A Possible Hypothalamic Site of Action of Progesterone in the Facilitation of Ovulation in the Rat

Barraclough, Charles A.; Yrarrazaval, S.; Hatton, R

doi:10.1210/endo-75-6-838

Cited by 91 publications

(38 citation statements)

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“…This is similar to the results reported by Barraclough et al(1964), who failed to induce ovulation by progesterone in POA-SC lesioned rats, and to the recent works of Taleisnik et al (1970) and Terasawa and Sawyer (1970), who demonstrated that anterior deafferentation of the hypothalamus blocked the increase by progesterone of plasma LH level and modified the changes of hypothalamic multiunit activity in this process, respectively. All of these results suggest that the POA-SC region of the hypothalamus or the extrahypothalamic location in the higher CNS may be responsible for the induction of ovulating hormone release by progesterone.…”

Section: Discussionsupporting

confidence: 91%

Acute Effect of Hypothalamic Deafferentation on Progesterone-Induced Ovulating Hormone Release in the Rats

Kobayashi

Miyake

1971

Endocrinol Japon

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SynopsisA study was made to analyze the facilitatory effect of progesterone on ovulating hormone (OH) release in proestrous rats. Neural connections to the medial basal hypothalamus (MBH) or to the preoptic-suprachiasmatic (POA-SC) region of the hypothalamus were transected on the morning of proestrus with a curved knife or with an Lshaped knife. After the recovery from the surgical anesthesia, the rats were injected subcutaneously with progesterone, 1 mg per rat, and anesthetized again with pentobarbital during the time corresponding to the critical period for OH release in the intact rat. Facilitation by progesterone of OH release was confirmed in the next morning by counting the ova in the oviducts. Posterior deafferentation of the hypothalamus at the level of the mammillary body did not block the progesterone-induced ovulation. Anterior deafferentation at the retrochiasmatic level completely blocked the ovulation. Progesterone-induced ovulation was also blocked by more rostral or broad dorsal deafferentation with a large curved or an L-shaped knife, the operation of which did not provide any damage on the structures of the POA-SC region. It is concluded that the facilitation of OH release by exogenous progesterone is due to the increase in the responsiveness of MBH to the ovulatory stimulus coming from the higher CNS via the POA-SC region, rather than due to the direct stimulation of the hypothalamus to secrete releasing factor(s).

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Section: Discussionsupporting

confidence: 91%

Acute Effect of Hypothalamic Deafferentation on Progesterone-Induced Ovulating Hormone Release in the Rats

Kobayashi

Miyake

1971

Endocrinol Japon

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“…Earlier studies on the induction of persistent estrus in female rats by anterior deafferentation (Halasz and Pupp, 1965;Halasz and Gorski, 1967) or by large lesions of the preoptic suprachiasmatic region (Flerko and Bardos, 1959;Barraclough et al, 1964;Antunes-Rodriguez, 1967), suggest that a signal arising from the preoptic and anterior hypothalamus is necessary for cyclic ovulation in this species.…”

Section: Discussionmentioning

confidence: 95%

The LHRH neuronal system in female rats: Relation to the medial preoptic nucleus.

Terasawa¹,

Davis²

1983

Endocrinol Japon

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Previously we have found that small lesions confined to the medial preoptic nucleus (MPN) or the suprachiasmatic nucleus (SCN) blocked the cyclic release of gonadotropins in the female rat, inducing a persistent estrous state. Since the MPN is located just caudal to the organum vasculosum of the lamina terminalis (OVLT) where LHRH cell bodies are most concentrated, we applied an immunocytochemical technique to examine the possibility that the lesions had simply disrupted LHRH neurons or fibers.Using a new anti-LHRH provided by Dr. V. D. Ramirez, we found that the distribution pattern of immunoreactive LHRH cell bodies and fibers was similar to that previously reported, although the staining was more intense and extensive with low background.There was no concentration of LHRH cell bodies and fibers in the MPN or SCN and, in fact, these nuclei generally showed a lower density of stained elements than did sorrounding tissue. In persistent estrous animals with lesions confined to the MPN there was no detectable reduction of staind fibers in the median eminence.These results, along with the results of other workers, suggest that persistent estrus following lesions of the MPN or SCN is not due to reduction of LHRH neurons or fibers. Rather, they support the hypothesis that these nuclei are critical for triggering the ovulatory release of LHRH.

