PHOTOPERIODIC MODULATION OF GONADOTROPHIN SECRETION IN CASTRATED JAPANESE QUAIL

1982 ◽  
Vol 92 (1) ◽  
pp. 73-83 ◽  
Author(s):  
H. F. URBANSKI ◽  
B. K. FOLLETT
Keyword(s):  
Japanese Quail ◽  
Plasma Levels ◽  
Time Course ◽  
Neural Mechanisms ◽  
Gonadal Steroids ◽  
Photoperiodic Control ◽  
Gonadotrophin Secretion ◽  
Lh Secretion ◽  
Sexually Mature ◽  
Short Days

Male Japanese quail were castrated when sexually immature and immediately exposed to one of the following stimulatory lighting regimes for 52 days: 11 h light: 13 h darkness/day (11L : 13D), 12L : 12D, 13L : 11D, 14L : 10D, 15L : 9D, 16L : 8D, 20L : 4D or 23L : 1D. One group was retained on short days (8L : 16D). Clearcut differences in the plasma levels of LH and FSH emerged between the various groups. Levels remained very low in castrated quail on 8L : 16D but were much greater in those on 14L : 10D, 15L : 9D, 16L : 8D, 20L : 4D and 23L : 1D, eventually becoming 15 to 20 times higher. Less pronounced castration responses developed on 13L : 11D, 12L : 12D or 11L : 13D. Alterations in photoperiod after day 52 caused an appropriate rise or fall in LH secretion. Photoperiodically induced suppressions were rapid, being highly significant within 4 days, but increases usually had a slower time course. When sexually mature quail (on 16L : 8D) were castrated and transferred to 8L : 16D they also exhibited a rapid suppression in LH secretion. Thus in quail, unlike some mammals, the photoperiodic control over gonadotrophin secretion is independent of the reproductive status of the animal at the time of castration. The results confirm the view that changes in sensitivity of the hypothalamo-pituitary axis to gonadal steroids are not a primary factor in the neural mechanisms underlying photoperiodism in quail.

PLASMA LEVELS OF LUTEINIZING HORMONE IN GONADECTOMIZED JAPANESE QUAIL EXPOSED TO SHORT OR TO LONG DAYLENGTHS

1975 ◽  
Vol 64 (1) ◽  
pp. 87-101 ◽  
Author(s):  
W. R. GIBSON ◽  
B. K. FOLLETT ◽  
BARBARA GLEDHILL
Keyword(s):  
Luteinizing Hormone ◽  
Japanese Quail ◽  
Plasma Levels ◽  
Photoperiodic Regulation ◽  
Male Plumage ◽  
Low Levels ◽  
Lh Secretion ◽  
Very High ◽  
Cloacal Gland ◽  
Short Days

SUMMARY Plasma levels of luteinizing hormone (LH) were measured by radioimmunoassay in gonadectomized male and female Japanese quail, exposed either to 8 h light: 16 h darkness per day (8L:16D; short days) or to 20L:4D (long days). In both sexes, exposure to long days increased LH levels and in the gonadectomized quail LH continued to rise over several weeks. Eventually the castrated quail had levels about five times higher than the control birds and the ovariectomized quail had levels about 14 times higher than their controls. Quail kept on short days had low LH levels while birds kept on long days and returned to short days resumed low levels after a delay of some days. Since very high levels of LH occurred in gonadectomized quail only when they were on long days, we conclude that the photoperiodic regulation of LH secretion does not operate solely by adjusting sensitivity to gonadal feedback, but works in a more direct manner. Ovariectomized females whether on long days (high LH) or short days (low LH) grew masculine plumage and castrated males retained male plumage. This confirms that the ovary is responsible for sexual dimorphism of plumage and shows that the action of the ovary is not mediated by LH (through feedback). The remaining rudimentary (right) gonad in ovariectomized females did not undergo visible hypertrophy and did not secrete enough hormone to stimulate the cloacal gland or oviduct.

The inhibitory effect of opiates on gonadotrophin secretion is dependent upon gonadal steroids

1984 ◽  
Vol 102 (2) ◽  
pp. 133-141 ◽  
Author(s):  
R. Bhanot ◽  
M. Wilkinson
Keyword(s):  
Negative Feedback ◽  
Prolactin Secretion ◽  
Gonadal Steroids ◽  
Female Rats ◽  
Inhibitory Effects ◽  
Endogenous Opiates ◽  
Gonadotrophin Secretion ◽  
Oestradiol Benzoate ◽  
Lh Secretion

