Exogenous corticosterone induces the expression of the clock protein, PERIOD2, in the oval nucleus of the bed nucleus of the stria terminalis and the central nucleus of the amygdala of adrenalectomized and intact rats.

The cyclical expression of the clock protein PERIOD2 (PER2) in select regions of the limbic forebrain is contingent upon the rhythmic secretion of the adrenal glucocorticoid, corticosterone. Daily rhythmic PER2 expression in the oval nucleus of the bed nucleus of the stria terminalis (BNSTov) and the central nucleus of the amygdala (CEA) is abolished with the removal of the adrenal glands but restored with rhythmic hormone replacement via the drinking water at a time corresponding to the endogenous peak of circulating glucocorticoids. Here, we investigated the effects of serial or acute systemic injections of corticosterone on the expression of PER2 in the BNSTov and CEA of both adrenalectomized (ADX) and intact rats.

Glucocorticoid regulation of clock gene expression in the mammalian limbic forebrain.

Glucocorticoids regulate a wide variety of functions, including synaptic plasticity, hypothalamic-pituitary-adrenal axis activation, conditional fear learning, metabolism, and sensitization to drugs of abuse. The diurnal secretion of glucocorticoids, driven by the mammalian master clock located in the suprachiasmatic nucleus of the hypothalamus, has been shown to induce and entrain clock gene expression in peripheral tissues. However, little attention has been given to the form and function of centrally located subordinate oscillators, and the synchronizing factors that influence them.

The expression of the clock protein PER2 in the limbic forebrain is modulated by the estrous cycle.

Daily behavioral and physiological rhythms are linked to circadian oscillations of clock genes in the brain and periphery that are synchronized by the master clock in the suprachiasmatic nucleus. In addition, there are a number of inputs that can influence circadian oscillations in clock gene expression in a tissue-specific manner. Here we identify an influence on the circadian oscillation of the clock protein PER2, endogenous changes in ovarian steroids, within two nuclei of the limbic forebrain: the oval nucleus of the bed nucleus of the stria terminalis and central nucleus of the amygdala.