NEUROPHARMACOLOGY OF THYROTROPIN RELEASING HORMONE (TRH)

In this review the effects of exogenously administered TRH on behavior and other neuronally mediated phenomena in experimental animals are documented. A more cursory account of the limited neuropharmacological studies performed to date with TRH in human subjects is also provided. Where appropriate to facilitate our understanding of the actions (and their underlying mechanisms) of TRH, the behavioral and other effects of a novel TRH agonist, MK-771, are included in this discussion. The effects of these peptides on neuronal excitability, putative transmitter metabolism and certain organ systems of the body along with the attempts to pharmacologically dissect the mechanisms underlying their unique actions are described. It would appear from the available information that a unifying hypothesis regarding the mode of action of TRH is not available to account for the multiple neurobiological effects of this peptide. However, a facilatory interaction of TRH with central cholinergic mechanisms may at least partially account for several of the actions of TRH including its remarkable antinarcosis effects. Finally, predicated on its pharmacological profile and our limited insight into the mode of action, some of the potential therapeutic applications of a potent and selective TRH agonist, such as MK-771, are briefly described. © 1979.