Influence of Gonadotropic Hormones on the Hypothalamic Neurosecretory Activity in the Rat

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Abstract
The present work deals with the relationship between gonadotropic hormones and neurosecretory activity. For this purpose, the oestrous cycle was studied during elevated vasopressin blood levels due to thirst. In addition, the neurosecretory activity in the magnocellular supraoptic and paraventricular nuclei (SON and PVN) was determined after administration of oestrogens and gonadotropic hormones. The parameter for neurosecretory activity in this investigation was the distribution of the Golgi-apparatus specific enzyme, thiamine diphosphate-phosphohydrolase (TPP-ase), as measured by a semi-quantitive histochemical method. During water deprivation, no increase in the amount of pro-oestrous and oestrous smears was found. After injection of oestrogens in ovariectomized rats, the neurosecretory activity decreased, while a reactivation was observed after gonadotropic hormone (HMG, HCG, NIH-LH, NIH-FSH) administration. This reactivation was not observed after prolactin (NIH) administration. The changes in neurosecretory activity found under conditions that cause alterations in the gonadotropic-hormone and oestrogen levels are, therefore, due to the influence of FSH and LH on the neurosecretory activity.

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