Synthesis and Pharmacology of TRH Analogs to separate Central Nervous Action from Endocrine Activity

Various TRH analogs, γ-butyrolactone-γ-carbonyl-His-Pro-NHR, γ-butyrolactone-γ-carbonyl-N3-im-methyl-His-Pro-NHR, 2-ketopiperidine-6-carbonyl-His-Pro-NHR and 3-oxoperhydro-1, 4-thiazine-5-carbonyl-His-Pro-NHR (R=H, methyl, ethyl, n-propyl, n-butyl, n-amyl, n-hexyl, β-phenethyl) were synthesized and pharmacologically tested in the hope of separating the central nervous action from endocrine activity. Among them, γ-butyrolactone-γ-carbonyl-His-Pro-NH2 was found to have potent central nervous actions in antagonizing pentobarbital sleep and in potentiating apomorphine-induced circling in mice, and only nominal TSH-releasing activity in rats.