EFFECT OF AN OESTROGEN ANTAGONIST ETHAMOXY-TRIPHETOL (MER-25) ON OESTROUS BEHAVIOUR IN RATS

1968 ◽  
Vol 59 (1) ◽  
pp. 41-48 ◽  
Author(s):  
Bengt J. Meyerson ◽  
Leif Lindström
Keyword(s):  
Ovariectomized Rats ◽  
High Dose ◽  
Time Intervals ◽  
Progesterone Treatment ◽  
Oestradiol Benzoate

ABSTRACT MER-25, 75–150 mg/kg, inhibited oestrous behaviour induced by oestradiol benzoate/progesterone treatment in ovariectomized rats. In experiments in which MER-25 was administered 2 hours before oestradiol benzoate, the extent of antagonism was dependent on the dose of MER-25. Single injections of MER-25, given at different time intervals in conjunction with oestrogen administration, showed that MER-25 effectively decreased the response when administered either 2 hours before, or 2 or 8 hours after oestradiol benzoate treatment. No significant effect occurred when MER-25 was given simultaneously with, 12 hours before, or 24 hours after the oestrogen injection. MER-25 had no effect when oestradiol was given instead of oestradiol benzoate in otherwise analogous experiments. It seems probable that the inability of MER-25 to antagonize the effect of oestradiol in these experiments was due to the fact that MER-25 cannot compete with the comparatively high dose of oestradiol which was necessary to obtain the same response as in the oestradiol benzoate experiments.

INDUCTION OF SEXUAL RECEPTIVITY BY OESTRADIOL BENZOATE IN CYCLIC FEMALE RATS: INFLUENCE OF OVARIAN SECRETIONS BEFORE INJECTION OF OESTRADIOL BENZOATE

1979 ◽  
Vol 80 (3) ◽  
pp. 389-395 ◽  
Author(s):  
P. SÖDERSTEN ◽  
S. HANSEN
Keyword(s):  
Sexual Behaviour ◽  
Oestrous Cycle ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Sexual Receptivity ◽  
Behavioural Effect ◽  
Progesterone Treatment ◽  
Oestradiol Benzoate

The ability of cyclic female rats to show sexual receptivity 24 h after an injection of 2 μg oestradiol benzoate (OB) was lost 24 h after ovariectomy. Exposure of cyclic rats to anti-oestrogen (nitromophene monocitrate) implants 24 h before ovariectomy and OB treatment prevented the latter from inducing sexual receptivity within 24 h of administration. Treatment of ovariectomized rats with constant release implants filled with an oil solution of 15 μg oestradiol/ml had no behavioural effect in itself, but prepared the rats to show lordosis 24 h after administration of OB. Progesterone treatment (4 mg) induced sexual behaviour in cyclic rats on days other than that of the oestrous cycle when the rats are normally receptive. Evidence is presented that a lower level of oestradiol stimulation than that present during pro-oestrus was needed for the induction of sexual receptivity in ovariectomized rats. It is suggested that the low basal level of oestradiol which was present throughout the oestrous cycle was necessary for the induction of sexual receptivity and that an increase in oestradiol stimulation served to increase the behavioural sensitivity to progesterone.

INDUCTION OF SEXUAL RECEPTIVITY IN OVARIECTOMIZED RATS BY PULSE ADMINISTRATION OF OESTRADIOL-17β

1981 ◽  
Vol 89 (1) ◽  
pp. 55-62 ◽  
Author(s):  
P. SÖDERSTEN ◽  
P. ENEROTH ◽  
S. HANSEN
Keyword(s):  
Single Injection ◽  
Serum Levels ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Sexual Receptivity ◽  
Behavioural Responses ◽  
Time Points ◽  
Progesterone Treatment ◽  
Oestradiol Benzoate ◽  
Stimulation Of

Constant-release implants filled with oestradiol-17β induced sexual receptivity in ovariectomized rats in response to progesterone treatment if they were implanted 32 h before behavioural testing. A 20 h period of exposure to oestradiol, by implantation 32 h before testing and removal of the implants 20 h later, was sufficient for induction of the behaviour. The exposure time necessary for behavioural responses could be further reduced to two 4 h periods, between 32 and 28 h and between 16 and 12 h, before testing. Serum levels of oestradiol were raised within 1 h of oestradiol implantation and declined rapidly after implant removal. A single injection of oestradiol benzoate was much more potent than a single injection of oestradiol in inducing sexual receptivity in ovariectomized rats, but this difference in potency was reversed if two appropriately timed injections were given. Oestrone- or oestriol-filled implants were relatively ineffective in inducing sexual receptivity. It is suggested that oestradiol has to be present at crucial time points to prepare an ovariectomized rat to respond behaviourally to progesterone treatment and that oestradiol is the principal oestrogen in the stimulation of sexual behaviour in female rats.

