Response of neurons in the dorsal motor nucleus of the vagus to thyrotropin-releasing hormone

Abstract

Autonomic motoneurons in the dorsal motor nucleus of the vagus (DMX) were recorded intracellularly in an vitro in slice preparation of the guinea pig brainstem. Bath-applied thyrotropin releasing hormone (TRH) (1–10 μM) induced a reversible depolarization of neurons that was typically accompanied by an increase in the spontaneous firing of the cells. In some cells, TRH induced rhythmic bursting activity. The TRH-induced depolarization occurred also in the presence of reduced Ca 2+ and TTX. The response was dose-dependent over TRH concentrations of 0.1–10 μM. The TRH-induced depolarization was accompanied by an increase in input resistance. The reversal potential of this effect corresponded to that of K +. Our results indicate that TRH increases the excitability of DMX neurons by reducing a resting K + conductance.