Inhibition by corticosterone of paraventricular nucleus multiple-unit activity responses to sensory stimuli in freely moving rats.

In order to determine possible electrophysiologic correlates of negative feedback influences of glucocorticoids upon neuroendocrine secretory activity, the effects of various doses of corticosterone on paraventricular nucleus multiple-unit activity responses to neural stimuli were examined in conscious, freely moving male rats. In control animals, photic and acoustic stimulation significantly increased multiple-unit activity of the paraventricular nucleus by increments of 75% and 117% (P less than 0.005), respectively. Doses between 0.1 and 5.0 mg of corticosterone produced a dose-dependent inhibition of responses to photic stimulation with a high correlation coefficient (r = -0.990). Corticosterone also caused an inhibition of paraventricular multiple-unit activity in response to acoustic stimulation, which was more effective than for photic stimulation, with complete blockade of response occurring with a dose of 1 mg corticosterone. These electrophysiologic findings, within a region of the hypothalamus known to contain corticotrophin-releasing factor cell bodies, may be related to reduced secretion of the hormone in response to the neurogenic stimuli employed, following glucocorticoid administration.