Electrical stimulation of the hypothalamus and luteinizing hormone secretion in Japanese quail.

Experiments were undertaken to localize those hypothalamic areas in the male quail (Coturnix coturnix japonica) where electrical stimulation would increase LH secretion. The posterior basal hypothalamus was stimulated with rectangular pulses (height 500 muA) through a bipolar electrode for 6 min, blood samples being taken for LH assay 20 min before, and 2, 10, 20 and 30 min after stimulation. The highest plasma concentration was observed in the 2 min sample. Over the next 30 min the LH level decreased to the resting concentration. The relative increase in LH level was greatest in sexually immature quail and least in photostimulated castrated birds, although the highest absolute levels were seen in the castrated quail. There were no statistical differences between the magnitude of the LH increases in sexually immature, mature and castrated quail. Various hypothalamic regions were then stimulated with a smaller current (200 muA) applied for only 2 min. A highly significant rise in LH followed stimulation of either the tuberal hypothalamus (postero-dorsal part of the infundibular nuclear complex, PD-INC), or the preoptic region (POR) while stimulation 0-5-1-5 mm away from these regions did not change LH secretion. Stimulation of the anterior basal hypothalamus, or of the suprachiasmatic area, caused a significant rise in LH concentration although this was less than that seen after stimulation of the POR. Stimulation in the POR or the PD-INC was ineffective if the tuberal hypothalamus had been deafferentated surgically some days previously. The data complement the studies in which destruction of the PD-INC or the POR by electrolytic lesions has been shown to block photoperiodically induced testicular growth and LH secretion.     

Steroid secretion by ovarian cells of the Japanese quail (Coturnix coturnix japonica)

Mixed cell preparations (theca plus granulosa) prepared from the hierarchy of follicles of quails ovaries were incubated under defined conditions with or without the addition of ovine luteinizing hormone (oLH), ovine follicle stimulating hormone (oFSH), theophylline, cycloheximide, or dibutyryl cyclic adenine monophosphate (db cAMP); or in the presence of androstenedione or testosterone as aromatizable substrate. Steroids secreted into the medium during the 4-hr incubation period were assayed by radioimmunoassay. Cells from the largest follicles (F1) secreted predominantly progesterone, were stimulated by LH and db cAMP, and the response was potentiated by theophylline, but FSH had no stimulatory effect. The F1 cells showed increasing basal and LH-stimulated responses between 18 and 12 hr before the next expected oviposition. Cells from the smaller follicles (F3 and F4) secreted predominantly estrogens, and were stimulated by FSH but not by db cAMP and only to a small extent by theophylline. Addition of androstenedione (10(-7) M) or testosterone (10(-7) M) enhanced estrogen secretion, which was further raised by the simultaneous addition of FSH. These results confirm previous reports on the sites of steroid secretion within quail follicles and suggest that while the action of LH on the cells from F1 follicles may be mediated in part through the adenylate cyclase system, the action of FSH on the smaller follicles may be substantially independent of cAMP.     

The endocrine control by luteinizing hormone of testosterone secretion from the testis of the Japanese quail

Injections of chicken or ovine luteinizing hormone (LH) into sexually mature male Japanese quail greatly increased plasma levels of testosterone. Maximal responses were obtained within 15 min of an iv injection and between 1 and 2 hr following sc or im injections. Saline treatment had no effect on plasma testosterone. In chronically castrated quail LH was not effective in altering androgen levels. The responses to LH were dose related, significant increases being obtained following sc injections of 5 μg of chicken LH (fraction AE1) or 10 μg of ovine LH (NIH-LH-S19). Chicken LH (AE1) was appropriately 1.8 times as potent as NIH-LH-S19. Ovine FSH (NIH-FSH-S10) stimulated testosterone release in very large doses (1 mg) but was at least 100 times less active than LH-S19. An iv injection of an antiserum raised against chicken LH into mature male quail caused a rapid decrease in plasma testosterone levels. Treatment with FSH-S-10 for up to 1 week failed to facilitate the subsequent response to an injection of LH. The responsiveness of the testis to exogenous LH was tested at various times during a photoinduced gonadal growth cycle. Sexually immature quail showed only a marginal response to an sc injection of 20 μg of NIH-LH-S19. A marked increase in responsiveness occurred after 6 long days. This coincides with the time when plasma testosterone levels increase naturally after transfer to long daylengths and with the period when Leydig cell maturation becomes complete. These in vivo results add further weight to the belief that, in birds, or at least in the quail, peripheral androgens are controlled by pituitary LH and that FSH plays no significant role in the acute release of testosterone from the mature testis.     