REVERSAL OF PROGESTERONE INHIBITION OF SEXUAL BEHAVIOUR IN OVARIECTOMIZED RATS BY HIGH DOSES OF PROGESTERONE

1979 ◽  
Vol 80 (3) ◽  
pp. 381-388 ◽  
Author(s):  
S. HANSEN ◽  
P. SÖDERSTEN
Keyword(s):  
Sexual Behaviour ◽  
Inhibitory Effect ◽  
Behavioural Response ◽  
Ovariectomized Rats ◽  
Sexual Receptivity ◽  
High Dose ◽  
Progesterone Treatment ◽  
High Doses ◽  
Sequential Inhibition ◽  
Very High

Considerably less progesterone was needed to facilitate than was required to inhibit sexual receptivity induced by oestradiol benzoate (OB) and progesterone in the ovariectomized rat. Inhibition of sexual receptivity occurred if progesterone was given at the time of OB treatment (concurrent inhibition). If progesterone was given 42 h after the OB treatment it first acted to facilitate the behaviour and then to inhibit the response to renewed progesterone treatment 24 h later (sequential inhibition). Both concurrent and sequential inhibition of sexual receptivity by progesterone could be reversed by increasing the dose of progesterone before behavioural testing. Sexual receptivity could be induced in the pseudopregnant rat by using a low dose of OB (2 μg) in combination with a very high dose of progesterone (50 mg). Sexual receptivity induced in ovariectomized rats by injection of a single large dose of OB was unaffected by progesterone treatment in both the concurrent and sequential paradigm. Concurrent and sequential inhibition of sexual behaviour by antioestrogen (nitromophene monocitrate, CI-628) treatment could not be reversed by increasing the dose of progesterone before testing. The behavioural response to OB treatment in combination with progesterone and OB treatment alone was markedly inhibited by CI-628 treatment. It is suggested that prior treatment with progesterone raises the threshold of the behavioural response to subsequent progesterone treatment. It is also suggested that the inhibitory effect of progesterone on sexual behaviour cannot only be accounted for by the previously suggested antioestrogenic effect of progesterone.

Plasma gonadotrophin concentrations, pituitary gonadotrophin content and pituitary responsiveness to LHRH in rats treated with LHRH and oestradiol benzoate

1987 ◽  
Vol 115 (3) ◽  
pp. 469-475 ◽  
Author(s):  
G. A. Schuiling ◽  
N. Pols-Valkhof ◽  
H. Moes ◽  
T. R. Koiter
Keyword(s):  
Plasma Concentration ◽  
Plasma Concentrations ◽  
Ovariectomized Rats ◽  
Prolonged Treatment ◽  
High Dose ◽  
Response Curves ◽  
Simultaneous Treatment ◽  
Control Value ◽  
Oestradiol Benzoate

ABSTRACT Suppression of gonadotrophin secretion during prolonged treatment with a high dose of LHRH was studied. Long-term ovariectomized rats were infused for 6 days with various doses of LHRH (25, 50, 100, 250 or 500 ng/h) with or without simultaneous treatment with oestradiol benzoate (OB; 3 μg/s.c. injection); a further group was treated with OB only. The effects of these treatments were studied on plasma concentrations of LH and FSH, the pituitary content of LH and FSH and on LH and FSH secretion in vitro (perifusion) in the unstimulated state and following maximal LHRH stimulation (1 μg LHRH/ml perifusion medium). Administration of LHRH caused a dose-dependent reduction in plasma concentrations of LH and FSH and depleted the pituitary LH/FSH stores. Treatment with OB lowered the plasma concentration of LH to about 30% and that of FSH to about 65% of the control values. Administration of OB plus a low dose of LHRH (25 or 50 ng/h) markedly stimulated the secretion of LH but not of FSH, so that the plasma concentrations of LH were fully restored to the control value. With higher rates of LHRH infusion, OB caused no enhancement of the plasma concentrations of LH and FSH. The experiments in vitro revealed a sensitizing, i.e. stimulatory effect, of OB on LHRH-stimulated LH and FSH secretion. However, the higher the rate of infusion of LHRH the smaller the sensitizing effect. Interpolation from dose–response curves showed that an LHRH infusion rate of about 150 ng/h (which would establish a plasma concentration of LHRH of about 68 pmol/l) would have no effect. With still higher rates of infusion of LHRH, the effect of OB was either inhibitory (LH) or absent (FSH). The present experiments show that, depending on dose and length of treatment, both LHRH and OB can have variable effects on the secretion of LH and FSH: LHRH, while depleting and desensitizing the pituitary gland, stimulates the release of LH, whilst OB, which is known to suppress the secretion of LHRH by the hypothalamus, augments the rates of unstimulated and LHRH-stimulated LH and FSH secretion. The augmenting effect of OB on the latter component of LH and FSH secretion can be suppressed with high doses of LHRH. However, these experiments also show that even with doses as high as 500 ng LHRH/h, infused continuously for 6 days, plasma concentrations of LH and FSH are not reduced by more than 60–70%. J. Endocr. (1987) 115, 469–475

