Minireview. Thyrotropin releasing hormone and CNS cholinergic neurons

The centrally mediated pharmacological effects of thyrotropin releasing hormone (TRH), their mechanistic basis and therapeutic implications, along with the possible physiological significance of extrahypothalamic TRH, have been the subject of numerous investigations for over a decade. Despite this effort a holistic perspective on these issues and considerations does not exist. However, with continued research employing multiple and diverse experimental approaches, many interactions of TRH and related peptides with central cholinergic mechanisms have been revealed. These interactions are documented in this review and it is proposed that they can account for several of the more prominent pharmacological actions of these peptides. Additionally, it is suggested that a function of endogenous YHR, throughout the neuroaxis, may be to regulate the excitability of central cholinergic neurons.