Possible Changes in the Regulatory Mechanisms of Pulsatile Luteinizing Hormone Secretion in Adult Pituitary-Grafted Female Rats

Immature female rats were required to run for prolonged periods of time to obtain food. The amount of food they earned was adequate for full pubertal development and moderate growth under nonworking conditions, but both processes were blocked by the exercise requirement. Prolonged exercise also blocked the pulsatile release of luteinizing hormone (LH); only two LH pulses were seen in seven exercising females during a total of 24 h of monitoring at 8 wk of age. By comparison, almost 1 pulse/h was seen in postpubertal, normally growing females of this same age during metestrus. When the exercising females' running requirement was relaxed at 8 wk of age they experienced rapid catch-up growth and reproductive development. Both basal secretion and LH pulse frequency increased markedly within 48 h, and most of these females ovulated during the third dark period after relaxation. Altogether, the experimental paradigm and techniques employed here yield highly predictable results, and they should prove useful for exploring other neuroendocrine pathways through which excessive exercise antagonizes reproduction.

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EFFECTS OF STEROID HORMONES ON GONADOTROPHIN SECRETION IN FEMALE RATS AFTER OVARIECTOMY DURING THE OESTROUS CYCLE

Journal of Endocrinology ◽

10.1677/joe.0.0620511 ◽

1974 ◽

Vol 62 (3) ◽

pp. 511-525 ◽

Cited By ~ 23

Author(s):

C. M. TAPPER ◽

FENELLA GREIG ◽

K. BROWN-GRANT

Keyword(s):

Luteinizing Hormone ◽

Hormone Secretion ◽

Female Rats ◽

Vaginal Smear ◽

Normal Pattern ◽

Adequate Explanation ◽

Luteinizing Hormone Secretion ◽

Gonadotrophin Secretion ◽

Exogenous Oestrogen ◽

Plasma Oestradiol

SUMMARY After ovariectomy at dioestrus, a dose of 2·5 μg oestradiol or oestradiol benzoate restored uterine weights and the vaginal smear pattern to normal but did not reproduce the normal ovulatory surge of luteinizing hormone secretion at pro-oestrus. Progesterone in addition to oestrogen was more effective than oestrogen alone in stimulating luteinizing hormone secretion but responses at pro-oestrus or at oestrus were not normal. Deviations from the normal pattern of changes in plasma oestradiol concentration do not provide an adequate explanation for the failure of steroid replacement in these circumstances. Inhibition of the priming effect of exogenous oestrogen by adrenal progesterone released by the stress of operation may provide an explanation.

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COMPARISON OF FOLLICLE-STIMULATING HORMONE AND LUTEINIZING HORMONE SECRETION AFTER ELECTRICAL STIMULATION OF THE PREOPTIC PART OF THE HYPOTHALAMUS IN FEMALE RATS ANAESTHETIZED WITH ETHYL CARBAMATE OR SODIUM PENTOBARBITONE

Journal of Endocrinology ◽

10.1677/joe.0.0780151 ◽

1978 ◽

Vol 78 (1) ◽

pp. 151-152 ◽

Cited By ~ 3

Author(s):

R. G. DYER ◽

M. B. TER HAAR ◽

LINDA C. MAYES

Keyword(s):

Electrical Stimulation ◽

Luteinizing Hormone ◽

Follicle Stimulating Hormone ◽

Hormone Secretion ◽

Control Process ◽

Female Rats ◽

Female Rat ◽

Luteinizing Hormone Secretion ◽

Stimulation Of ◽

Stimulating Hormone

A.R.C. Institute of Animal Physiology, Babraham, Cambridge, CB2 4AT (Received 17 January 1978) For over 30 years, the method by which the brain regulates the secretion of gonadotrophic hormones has been studied by electrical stimulation of those parts of the central nervous system thought to be implicated in the control process. Much of the work has been performed on the female rat. In this species, anaesthetic doses of sodium pentobarbitone, administered immediately before the pro-oestrous 'critical period', block the preovulatory surge of luteinizing hormone (LH) for 24 h. The same treatment also reduces the early phase of the pro-oestrous secretion of follicle-stimulating hormone (FSH; Daane & Parlow, 1971). Electrical stimulation of the preoptic part of the hypothalamus can overcome this blocking effect and analysis of the optimum parameters required to restore normal secretion of gonadotrophins may give some insight into the endogenous process (e.g. Everett, 1965; Fink & Aiyer, 1974;

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Galanin Enhancement of Gonadotropin-Releasing Hormone-Stimulated Luteinizing Hormone Secretion in Female Rats Is Estrogen Dependent

Endocrinology ◽

10.1210/en.2002-220855 ◽

2003 ◽

Vol 144 (2) ◽

pp. 484-490 ◽

Cited By ~ 22

Author(s):

Cynthia L. Splett ◽

Joseph R. Scheffen ◽

Joshua A. Desotelle ◽

Vicky Plamann ◽

Angela C. Bauer-Dantoin

Keyword(s):

Luteinizing Hormone ◽

Hormone Secretion ◽

Gonadotropin Releasing Hormone ◽

Gonadal Steroids ◽

Female Rats ◽

Luteinizing Hormone Secretion ◽

Ovx Rats ◽

Lh Secretion ◽

Lines Of Evidence

The hypothalamic peptide GnRH is the primary neuroendocrine signal regulating pituitary LH in females. The neuropeptide galanin is cosecreted with GnRH from hypothalamic neurons, and in vitro studies have demonstrated that galanin can act at the level of the pituitary to directly stimulate LH secretion and also augment GnRH-stimulated LH secretion. Several lines of evidence have suggested that the hypophysiotropic effects of galanin are important for the generation of preovulatory LH surges. To determine whether the pituitary actions of galanin are enhanced by the preovulatory steroidal milieu, LH responses to galanin administration (with or without GnRH) were examined in: 1) ovariectomized (OVX); 2) OVX, estrogen (E)-primed; and 3) OVX, E- and progesterone-treated female rats. Results from the study indicate that galanin enhances GnRH-stimulated LH secretion only in the presence of E (in OVX, E-primed, or E- and progesterone-treated rats). Galanin alone does not directly stimulate LH secretion under any of the steroid conditions examined. In the absence of gonadal steroids (OVX rats), galanin inhibits GnRH-stimulated LH secretion. These findings suggest that the primary pituitary effect of galanin is to modulate GnRH-stimulated LH secretion, and that the potentiating effects of galanin occur only in the presence of E.

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