ABSTRACT We have attempted to clarify the physiological involvement of endogenous opiates in the steroid-mediated control of gonadotrophin release. Our studies showed that there was an acute reduction in the inhibitory effects of endogenous opiates on LH and FSH release following gonadectomy in the rat. This was indicated by a significant reduction in the ability of naloxone to stimulate serum LH/FSH levels (sampled at 15 min) in 26-day-old female rats 48 h after ovariectomy. Luteinizing hormone was highly sensitive to the inhibitory effects of the synthetic met-enkephalin analogue, FK 33-824, at this time (sampled at 90 min). An unexpected observation was that long-term absence of gonadal steroids also disrupted the ability of exogenous opiates, FK 33-824 and morphine, to influence LH release. This was seen as an inability of FK 33-824 (1·0 or 3·0 mg/kg) to inhibit LH secretion. The effects of gonadectomy on opiate control of LH occurred at all developmental stages and were not due to a disruption of sexual maturation. Opiate involvement in prolactin secretion did not appear to be adversely affected by an absence of gonadal steroids. Another novel aspect of this work was that the opiatergic component in the control of gonadotrophin secretion could be reinstated in long-term gonadectomized rats by treatment with oestradiol benzoate or testosterone propionate. Similarly, priming with increasing dosages of oestradiol benzoate which resulted in progressively lower LH levels gave larger naloxone responses. This steroid–opiate interdependency suggests that the negative feedback influence of gonadal steroids on LH secretion is conveyed, in part, by hypothalamic opiate peptides. Our results therefore provide a neurochemical basis for gonadal steroid negative feedback. J. Endocr. (1984) 102, 133–141

The neuroendocrine control of gonadotrophin release in the Japanese quail. I. The role of the tuberal hypothalamus

1975 ◽  
Vol 191 (1103) ◽  
pp. 285-301 ◽  
Keyword(s):  
Japanese Quail ◽  
Bird Species ◽  
Photoperiodic Response ◽  
Coturnix Coturnix ◽  
Testicular Growth ◽  
Gonadotrophin Secretion ◽  
Electrolytic Lesions ◽  
Sexually Mature ◽  
Basal Concentration

Reproduction in the Japanese quail ( Coturnix coturnix japonica ), as in many other bird species, is controlled by the daily photoperiod. The present experiments have investigated the role of the posterior or tuberal hypothalamus in the neuroendocrine regulation of this photoperiodic response. By using various types of small knives the tuberal hypothalamus was isolated surgically in male quail maintained on short daylengths. The birds were then transferred to long daily photoperiods and after fourteen days the effects on gonadotrophin secretion assessed by measuring testicular growth and the circulating level of luteinizing hormone (LH). Complete deafferentation of the tuberal hypothalamus blocked testicular growth and the plasma level of LH remained low. Partial cuts that severed the afferents entering from anterior and antero-lateral directions also blocked gonadotrophin secretion but cuts severing posterior connections were without effect. Following deafferentation of sexually mature males the LH level fell rapidly to reach a basal concentration within two days. The normal rise in LH that follows the castration of quail on long days was blocked by complete tuberal deafferentation. Electrolytic lesions were placed medially in the tuberal hypothalamus. Those in the postero-dorsal part of the infundibular nuclear complex (p.d.-i.n.c.) completely blocked testicular growth, while those in the ventral portion of the nucleus (v.-i.n.c.) only partially disrupted gonadotrophin secretion.

A comparison of the effects of gonadal steroids on naloxone-induced LH secretion in gonadectomized rats

1986 ◽  
Vol 110 (2) ◽  
pp. 327-334 ◽  
Author(s):  
G. M. Spencer ◽  
S. A. Whitehead
Keyword(s):  
Inhibitory Effect ◽  
Gonadal Steroids ◽  
Ovariectomized Rats ◽  
Endogenous Opioid ◽  
Feedback Effects ◽  
Serum Lh ◽  
Gonadotrophin Secretion ◽  
Endogenous Opioid Systems ◽  
Hypothalamic Pituitary Axis ◽  
Lh Secretion

ABSTRACT The effects of the opiate antagonist naloxone on serum LH concentrations was investigated in gonadectomized rats given different regimes of steroid pretreatment. Two injections of testosterone given 48 and 24 h before naloxone treatment failed to reinstate LH responses to this drug in castrated rats while subcutaneous testosterone-filled silicone elastomer capsules implanted for a week were effective in this respect. Injections of oestrogen, oestrogen plus progesterone or progesterone alone all restored LH responses to naloxone in ovariectomized rats when given 48 and/or 24 h before drug treatment, although the magnitude of these responses varied according to the precise steroid treatments. The hypothalamic-pituitary axis was also responsive to naloxone just before the progesterone-induced LH surge in oestrogen-primed ovariectomized rats. Results show that gonadal steroids are permissive to the effects of opiate drugs, but they suggest that endogenous opioid systems do not necessarily mediate the negative feedback effects of steroids. Some other factor(s), as yet unidentified in the rat, may control the opioid modulation of gonadotrophin secretion or exert an independent inhibitory effect on gonadotrophin release. J. Endocr. (1986) 110, 327–334