Synergistic action of follicle-stimulating hormone and testosterone on radioactive phosphorus incorporation into testes of the immature Japanese quail.

Injections of 2 to 80 μg of NIH-FSH-S12 induced a log-dose-dependent increase in the ³²P incorporation into testes of newly hatched cockerels of the Japanese quail, but injections of 4 μg of NIH-LH-S19 did not. Injections of 2 mg of testosterone increased the response of the Japanese quail cockerel to FSH. Both the level of the incorporation and the slope of the dose-response curve were increased by the treatment. Treatment with testosterone alone induced no or slight response. The potentiation of the effect of FSH by testosterone is considered to be due to the increase in the density of FSH receptors induced by testosterone, since Ishii and Tsutsui (1978, Gen. Comp. Endocrinol.36, 297–305) recently found that administration of testosterone or testosterone and FSH increased the density of FSH receptors in the testis of immature Japanese quails.     

Improvements in the determination of the turnover rate of plasma thyroxine in avian species: application to the Japanese quail

The disappearance of the thyroid hormone thyroxine (T4) from plasma in fully grown male Japanese quail can be described as a first order process with a rate constant of 0.178 +/- 0.013/h (mean +/- S.E.M., n = 8), which represents a half-life of 3.90 h. A small amount of [125I]T4 in relation to total circulating T4 was injected i.v. into Japanese quail and plasma samples were taken at appropriate time-intervals for the determination of residual plasma radioactivity. The rate of disappearance of [125I]T4 was subsequently equated to the turnover rate of the endogenous hormone. Previous methods were modified to overcome problems arising from possible disturbance of plasma T4 metabolism, recirculation of radiolabelled iodide, and to purify the [125I]T4 from the plasma samples. By using labelled T4 of very high specific activity, the amount of [125I]T4 administered was kept much smaller than has been used in previous studies on Japanese quail, thus limiting any interference with plasma T4 dynamics. To minimize any disturbance of plasma T4 metabolism, only four blood samples were taken, at three-hourly intervals after the injection of [125I]T4. The rapid turnover of T4 produced a large amount of labelled inorganic iodide, the re-entry of which into the plasma T4 pool was inhibited by s.c. administration of sodium thiocyanate 1 h before injection of [125I]T4. Assay of the true [125I]T4 turnover was significantly improved over that used in previous studies by purifying the [125I]T4 from the plasma samples chromatographically. The samples were applied to small Sephadex G-25 columns with sodium hydroxide (0.1 mol/l) as the eluant.(ABSTRACT TRUNCATED AT 250 WORDS)     

Catecholamine inhibition of thyrotropin-induced secretion of thyroxine: mediation by an alpha-adrenergic receptor.

Thyroxine secretion by mouse thyroid gland incubated in vitro was measured. Thyrotropin or dibutyryl cAMP increased thyroxine secretion several-fold. l-Epinephrine and l-norepinephrine strongly inhibited this stimulated release; l-isoproterenol was relatively ineffective. Phentolamine prevented the inhibition by catecholamines of thyroxine release; l-propranolol had no effect. These findings indicate that stimulation of alpha-adrenergic receptors opposes the action of thyrotropin in the regulation of thyroxine secretion.     

Termination of LH secretion in Japanese quail due to high- and low-temperature cycles and short daily photoperiods.

Mature male Japanese quail were transferred from 16L:8D (19 degrees) to one of the following combinations of daily light-dark and temperature cycles, 8L:16D (12 hr, 19 degrees:12 hr, 9 degrees), 12L:12D (12 hr, 19 degrees:12 hr, 9 degrees) and 12L:12D (16 hr, 19 degrees:8 hr, 9 degrees). The low temperature is for the middle of the dark period in each treatment. In the control groups, birds were transferred to the same photoperiodic conditions as the experimental groups, but without changes in ambient temperature. Blood samples were collected every other day for 30 days and circulating levels of plasma LH were estimated by radioimmunoassay. Both the change in conditions from 16L:8D to 8L:16D with the temperature lowered for 12 hr and that from 16L:8D to 12L:12D with temperatures lowered in one case for 12 hr and in the other for 8 hr caused a lowering in plasma LH levels in all the birds to reproductively quiescent levels. The cloacal protrusion of all these birds regressed completely. In control groups, however, most if not all the birds remained in active breeding states although the levels of circulating LH decreased to basal breeding levels of 1-2 ng/ml. The results indicated that in addition to a change from long to short days an alternation of high and low temperatures was sufficient supplementary information in causing termination of LH secretion and inducing regression of the gonads and the accessory sex organs in this species.     

