Study on the central mechanism for gonadotropin secretion in the female rat by brain transplantation technique.

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1. Method for transplantation of catecholamine-neuron in the brain: The neural tissue including A-6 group noradrenaline (NA)-neurons in the locus coeruleus (for NA-rich transplant) or A-10 group doapmine (DA)-neurons in the substantia nigra (for DA-rich transplant) was punched out of the coronal slice dissected from the medulla or midbrain of newborn rats, respectively, with a metal cannula and was stereotaxically positioned in the third ventricle at the level of the preoptic region of cycling rats. Surviving transplant was confirmed to have catecholaine neurons in the Falck-Hillarp fluorescence method.2. Reproductive function of the female rats with catecholamine-neuron transplants in the third ventricle: The female rat that had surviving NA-neuron rich transplant frequently showed prolongation of estrus, indicating that ovulation was severely impaired. However, after ovariectomy, they showed a pulsatile secretion of LH with a remarkably large amplitude. The DA-neuron rich transplants … More sustained the estrous cycle unchanged, and did not change pulsatile secretion of LH after ovariectomy, too. The results suggested that the NA-neurons rich transplants at the preoptic region somehow inhibited gonadotropin secretion in the intact rat, whereas they facilitated it in ovariectomized rats.3. Blood pressure of the rats with catecholamine-neuron transplant in the third ventricle: The rats with either transplant, NA-neurone ro DA-neuron, showed a long lasting hypotension. The hypotensive effect was exerted even on the hypertension produced by salt-loading.4. Effect of estrogen-progesterone treatment on the gonadotropin secretion in the gonadectomized male rat with the ventricular implantation of the preoptic suprachiasmatic nucleus from the female newborn: The preoptic suprachiasmatic nucleus has been considered as the key locus for positive feedback action of progesterone on gonadotropin secretion in the female rat. Transplantation of such a neural tissue in the male brain was not effective to induce LH surge, while FSH secretion was induced. Less