Influence of Age on the Release of Luteinizing Hormone Induced by Oestrogen and Progesterone in Immature Rats

Caligaris, L.; Astrada, J. J.; Taleisnik, S.

doi:10.1677/joe.0.0550097

Cited by 97 publications

(57 citation statements)

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“…Brain-pituitary mechanisms subserving the gonadotrophin response to an oestrogen stimulus are also fully developed and functional well before the occurrence of first oestrus (Caligaris, Astrada & Taleisnik, 1972;Puig-Duran & MacKinnon, 1978). A single injection (s.c.) ot oestrogen at 12:00 h will cause an LH surge about 50-54 h later in 21-day-old (Text- fig.…”

Section: Positive Feedbackmentioning

confidence: 99%

Reflections on the attainment of puberty in the rat: have circadian signals a role to play in its onset?

Mackinnon¹,

Puig-Duran²,

Laynes³

1978

Reproduction

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Section: Positive Feedbackmentioning

confidence: 99%

Reflections on the attainment of puberty in the rat: have circadian signals a role to play in its onset?

Mackinnon¹,

Puig-Duran²,

Laynes³

1978

Reproduction

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“…In 1932, Holweg described the luteinizing effect of a single injection of oestrogens in the female rat. In rats (Caligaris et al, 1972;Steele & Weisz, 1974), as well as sheep (Land et al, 1970;Short, 1974) and monkeys (Knobil, 1974), the positive feedback mechanism which causes the preovulatory LH surge only becomes mature at the end of puberty. Likewise in girls this positive feedback effect of oestrogens on LH secretion does not exist before puberty .…”

Section: (B) Increase Of Hypothalamic-pituitary-gonadal Sensitivity Tmentioning

confidence: 99%

Hypothalamic‐pituitary‐gonadal Relationships in Man From Birth to Puberty

Forest

Peretti

Bertrand

1976

Clinical Endocrinology

134

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Gonadal function depends upon activities at various levels. Thus there is: (a) a central level (extra-hypothalamic, hypothalamic, and anterior pituitary); (b) an intermediate level (gonadal and plasma), and (c) a peripheral level consisting of the target organs to which the hormonal message is directed. These determine both the expression of gonadal function (physical, physiological, or psychological) and the feedback regulation of the secretion of gonadotrophins.(a) Central level (i) Extra-hypothalamic centres. The production of LH releasing hormone (LHRH) is affected in the rat, and probably in primates as well, by extra-hypothalamic stimuli coming, in particular, from the amygdala and the hippocampus. Adrenergic regulation exists at this level, noradrenaline having a stimulatory and dopamine an inhibitory effect (Bliss et al., 1972).(ii) Hypothalamic centres. These are localized in particular in the pre-optic area. Immunochemical techniques have demonstrated that LHRH is secreted by neurones of the arcuate nucleus, and released into the capillary plexus proximal to the hypophyseal portal system at the level of the median eminence, thereby reaching the anterior pituitary (Barry & Dubois, 1974;Setalo et al., 1975).(iii) Gonadotrophin secreting cells of the anterior pituitary. These synthesize and secrete the gonadotrophins, LH and FSH, under the influence of LHRH (Schally et al., 1972). The pituitary gonadotrophins stimulate the synthesis and the secretion of the gonadal

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“…During the prepubertal state in female rats, the positive feedback effect of sexual hormones on gonadotropin matures [8][9][10] this being the mechanism directly related to the onset of puberty and sexual cycles in the adult female rat. This mechanism matures around 20-22 days of age.…”

Section: Introductionmentioning

confidence: 99%

Effect of Ovarian Hormones on the Hypothalamic Excitatory Amino Acids System during Sexual Maturation in Female Rats

Carbone¹,

Szwarcfarb²,

Me³

et al. 1995

Neuroendocrinology

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The present experiments were designed to study in female rats during sexual maturation: (1) the hypothalamic release of aspartate (Asp), glutamate (Glu) and glycine (Gly) which are the excitatory amino acids (EAAs) involved in NMDA neurotransmission and of taurine (Tau), a putative inhibitory amino acid of GnRH secretion; (2) the relationships between the effect of estrogen-progesterone (EP) on the release of these EAAs and the secretion of gonado-tropins, and (3) the effect of hypothalamic NMDA receptor stimulation on EAAs release by the hypothalamus as well as the effect of EP on this release. The release of EAAs by the anterior preoptic and medial-basal hypothalamic areas (APOA-MBH) is significantly higher in peripubertal than in prepubertal rats (p < 0.01). EP treatment in prepubertal rats (16 days of age) decreased LH and FSH plasmatic levels and also the in vitro release of Asp, Glu, Gly and Tau. Contrary to the observations in prepubertal rats, in 30-day-old peripubertal rats the ovarian hormones significantly (p < 0.01) increased the levels of LH and FSH as well as the release to the medium of these amino acids. In prepubertal rats, the addition of NMDA to the incubation media significantly increased the release of Asp and of Glu. The NMDA receptor agonist did not modify the hypothalamic release of Gly and Tau to the incubation media. On the other hand, pretreatment with EP did not modify either the Asp and Glu release response to NMDA or the lack of response on Gly and Tau. In peripubertal rats NMDA also significantly increased the in vitro release of Asp and Glu, but at this age pretreatment with EP significantly potentiated the release of these amino acids induced by NMDA. On the other hand, the ovarian hormones induced Gly and Tau release by NMDA, this not being observed in control rats. In conclusion, the present results indicate that during sexual maturation the in vitro release of Asp, Glu and Gly by APOA-MBH increases and Tau release decreases. EP pretreatment of prepubertal rats decreases the hypothalamic release of EAAs as well as the serum LH and FSH levels but increases both EAAs release and plasmatic gonadotropin in peripubertal rats. On the basis of these results it is proposed that the increase in EAAs release by the hypothalamus is directly connected with the onset of puberty and that the maturation of the positive feedback effect of ovarian hormones on gonadotropin secretion is related to the maturation of the capacity of EP to increase hypothalamic EAAs. Before this maturational event EP inhibits EAAs release as well as gonadotropin release (prepubertal rats). NMDA receptor stimulation leads to a positive mechanism which increases the release of Asp and Glu from APOA-MBH both in prepubertal and peripubertal rats, but EP potentiates this mechanism only in peripubertal rats. This could be an additional neuroendocrine mechanism involved in the increase of gonadotropin during sexual maturation which induces the onset of puberty and the preovulatory discharge of these pituitary hormones.

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Influence of Age on the Release of Luteinizing Hormone Induced by Oestrogen and Progesterone in Immature Rats

Cited by 97 publications

References 0 publications

Reflections on the attainment of puberty in the rat: have circadian signals a role to play in its onset?

Reflections on the attainment of puberty in the rat: have circadian signals a role to play in its onset?

Hypothalamic‐pituitary‐gonadal Relationships in Man From Birth to Puberty

Effect of Ovarian Hormones on the Hypothalamic Excitatory Amino Acids System during Sexual Maturation in Female Rats

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