[Reaction of certain hypothalamic centers of rats to a single dose of thyroliberin].

It has been shown that excess intramuscular injection of exogenous thyrotropin releasing hormone in a dose of 8 micrograms leads to a lowering of functional activity of the supraoptic and suprachiasmatic centers. This lowering was manifested by the reduced nucleolar size of neurosecretory cells. Nucleolar segregation seen in paraventricular and ventromedial nuclei of the hypothalamus attested to a pronounced suppression of RNA synthesis. No morphological changes were found in the arcuate nucleus. The role of the hypothalamic centers in the regulation of thyrotropin releasing hormone level is discussed.