The interaction between day length and the gonads in the regulation of levels of plasma thyroxine and triiodothyronine in the Japanese quail

Changes in the concentrations of plasma thyroxine (T₄) and triiodothyronine (T₃) were measured in intact and gonadectomized quail of both sexes after transfer from short (6L:18D) to long (18L:6D) days and upon return to short days. The concentration of free thyroxine (FT₄) was also measured in intact birds after transfer from short to long days. In both intact and gonadectomized birds, the concentration of plasma T₄ increased after transfer to long days while no consistent change was seen in the concentration of plasma T₃. However, after 15–24 days of photostimulation, the concentrations of plasma T₄ and T₃ began to fall in the intact birds but remained unchanged in the gonadectomized birds. The transitory increase in plasma T₄ observed in intact birds after photostimulation was associated with an increase in concentrations of plasma FT₄. The decrease in plasma T₄ and T₃ in photostimulated intact birds began when gonadal growth was nearly complete. The concentration of plasma T₃ in sexually mature male and female quail was lower than in sexually immature birds. In gonadectomized birds of both sexes, the concentration of plasma T₄ fell while that of plasma T₃ remained unchanged after transfer from long to short days. In sexually mature males and females, the transfer back to short days did not change the concentration of plasma T₄ but caused an increase in that of plasma T₃. These observations are consistent with the view that in the quail long day lengths may directly stimulate the hypothalamo-pituitary-thyroid axis and the production of T₄ and that the production of T₃ is not directly dependent on day length. It is suggested that in sexually mature birds the concentrations of plasma T₄ and T₃ are depressed because of a reduction in the concentration of plasma thyroid-hormone-binding proteins. The production of these proteins is suggested to be inhibited by gonadal steroids.     

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

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.     

Prolactin concentrations in the pituitary gland and plasma of Japanese quail in relation to photoperiodically induced sexual maturation and egg laying

A heterologous radioimmunoassay was used to measure pituitary and plasma concentrations of prolactin in Japanese quail (Coturnix coturnix japonica). The pituitary content increased significantly during photoperiodically induced sexual maturation and declined during gonadal regression on short days. Higher pituitary prolactin levels were attained in females than in males, and laying females had higher concentrations than nonlaying females. Plasma concentrations were similar in all groups. It is suggested that the high pituitary levels and the consistent plasma concentrations in laying females are related to the suppression of incubation behaviour in caged birds.     

Distribution of benzodiazepine binding sites in the brain of the male Japanese quail and its correlation to a hormonal control: quantitative autoradiography study.

Quantitative receptor autoradiography was used to study the neuroanatomical distribution and effects of gonadal hormones on [3H] flunitrazepam binding in the male Japanese quail brain. In gonadally intact quail brains, [3H] flunitrazepam displayed a heterogeneous distribution, with elevated levels in the posterior brain regions such as the stratum griseum et fibrosum superficiale and stratum griseum centrale of the optic tectum. Lower values were observed in the anteriorly located brain sites such as the nucleus septalis (lateralis et medialis), the cortex dorsolateralis and the nucleus lateralis hypothalami. Castration affected [3H] flunitrazepam binding levels in brain areas known to contain gonadal steroid receptors as well as in some areas which were devoid of gonadal steroid receptors. Castration in fact, elevated [3H] flunitrazepam binding in the nucleus preopticus anterior and reduced binding levels in archistriatum dorsalis et ventralis and in the nucleus intercollicularis; all of these areas are known to have gonadal steroid receptors. In two regions which do not contain such receptors, namely the hyperstriatum ventrale and the cerebellum pars granularis, castration increased [3H] flunitrazepam binding. In order to determine whether the gonadal steroid effect is due to changes either in the number of binding sites (Bmax) and or affinity binding state (KD), saturation binding studies were carried out in some of the areas described above in brains of quail which were castrated or castrated and given replacement therapy with testosterone or estradiol for 2 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)     

Leptin and thyroxine during sexual development in male monkeys: effect of neonatal gonadotropin-releasing hormone antagonist treatment and delayed puberty on the developmental pattern of leptin and thyroxine secretion

