[LH-RH content in different parts of the hypothalamus and blood of rats with an altered level of thyroid hormones].

Luliberin (LH-RH) in the preioptic region of the hypothalamus, the region of the arcuate nuclei, and of the medial eminence, the region of the dorsomedial nuclei and in the blood serum was studied in intact female rats with a stable 4-day cycle, and also in thyroidectomized female animals. LH-RH content rose significantly during the morning hours of the proestrus both in the cyclic and in the tonic centres of the hypothalamus. At the same time there was an increase of this hormone secretion. Thyroidectomy blocked the LH-RH synthesis and secretion elevation in both areas at the proestrus stage. In the region of the dorsomedial nuclei LH-RH content remained at the same level in the both groups of the animals. During the day at the proestrus stage, intact animals displayed definite regularities in the LH-RH synthesis in both the hypothalamic centres, and also in its secretion (absent in thyroidectomized animals). The data obtained indicated disturbance of cyclic discharge of LH-RH after thyroidectomy to be largely connected with reduciton of the hormone level in the cyclic centre localized in the preoptic region of the hypothalamus.