THE GROWTH-HORMONE (GH) GENE IS EXPRESSED IN THE LATERAL HYPOTHALAMUS- ENHANCEMENT BY GH-RELEASING HORMONE AND REPRESSION BY RESTRAINT STRESS

Recent studies suggest that GH may modulate emotion, behavior, or stre ss response by its direct actions on the brain, and possible expressio n of the GH gene in the brain has been predicted. In this study we hav e investigated whether and where the GH gene is expressed in the brain and how it is regulated. Ribonuclease protection assay and 5'-rapid a mplification of complementary DNA ends-PCR analyses indicated that the GH gene was expressed in rat brain, initiating at the identical trans cription start point as that for pituitary GH gene expression. The bra in GH messenger RNA was predominantly detected in the lateral hypothal amus (Ih) by in situ reverse transcription-PCR analysis. GK gene expre ssion in the brain was significantly enhanced by GH-releasing hormone administration and was rapidly repressed by exposure to restraint stre ss in the water, whereas the changes in pituitary GH messenger RNA con tents in these circumstances were relatively smaller. The results of t he present study suggest that the brain GH is predominantly expressed in Ih under the control of physiological conditions to play a role in the modulation of brain functions.