Diurnal changes in corticotropin-releasing hormone messenger RNA in the rat thalamus

Corticotropin-releasing hormone (CRH) is critical for mediating the stress response. CRH messenger RNA (mRNA) is present in a variety of brain regions including the thalamus and thalamic CRH mRNA concentrations increase in response to stress exposure. The present study assessed changes in basal CRH mRNA concentrations in the rat thalamus during different times of the day. Using in situ hybridization, we demonstrated that thalamic CRH mRNA levels exhibited more than two-fold increases during the dark phase between 20:00 and 02:00 h, followed by a decrease at 08:00 and 14:00 h during the light phase. Dramatic changes in thalamic CRH mRNA levels may have important implications for the possible role of thalamic CRH systems in waking, arousal, and the stress response.