Cerebrovascular Effects of the TRH Analogues pGlu-3-methyl-His-Pro Amide and pGlu-Glu-Pro Amide: A Comparison with TRH

Abstract The goal of the study was to assess whether TRH analogues possess cerebrovascular effects similar to the native peptide. The neuropeptide thyrotropin releasing hormone (TRH) elicits cerebrovasodilation in several species under various conditions. The laser-Doppler method was employed to study the effects of TRH and the analogues pGlu-3-methyl-His-Pro amid (M-TRH) and pGlu-Glu-Pro amide. Intravenous (iv.) injection of 300 μg kg−1 of TRH elicited cerebrovasodilation and a 62% increase in blood flow within 1 minute. M-TRH, in a dose of 300 μg kg−1 iv., elicited a 80 % increase in cerebral blood flow. Even a minute dose of M-TRH (625 ng kg−1) caused an increase in cerebral blood flow. No clear difference in effects on the cerebral blood flow was observed between spontaneously and mechanically ventilated animals. pGlu-Glu-Pro amide had no cerebrovascular effect.