Varying sensitivity to the negative oestrogen feedback during the ovarian cycle of female rats: evidence for the involvement of oestrogen and the medial preoptic area

ABSTRACT The gonadotrophic response to a single injection of oestradiol benzoate (OB) was studied in acutely ovariectomized adult rats during the different stages of a 4-day ovarian cycle. The results showed a sudden decline of the sensitivity to the gonadotrophin-inhibiting effect of OB between metoestrus and dioestrus. This desensitization to the negative oestrogen feedback was probably caused by an oestrogen action on the medial preoptic area (MPOA). In rats ovariectomized and implanted with OB in the MPOA in metoestrus, an s.c. injection of OB on the presumptive day of pro-oestrus did not lower the circulating LH and FSH levels, whereas a clear suppression of gonadotrophin secretion was seen in females implanted with cholesterol in the MPOA or implanted with OB in the hypothalamic ventromedial–arcuate region. Similar findings were obtained in rats which had been ovariectomized 3–4 weeks before implantation. A final experiment demonstrated that bilateral lesioning of the MPOA also reduced the sensitivity to the negative feedback action of oestrogen in long-term ovariectomized rats. In all experiments performed, diminution of the oestrogen-induced inhibition of LH secretion was more marked than that of suppression of FSH secretion. It is proposed that desensitization to the negative oestrogen feedback, probably resulting from an inhibitory oestrogen action on medial preoptic neurones, is a prerequisite for adequate gonadotrophic support of preovulatory follicle maturation in the presence of a continuously rising oestrogen concentration in the blood. J. Endocr. (1984) 102, 287–294

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Retardation of preovulatory desensitization to negative oestrogen feedback: mechanism of the effect of progesterone in 5-day cyclic rats

Journal of Endocrinology ◽

10.1677/joe.0.1140409 ◽

1987 ◽

Vol 114 (3) ◽

pp. 409-414 ◽

Cited By ~ 1

Author(s):

F. Döcke ◽

W. Rohde ◽

R. Chaoui ◽

J. Stürzebecher ◽

G. Dörner

Keyword(s):

Preoptic Area ◽

Feedback Mechanism ◽

Ovarian Cycle ◽

Female Rats ◽

Mediobasal Hypothalamus ◽

Inhibiting Effect ◽

Gonadotrophin Secretion ◽

Oestradiol Benzoate ◽

Lh Secretion ◽

Follicle Maturation

ABSTRACT Recent studies have shown that oestrogen can induce desensitization to its own gonadotrophin-inhibiting effect in female rats by an action on the medial preoptic area (MPOA). Probably as a consequence of this action, sensitivity to the negative oestrogen feedback declines markedly between metoestrus and dioestrus of the 4-day ovarian cycle. To study this desensitization process in 5-day cyclic rats, females exhibiting regular 5-day vaginal cyclicity were ovariectomized on consecutive days of the cycle, injected with oestradiol benzoate (OB) or oil on the day of ovariectomy and autopsied 24 h after the injection. Estimation of the serum concentration of LH revealed that desensitization to negative oestrogen feedback occurred only between day 2 of dioestrus and pro-oestrus, i.e. 2 days later than in females with a 4-day cycle. In the latter animals, an injection of progesterone in metoestrus or early dioestrus, which induced lengthening of the ovarian cycle for 1 day, delayed the onset of desensitization to a degree similar to that found in spontaneously 5-day cyclic rats. In acutely ovariectomized females, progesterone implants placed in the MPOA, but not those located in the mediobasal hypothalamus, increased the LH-inhibiting effect of low doses of OB. The results suggest that the prolonged secretion of progesterone recorded in 5-day cyclic rats retards follicle maturation and delays the forthcoming ovulation by acting, at least partly, on the MPOA and antagonizing the desensitizing effect of oestrogen. In this way, inhibition of gonadotrophin secretion by oestrogen is enhanced and the increase in tonic LH secretion necessary for the completion of follicle maturation is retarded. J. Endocr. (1987) 114, 409–414

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EFFECT OF NEONATAL ADMINISTRATION OF STEROIDS OR GONADECTOMY UPON OESTRADIOL-INDUCED LUTEINIZING HORMONE RELEASE IN RATS OF BOTH SEXES

Journal of Endocrinology ◽

10.1677/joe.0.0850069 ◽

1980 ◽

Vol 85 (1) ◽

pp. 69-74 ◽

Cited By ~ 27

Author(s):

F. GOGAN ◽

I. A. BEATTIE ◽

M. HERY ◽

E. LAPLANTE ◽

C. KORDON

Keyword(s):

