The neuropeptide TRH has a minor effect on the enzymatic activity of acetylcholinesterase in vitro

The neuropeptide thyrotropin-releasing hormone (TRH) elicits a variety of p hysiological effects of which some are due to cholinergic mechanisms. TRH m odulates in vivo the effects of compounds affecting acetylcholinesterase (A ChE). In the present study the in vitro effects of TRH on the activity of A ChE were explored. TRH has no effect at physiologically relevant concentrat ions. At unphysiologically high concentrations (>5 mM) a slight inhibition was found. This was noticed also when the enzyme was exposed to the amide-f ree tripeptide analog p-Glu-His-Pro. We conclude that any cholinergic effec t of TRH observed in vivo is unlikely to be due to a direct interaction of the peptide with AChE. (C) 1998 Elsevier Science Inc.