Localization of TRH-sensitive sites in rat brain mediating intestinal transit.

Stereotaxic microinjection of thyrotropin releasing hormone (TRH) into 16 brain areas revealed that only three sites, the medial septum and the lateral and anterior hypothalami, were sensitive to a 1.0 ug dose in stimulating intestinal transit in anesthetized rats. The medial septum and anterior hypothalamus also responded to 0.1 ug, but not to 0.01 ug, of TRH. Because TRH and its receptors are distributed in these brain areas, the present results suggest a possible role for this peptide in the central regulation of gastrointestinal activity.