SEXUAL DIFFERENTIATION OF THE PHOTOPERIODIC RESPONSE IN JAPANESE QUAIL

1982 ◽  
Vol 92 (2) ◽  
pp. 279-282 ◽  
Author(s):  
H. F. URBANSKI ◽  
B. K. FOLLETT
Keyword(s):  
Japanese Quail ◽  
Sexual Differentiation ◽  
Plasma Levels ◽  
Photoperiodic Response ◽  
Breeding Cycle ◽  
Response System ◽  
Female Quail ◽  
The Difference ◽  
Short Days

Plasma levels of LH are generally higher in male than in female quail. This dimorphism was found to persist in quail which had been through a breeding cycle and then gonadectomized. Under long daylengths (12 h light: 12 h darkness (12L : 12D) or 16L : 8D) ovariectomized quail had plasma levels of LH that were 55–70% of those seen in castrated birds. The difference was reduced after transfer to short days (8L : 16D) when LH concentrations fell to basal levels, but again became more pronounced when the quail were restimulated with long photoperiods. Thus, the photoperiodic response system is sexually differentiated.

Endogenous opioid control of pulsatile LH secretion in rams: modulation by photoperiod and gonadal steroids

1987 ◽  
Vol 115 (3) ◽  
pp. 425-438 ◽  
Author(s):  
G. A. Lincoln ◽  
F. J. P. Ebling ◽  
G. B. Martin
Keyword(s):  
Reproductive Cycle ◽  
Active Phase ◽  
Gonadal Steroids ◽  
Dependent Manner ◽  
Sexually Active ◽  
Endogenous Opioid ◽  
Opioid Agonist ◽  
Inactive Phase ◽  
Lh Secretion ◽  
Short Days

ABSTRACT The role of endogenous opioid peptides in the inhibitory control of pulsatile LH secretion was studied in adult Soay rams at different stages of the seasonal reproductive cycle, entrained by an artificial lighting regimen of alternating 16-week periods of long and short days. The LH responses to the acute administration of naloxone (opioid antagonist) and morphine (opioid agonist) were measured in intact rams (n = 7), testosterone-implanted castrated rams (n = 8) and castrated rams (n = 8) to assess the interaction between photoperiod and gonadal steroids in the opioid control of LH secretion. In the intact and testosterone-implanted castrated rams, naloxone (1·7 mg/kg i.v.) increased and morphine (1·0 mg/kg i.v.) decreased mean LH concentrations and LH pulse frequency during the sexually active phase under short days, but these effects were reduced or absent during the inactive phase under long days. The changes in the LH responses occurred in close parallel with the photoinduced changes in endogenous LH secretion. In the castrated rams receiving no supplementary testosterone, plasma LH concentrations were permanently raised and there were only minor changes related to the photoperiod. Naloxone (1·7 mg/kg) induced transient increases in LH secretion at all stages, and morphine (1·0 mg/kg) failed to suppress LH levels under both short and long days. LHRH stimulation tests revealed that there were changes in LH release related to the induced reproductive cycle in the intact and testosterone-implanted rams but not in the castrated rams; these changes in the responsiveness of the pituitary gonadotrophs to LHRH could not account for the changes in the LH response to the opiate drugs. These results illustrate that an endogenous opioid mechanism is involved in the tonic inhibition of LH secretion acting to regulate the pulsatile release of LHRH from the hypothalamus. This system can be shown to be functional in a steroid-dependent manner in the sexually active phase of the seasonal cycle, but not in the inactive phase of the cycle when non-opioidergic mechanisms are presumed to predominate in the inhibition of LH secretion. J. Endocr. (1987) 115, 425–438

The pineal gland and the photoperiodic control of luteinizing hormone secretion in intact and castrated Japanese quail

1983 ◽  
Vol 99 (2) ◽  
pp. 281-287 ◽  
Author(s):  
S. M. Simpson ◽  
H. F. Urbanski ◽  
J. E. Robinson
Keyword(s):  
Pineal Gland ◽  
Japanese Quail ◽  
Prolonged Exposure ◽  
Hormone Secretion ◽  
Quantitative Relationship ◽  
Luteinizing Hormone Secretion ◽  
Photoperiodic Responses ◽  
Induced Changes ◽  
Lh Secretion ◽  
Sexually Mature

The effects of pinealectomy on a range of photoperiodic responses were investigated in male Japanese quail by measuring plasma LH concentrations in intact, sham-operated and pinealectomized birds in the following four experiments: (1) transfer of sexually quiescent birds from a short photoperiod of 8 h light: 16 h darkness (8L: 16D) to a photostimulatory daylength of 16L: 8D; (2) transfer of sexually mature birds from 16L: 8D to 8L: 16D; (3) castration in 16L: 8D and exposure to 13L: 11D; (4) castration in 8L: 16D and exposure to 13L: 11D. There was no evidence of effects of the pineal gland on the photoperiodically induced changes in LH secretion, the quantitative relationship between LH secretion and photoperiod in intact and castrated birds, or the induction of relative photorefractoriness by prolonged exposure to 16L: 8D. This suggests that there is no pineal influence on the photoperiodic clock or its effectors in this bird.

