[Karyometric changes in the neurons of the hypothalamic and ependymal nuclei of the 3d cerebral ventricle in sheep after administration of Gn-RH and subsequent irradiation].

Caryometric analysis was used for the study of changes in the cell nucleus volume of the neurons of nucleus paraventricularis, nucleus arcuatus, and ependyma of the third cerebral ventricle of sheep after the administration of Gn-RH, followed by exposure to X-rays. The test animals were 12 ewes in physiological anoestrus and two rams. The trials were conducted in spring. The first group of four sheep and two rams were left as controls; in the ewes of the second group the hypothalamo-hypophysial region was irradiated by exposure to 516.5 mC/kg (200 R); in the four ewes of the third group, ovaries were directly irradiated at laparotomy by exposure to 64.4 mC/kg (250 R). The ewes of the second and third group were treated with an i. m. administration of 400 micrograms Gn-RH per head before irradiation. The excisions were collected and processed the tenth day from irradiation. The studied material was fixed by injection of 10% formalin and finished by another dose of 10% formalin after the excision of the brains. The paraffin slices were stained with haematoxylin-eosine. The caryometric analysis was performed at 3000-fold magnification, 200 cells being measured in each sample. Changes in neurosecretory cells were described in the regions of nucleus paraventricularis, nucleus arcuatus and in the ependyma of the third cerebral ventricle. The results of the caryometric analysis of nucleus paraventricularis and nucleus arcuatus suggest that the administration of Gn-RH and irradiation of the hypothalamo-hypophysial region, and direct irradiation of ovaries, stimulate the studied cerebral structures. The changes observed in the ependyma of the third cerebral ventricle after the administration of Gn-RH and subsequent irradiation of the hypothalamo-hypophysial region are insignificant; it is only after the direct irradiation of ovaries that these cells are inhibited by an indirect effect through the feedback mechanism.