EFFECTS OF PHOTOPERIOD ON HYPOTHALAMIC LUTEINIZING HORMONE RELEASING HORMONE IN THE MALE HAMSTER

1979 ◽  
Vol 83 (3) ◽  
pp. 421-428 ◽  
Author(s):  
G. E. PICKARD ◽  
A. J. SILVERMAN
Keyword(s):  
Luteinizing Hormone ◽  
Male Hamster ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Long Day ◽  
Testicular Regression ◽  
Significant Difference ◽  
Accessory Sex Organs ◽  
Lh Rh ◽  
Short Days

Male hamsters were maintained on long (14 h light: 10 h darkness; 14L: 10D) or short (6L: 18D) photoperiods. Animals on short-days had reduced levels of LH in the serum and anterior pituitary gland, decreased androgen in the circulation and regressed testes and accessory sex organs. These same hamsters had significantly raised concentrations of hypothalamic luteinizing hormone releasing hormone (LH-RH). There was no significant difference in the response to exogenous LH-RH between groups maintained on long- and shortdays. Castration significantly reduced levels of LH-RH in the hypothalamus in the long-day animals but had little effect on this parameter in short-day animals which had already undergone testicular regression. The increased levels of LH-RH in the hypothalami of both intact and castrated hamsters on non-stimulatory photoperiods is interpreted as a decreased release of the neurohormone which subsequently results in a decreased release of LH.

EFFECT OF CORTISOL OR ADRENOCORTICOTROPHIN ON RELEASE OF LUTEINIZING HORMONE INDUCED BY LUTEINIZING HORMONE RELEASING HORMONE IN THE DAIRY HEIFER

1982 ◽  
Vol 92 (1) ◽  
pp. 141-146 ◽  
Author(s):  
R. L. MATTERI ◽  
G. P. MOBERG
Keyword(s):  
Luteinizing Hormone ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Dairy Heifers ◽  
Significant Difference ◽  
Significant Depression ◽  
Lh Rh ◽  
Lh Releasing Hormone ◽  
And Control ◽  
Slight Depression

During treatment with cortisol or ACTH, dairy heifers were given two doses of LH releasing hormone (LH-RH) spaced 1·5 h apart. Serum concentrations of cortisol and LH were monitored during each treatment. Treatment with both ACTH and cortisol raised plasma cortisol levels above the respective saline controls (P<0·001). Neither treatment affected basal LH concentrations. A slight depression in LH response was seen in the cortisol-treated animals after the first LH-RH injection, as shown by a statistically significant depression at three of the sample times. There was no significant difference between treated and control LH values after the second LH-RH administration. Treatment with ACTH resulted in significantly reduced LH values at all sample times after both injections of LH-RH.

EFFECT OF ACTIVE IMMUNIZATION TO LUTEINIZING HORMONE RELEASING HORMONE ON SERUM AND PITUITARY GONADOTROPHINS, TESTES AND ACCESSORY SEX ORGANS IN THE MALE RAT

1974 ◽  
Vol 63 (2) ◽  
pp. 399-NP ◽  
Author(s):  
H. M. FRASER ◽  
A. GUNN ◽  
S. L. JEFFCOATE ◽  
DIANE T. HOLLAND
Keyword(s):  
Luteinizing Hormone ◽  
Active Immunization ◽  
Male Rats ◽  
Male Rat ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Accessory Sex Organs ◽  
Gonadotrophin Releasing Hormone ◽  
Low Levels ◽  
Lh Rh

SUMMARY Autoimmunity to luteinizing hormone releasing hormone (LH-RH) in adult male rats, induced by immunization with LH-RH conjugated to bovine serum albumin, resulted in atrophy of the testes and secondary sex organs and aspermatogenesis. Both immunoreactive luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in serum and the pituitary were reduced to low levels compared with those of control animals. It is suggested that antibodies to LH-RH can inhibit the action of endogenous hormone and that LH-RH is, in fact, the gonadotrophin-releasing hormone in the rat, required for the release of both LH and FSH.

LUTEINIZING HORMONE RELEASE AFTER TWO INJECTIONS OF SYNTHETIC LUTEINIZING HORMONE RELEASING HORMONE IN THE EWE

1977 ◽  
Vol 72 (1) ◽  
pp. 59-67 ◽  
Author(s):  
D. B. CRIGHTON ◽  
J. P. FOSTER
Keyword(s):  
Luteinizing Hormone ◽  
Steroid Hormones ◽  
The Other ◽  
Sex Steroid ◽  
Hormone Release ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Significant Difference ◽  
Lh Release ◽  
Lh Rh

SUMMARY Anoestrous ewes were given two injections of 30 μg synthetic luteinizing hormone releasing hormone (LH-RH) separated by one of the following intervals: 1·5, 3, 6, 12 or 24 h. The first injection caused an increase in the plasma LH concentration in each animal. The response to the second injection was dependent on the interval between the injections. When the second injection was administered 1·5 h after the first it caused a further increase in the LH concentration to maximal levels which were significantly greater than those induced in the other anoestrous groups. When the second injection was administered 3 h after the first, there was no significant difference between the responses to the two injections although the time to reach the maximal LH concentration was shorter and the height of the LH peak was greater in each animal following the second injection. When the second injection was administered 6,12 or 24 h after the first, the LH response was significantly less, in terms of height and area of the induced peak, than following the first injection. The LH response to the second injection was particularly low in the 12 and 24 h groups. Two injections of 30 μg synthetic LH-RH were also administered at 1·5 h intervals to ewes on either day 10 of the oestrous cycle or at onset of oestrus. The pattern of LH responses in all these animals was similar to that observed in anoestrous ewes injected at 1·5 h intervals. The total LH release, as assessed in terms of area of the induced peaks, was significantly greater in the onset of oestrus group than in the day 10 group or any of the anoestrous groups. Presumably the sensitization–desensitization sequence of the pituitary gland to LH-RH which has been demonstrated, together with the effects of sex steroid hormones, must play an important part in the development and decay of the natural preovulatory LH peak.

