Corticotropin-releasing hormone messenger RNA distribution and stress-induced activation in the thalamus

Corticotropin-releasing hormone plays a critical role in mediating the stre ss response. Brain circuits hypothesized to mediate stress include the thal amus, which plays a pivotal role in distributing sensory information to cor tical and subcortical structures. In situ hybridization revealed neurons co ntaining corticotropin-releasing hormone messenger RNA in the posterior tha lamic nuclear group and the central medial nucleus of the thalamus, which i nterfaces with the ventral posteromedial nucleus (parvicellular part). Thes e regions are of interest because they process somatosensory and visceral i nformation. In the first experiment, the effect of acute stress on thalamic corticotropin-releasing hormone messenger RNA levels was assessed. Rats re strained for 1 h and killed 1 h later were found to have increased corticot ropin-releasing hormone messenger RNA in the posterior thalamic nuclear gro up. The time course of these changes was examined in a second experiment in which rats were killed immediately or 3 h after restraint. While no change s occurred in the thalamus immediately after restraint, 3 h after restraint , increases in corticotropin-releasing hormone messenger RNA occurred in bo th the posterior thalamic nuclear group and the central medial-ventral post eromedial nucleus (parvicellular part) of the thalamus. A different pattern of activation was observed in the paraventricular nucleus of the hypothala mus with increased corticotropin-releasing hormone messenger RNA immediatel y after restraint, but not I or 3 h later. In addition to the stress-induce d changes, a prominent decrease in baseline thalamic corticotropin-releasin g hormone messenger RNA was observed from 1000 to 1300 h. These results show that the thalamus contains corticotropin-releasing hormo ne messenger RNA that increases after restraint stress, indicating a role f or thalamic corticotropin-releasing hormone systems in the stress response. Stress-induced changes in thalamic corticotropin-releasing hormone messeng er RNA expression appears to be regulated differently than that in the para ventricular nucleus of the hypothalamus, and may be influenced by diurnal m echanisms. (C) 2001 IBRO. Published by Elsevier Science Ltd. All rights res erved.