Photoperiodic control of the development of the LHRH neurosecretory system of European starlings (Sturnus vulgaris) during puberty and the onset of photorefractoriness

1989 ◽  
Vol 122 (1) ◽  
pp. 255-268 ◽  
Author(s):  
A. R. Goldsmith ◽  
W. E. Ivings ◽  
A. S. Pearce-Kelly ◽  
D. M. Parry ◽  
G. Plowman ◽  
...  
Keyword(s):  
Median Eminence ◽  
Sexual Maturation ◽  
Staining Intensity ◽  
Neurosecretory System ◽  
Inhibitory Influence ◽  
European Starlings ◽  
Testicular Regression ◽  
Lhrh Release ◽  
Prolactin Content ◽  
Pituitary Prolactin

ABSTRACT The development of the reproductive system was studied in juvenile starlings during the acquisition of photosensitivity, the attainment of sexual maturation after photostimulation and the subsequent onset of photorefractoriness, using immunohistochemistry for LHRH and radioimmunoassay measurements of hypothalamic, pituitary and plasma hormone concentrations. The first stage of sexual development induced by exposure of photorefractory immature starlings to short days (8 h light:16 h darkness; 8L:16D) was characterized by a decrease in pituitary prolactin content within 1 week and an increase in hypothalamic LHRH content, in the size of the LHRH perikarya and in the intensity of immunostaining in the median eminence in 4–6 weeks. Sexual maturation occurring after exposure to long days (18L:6D) was associated with further increases in LHRH content and cell size, and increases in LH and prolactin concentrations. During testicular regression, LHRH perikarya were reduced in size and staining intensity but LHRH immunostaining in the median eminence and content in the hypothalamus remained high until gonadal regression was almost complete. Prolactin levels were maximal during testicular regression. These results suggest that gonadal regression is initiated by a reduction in LHRH synthesis and possibly, in addition, an external inhibitory influence on LHRH release. Hypothalamic LHRH content eventually declined and LHRH immunostaining in the median eminence was much reduced in fully photorefractory starlings maintained under long days. Journal of Endocrinology (1989) 122, 255–268

Immunohistochemical demonstration of marked changes in the LHRH system of photosensitive and photorefractory European starlings (Sturnus vulgaris)

1987 ◽  
Vol 115 (2) ◽  
pp. 211-NP ◽  
Author(s):  
R. G. Foster ◽  
G. Plowman ◽  
A. R. Goldsmith ◽  
B. K. Follett
Keyword(s):  
Median Eminence ◽  
Sturnus Vulgaris ◽  
Cell Number ◽  
Neurosecretory System ◽  
Neural Pathways ◽  
European Starlings ◽  
Long Day ◽  
Mean Diameter ◽  
Fibre Number ◽  
The Brain

ABSTRACT Immunocytochemistry was used to determine the effects of photoperiod on the LHRH neurosecretory system in the brain of male European starlings. In this species, as in other birds, reproduction is triggered by long daylengths but continued exposure leads to photorefractoriness and to a complete shut-down of the reproductive system. These effects are thought to be mediated through changes in the secretion of LHRH. In starlings exposed to a photoperiod of 11 h light: 13 h darkness (11L: 13D) and with fully developed testes there was strong immunostaining of both LHRH perikarya (n = 522 ± 43 s.e.m.) and fibres. Photosensitive short-day (8L: 16D) starlings with undeveloped testes had an almost identical distribution of strongly immunoreactive perikarya (n = 523 ± 62) but there were fewer fibres. In the median eminence, fibre number was reduced significantly (P < 0·01) by some 30%. In long-day (18L: 6D) photorefractory starlings with fully regressed testes there was an even more obvious change in the LHRH system. Perikarya were only weakly immunoreactive and there was a significant (P < 0·01) reduction in mean diameter from 10 to 6·5 μm. In addition, there was a significant (P < 0·05) reduction in cell number (312 ± 62), although this may well result from the fact that some weakly stained cells fell below the limits of resolution and could not be counted. LHRH fibres disappeared almost entirely from the median eminence, and were not visible elsewhere in the brain. The higher neural pathways regulating photorefractoriness induced by long days are unknown but clearly both production of LHRH in the perikarya and release/storage of LHRH in the terminals is being profoundly modified. J. Endocr. (1987) 115, 211–220

scholarly journals Neurobiological Mechanisms of the Onset of Puberty in Primates*

