Timing of Gonadotrophin and Ovarian Steroid Secretion at Diestrus in the Rat

Lawton, Irene E.; Sawyer, Charles H.

doi:10.1210/endo-82-4-831

Cited by 18 publications

(16 citation statements)

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“…This FSH may be responsible for the increase in estrogen secretion that occurs on the afternoon of diestrus as has been reported by Kobayashi et al [1969a]. Lawton and Sawyer [1968] demonstrated that hypophysectomy blocked vaginal cornification if performed after 3 p.m. on the day of diestrus. That this pituitary-dependent estrogen output clearly stimu lates the release of the ovulatory burst of LH has been demonstrated by Kobayashi et al [1969b], Unpublished data on LH measurements of the same plasma samples as assayed for FSH indicate that, in addi tion to the 7 p.m. proestrous elevation, LH also increases during diestrus.…”

Section: Discussionmentioning

confidence: 54%

Development of Neural Regulation of Follicle Stimulating Hormone (FSH) Secretion

Kragt

Dahlgren²

1972

Neuroendocrinology

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Hypothalamic follicle stimulating hormone releasing factor (FSHRF) content, pituitary and plasma follicle stimulating hormone (FSH) concentrations have been determined in female rats between 5 and 75 days of age. FSHRF was present by at least 10 days of age and at levels that exceeded those observed at any age thereafter. No fluctuations in FSHRF were detected during the estrous cycle. Plasma FSH levels determined by radioimmunoassay increased threefold between 5 and 15 days of age, at which time, values were approximately 1,300 ng/ml. At no other age were levels of this magnitude observed. During the estrous cycle, values ranged between 136 and 261 ng/ml, with the lowest during the morning of proestrus and the highest, the morning of estrus. Pituitary FSH stores during the cycle determined by bioassay were 16.5 (proestrus), 19.5 (estrus), 22.8 (metestrus), and 21.2 µg (diestrus) per pituitary. Neural regulation of FSH secretion exists by at least 10 days of age in the female rat. FSH secretion decreases between 15 days of age and puberty, and fluctuates at least twofold during the adult cycle.

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Section: Discussionmentioning

confidence: 54%

Development of Neural Regulation of Follicle Stimulating Hormone (FSH) Secretion

Kragt

Dahlgren²

1972

Neuroendocrinology

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“…A single injection of estrogen at diestrus II in 5-day cyclic rats advances ovulation by 24hr, while estrogen injection on the day of estrus delays ovulation in 4-day cyclic rats (Everett, 1948;Sawyer et al, 1949). Estrogen starting to increase on the afternoon of the day before proestrus (that is the day of diestrus II in 4-day cyclic rats) appears to be responsible for the release of LH during the critical period as well as for the changes in the uterus and the vagina on the days of proestrus and estrus (Schwartz, 1962;Lawton and Sawyer, 1968;Kobayashi et al, 1969 b, c).…”

Section: Synopsismentioning

confidence: 99%

Positive Feedback Sites of Estrogen in the Brain on Ovulation

Terasawa

Kawakami

1974

Endocrinol Japon

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SynopsisDirect effects of estrogen on the brain inducing ovulation have been studied on the late night of diestrus II in 4-day cyclic rats. Injection of 3mg of progesterone on the evening of diestrus II (23:00) delayed ovulation. However, the inhibitory effect of progesterone was restored by the simultaneous injection of estradiol benzoate (8/10) or bilateral implantation of crystalline estrogen into the medial amygdala (8/12). Implantation of estrogen into the medial preoptic area, the bed nucleus of the stria terminalis and the lateral amygdala resulted in making ovulated rats fewer such as, 1/8, 3/8 and 1/6, respectively. Positive feedback effect of implanted estrogen into the medial amygdal a blocked by chronical transection of the surrounding area of the bed nucleus of the stria terminalis (0/5). Estrogen implantation to the medial amygdala and the bed nucleus of the stria terminalis on the night of diestrus II overcame the inhibitory effect of progesterone on LH release during the critical period of proestrus, while estrogen implantation to the medial preoptic area was relatively ineffective. Thus, estrogen appears to feed back to the medial amygdala and the bed nucleus of the stria terminalis inducing the release of ovulatory hormone.

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“…It has been suggested that this is the only time when gonadotropin release and ovulation are consistently susceptible to barbiturate blockade [Schwartz and Lawton, 1968;Lawton and Sawyer, 1968]. Weick et al [1971] reported that the estrogen-induced advancement of ovulation could be blocked by pentobarbital administered at the time of estrogen treatm ent (on the day following metestrus).…”

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confidence: 99%

Barbiturate Blockade of Ovulation on Days Other Than Proestrus in the Rat

Domı́nguez¹,

Smith²

1974

Neuroendocrinology

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Sodium pentobarbital (50 mg/kg) was administered oneach day of the estrous cycle to 4- and 5-day cyclic Long-Evans rats. In rats with 4-day cycles, the incidence of ovulation was significantly decreased when barbiturate was administered as a single injection at various times from 12.45 h on estrus to 12.45 h on diestrus-2. A delay in vaginal cornification and uterine ballooning measured on estrus, as well as decreased sexual receptivity on proestrus, was also found to result from barbiturate injections on diestrus-1, indicating a suppression of estrogen secretion. The deleterious effects of barbiturate treatment could be reversed by the simultaneous administration of gonadotropin. A generally similar pattern of blockade by barbiturate during this time period was found in 5-day cyclic rats, although the inhibitory effects were less than in 4-day cyclic rats. Furthermore, no inhibition of ovulation was found following drug administration on diestrus-3. The pattern of ovulatory blockade by barbiturate on the afternoon of proestrus was also generally similar in the 4- and 5-day cyclic rats. Again, however, more complete suppression was found in the 4-day cycle, and the duration of the inhibitory effects was more prolonged. It was concluded that the inhibitory effects of barbiturate administered early in the estrous cycle (estrus, diestrus-1 and diestrus-2) probably reflect a daily pattern of neural activity which is causally related to gonadotropin and estrogen secretion necessary for the final occurrence of ovulation.

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Timing of Gonadotrophin and Ovarian Steroid Secretion at Diestrus in the Rat

Cited by 18 publications

References 0 publications

Development of Neural Regulation of Follicle Stimulating Hormone (FSH) Secretion

Development of Neural Regulation of Follicle Stimulating Hormone (FSH) Secretion

Positive Feedback Sites of Estrogen in the Brain on Ovulation

Barbiturate Blockade of Ovulation on Days Other Than Proestrus in the Rat

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