CRH mRNA expression in the hypothalamic paraventricular nucleus is inhibited despite the activation of the hypothalamo-pituitary-adrenal axis during starvation

Corticotropin-releasing hormone (CRH) is one of the anorexigenic neuropeptides, and indeed the expression of hypothalamic CRH is known to be inhibited by starvation. To clarify whether elevated plasma glucocorticoid during starvation is responsible for the CRH suppression, we examined the expression level of hypothalamic CRH mRNA after food deprivation in adrenalectomized, plasma corticosterone (B)-clamped animals. Male Wistar rats were divided into 2 groups: one group had adrenalectomy (ADX) and B pellet implantation (ADX + B, n = 42), and the other group had only sham operation (sham, n = 42). Rats were then treated with either ad libitum food supply or food deprivation for up to 96 h. The expression of CRH mRNA in the paraventricular nucleus (PVN) was estimated by in situ hybridization. After food deprivation, mean plasma B level was markedly elevated in sham group, but almost clamped in the ADX + B group. In this experimental condition, CRH mRNA in the PVN was significantly decreased in the sham group, whereas no change was obtained in the ADX + B group. Our data suggest the decrease in CRH mRNA seems to be related to the elevated glucocorticoid level during starvation. The status of hyperadrenocorticism without activation of CRH led us to speculate that adrenocortical function is predominant in the hypothalamic-pituitary-adrenal (HPA) axis during starvation.