Luteinizing Hormone ◽

Sexual Differentiation ◽

Female Rats ◽

Male Rats ◽

Ovariectomized Rats ◽

Hormone Release ◽

Adult Rats ◽

Luteinizing Hormone Release ◽

Neonatal Administration ◽

Lh Secretion

SUMMARY Implantation of oestradiol into adult rats of both sexes induced different patterns of LH secretion depending on the time at which gonadectomy or testosterone injection were performed. Castration 2 h after birth allowed an LH peak to occur daily at 18.00 h, but its amplitude was lower than that of adult gonadectomized female rats treated with oestradiol. Castration 24 h after birth elicited two kinds of response; a circadian discharge of LH lower than that of male rats gonadectomized 2 h after birth or a steady low level of LH. The LH rhythmicity induced by implantation of oestradiol was not seen after castration at 8 weeks of age. Neonatal administration of testosterone to female rats prevented the LH peak induced by oestradiol that was seen in adult ovariectomized rats. Neonatal or adult ovariectomy did not interfere with the rhythmical response of LH after implantation of oestradiol. Thus, it is concluded that sexual differentiation of the hypothalamus is primarily of masculine origin.

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Sexual differences in the effect of serotonin on LH secretion in rats

Acta Endocrinologica ◽

10.1530/acta.0.1090320 ◽

1985 ◽

Vol 109 (3) ◽

pp. 320-325 ◽

Cited By ~ 11

Author(s):

Jaime A. Moguilevsky ◽

María R. Faigón ◽

Modesto C. Rubio ◽

Pablo Scacchi ◽

Berta Szwarcfarb

Keyword(s):

Sexual Differences ◽

Female Rats ◽

Ovariectomized Rats ◽

Adult Rats ◽

Serotoninergic Neurons ◽

Male And Female Rats ◽

Lh Release ◽

Prepubertal Rats ◽

Lh Secretion ◽

The Brain

Abstract. The effect of 5-hydroxytryptophan (5-HTP), a serotonin (5-HT) precursor, on luteinizing hormone (LH) secretion was studied in prepubertal male and female rats of different ages. In females 5-HTP stimulated LH release on days 16, 18 and 20 but not in older rats (26, 30, 35 days of age). No effects of 5-HTP on LH levels were observed in males. The positive feed-back mechanism of oestrogen-progesterone (E-P), that normally matures in the female between 20 and 26 days, was inhibited by 5-HTP in all the ages studied during prepuberty (26, 30 and 35 days old). On the other hand, in adult ovariectomized rats, 5-HTP administration not only decreased the high LH levels induced by ovariectomy, but the LH release response to E-P as well. These results indicate that there are sexual differences in the effect of 5-HT on LH in prepubertal rats younger than 26 days old. Administration of p-chloroamphetamine (PCA) a serotonin neurotoxin selective for serotoninergic neurons that depletes 5-HT levels in the brain, induced a significant increase in the LH release response to LRH in females, but had no effect in males. These results, besides suggesting a probable pituitary participation in the 5-HT action on LH secretion in the female, appear to indicate the existence of sexual differences in the effect of 5-HT in adult rats.

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The Effects of Electrical Stimulation of the Medial Preoptic Area and the Medial Amygdala on Maternal Responsiveness in Female Rats

Annals of the New York Academy of Sciences ◽

10.1111/j.1749-6632.1997.tb51980.x ◽

1997 ◽

Vol 807 (1 Integrative N) ◽

pp. 602-605 ◽

Cited By ~ 17

Author(s):

HYWEL D. MORGAN ◽

JASON A. WATCHUS ◽

ALISON S. FLEMING

Keyword(s):

Electrical Stimulation ◽

Preoptic Area ◽

Medial Preoptic Area ◽

Female Rats ◽

Maternal Responsiveness ◽

Medial Amygdala ◽

Stimulation Of

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The Increase in Signaling by Kisspeptin Neurons in the Preoptic Area and Associated Changes in Clock Gene Expression That Trigger the LH Surge in Female Rats Are Dependent on the Facilitatory Action of a Noradrenaline Input

Endocrinology ◽

10.1210/en.2015-1323 ◽

2016 ◽

Vol 157 (1) ◽

pp. 323-335 ◽

Cited By ~ 7

Author(s):

Bruna Kalil ◽

Aline B. Ribeiro ◽

Cristiane M. Leite ◽

Ernane T. Uchôa ◽

Ruither O. Carolino ◽

...