2001 ◽  
Vol 22 (1) ◽  
pp. 111-151 ◽  
Author(s):  
Ei Terasawa ◽  
David L. Fernandez
Keyword(s):  
Rhesus Monkeys ◽  
Neonatal Period ◽  
Developmental Changes ◽  
Neurosecretory System ◽  
Neuronal System ◽  
Inhibitory Neurotransmitter ◽  
Gaba Inhibition ◽  
Female Rhesus ◽  
Lhrh Release ◽  
Low Levels

Abstract An increase in pulsatile release of LHRH is essential for the onset of puberty. However, the mechanism controlling the pubertal increase in LHRH release is still unclear. In primates the LHRH neurosecretory system is already active during the neonatal period but subsequently enters a dormant state in the juvenile/prepubertal period. Neither gonadal steroid hormones nor the absence of facilitatory neuronal inputs to LHRH neurons is responsible for the low levels of LHRH release before the onset of puberty in primates. Recent studies suggest that during the prepubertal period an inhibitory neuronal system suppresses LHRH release and that during the subsequent maturation of the hypothalamus this prepubertal inhibition is removed, allowing the adult pattern of pulsatile LHRH release. In fact,γ -aminobutyric acid (GABA) appears to be an inhibitory neurotransmitter responsible for restricting LHRH release before the onset of puberty in female rhesus monkeys. In addition, it appears that the reduction in tonic GABA inhibition allows an increase in the release of glutamate as well as other neurotransmitters, which contributes to the increase in pubertal LHRH release. In this review, developmental changes in several neurotransmitter systems controlling pulsatile LHRH release are extensively reviewed.

scholarly journals Changes in pituitary prolactin content in rats at mid-pseudopregnancy.

1991 ◽  
Vol 37 (1) ◽  
pp. 51-57
Author(s):  
Mitsumori KAWAMINAMI ◽  
Inoru HASHIMOTO ◽  
Michio TAKAHASHI ◽  
Kazutaka HOMMA
Keyword(s):  
Prolactin Content ◽  
Pituitary Prolactin

N-Tosyl-L-Phenylalanine Chloromethyl Ketone Inhibits LHRH-Degrading Activity and Increases in vitro LHRH Release from the Immature Rat Median Eminence

1988 ◽  
Vol 47 (2) ◽  
pp. 102-108 ◽  
Author(s):  
Juan P. Advis ◽  
Ann M. Contijoch ◽  
Henryk F. Urbanski ◽  
Sergio R. Ojeda
Keyword(s):  
Median Eminence ◽  
Immature Rat ◽  
Chloromethyl Ketone ◽  
Lhrh Release

β-Endorphin Regulation of LHRH Release at the Median Eminence Level: Immunocytochemical and Physiological Evidence in Hens

1993 ◽  
Vol 57 (2) ◽  
pp. 365-373 ◽  
Author(s):  
Ann M. Contijoch ◽  
Sasha Malamed ◽  
Dipak K. Sarkar ◽  
Juan-Pablo Advis
Keyword(s):  
Median Eminence ◽  
Physiological Evidence ◽  
Lhrh Release

Effects of hypothalamic estrogen implants on pituitary LH and prolactin in rabbits

1963 ◽  
Vol 205 (6) ◽  
pp. 1073-1076 ◽  
Author(s):  
Shigeto Kanematsu ◽  
Charles H. Sawyer
Keyword(s):  
Ascorbic Acid ◽  
Median Eminence ◽  
Mammary Glands ◽  
Estradiol Benzoate ◽  
Minute Amount ◽  
Posterior Median ◽  
Prolactin Content ◽  
Estrogen Implants ◽  
The Brain

A minute amount of estradiol benzoate was implanted into the posterior median eminence-basal tuberal region of the hypothalamus or hypophysis in female rabbits. Pituitary LH was measured by the ovarian ascorbic acid depletion method. Prolactin assays were performed on the same hypophyses by the intradermal pigeon crop sac method. Pituitary LH content was 0.47 µg/mg wet wt. following implantation of estrogen into parts of the brain other than the posterior median eminence-basal tuberal area. However, when estrogen was implanted into the posterior median eminence-basal tuberal area the pituitary LH content decreased markedly to less than 0.05 µg/mg and this decline was associated with ovarian atrophy. The prolactin content was significantly elevated ( P < 0.01) but the mammary glands were not activated. Estrogen implantation into the adenohypophysis appeared to cause release of prolactin but failed to affect the LH content (0.50 µg/mg) or to induce ovarian atrophy. The results indicate that estrogen acts on the posterior median eminence-basal tuberal area to stimulate production but not release of prolactin and, simultaneously, to inhibit synthesis of LH.

