Entrainment by red light of running activity and ovulation rhythms of rats

1980 ◽  
Vol 239 (5) ◽  
pp. R450-R453 ◽  
Author(s):  
C. E. McCormack ◽  
C. R. Sontag
Keyword(s):  
Circadian Rhythm ◽  
Circadian Rhythms ◽  
Luteinizing Hormone ◽  
Hormone Secretion ◽  
Red Light ◽  
Albino Rats ◽  
Luteinizing Hormone Secretion ◽  
Continuous Darkness ◽  
Running Activity ◽  
Free Running

Controversy exists regarding whether or not the circadian rhythms of nocturnal rodents can be entrained by red light. Female albino rats that were free-running in continuous darkness (DD) were exposed to 2 h of red light (> 650 nm) near the beginning (dusk signals) or the end (dawn signals) of their active 12-h period of running. Red dawn signals advanced and red dusk signals delayed the onset of running on subsequent days. Because the altered onsets of running persisted in DD, the red light had produced a true entrainment of the circadian rhythm of running activity. The fact that the time of ovulation was similarly shifted by red light suggests that the circadian rhythm of luteinizing hormone secretion was also entrained by red light.

TIMING OF OVULATION IN RATS DURING EXPOSURE TO CONTINUOUS LIGHT: EVIDENCE FOR A CIRCADIAN RHYTHM OF LUTEINIZING HORMONE SECRETION

1978 ◽  
Vol 76 (1) ◽  
pp. 135-144 ◽  
Author(s):  
C. E. MCCORMACK ◽  
RAJAGOPALA SRIDARAN
Keyword(s):  
Circadian Rhythm ◽  
Luteinizing Hormone ◽  
Hormone Secretion ◽  
Continuous Light ◽  
Vaginal Smear ◽  
Luteinizing Hormone Secretion ◽  
Continuous Darkness ◽  
Adult Rats ◽  
Endogenous Circadian Rhythm ◽  
Cyclic Changes

SUMMARY In order to determine whether the timing of ovulation in rats was controlled by an endogenous circadian rhythm, the hour of ovulation was determined by observing tubal ova during laparotomy in adult rats exposed to full animal room illumination (150 lux) during daily photoperiods of 14 h (full LD), continuous 150 lux illumination (full LL), daily dim (0·2 lux) photoperiods of 14 h (dim LD), continuous 0·2 lux illumination (dim LL) or continuous darkness (DD). Rats in all groups except those exposed to full LL continued normal cyclic ovulation. By the second oestrous cycle, most rats in the full LL group failed to ovulate, even though they showed characteristic cyclic changes in the vaginal smear pattern. The hour at which ovulation occurred was similar in rats exposed to full LD, dim LD or DD but was delayed in rats exposed to full LL or dim LL; the longer the period of exposure, the greater was the delay. For a given length of exposure, ovulation was delayed more in full LL than in dim LL. The full LL used in this study produced persistent vaginal oestrus within 40 days, whereas the dim LL did not. The delayed ovulation in rats exposed to dim LL was associated with a delayed preovulatory surge of LH. These results are consistent with the hypothesis that the timing of the preovulatory surge of LH and ovulation are controlled by an endogenous circadian rhythm, which in most rats has a periodicity in continuous light of slightly longer than 24 h.

Using a classic paper by I. E. Lawton and N. B. Schwartz to consider the array of factors that control luteinizing hormone production

2007 ◽  
Vol 31 (4) ◽  
pp. 318-322 ◽  
Author(s):  
Angela C. Bauer-Dantoin ◽  
Craig J. Hanke
Keyword(s):  
Circadian Rhythm ◽  
Luteinizing Hormone ◽  
Hormone Secretion ◽  
Historical Context ◽  
Ovariectomized Rats ◽  
Complex Nature ◽  
Pituitary Hormone ◽  
Luteinizing Hormone Secretion ◽  
Hormone Production ◽  
Classic Paper

Two significant benefits derived from reading and discussing classic scientific papers in undergraduate biology courses are 1) providing students with the realistic perspective that science is an ongoing process (rather than a set of inarguable facts) and 2) deepening the students' understanding of physiological processes. A classic paper that is useful in both of these regards is by I. E. Lawton and N. B. Schwartz (A circadian rhythm of luteinizing hormone secretion in ovariectomized rats. Am J Physiol 214: 213–217, 1968). The primary objective of the study is to determine whether tonic (pulsatile) secretion of luteinizing hormone (LH) from the pituitary gland exhibits a circadian rhythm. While this hypothesis seems relatively straightforward, its in vivo investigation necessitates an awareness of the multitude of factors, in addition to the circadian clock, that can influence plasma LH levels (and a consideration of how to control for these factors in the experimental design). Furthermore, discussion of the historical context in which the study was conducted (i.e., before the pulsatile nature of LH secretion had been discovered) provides students with the realistic perspective that science is not a set of facts but rather a systematic series of attempts by scientists to understand reality (a perspective that is difficult to convey using a traditional textbook alone). A review of the historical context in which the study was conducted, and a series of discovery learning questions are included to facilitate classroom discussions and to help deepen students' understanding of the complex nature of pituitary hormone regulation.

