PHORBOL ESTER OR CAMP ENHANCE THYROTROPIN-RELEASING-HORMONE MESSENGER-RNA IN PRIMARY CULTURES OF HYPOTHALAMIC CELLS

Thyrotropin releasing hormone (TRH) biosynthesis is subject to a multi factorial control. TRH mRNA levels are negatively regulated by thyroid hormones in the paraventricular hypothalamic nucleus, and positively in cold exposure or suckling. Effect of second messenger pathways stim ulation, a known response of membrane receptors, was studied in vitro; cultures of rat embryonic hypothalami (is day gestation) were treated with 12-O-tetradecanoylphorbol-13-acetate (TPA, 100 nM) or dibutiryl cAMP (dBcAMP, 1 mM) for various times. Levels of TRH mRNA were raised after the first hour of dBcAMP or 2 h of TPA treatment and were still increased at 24 h. These results suggest a neural regulation of TRH bi osynthesis.