Keyword(s):

Gene Expression ◽

Median Eminence ◽

Preoptic Area ◽

Clock Genes ◽

Third Ventricle ◽

Female Rats ◽

Ovariectomized Rats ◽

Lh Surge ◽

Clock Gene Expression

Abstract In rodents, kisspeptin neurons in the rostral periventricular area of the third ventricle (RP3V) of the preoptic area are considered to provide a major stimulatory input to the GnRH neuronal network that is responsible for triggering the preovulatory LH surge. Noradrenaline (NA) is one of the main modulators of GnRH release, and NA fibers are found in close apposition to kisspeptin neurons in the RP3V. Our objective was to interrogate the role of NA signaling in the kisspeptin control of GnRH secretion during the estradiol induced LH surge in ovariectomized rats, using prazosin, an α1-adrenergic receptor antagonist. In control rats, the estradiol-induced LH surge at 17 hours was associated with a significant increase in GnRH and kisspeptin content in the median eminence with the increase in kisspeptin preceding that of GnRH and LH. Prazosin, administered 5 and 3 hours prior to the predicted time of the LH surge truncated the LH surge and abolished the rise in GnRH and kisspeptin in the median eminence. In the preoptic area, prazosin blocked the increases in Kiss1 gene expression and kisspeptin content in association with a disruption in the expression of the clock genes, Per1 and Bmal1. Together these findings demonstrate for the first time that NA modulates kisspeptin synthesis in the RP3V through the activation of α1-adrenergic receptors prior to the initiation of the LH surge and indicate a potential role of α1-adrenergic signaling in the circadian-controlled pathway timing of the preovulatory LH surge.

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Ovarian steroids alter dopamine receptor populations in the medial preoptic area of female rats: implications for sexual motivation, desire, and behaviour

European Journal of Neuroscience ◽

10.1111/ejn.13121 ◽

2015 ◽

Vol 42 (12) ◽

pp. 3138-3148 ◽

Cited By ~ 12

Author(s):

M. Dean Graham ◽

James Gardner Gregory ◽

Dema Hussain ◽

Wayne G. Brake ◽

James G. Pfaus

Keyword(s):

Dopamine Receptor ◽

Preoptic Area ◽

Sexual Motivation ◽

Medial Preoptic Area ◽

Female Rats ◽

Ovarian Steroids

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Projection Sites of Medial Preoptic Area and Ventral Bed Nucleus of the Stria Terminalis Neurons that Express Fos during Maternal Behavior in Female Rats

Journal of Neuroendocrinology ◽

10.1046/j.1365-2826.1997.t01-1-00597.x ◽

1997 ◽

Vol 9 (5) ◽

pp. 369-384 ◽

Cited By ~ 93

Author(s):

Michael Numan ◽

Marilyn J. Numan

Keyword(s):

Maternal Behavior ◽

Preoptic Area ◽

Medial Preoptic Area ◽

Female Rats ◽

Stria Terminalis ◽

Bed Nucleus

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Pup removal suppresses estrogen-induced surges of LH secretion and activation of GnRH neurons in lactating rats

Journal of Endocrinology ◽

10.1677/joe.1.06728 ◽

2006 ◽

Vol 191 (1) ◽

pp. 339-348 ◽

Cited By ~ 3

Author(s):

Atsushi Fukushima ◽

Ping Yin ◽

Maho Ishida ◽

Nobuhiro Sugiyama ◽

Jun Arita

Keyword(s):

Third Ventricle ◽

Acute Effect ◽

Suppressive Effect ◽

Female Rats ◽

Ovariectomized Rats ◽

Indwelling Catheter ◽

Lh Surge ◽

Gnrh Neurons ◽

Double Immunohistochemical Staining ◽

Lh Secretion

During lactation, the suckling stimulus exerts profound influences on neuroendocrine regulation in nursing rats. We examined the acute effect of pup removal on the estrogen-induced surge of LH secretion in ovariectomized lactating rats. Lactating and nonlactating cyclic female rats were given an estradiol-containing capsule after ovariectomy, and blood samples were collected through an indwelling catheter for serum LH determinations. In lactating, freely suckled ovariectomized rats, estrogen treatment induced an afternoon LH surge with a magnitude and timing comparable to those seen in nonlactating rats. Removal of pups from the lactating rats at 0900, 1100, or 1300 h, but not at 1500 h, suppressed the estrogen-induced surge that normally occurs in the afternoon of the same day. The suppressive effect of pup removal at 0900 h was completely abolished when the pups were returned by 1400 h. In contrast, pup removal was ineffective in abolishing the stimulatory effect of progesterone on LH surges. Double immunohistochemical staining for gonadotropin-releasing hormone (GnRH) and c-Fos, a marker for neuronal activation, revealed a decrease, concomitantly with the suppression of LH surges, in the number of c-Fos-immunoreactive GnRH neurons in the preoptic regions of nonsuckled rats. An LH surge was restored in nonsuckled rats when 0.1 μg oxytocin was injected into the third ventricle three times at 1-h intervals during pup removal. These results suggest that the GnRH surge generator of lactating rats requires the suckling stimulus that is not involved in nonlactating cyclic female rats.

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