Histamine-induced release of thyrotropin releasing hormone from hypothalamic slices

In vitro release of TRH from mediobasal hypothalamic (MBH) slices was increased in the presence of 56 mM K+ in a Ca2+-dependent manner. Addition of histamine (HA) induced a concentration-dependent release of TRH; concentrations of 3 x 10(-7) M and 10(-6) M elicited maximal and maximal stimulation respectively. Cimetidine 10(-6) M, a potent antagonist of HA H2-receptors, inhibited the effect of HA. The present results suggest that HA can trigger the release of TRH from neurosecretory nerve endings and that MBH slices are a useful preparation for studying neurohormone release.