was followed by the excitation of most pools of neurons in MHA, and by inhibition in AHA and LHA. When immobilization failed to induce stimulation of MHA (as a result of pretreatment with large doses of cortisol), it did not cause blood-corticosteroid levels to rise, either. The switching off activity in AHA and MHA is considered to be a manifestation of functional changes which are responsible for stress-induced activation of the adrenocortical system.