Alterations Produced by Cortisol in the Spontaneous Activity and Responsiveness to Sensory Stimuli of Single Cells in the Tuberal Hypothalamus of the Rat

Abstract

The effects of cortisol on the spontaneous activity of single cells in the tuberal hypothalamus and their responsiveness to photic, acoustic, and sciatic stimulation were studied in rats. The over-all rate of firing of the spontaneous activity of the majority of the units was changed significantly by the hormone, with approximately equal numbers showing facilitation and inhibition. The hormone also produced significant changes in the fluctuations of firing, as well as alterations in the time-interval histograms. When the responses were divided into facilitatory and inhibitory to sensory stimulation, it was found that cortisol significantly decreased the amount of facilitation and, to some extent, increased the amount of inhibition. The changes in firing in individual cells following cortisol administration did not depend upon the rate of spontaneous discharge. This and other data would indicate that the change in the sensory responsiveness of the hypothalamic units is an independent phenomenon produced by the hormone. The possible relationship of the electrophysio-logical findings to the role of cortisol in the neuroendocrine regulation of ACTH secretion is discussed.