OBJECTIVE: Neonatal treatment of male monkeys with a gonadotropin-releasing hormone antagonist (Ant) increased the incidence of delayed puberty. Using blood samples that had been collected from monkeys with normal or delayed puberty, we assessed the potential involvement of leptin and thyroxine (T4) in sexual development. DESIGN AND METHODS: Monkeys were treated from birth until 4 months of age with vehicle, Ant or Ant/androgen and blood samples were drawn from 10 to 62 months of age. RESULTS: Serum leptin and total T4 concentrations declined in parallel throughout adolescence in all treatment groups. There was no transient rise in leptin before or in association with the onset of puberty. Also, leptin did not differ during the peripubertal period between animals experiencing puberty at that time versus those in which puberty was being delayed. Neonates treated with Ant either alone or with androgen replacement had higher leptin levels than controls throughout development. While leptin exhibited no significant changes during the peripubertal period, T4 values increased and declined in parallel with the peripubertal changes in hypothalamic-pituitary-testicular activity. CONCLUSIONS: These data do not support the concept that a transient rise in leptin triggers the onset of puberty in male monkeys. However, the disruption of neonatal activity of the pituitary-testicular axis alters the developmental pattern of leptin. The changes in T4 levels during the peripubertal period suggest that thyroid status may be a significant contributor to the process of sexual development in the male monkey and that peripubertal changes in secretion of this hormone may serve as an effective physiological response during a critical period of elevated energy expenditure.     

Circulating estradiol and the activation of male and female copulatory behavior in Japanese quail (Coturnix japonica)

Previous experiments using systemic and preoptic area (POA) hormone treatments have shown that aromatization of testosterone (T) to estrogen (E) is essential for activation of male-typical copulatory behavior in castrated male Japanese quail (Coturnix japonica). Two experiments were conducted to determine whether circulating estrogen levels characteristic of normal intact males are high enough to activate male-typical or female-typical copulatory behavior. In Experiment 1, blood samples were drawn every 4 hr from groups of sexually active male quail housed under a 16L:8D light-dark cycle, and assayed for estradiol (E2) concentration. The mean +/- SEM serum E2 was 54.2 +/- 3.6 pg/ml, and no daily cycle in serum E2 was seen. The males were then tested for sexual behavior; 88% mounted females, and 23% crouched when mounted by males. In Experiment 2, 51 males were castrated and implanted with Silastic tubes containing estradiol benzoate (EB) and/or cholesterol designed to produce five different levels of serum E2, then tested for male- and female-typical copulatory behavior and bled. The serum E2 in EB-implanted quail which mounted (253 +/- 30 pg/ml) was significantly higher than that of intact quail in Experiment 1, and only 10.2% of intact males had serum E2 as high as the minimum associated with mounting in EB-implanted males. These results show that serum E2 levels in intact males are not high enough to support male-typical copulation, and that aromatization in the POA to produce locally high E2 levels may be required. In addition, it was found that the threshold serum E2 to elevate receptivity significantly was 3.6 times the intact male level, and only slightly higher than serum E2 reported for intact females. Thus the lack of receptivity in intact males is probably due to insufficient circulating E2, and the male is not defeminized with respect to sensitivity to E2 for activation of receptivity.     

Inhibition of thyrotropin- and dibutyryl cyclic AMP-induced secretion of thyroxine and triiodothyronine by catecholamines.

Thyrotropin (TSH), 1 MU/ml and N6, O2'-dibutyryl adenosine 3',5-cyclic monophosphoric acid (dbcAMP) greatly enhanced the release of thyroxine (T4) and triiodothyronine (T3) from mouse thyroids incubated in vitro. L-Epinephrine (E) and L-norepinephrine (NE) strongly inhibited the TSH and dbcAMP-stimulated release of thyroid hormones; L-isoproterenol (IPNE) exerted a relatively weak inhibition. The inhibition by catecholamines was prevented by the alpha-adrenergic blocker, phentolamine; L-propranolol, a beta-adrenergic blocker, had no effect on the inhibition. The TSH-induced release of thyroid hormones was not affected by adrenergic blockers. Epinephrine did not affect the increase in thyroidal cAMP content induced by TSH. These results indicate that catecholamines act by way of an alpha-adrenergic receptor to suppress TSH-stimulated release of thyroid hormones at a point beyond cAMP formation.