Luteinizing Hormone Releasing Factor in Rats Exposed to Constant Light: Effects of Mating

1974 ◽  
Vol 14 (3-4) ◽  
pp. 129-138 ◽  
Author(s):  
Erla R. Smith ◽  
J.M. Davidson
Keyword(s):  
Luteinizing Hormone ◽  
Constant Light ◽  
Light Effects

Effects of multiple injections of luteinizing hormone on secretion of pregnane compounds from polycystic ovaries of rats exposed to constant light

1987 ◽  
Vol 116 (3) ◽  
pp. 390-394 ◽  
Author(s):  
Tsutomu Sawada ◽  
Tadashi Kosaka ◽  
Shigetaka Ichikawa
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Reductase Activity ◽  
Venous Blood ◽  
Constant Light ◽  
Polycystic Ovaries ◽  
Lh Surge ◽  
Multiple Injections ◽  
Classic Approach

Abstract. Differences in the secretion of pregnane compounds by ovaries with cystic follicles of rats exposed to constant light (light-induced oestrous rats) and by ovaries with normal follicles of early pro-oestrous rats were studied. Some rats were injected iv with 2 μg of LH to stimulate the secretion of steroids 30 min before their blood was sampled. The injection greatly increased the secretion of progesterone by both kinds of ovaries. The secretion of 5α-pregnane-3,20-dione and 3α-hydroxy-5α-pregnan-20-one also increased in normal rats, but not in the polycystic ovaries of light-induced oestrous rats, which suggested that the 5α-reductase activity was low. The pre-ovulatory LH surge is absent in light-induced oestrous rats, so a classic approach was taken to circumvent the probable deficit in the cyclic release of LH; we gave multiple injections of 10 μg of LH. Five such injections were given at intervals of 4 days, and ovarian venous blood was collected 4 days after the last injection. Cystic follicles in the ovaries of rats disappeared when the injections of LH were given every 4 days. The production of 5α-pregnane-3,20-dione and 3α-hydroxy-5α-pregnan-20-one from the ovaries of such rats was significantly higher (P < 0.01) than in controls given multiple injections of saline. These results suggest that the low 5α-reductase activity in polycystic ovaries of light-induced oestrous rats may be due to the absence of an LH surge from the pituitary gland.

Hypoprolactinemic rats under conditions of constant darkness or constant light. Effects on the sleep–wake cycle, cerebral temperature and sulfatoxymelatonin levels

1999 ◽  
Vol 835 (2) ◽  
pp. 282-289 ◽  
Author(s):  
Letı́cia Leite Lobo ◽  
Bruno Claustrat ◽  
Gabriel Debilly ◽  
Luce Paut-Pagano ◽  
Michel Jouvet ◽  
...  
Keyword(s):  
Constant Light ◽  
Constant Darkness ◽  
Light Effects

EFFECTS OF CONTINUOUS LIGHT ON THE REPRODUCTIVE CYCLE OF THE FEMALE RAT: INDUCTION OF OVULATION AND PITUITARY GONADOTROPHINS DURING PERSISTENT OESTRUS

1967 ◽  
Vol 38 (4) ◽  
pp. 389-394 ◽  
Author(s):  
K. B. SINGH ◽  
G. S. GREENWALD
Keyword(s):  
Luteinizing Hormone ◽  
Single Injection ◽  
Follicle Stimulating Hormone ◽  
Continuous Light ◽  
Chorionic Gonadotrophin ◽  
Human Chorionic Gonadotrophin ◽  
The Other ◽  
Constant Light ◽  
Female Rat ◽  
Control Light

SUMMARY The majority of rats exposed to constant light for approximately 6 weeks ovulated within 24 hr. after an injection of human chorionic gonadotrophin (HCG), but required 24–48 hr. after a single injection of progesterone. This suggests that HCG acted directly on the ovary but that progesterone acted indirectly by way of the hypothalamo-hypophysial system. Animals injected with progesterone after 6 weeks of constant light failed to ovulate after single or spaced injections of progesterone at 90 days of constant light while HCG administration was still effective. Pituitary content and concentration of luteinizing hormone (LH) in constant-light animals (duration of constant light: 45 days) were below normal pituitary levels during prooestrus and were in the range of normal oestrous values. On the other hand, follicle-stimulating hormone (FSH) content and concentration were similar to those in cyclic rats. Single injections of 1 mg. progesterone changed neither LH nor FSH concentration, despite the fact that such treatment induced ovulation. Bilateral ovariectomy increased both LH and FSH content and concentration in constant-light animals to the same extent as in control light—dark animals.

THE RESPONSIVENESS OF THE ANTERIOR PITUITARY GLAND TO LUTEINIZING HORMONE RELEASING FACTOR IN RATS EXPOSED TO CONSTANT LIGHT

1975 ◽  
Vol 65 (3) ◽  
pp. 439-445 ◽  
Author(s):  
G. FINK
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Anterior Pituitary Gland ◽  
Constant Light ◽  
Blood Samples ◽  
Portal Vessel ◽  
Readily Releasable Pool ◽  
The Mean ◽  
Hypophysial Portal

SUMMARY The responsiveness of the anterior pituitary gland to synthetic luteinizing hormone releasing factor (LH-RF) was tested in rats exposed to constant light. At a dosage of 50 ng LH-RF/ 100 g body wt the mean maximal increments in plasma LH and FSH were similar to those at 10.00 h of pro-oestrus. The increments in the plasma gonadotrophins at dosages of 500 and 1000 ng LH-RF/100 g body wt did not differ significantly from those at 250 ng LH-RF/ 100 g body wt. These findings suggest that, in contrast to rats which exhibit regular oestrous cycles, the preovulatory (post-coital) release of LH in rats exposed to constant light may depend almost entirely on the release of a relatively large amount of LH-RF into hypophysial portal vessel blood. Whereas in pro-oestrous animals a relatively small fraction of the readily releasable pool of LH is released during the spontaneous preovulatory surge, in rats exposed to constant light most releasable LH appears to be discharged during the reflex preovulatory surge of this hormone. The concentrations of radioimmunoassayable FSH in blood samples withdrawn before the injection of LH-RF support the view that FSH secretion in the rat is increased by constant exposure to light.

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