Effect of intracerebroventricular administration of thyrotropin-releasing hormone upon the electroenteromyogram of rat duodenum.

Electroenteromyographic activity (EMG) of the duodenum was recorded in pentobarbital-anesthetized rats. TRH intraventricularly administered to rats produced changes in EMG such as increased amplitude, decreased frequency of slow waves and the association of bursts of spike potentials with nearly every cycle of the basal electric rhythm (BER). The effect was selectively prompt and marked in the EMG of proximal duodenum. The response was abolished by vagotomy or atropine injection and no response was elicited in the neonatally 6-OHDA-treated rat. Hypophysectomy, cord-transection or acute i.v. injection of 6-OHDA did not block the response. In the brain, TRH seems to stimulate the neuronal system controlling the vagus efferents involved in the regulation of the duodenal enteric nervous system which in turn modulates the myogenic excitability of the duodenum.