PRE-TRAUMA OESTROGEN REQUIREMENTS FOR INDUCTION OF DECIDUALIZATION IN SPAYED, PROGESTERONE-TREATED RATS

1966 ◽  
Vol 53 (2) ◽  
pp. 212-224 ◽  
Author(s):  
Carla Rossi Cartoni ◽  
G. Bignami
Keyword(s):  
Single Dose ◽  
Hormonal Treatment ◽  
Normal Pregnancy ◽  
Carbonic Anhydrase Activity ◽  
The Other ◽  
Ovariectomized Rats ◽  
Uterine Weight ◽  
Experimental Conditions ◽  
Progesterone Treatment ◽  
Oestradiol Benzoate

ABSTRACT The formation of deciduomata was investigated in ovariectomized rats treated with various combinations of oestrogen and progesterone before traumatization. The hormonal treatment was kept constant for all groups of animals during the period between traumatization and autopsy (4 mg of progesterone and 0.2 μg of oestradiol benzoate daily). Uterine weight and carbonic anhydrase activity were measured 96 hours after trauma and compared with those of intact controls receiving traumatization on day 4 of pseudopregnancy. When a single dose of oestrogen was given on the day before traumatization, induction of decidualization was successful under a wide variety of experimental conditions (presence or absence of oestrogen »priming« before the beginning of the progesterone treatment; progesterone treatment of varying duration). On the contrary, treatment with divided doses of oestrogen, given for 3 days before trauma, allowed extensive decidualization only in rats »primed« with oestrogen, and traumatized on the fourth day of a progesterone treatment started 24 hours after vaginal keratinization. It appears therefore that only the »oestrogen surge« hypothesis of Shelesnyak and his collaborators can account for those conditions in which implantation occurs at variable intervals of time after the last oestrus (lactation, hypophyseal autotransplantation, administration of a tranquilizer and early ovariectomy followed by hormonal treatment). On the other hand, both the hypothesis of Shelesnyak and that proposed by Yochim & DeFeo (1963) (i. e. continuous secretion of small amounts of oestrogen during the first three days of pregnancy and pseudopregnancy) could account for the rapid waxing and waning of endometrial sensitivity to deciduoma-inducing stimuli observed in normal pregnancy and pseudo-pregnancy.

HORMONAL REQUIREMENTS FOR THE MAINTENANCE OF OESTRADIOL-INDUCED INHIBITION OF UTERINE SENSITIVITY IN THE OVARIECTOMIZED RAT

1970 ◽  
Vol 46 (3) ◽  
pp. 341-346 ◽  
Author(s):  
K. P. MEYERS
Keyword(s):  
Subcutaneous Injection ◽  
Ovariectomized Rats ◽  
Ovariectomized Rat ◽  
Single Subcutaneous Injection ◽  
The Third ◽  
Oestradiol Treatment ◽  
Progesterone Treatment ◽  
Endometrial Scratching

SUMMARY Ovariectomized rats treated with 2·5 or 5·0 mg. progesterone daily received a single subcutaneous injection of 0·2 μg. oestradiol on the third day of the progesterone treatment. The deciduomal response to trauma by endometrial scratching was used to determine the degree of uterine sensitivity at various times after oestradiol. Uterine sensitivity was partially and then completely lost 36 and 48 hr. after oestradiol administration. The inhibition of uterine sensitivity persisted until 9 and 11 days after oestradiol when the animals received 2·5 and 5·0 mg. progesterone daily. Uterine sensitivity was completely inhibited on day 11 with doses of oestradiol from 0·2 to 0·05 μg. Withdrawal of progesterone treatment for 48 or 72 hr., but not for 24 hr., after oestradiol treatment restored uterine sensitivity. These results show that the oestradiol-induced inhibition of uterine sensitivity in the progestational endometrium is maintained by continuous progesterone treatment and that the duration of this effect is dependent on the dose of progesterone given.