LHRH self priming of gonadotrophin secretion: time course of development

1983 ◽  
Vol 244 (5) ◽  
pp. C410-C418 ◽  
Author(s):  
D. W. Waring ◽  
J. L. Turgeon
Keyword(s):  
Luteinizing Hormone ◽  
Time Course ◽  
Interpulse Interval ◽  
Time Curve ◽  
Luteinizing Hormone Releasing Hormone ◽  
First Derivative ◽  
Gonadotrophin Secretion ◽  
Time Required ◽  
Lh Secretion

The luteinizing hormone-releasing hormone (LHRH) self-priming effect, in which the gonadotrophin secretory response to LHRH is augmented by prior exposure to LHRH, was studied in vitro using pituitaries of proestrous rats. Individual, quartered anterior pituitaries were superfused for 6 h at 1 ml/min. Using two or three 10-min LHRH pulses of 0.8 nM in which the interpulse interval was 20-170 min or a single 2-h LHRH pulse of 0.8 nM, LHRH self priming of luteinizing hormone (LH) secretion was demonstrable within 30-40 min of LHRH exposure. LHRH self priming of follicle-stimulating hormone occurred 40-50 min after the start of LHRH exposure. The first derivative of the 2-h LHRH pulse rate of secretion vs. time curve provided a sensitive indicator of the time required for development of the self-priming response. Once initiated by a 10-min LHRH pulse, priming of LH secretion persisted with no decrease, as determined by the area under the secretion rate vs. time curve and by the slope of the rise of this curve, over the longest interpulse interval examined, 170 min. The observed time course of development and persistence of LHRH self priming are consistent with its presumed important role in development of the preovulatory gonadotrophin surges.

RATE OF TESTICULAR MATURATION, IN RELATION TO GONADOTROPHIN AND TESTOSTERONE LEVELS, IN QUAIL EXPOSED TO VARIOUS ARTIFICIAL PHOTOPERIODS AND TO NATURAL DAYLENGTHS

1978 ◽  
Vol 78 (2) ◽  
pp. 267-280 ◽  
Author(s):  
B. K. FOLLETT ◽  
S. L. MAUNG
Keyword(s):  
Japanese Quail ◽  
Growth Rates ◽  
Plasma Levels ◽  
Seminiferous Tubule ◽  
Maximum Growth ◽  
Testosterone Levels ◽  
Testicular Growth ◽  
Small Peak ◽  
Lh Secretion ◽  
Tubule Diameter

SUMMARY Rates of testicular growth and plasma levels of FSH, LH and testosterone were determined in Japanese quail exposed to various fixed photoperiods (number of hours of light: number of hours of darkness): 12L: 12D, 13L: 11D, 14L: 10D, 16L: 8D and 20L: 4D and to natural daylengths. All five artificial photoperiods stimulated spermatogenesis, with the testes reaching maturity after 30–40 days. Maximum rates of testicular growth occurred with 14L: 10D, 16L: 8D or 20L: 4D but the rate was reduced by 50% in birds exposed to 12L: 12D. This reduction was due to decreased growth in the seminiferous tubule epithelium (and hence in tubule diameter); the duration of spermatogenesis hardly being affected. Near maximum growth rates occurred with 13L: 11D. The hormone profiles offer an explanation for the differential rates of testicular growth. In the three longest photoperiods, FSH rose from 20 ng/ml to peak levels of 300–400 ng/ml after 10 days. As the testes matured, so the level of FSH decreased to 50–100 ng/ml. This pattern was not seen under 12L: 12D; the level of FSH rose slowly to about 100 ng/ml and showed no peak of secretion. With 13L: 11D a small peak was found, which decreased at maturity. In quail with testes > 1500 mg, the level of FSH was invariably about 100 ng/ml. Patterns of LH secretion were rather similar with all treatments, but testosterone was affected by photoperiod; lower levels were found under 12L: 12D than 20L: 4D. The rate of photoperiodically induced testicular growth was proportional to the levels of FSH, and possibly also testosterone, in the circulation. Outdoors, testicular growth began when daylengths reached about 12 h. Maturity occurred within the next 40 days. The levels of FSH rose steadily but did not show a peak of secretion. In general, the highest levels of hormone were found in July just before gonadal regression which occurred when the daylengths were still quite long.

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