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“…This direct action on the pituitary is excluded, however, by the finding that bilateral intrapituitary implantation of progesterone was completely inefective in facilitating LH-release. The anterior hypothalamic region, which was initially considered as a stimulatory feedback site of progesterone (Barraclough et al, 1964), is also excluded as a progesterone feedback site facilitating the ovulatory release of LH. The results obtained from the present study suggest, therefore, that the median eminence-arcuate region of hypothalamus is the primary site of progesterone action in facilitating LH-release.…”

Section: Discussionmentioning

confidence: 99%

Facilitation of Luteinizing Hormone Release by Progesterone in Proestrous Rats

1970

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SynopsisIn order to elucidate the facilitation of ovulatory release of luteinizing hormone (LH) and subsequent ovulation, subcutaneous injection or intrahypothalamic implantation of progesterone was carried out on the morning of proestrus in 4-day cyclic rats . By injecting progesterone on the morning or early afternoon of proestrus , an approximate 3 hr advancement of ovulatory release of LH was demonstrated by confirming the occurrence of ovulation on the next morning after timed hypophysectomy performed on the afternoon of proestrus. Ovulation also occurred about 3 hr earlier in the estrous morning when progesterone had been given on the morning of proestrus. The minimum effective dose of progesterone to facilitate LH-release was somewhere between 0 .1 and 0.625mg per rat. Facilitation of LH-release by steroid administration on the morning of proestrus is not entirely specific for progesterone. Norethisterone, medroxyprogesterone acetate , and desoxycorticosterone(DOC) also induced the advanced release of LH. Facilitation of ovulatory release of LH was induced also in the rats having progesterone crystals implanted in the median eminence-arcuate region of the hypothalamus on the morning of proestrus. These results indicate that a neural timing factor regulating the onset of LHrelease in proestrus is labile to a certain extent, and that it operates about 3 hr in advance when it is exposed to progesterone given on the morning of proestrus , and that the appearance of facilitatory action of progesterone depends on the pre-existing estrogen level in the circulating blood.It is well known that progesterone has a biphasic effect on ovulation and, according to the conditions, it can either stimulate or inhibit the release of luteinizing hormone (LH) (for a review see Everett, 1964; Sawyer, 1964;Rothchild, 1965;Davidson, 1969). A lack of spontaneous ovulation during pregnancy or pseudopregnancy is evidence of the inhibitory effect on LH-release of endogenous progesterone, the secretion of which is increased during gestation. Exogenous progesterone also inhibits or delays spontaneous ovulation in rats and in many other species. The stimulating effect of progesterone on ovulation has been shown under several conditions, e. g. in persistent estrous rats (Everett, 1940), in normal 5-day cyclic rats (Everett, 1948; BrownGrant, 1967) and in immature rats primed with pregnant mare's serum gonadotropin Meyer, 1963 and1965).With regard to the ovulation induction in adult rats, it was previously suggested by Everett(1948) that the appearance of stimulating action of progesterone depends on the pre-existing estrogen level in the circulating blood. In our previous work, progesterone administered into 4-day cyclic rats induced a delayed ovulation only when injected before 2 a. m. proestrus, by which time estrogen secretion had not attained the maximum (Hori et al., 1968), and it accounted for uterine distension and uterine weight increase on the day of proestrus though it was not enough for the release of LH on the same day (Kob...

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A Possible Hypothalamic Site of Action of Progesterone in the Facilitation of Ovulation in the Rat

Cited by 91 publications

References 0 publications

Acute Effect of Hypothalamic Deafferentation on Progesterone-Induced Ovulating Hormone Release in the Rats

Acute Effect of Hypothalamic Deafferentation on Progesterone-Induced Ovulating Hormone Release in the Rats

The LHRH neuronal system in female rats: Relation to the medial preoptic nucleus.

Facilitation of Luteinizing Hormone Release by Progesterone in Proestrous Rats

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