Anti-estrogenic suppression of the lordosis response in female rats

Jb, Powers

doi:10.1016/0018-506x(75)90005-7

Cited by 27 publications

(8 citation statements)

References 37 publications

(47 reference statements)

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“…Another explanation of the difference is that a depot injection of OB in oil was given intramuscularly in the present study, whereas Findlay et al (1973) infused oestradiol-17ß in saline into the jugular vein. The more prolonged exposure to oestrogen in the present work may have diminished the effects of hypothalamic insensitivity, as suggested by Powers (1975). It is likely that the duration of exposure to oestrogen at natural oestrus would also be sufficient to diminish the effects of reduced sensitivity to oestrogen for LH release by the hypothalamus.…”

Section: Discussionmentioning

confidence: 55%

Sexual behaviour responses of the ovariectomized ewe to oestradiol benzoate, and their persistent reduction after exposure to phyto-oestrogens

Adams¹

1978

Reproduction

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Characteristics of oestrous behaviour were recorded for 14 control ovariectomized ewes treated with 15, 25 or 40 \g=m\g oestradiol benzoate (OB), and for 24 ovariectomized ewes, 11 of which were infertile after prolonged intake of oestrogenic clover, which were each treated successively with 0, 10, 15\m=.\6 and 24\m=.\3 \g=m\g OB. Squatting by the ewe and Flehmen by a ram after sniffing the ewe were not associated with oestrogen treatment. 'Looking over the shoulder' was a sign exhibited by most ewes treated with 10 \g=m\g OB, but not by ewes that did not receive oestrogen. There were no differences between clover-affected and control ewes for these responses. Active soliciting by the ewe, standing for mounting, and being mounted by the ram, were behavioural responses closely associated with doses of OB greater than 15 \g=m\g. Tail fanning and kicking by the ewe were less closely associated with higher doses of OB. All of these responses were slightly but significantly diminished in clover-affected ewes, either in incidence, duration, or by a later time to onset. The results support the hypothesis that prolonged exposure to plant oestrogens causes persistent desensitization of the hypothalamus of the ewe to oestrogen.

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Section: Discussionmentioning

confidence: 55%

Sexual behaviour responses of the ovariectomized ewe to oestradiol benzoate, and their persistent reduction after exposure to phyto-oestrogens

Adams¹

1978

Reproduction

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“…This means that the magnitude of the inhibition of a given antiestrogen dose depends on the amount of estradiol administered, such that high doses of estradiol can prevent the behavioral inhibition of the antiestrogen [13]. In experi ment I, we found that 1% TAM, intracranially, antagonized a systemic treatment of 5% estradiol compared with control females, yet we saw no behavioral inhibition the following week when intracranial treatment conditions were reversed.…”

Section: Discussionmentioning

confidence: 67%

Antagonism of Sexual Behavior in Female Rats by Ventromedial Hypothalamic Implants of Antiestrogen

et al. 1987

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The present experiments sought to identify brain regions in which implants of an antiestrogen would antagonize the ability of a systemic estradiol treatment to activate sexual behavior in female rats. In experiment 1, ovariectomized female rats were implanted subcutaneously with 5-mm Silastic capsules containing a 5% concentration of estradiol and injected with 500 µg progesterone 2 days later, 4–5 h before testing for sexual behavior. Bilateral intracranial implants of 1% crystalline concentrations of the high-affinity antiestrogens monohydroxytamoxifen (TAM) or keoxifene placed into the ventromedial nucleus of the hypothalamus (VM) 24 h prior to estradiol treatment significantly reduced lordosis responsivity compared with control females receiving empty cannulae. Implants of 1% TAM into the medial preoptic area or medial amygdala 24 h prior to estradiol hat no significant effect on lordosis. Similarly, implants of 1% TAM into the VM 12 h after estradiol had no effect on lordosis. In experiment 2, lordosis was activated by subcutaneous implants of Silastic capsules containing 1% estradiol plus 500 µg progesterone. In this experiment, implants of 1% TAM into the VM 24 h prior to estradiol significantly reduced lordosis only if both cannulae tips were in, or adjacent to, the VM. Females receiving intracranial 1% TAM, but whose cannulae (even unilaterally) were outside the VM, had levels of lordosis equivalent to those of control females. Increasing the concentration of intracranial TAM to 10% virtually eliminated lordosis in females with bilateral implants in the VM, whereas females receiving intracranial 10% TAM in the region of, but outside, the VM showed no evidence of a lordosis deficit. These results indicate that selectively blocking estradiol receptors in VM neurons can antagonize the effects of systemically delivered estradiol on lordosis. Taken together with previous data, these results suggest that stimulation of VM estrogen receptors is both necessary and sufficient for the hormonal activation of lordosis in rats.

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“…Some insight into the nature of these mechanisms has been gained by testing the effects on lordosis of various pharmacological agents which can disrupt potentially relevant neurochemical processes. These studies have suggested that estradiol interactions with brain cell nuclei, resulting in altered protein synthetic activities, are necessary for the eventual expression of lordosis [35,37,41,45]. Because approximately 18-24 hr must elapse after estradiol administration before progesterone can facilitate sexual receptivity [13,18,38], it is reasonable to suppose that this latent period represents the time during which relevant metabolic processes occur.…”

Section: Lordosismentioning

confidence: 99%

Effects of acute ovariectomy on the lordosis response of female rats

Moreines

Powers

1977

Physiology & Behavior

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The sexual receptivity of intact females with 4- or 5-day estrous cycles was compared to that of other females which had been ovariectomized at particular times during their cycles. The quality and frequency of lordosis responding were more degraded the earlier during the cycle ovariectomy was performed. This effect was more pronounced in 4-day than in 5-day cyclic females. Because exogenous progesterone was administered to all ovariectomized females, these behavioral deficits were attributed to removal of ovarian estradiol. Ovariectomy 6 hr before the critical period for luteinizing hormone release significantly shortened the duration of behavioral estrus, even though it had no effect when lordosis was tested at the time intact estrous females are maximally receptive. These findings are consistent with the hypothesis that the continual availability of estradiol throughout the 18--24 hr interval perior to the onset of behavioral estrus is essential for optimal conditioning of sexual receptivity to occur under physiological conditions. The relevance of triggering and maintenance functions of estradiol to these results is discussed.

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Anti-estrogenic suppression of the lordosis response in female rats

Cited by 27 publications

References 37 publications

Sexual behaviour responses of the ovariectomized ewe to oestradiol benzoate, and their persistent reduction after exposure to phyto-oestrogens

Sexual behaviour responses of the ovariectomized ewe to oestradiol benzoate, and their persistent reduction after exposure to phyto-oestrogens

Antagonism of Sexual Behavior in Female Rats by Ventromedial Hypothalamic Implants of Antiestrogen

Effects of acute ovariectomy on the lordosis response of female rats

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