Modifications in single cell activity in the rat midbrain during the iontophoretic application of cortisol.

In view of the modulatory role of the midbrain in the regulation of adrenocorticotrophic functions, the effects of iontophoretic application of cortisol to central gray and midbrain reticular formation units was studied. Two-thirds of the cells responded by a change in the rate of firing, mainly by inhibition, which in some cells lasted more than 1 min. These modifications in the excitability of midbrain neurons, produced by changing concentrations of glucocorticoids, may affect indirectly hypothalamic neuroendocrine mechanisms controlling ACTH secretion.