Effect of Median Eminence Implants of LH on Pituitary LH of Female Rats1

Corbin, Alan; Cohen, Arthur I.

doi:10.1210/endo-78-1-41

Cited by 52 publications

(17 citation statements)

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“…It is believed that such secretions are regulated by at least two forms of feedback mechanisms, a long-loop control mediat ed by hormone signals from target glands and a short-loop or internal feedback mechanism mediated, in some fashion, by pituitary hormones themselves [28], A variety of studies in animals and in women has yielded data in support of the existence of a short-loop feedback for pituitary LH secretion. Kawakaini and Sawyer proposed such a phenomenon in 1959 [3,7], when they observed that exogenously administered HCG or LH was associated with the induction of electroencephalographic changes in the rabbit [19]. Hippocampal hyperactivity was induced and this was characterized by 8/s high amplitude synchronous spikes from both the hippocampus and its projections [18,35], These original studies have been confirmed by others who have shown that peripherally and intraventricularly administered LH alters the electrical activity of both cells within the hypothalamus and in the hippocampus [8,11,18,35,36].…”

Section: Discussionmentioning

confidence: 97%

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Hypothalamic LH May Play a Role in Control of Pituitary LH Release

Emanuele¹,

Oslapas²,

Connick³

et al. 1981

Neuroendocrinology

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We have recently reported immunoassayable luteinizing hormone (LH) in several areas of the rat brain and conspicuously present in the hypothalamus. In this report, we focus on the presence of LH in the hypothalamus and its potential role in regulation of pituitary LH release. In adult female rats, examined during the course of the estrous cycle, a significant fall in hypothalamic LH coincides with the surge in pituitary and serum LH at the time of proestrus, signaling ovulation. Ovariectomized adult rats show no change in hypothalamic LH at a time when there is a dramatic rise in both anterior pituitary and serum LH. These data support the concept that hypothalamic LH is not of pituitary origin and that it may play a role in the short-loop negative feedback system controlling the surge in anterior pituitary LH release, an event initiating ovulation.

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Section: Discussionmentioning

confidence: 97%

“…Significant decreases in circulating LH and in pitui tary LH content have been noted with such manipulations in animals [3,16,42]. Inhibition of ovulation, ovarian atro phy, and delayed vaginal opening in immature animals have also been observed in animals with LH implants in the basal hypothalamus [7,30].…”

Section: Discussionmentioning

confidence: 98%

Hypothalamic LH May Play a Role in Control of Pituitary LH Release

Emanuele¹,

Oslapas²,

Connick³

et al. 1981

Neuroendocrinology

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“…David et al (1966) and claimed that the LH implantation in ME in rats demonstrated a consistently and significantly lower pituitary LH content, despite of the fact that the confidence limits of their data overlapped each other between the implanted group and the (Corbin and Cohen, 1966; This investigation first demonstrated that LH release, but not FSH release was inhibited by LH implantation into the pituitary. These results were different from the result when LH was implanted into the ME.…”

Section: Discussionmentioning

confidence: 97%

Short-and Auto-Feedback Mechanism of LH

1971

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SynopsisThe effect of implantation of LH (NIH LH Ovine) into the median eminence (ME) area or into the anterior pituitary of ovariectomized rats on pituitary and plasma gonadotropin was investigated. Seven days after implantation, the animals were sacrificed, and FSH and LH activity was determined according to Igarashi-McCann (Igarashi et al., 1964) method and Parlow-McCann-Yokota method (Yokoyama et al., 1965), respectively.LH implantation in ME significantly decreased plasma FSH levels in two out of the three experiments, and pituitary FSH content in one out of the three experiments. On the other hand, plasma LH levels of LH implanted animals showed a significant decrease in two out of the three experiments. Pituitary LH content of LH implanted animals showed no change in all the three experiments.LH implantation in anterior pituitary induced no constant change in plasma and pituitary FSH, a significant decrease in plasma LH levels in one and a tendency of decrease in the other two out of the three experiments, while pituitary LH content did not change.It is concluded that when LH exerts a direct action on the ME, release of FSH and LH is inhibited.On the other hand, when LH exerts a direct action on the anterior pituitary, release of LH only is inhibited.

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“…This sup position has been amply proved by implantation of hypophysiotrophins into the median eminence of the rat hypothalamus. When implanted in the median eminence of female rats, LH and FSFI have each been shown to significantly decrease their concentrations in the pituitary [5,6], On the basis of their observation that ACTH implants into the median eminence reduced the ACTH content in the pituitary of adrenalectomized rats, M a n g il i et al [10] favour the theory of a short feedback loop for ACTH secretion. K r u l ic h and M cC a n n [9] and Bakke and L a w r e n c e [1] assume that STH and TSH are involved in a similar feedback system.…”

Section: Discussionmentioning

confidence: 99%