THE DIURNAL RHYTHMS OF BIOGENIC AMINES IN HYPOTHALAMIC STRUCTURES AND THEIR POSSIBLE ROLE IN REGULATION OF ESTROUS CYCLE IN RATS

Gleb Kerkeshko

doi:10.1240/sav_gbm_2003_m_000295

Changes in Hypothalamic Biogenic Amines and Serum LH in the Ewe during the Estrous Cycle

Journal of Animal Science ◽

10.2527/jas1972.354801x ◽

1972 ◽

Vol 35 (4) ◽

pp. 801-804 ◽

Cited By ~ 3

Author(s):

J. E. Wheaton ◽

Susan K. Martin ◽

L. V. Swanson ◽

F. Stormshak

Keyword(s):

Biogenic Amines ◽

Estrous Cycle ◽

Serum Lh

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The Effect of Neurotoxic Xenobiotics and Exogenous Melatonin on Diurnal Rhythms of Biogenic Amines in Hypothalamic Structures Responsible for LH-RH Production.

10.1240/sav_gbm_2003_m_000293 ◽

2003 ◽

Vol 2003 (Spring) ◽

Cited By ~ 1

Author(s):

Andrew Korenevsky ◽

Gleb Kerkeshko ◽

Michael Stepanov ◽

Alexander Arutjunyan

Keyword(s):

Biogenic Amines ◽

Diurnal Rhythms ◽

Exogenous Melatonin ◽

Lh Rh

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Circadian Variation in Basal Plasma Corticosterone and Adrenocorticotropin in the Rat: Sexual Dimorphism and Changes across the Estrous Cycle*

Endocrinology ◽

10.1210/endo.138.9.5395 ◽

1997 ◽

Vol 138 (9) ◽

pp. 3842-3848 ◽

Cited By ~ 167

Author(s):

Helen C. Atkinson ◽

Brendan J. Waddell

Keyword(s):

Sexual Dimorphism ◽

Estrous Cycle ◽

Circadian Variation ◽

Sampling Technique ◽

Plasma Corticosterone ◽

Male Rats ◽

Diurnal Rhythms ◽

Basal Plasma ◽

Estrous Cycle Stage ◽

Clear Shift

Abstract Sexual dimorphism in the rat hypothalamic-pituitary-adrenal axis was investigated by determination of plasma corticosterone and immunoreactive (I-) ACTH in males and in females at each stage of the estrous cycle. A serial blood-sampling technique enabled assessment of covariation of the two hormones across the full circadian range of their concentrations within individual animals. Distinct diurnal rhythms in plasma corticosterone were evident in all rats, and the degree and timing of this rhythmicity, determined by cosinor analyses, did not vary with gender or cycle stage. There were, however, marked differences in absolute levels of corticosterone across the estrous cycle, with the average daily concentration (mesor) increasing progressively from a minimum at estrus (129 ± 11 ng/ml) to a maximum 3 days later at proestrus (246 ± 14 ng/ml). The mesor corticosterone value in male rats (102 ± 21 ng/ml) was not different from that in estrous females, but was lower than that in females at all other stages of the cycle. In contrast, no gender- or cycle-related differences were detected in absolute levels of I-ACTH, although distinct diurnal rhythms, synchronous with those for corticosterone, were evident in all groups. Accordingly, a strong and positive within-rat relationship between plasma corticosterone and I-ACTH was observed in all groups, but there was a clear shift in the nature of this relationship across the estrous cycle, such that the slope (i.e. concentration of plasma corticosterone per unit concentration of I-ACTH) was minimal in males and estrous females and maximal in proestrous females. In conclusion, this study shows that the extent of sexual dimorphism in resting plasma corticosterone levels is dependent on estrous cycle stage, being absent at estrus and maximal at proestrus. Moreover, this variation in plasma corticosterone was not accompanied by corresponding changes in plasma I-ACTH, suggestive of cycle-related changes in responsiveness of the adrenal cortex to trophic stimulation.

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Immunoreactive somatostatin diurnal rhythms in rat pineal, retina and Harderian gland: Effects of sex, season, continuous darkness and estrous cycle

Journal of Neural Transmission ◽

10.1007/bf01245446 ◽

1990 ◽

Vol 81 (1) ◽

pp. 63-72 ◽

Cited By ~ 15

Author(s):

M. A. Peinado ◽

N. Fajardo ◽

G. Hern�ndez ◽

M. Puig-Domingo ◽

M. Viader ◽

...