Androgenic and oestrogenic steroid participation in feedback control of luteinizing hormone secretion in male sheep

1983 ◽  
Vol 102 (4) ◽  
pp. 499-504 ◽  
Author(s):  
M. J. D'Occhio ◽  
B. D. Schanbacher ◽  
J. E. Kinder
Keyword(s):  
Luteinizing Hormone ◽  
Pulse Generator ◽  
Hormone Secretion ◽  
Pulse Interval ◽  
Serum Concentrations ◽  
Luteinizing Hormone Secretion ◽  
Lh Release ◽  
Lh Secretion ◽  
Additional Feedback ◽  
Male Sheep

Abstract. The acute castrate ram (wether) was used as an experimental model to investigate the site(s) of feedback on luteinizing hormone (LH) by testosterone, dihydrotestosterone and oestradiol. At the time of castration, wethers were implanted subdermally with Silastic capsules containing either crystalline testosterone (three 30 cm capsules), dihydrotestosterone (five 30 cm capsules) or oestradiol (one 6.5 cm capsule). Blood samples were taken at 10 min intervals for 6 h 2 weeks after implantation to determine serum steroid concentrations and to characterize the patterns of LH secretion. Pituitary LH response to exogenous LRH (5 ng/kg body weight) were also determined at the same time. The steroid implants produced serum concentrations of the respective hormones which were either one-third (testosterone) or two-to-four times (dihydrotestosterone, oestradiol) the levels measured in rams at the time of castration. Non-implanted wethers showed rhythmic pulses of LH (pulse interval 40–60 min) and had elevated LH levels (16.1 ± 1.6 ng/ml; mean ± se) 2 weeks after castration. All three steroids suppressed pulsatile LH release and reduced mean LH levels (to below 3 ng/ml) and pituitary LH responses to LRH. Inhibition of pulsatile LH secretion by all three steroids indicated that testosterone as well as its androgenic and oestrogenic metabolites can inhibit the LRH pulse generator in the hypothalamus. Additional feedback on the pituitary was indicated by the dampened LH responses to exogenous LRH.

A study of luteinizing hormone secretion in the cow

Reproduction ◽  
1972 ◽  
Vol 28 (1) ◽  
pp. 135-136 ◽  
Author(s):  
L. Cummins ◽  
M. Blockey ◽  
J. Brown ◽  
Goding
Keyword(s):  
Luteinizing Hormone ◽  
Hormone Secretion ◽  
Luteinizing Hormone Secretion

Opioid Control of Luteinizing Hormone Secretion in Patients with Hirsutism and Hyperandrogenemia

1987 ◽  
Vol 23 (2) ◽  
pp. 117-121 ◽  
Author(s):  
Felice Petraglia ◽  
Susanna Golinelli ◽  
Gerardo d’Ambrogio ◽  
Giuseppina Comitini ◽  
Fabio Facchinetti ◽  
...  
Keyword(s):  
Luteinizing Hormone ◽  
Hormone Secretion ◽  
Luteinizing Hormone Secretion

Effects of valproate-induced alteration of the GABAergic system on pulsatile luteinizing hormone secretion in ovariectomized women

1996 ◽  
Vol 135 (3) ◽  
pp. 293-298 ◽  
Author(s):  
Joaquin Lado-Abeal ◽  
Jose L Liz ◽  
Carlos Rey ◽  
Manuel Febrero ◽  
Jose Cabezas-Cerrato
Keyword(s):  
Luteinizing Hormone ◽  
Sodium Valproate ◽  
Pulse Generator ◽  
Hormone Secretion ◽  
Gabaergic System ◽  
Luteinizing Hormone Secretion ◽  
Serum Lh ◽  
Nutrition Service ◽  
Significant Difference ◽  
Lh Secretion

Lado-Abeal J, Liz JL, Rey C, Febrero M, Cabezas-Cerrato J. Effects of valproate-induced alteration of the GABAergic system on pulsatile luteinizing hormone secretion in ovariectomized women. Eur J Endocrinol 1996;135:293–8. ISSN 0804–4643 It is well established that valproate increases hypothalamic concentrations of γ-aminobutyric acid (GABA). Although little research has been done on the role of GABA in the control of pulsatile luteinizing hormone (LH) secretion in humans, our group recently found that administration of valproate had no significant effect on pulsatile LH secretion in late follicular and mid-late luteal phase normal women. However, the results of several studies of rats suggest that GABAergic regulation of LH secretion may depend on steroid levels. The objective of this work was to determine whether regular administration of sodium valproate inhibits pulsatile LH secretion in ovariectomized women. Twelve women who had undergone ovariectomy for causes other than malignant tumors were each studied in two 8 h sessions, in each of which blood samples were taken every 5 min. The first session was the control; for the second, 400 mg of sodium valproate was administered every 8 h during the seven preceding days and at 08.00 h and 14.00 h on the day of the study session. Serum valproate was determined by repolarization fluorescence spectrophotometry, and LH, estradiol and progesterone by radioimmunoassay. The serum LH series were subjected to a deconvolution procedure to reconstruct the pattern of pituitary LH secretion. Luteinizing hormone pulses were identified by the authors' nonparametric method. Control and post-valproate results were compared with regard to number of pulses, pulse duration, the quantity of LH secreted in each pulse, interpulse interval and mean serum LH level. There was no statistically significant difference between control and post-valproate results for any of the variables considered. It is concluded that sustained serum valproate levels do not alter pulsatile secretion of LH in ovariectomized women. This implies that, in humans, GABA is probably not a decisive factor in the regulation of the GnRH pulse generator. J Cabezas-Cerrato, Endocrinology and Nutrition Service, General Hospital of Galicia, c/Galeras s/n 15705, Santiago de Compostela, La Coruña, Spain

Pulsatile luteinizing hormone secretion pattern in hyperandrogenemic women

1994 ◽  
Vol 44 (1) ◽  
pp. 94-95
Author(s):  
M.A. Graf ◽  
P. Bielfeld ◽  
W. Distler ◽  
C. Weiers ◽  
W.N. Kuhn-Velten
Keyword(s):  
Luteinizing Hormone ◽  
Hormone Secretion ◽  
Luteinizing Hormone Secretion
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