Electrical Stimulation of the Hippocampus under the Chronic Preparation and Changes of LH, FSH and Prolactin Levels in Serum and Pituitary

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The effect of electrical stimulation of the dorsal hippocampus (DHPC) on the concentration of LH, FSH and prolactin in both serum and pituitary gland was studied by chronic preparation in Wistar rats. Electrical stimulation consisting of monophasic square wave pulses of 0.1ms, 100Hz, 60μA was applied for 30min between 10:00 and 14:00 during various stages of the estrous cycle, or between 12:00 and 13:00 on the day of proestrus. The results are as follows: 1) Electrical stimulation of the DHPC did not induce any changes in the serum and pituitary LH levels during estrous cycle. 2) Both serum and pituitary levels of FSH were elevated following the stimulation on the day of estrus, and serum levels of FSH were reduced on the day of diestrus II. 3) Prolactin levels in serum were reduced by the stimulation on the days of proestrus and estrus, whereas pituitary levels were elevated. 4) Stimulation of the DHPC prior to the onset of critical period on the day of proestrus did not affect the ovulatory discharge of LH, FSH and prolactin, however elevated the pituitary levels of prolactin. 5) When stimulation was applied under acute preparation, the DHPC stimulation prevented the ovulation, and also depressed FSH and prolactin as well as LH to be released.<BR>These results suggest that the hippocampus participates in the dual mechanism involved in the release and synthesis of FSH and prolactin.
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