Keyword(s):

Estrous Cycle ◽

Harderian Gland ◽

Diurnal Rhythms ◽

Continuous Darkness

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Impaired hypothalamic regulation of reproductive function when exposed to neurotoxic compounds and melatonin

Journal of obstetrics and women s diseases ◽

10.17816/jowd88851 ◽

2003 ◽

Vol 52 (2) ◽

pp. 77-85

Author(s):

A. V. Arutjunyan ◽

М. G. Stepanov ◽

G O. Kerkeshko ◽

Е. K. Ailamazyan

Keyword(s):

Pineal Gland ◽

Biogenic Amines ◽

Blood Level ◽

Female Rats ◽

Diurnal Rhythms ◽

Central Regulation ◽

Exogenous Melatonin ◽

Diurnal Dynamics ◽

Regulation Of Reproduction ◽

Hypothalamic Regulation

Diurnal rhythms of the contents of biogenic amines in the hypothalamus are considered to play an important role in regulation of many functions such as motor activity, feeding behaviour, sleep-awake cycle formation as well as hormonal and immune statuses. Mechanisms of regulation of reproduction that participate in a circadian signal transmission from the suprachiasmatic nuclei (SCN) of the hypothalamus to hypothalamic structures responsible for gonadoliberin (GnRH) synthesis and secretion (the preoptic area - PA, and the medial eminence - ME) are at present being intensively studied. It has been shown that the aging caused disturbances of estrous cycles in female rats are accompanied by a disappearance of diurnal rhythms of activity of monoaminergic and opioid hypothalamic systems playing a key role in regulation of GnRH synthesis and secretion. The experiments carried out have revealed diurnal rhythms of the contents of the studied biogenic amines in the PA, ME and SCN of the hypothalamus. The rhythms are due to the amines increasing in the morning hours when compared to their evening and night levels. The neurotoxic compounds used disturbed the rhythms of the amines. Chronic inhalation of toluene caused a disappearance of the dynamics of all the studied neurotransmitters that was typical of the control group. Meanwhile, a single administration of 1,2-dimethylhydrazine resulted in either a complete disappearance of the diurnal rhythms of the biogenic amines contents found in control, or their phase shifts. Severe disturbances of the GnRH content and of the ROS diurnal dynamics were also observed in the studied hypothalamic areas. The literature allowed supposition that melatonin possessing entraining and antioxidant properties can be used as a protector of disturbances of central mechanisms of regulation of reproduction. However, our experiments have shown that exogenous melatonin does not only eliminate the neurotoxic compounds caused disturbances of diurnal rhythms of the studied indices, but it itself causes deep changes in their dynamics. The effect of melatonin has been found to result in a significant decrease of the catecholamines contents in all the studied hypothalamic structures, particularly of the norepinephrine content, that is accompanied by a profound decrease of the GnRH content and by a disturbance of the diurnal dynamics of reactive oxygen species (ROS) in the PA and ME. The effect of 1,2-dimethylhydrazine on the studied indices was less pronounced when compared to that of melatonin, whereas an injection of the xenobiotic on the background of the pineal gland hormone administration resulted in a predominant effect of the latter. Both the data obtained and the literature review allow to offer a hypothesis for a possible mechanism of involvement of diurnal rhythms of biogenic amines in central regulation of reproduction. It is known that synthesis and secretion of endogenous opioid peptides in the mediobasal hypothalamus undergo diurnal oscillations with minimum in the morning and maximum in the evening and/or at night. The revealed diurnal rhythms of the biogenic amines contents had opposite oscillations. This fact allows a supposition that these rhythms are due to the opioid system activity changing. Both decreased endogenous opioids contents and simultaneously increased morning biogenic amines levels in proestrus can create a neurotransmitter background that is necessary for GnRH surge formation. An evaluation of diurnal rhythms of the biogenic amines contents, GnRH and ROS in the studied hypothalamic structures can be used for an assessment of disturbances of central mechanisms of regulation of reproduction that are caused by other neurotoxic compounds or developed in some diseases and in aging when the functional activity of the pineal gland is altered. The data obtained testify to possible negative side effects of melatonin on hypothalamic regulation of reproduction in therapeutic use of the hormone. The effects of melatonin realized via its receptors are known to highly depend on amplitude of its nocturnal surge and on duration of its increased blood level during a day. Therefore administration of melatonin on the background of its normal synthesis can lead to a number of negative effects due to its increased blood level when compared to its physiological level. Elucidation of the exogenous melatonin caused disturbance of the studied diurnal rhythms of central regulation of reproduction is of great practical use in development of prophylactics helping to eliminate or decrease an effect of damaging factors in unfavourable environmental conditions.

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