EFFECTS OF PINEALECTOMY AND CONSTANT LIGHT AND DARKNESS ON PROLACTIN LEVELS IN THE PITUITARY AND PLASMA AND ON PITUITARY ULTRASTRUCTURE OF THE RAT

1972 ◽  
Vol 54 (2) ◽  
pp. 263-NP ◽  
Author(s):  
R. RELKIN ◽  
M. ADACHI ◽  
S. A. KAHAN
Keyword(s):  
Plasma Concentrations ◽  
Virgin Female ◽  
Female Rats ◽  
Constant Light ◽  
Constant Darkness ◽  
Plasma Prolactin ◽  
Continuous Darkness ◽  
Prolactin Content ◽  
Intermediate Degree ◽  
Pituitary Prolactin

SUMMARY The effects of constant light, constant darkness and diurnal lighting, in combination with pinealectomy or sham-pinealectomy, on pituitary and plasma concentrations of radioimmunoassayable prolactin were investigated in 8-week-old male and virgin female rats. Two to three days after operation random groups of pinealectomized and sham-pinealectomized animals of the same sex were placed together in either continous light, continuous darkness or diurnal light, and killed 21 days later. Compared with sham-operated diurnally-illuminated controls, constant darkness caused a decrease in pituitary prolactin content and a rise in plasma prolactin levels. Pinealectomy or constant illumination reversed the effect of constant darkness, resulting in an increase in pituitary prolactin content and a fall in plasma prolactin levels when compared with sham-operated diurnally-illuminated controls. Electron microscopy of lactotrophic cells of the sham-pinealectomized animals exposed to constant darkness revealed few cytoplasmic granules, whereas these cells in the sham-pinealectomized animals exposed to constant light contained abundant granules; compared with the former groups, lactotrophic cells of sham-pinealectomized rats exposed to diurnal lighting revealed an intermediate degree of granulation.

Increased dopaminergic inhibition of prolactin in the hypoprolactinaemic IPL nude rat

1985 ◽  
Vol 107 (3) ◽  
pp. 325-329 ◽  
Author(s):  
H. Cohen ◽  
I. Sabbagh ◽  
P. Guillaumot ◽  
J. Bertrand
Keyword(s):  
Adult Male ◽  
Physiological Saline ◽  
Prolactin Secretion ◽  
Male Rats ◽  
Saline Control ◽  
Plasma Prolactin ◽  
Synthesis Inhibitor ◽  
Nude Rat ◽  
Prolactin Content ◽  
Pituitary Prolactin

ABSTRACT In this study, aimed at investigating whether dopaminergic regulation of prolactin could be implicated in the hypoprolactinaemia observed in the IPL nude rat, dopaminergic inhibition of prolactin was suppressed using a catecholamine synthesis inhibitor α-methyltyrosine (MT) and a dopaminergic antagonist sulpiride. Adult male rats (IPL nude and normal) were injected through implanted atrial cannulae with either MT (250 mg/kg) or physiological saline (control). Rats were decapitated 2 h after the injection. Plasma prolactin levels, compared with basal values, increased by 15·6 ± 1·9 (s.e.m.)- and 5·89 ± 0·6-fold in IPL nude and normal rats respectively. This difference was highly significant. The pituitary prolactin content was decreased in both groups. In a second experiment, adult male IPL nude or normal rats were injected with either sulpiride (1 mg/kg) or saline and decapitated 2, 4, 8, 12, 14 and 24 h later. Plasma prolactin levels, compared with basal values, were increased in rats injected with sulpiride by 9·2 ± 1·8 and 3·4 ± 0·7-fold in IPL nude and normal rats respectively. The pituitary prolactin content was reduced more in IPL nude than in normal sulpiride-injected rats. These data suggest that prolactin secretion, as well as synthesis, is under an increased dopaminergic inhibition in the male IPL nude rat. J. Endocr. (1985) 107, 325–329

Copper Stimulation of LHRH Release from Median Eminence Explants

1986 ◽  
Vol 44 (3) ◽  
pp. 276-282 ◽  
Author(s):  
Miriam Colombani-Vidal ◽  
Ayalia Barnea
Keyword(s):  
Median Eminence ◽  
Lhrh Release ◽  
Stimulation Of
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