CHANGES IN PITUITARY RESPONSIVENESS TO LUTEINIZING HORMONE RELEASING HORMONE IN RAMS EXPOSED TO ARTIFICIAL PHOTOPERIODS

1977 ◽  
Vol 73 (3) ◽  
pp. 519-527 ◽  
Author(s):  
G. A. LINCOLN
Keyword(s):  
Luteinizing Hormone ◽  
Seasonal Cycle ◽  
Testicular Development ◽  
Blood Samples ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Artificial Lighting ◽  
Lh Release ◽  
Lh Rh ◽  
Short Days

SUMMARY Six adult Soay rams were subjected to an artificial lighting régime of alternating 4 month periods of long days (16 h light: 8 h darkness) and short days (8 h light: 16 h darkness) which induced a seasonal cycle in testicular development and regression during a period of 32 weeks. On 15 occasions during the study pituitary responsiveness was assessed by measuring the concentration of luteinizing hormone (LH) in jugular blood samples collected at frequent intervals after the intravenous injection of 1 pg synthetic luteinizing hormone releasing hormone (LH-RH). It was shown that both the magnitude and duration of the induced release of LH changed in relation to the photoperiod; the magnitude was greatest during long days when the rams were sexually quiescent, while the duration of the LH release was greatest during short days at the peak of testicular activity. This pattern of responsiveness was modified by implantation of the rams with testosterone.

Acidic Aqueous Extraction of Hypothalamic Luteinizing Hormone Releasing Hormone to Study Biological Effects

1974 ◽  
Vol 52 (3) ◽  
pp. 754-758 ◽  
Author(s):  
S. H. Shin ◽  
C. J. Howitt
Keyword(s):  
Luteinizing Hormone ◽  
Biological Effects ◽  
Extraction Procedure ◽  
Extraction Methods ◽  
Water Soluble ◽  
Acid Extraction ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Aqueous Solvent ◽  
Lh Rh

Several aqueous solvent systems were tested for their efficiency in extracting luteinizing hormone releasing hormone (LH-RH) from rat hypothalamus. Although LH-RH is a water-soluble decapeptide, neutral distilled water extracted only 10% of the LH-RH obtained using acid extraction methods. The efficiency of the acid extraction procedure suggests that in the hypothalamus the releasing hormone is bound to a relatively large molecular weight compound. Using the acidic extraction procedure, we found that hypothalamic LH-RH content is significantly lower in the castrated animal than in the normal rat.

PROLONGED RELEASE BY DIOESTROUS RATS OF FOLLICLE-STIMULATING HORMONE DURING THE PERIOD OF OVULATION INDUCED BY LUTEINIZING HORMONE RELEASING HORMONE

1979 ◽  
Vol 81 (1) ◽  
pp. 109-118 ◽  
Author(s):  
SHUJI SASAMOTO ◽  
SHIGEO HARADA ◽  
KAZUYOSHI TAYA
Keyword(s):  
Luteinizing Hormone ◽  
Plasma Concentrations ◽  
High Plasma ◽  
Oestrous Cycle ◽  
Prolonged Release ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Follicular Maturation ◽  
Lh Rh ◽  
Premature Ovulation

When 1·0 μg luteinizing hormone releasing hormone (LH-RH) was given i.v. three times at 1 h intervals from 17.00 to 19.00 h on the day of dioestrus (day 0) to regular 4 day cyclic rats, premature ovulation was induced the next morning (day 1) with the number of ova present comparable to normal spontaneous ovulation. The next spontaneous ovulation occurred on the morning of day 5, 4 days after premature ovulation induced by LH-RH. Plasma concentrations of FSH and LH showed transient rises and falls within 1 h of administration of LH-RH; concentrations of FSH in the plasma decreased from 20.00 h on day 0 but markedly increased again from 23.00 h on day 0 to 02.00 h on day 1 and these high levels persisted until 14.00 h on day 1, with only a small increase of plasma LH during this period. The duration of increased FSH release during premature ovulation induced by LH-RH treatment was 6 h longer than the FSH surge occurring after administration of HCG on day 0. Surges of gonadotrophin were absent on the afternoon of day 1 (the expected day of pro-oestrus) and the surges characteristic of pro-oestrus occurred on the afternoon of day 4 and ovulation followed the next morning. The pituitary content of FSH did not decrease despite persisting high plasma levels of FSH during premature ovulation induced by either LH-RH or HCG on day 0. The changes in uterine weight indicated that the pattern of oestrogen secretion from the day of premature ovulation induced by LH-RH to the day of the next spontaneous ovulation was similar to that of the normal 4 day oestrous cycle. When 10 i.u. HCG were given on day 0, an increase in oestrogen secretion occurred on day 2, 1 day earlier than in the group given LH-RH on day 0. This advancement of oestrogen secretion was assumed to be responsible for the gonadotrophin surges on day 3. Similar numbers of fully developed follicles were found by 17.00 h on day 2 after premature ovulation induced by either LH-RH or HCG, suggesting that the shorter surge of FSH during premature ovulation induced by HCG had no serious consequences on the initiation of follicular maturation for the succeeding oestrous cycle in these rats. Administration of LH-RH on day 0 had no direct effect on the FSH surge during premature ovulation. Secretory changes in the ovary during ovulation may be responsible for this prolonged selective release of FSH.

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