Stress‐induced Changes in Tyrosine Hydroxylase Gene Expression in Rat Hypothalamic Paraventricular, Periventricular, and Dorsomedial Nuclei

Abstract

Particular hypothalamic nuclei--the paraventricular (PVN), periventricular (PeV), and dorsomedial (DMN)--are important centers regulating neuroendocrine and autonomic systems during stress. The present study investigated gene expression of catecholamines (CA)-synthesizing enzymes and protein levels, especially of tyrosine hydroxylase (TH), in response to acute (120 min) and repeated (7 x 120 min) immobilization (IMO) stress. Immunohistochemical staining revealed many TH-positive perikarya in the PeV, less in the DMN, and a few in the PVN. Analysis of microdissected tissue samples obtained from frozen brain sections by quantitative competitive PCR method revealed TH mRNA in the PVN, periventricular subdivision of the PVN (PePVN), and DMN. TH mRNA and TH protein levels were increased in all the nuclei investigated, in both acute and repeated stress conditions. Interruption of ascending CA pathways from the brain stem areas abolished TH gene expression in the PVN and DMN in response to stress. The present data suggest that cell groups expressing TH gene are present in all three hypothalamic nuclei studied and are highly activated by stress. The regulation of the majority of these TH-positive cells during stress is under modulatory control by brain stem or spinal cord areas.