Thyrotropin-releasing hormone content of rat brain and hypothalamus: results of endocrine and pharmacologic treatments.

Studies of hypothalamic and regional brain TRH content in the rat after administration of various hormonal and pharmacologic agents were performed. No consistent changes in TRH content in the hypothalamus or brain followed thyroidectomy, hypophysectomy or administration of thyroxine or dexamethasone. There was a significant fall in hypothalamic forebrain and brain stem TRH content 60 min after insulin administration and in brain stem TRH at 30 and 120 min as well. Administration of alpha-methyl-paratyrosine, parachlorophenylalanine or reserpine, in varying doses and for varying periods, did not alter hypothalamic or regional brain TRH content. Thus, little evidence that hypothalamic or brain TRH content is dependent on hormonal milieu or neurotransmitter content was found.