Restraint stress increases corticotropin-releasing hormone mRNA content in the amygdala and paraventricular nucleus.

Corticotropin-releasing hormone (CRH) neurons located in the paraventricular nucleus (PVN) of the hypothalamus are implicated in regulating the endocrine response to stress. The amygdala is an established component of the neural circuitry mediating the stress response. To obtain information concerning the effects of stress on amygdala CRH neurons, a time-course study was conducted to examine, in rats, whether a 1-h restraint period increases CRH mRNA levels. The effects of restraint were also measured in the PVN. Using a sensitive RNase protection assay, we found that CRH mRNA levels in both the amygdala and paraventricular nucleus were significantly elevated 1 h after cessation of restraint. CRH mRNA levels in the paraventricular nucleus, but not the amygdala, remained elevated at the 3-h post-stress interval. 48 h after the termination of restraint, CRH mRNA levels in both brain structures returned to control levels. These data provide the first direct evidence that stress activates amygdala CRH neurons.