EFFECTS OF OESTRADIOL AND PROGESTERONE ON THE INDUCTION AND DURATION OF SEXUAL RECEPTIVITY IN CYCLIC FEMALE RATS

1977 ◽  
Vol 74 (3) ◽  
pp. 477-485 ◽  
Author(s):  
P. SÖDERSTEN ◽  
S. HANSEN
Keyword(s):  
Behavioural Response ◽  
Female Rats ◽  
Sexual Receptivity ◽  
Repeated Treatment ◽  
Progesterone Treatment ◽  
Oestradiol Benzoate

SUMMARY Intact 4-day cyclic rats showed sexual receptivity 24 h after an injection of oestradiol benzoate (OB) on any day of the cycle except on the second day after the display of spontaneous oestrus. Ovariectomy at the time of OB treatment abolished the behavioural response, but receptivity was restored by progesterone. Progesterone treatment early on the day of behavioural oestrus advanced the display of receptivity but did not affect the time at which oestrus ended. Repeated treatment of sexually receptive rats with progesterone did not affect the duration of oestrus. These results show that sexual receptivity in the intact rat cannot occur in the absence of oestradiol and progesterone. The results further suggest that progesterone may not be associated with the mechanisms terminating behavioural oestrus in rats. Treatment with OB on the day of oestrus can prolong the duration of receptivity but only at a higher dosage than that needed for induction of receptivity.

OESTROGEN RESPONSES OF RATS NEONATALLY STERILIZED WITH STEROIDS

1969 ◽  
Vol 45 (3) ◽  
pp. 415-420 ◽  
Author(s):  
T. R. WRENN ◽  
JOAN R. WOOD ◽  
J. BITMAN
Keyword(s):  
Testosterone Propionate ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Uterine Weight ◽  
Oestradiol Benzoate

SUMMARY At 75 days of age, female rats neonatally sterilized with oestradiol benzoate or testosterone propionate were compared with normal and ovariectomized rats with regard to their 6-hr. response to 0·2 μg. oestradiol 17β. The greatest increases in uterine weight, glucose and glycogen concentrations and per cent uterine water occurred in the ovariectomized animals. A marked oestrogen response also occurred in the animals neonatally sterilized with oestradiol benzoate. The response of the normal rats was slight, and the testosterone propionate-treated rats were the least affected. Adrenal, pituitary, and ovarian weights were found to be affected by the neonatal hormone treatments. Vaginal patency was completely inhibited in the rats injected with testosterone propionate. It is concluded that rats neonatally sterilized with steroids are much less suitable than ovariectomized animals for oestrogen assays.

Antioestrogen inhibition of oestradiol-induced alterations in hypothalamic noradrenaline turnover

1985 ◽  
Vol 106 (1) ◽  
pp. 37-42 ◽  
Author(s):  
C. Hiemke ◽  
B. Poetz ◽  
R. Ghraf
Keyword(s):  
Brain Area ◽  
Serum Levels ◽  
Ovariectomized Rats ◽  
Noradrenaline Turnover ◽  
Stimulatory Action ◽  
Enhanced Sensitivity ◽  
Oestradiol Benzoate ◽  
Lh Release ◽  
Secretory System

ABSTRACT Long-term (4–6 weeks) ovariectomized rats were injected with either oestradiol benzoate (OB; 20 μg s.c.) or monohydroxytamoxifen (MTAM; 0·2 mg i.p.) plus OB. Oestradiol benzoate was administered at 12.00 h on day 0 and MTAM was given immediately before OB, followed by further injections twice daily to maintain sufficiently high antioestrogen levels. When given alone, OB reduced the serum levels of LH during the morning (08.00–09.00 h) and afternoon (17.30–18.30 h) hours of day 3 after priming. The feedback actions of OB on LH release were accompanied by time-dependent alterations of noradrenaline turnover in the preoptic–anterior hypothalamic brain area (POAH). On day 3 after priming the noradrenaline turnover rate was reduced in the morning and increased in the afternoon. The increase correlated with an enhanced sensitivity of the LH secretory system to progesterone. The antioestrogen MTAM blocked the OB-induced sensitization of LH release to the stimulatory action of progesterone and interfered with the stimulatory long-term effect of oestradiol on hypothalamic noradrenaline turnover. The data strongly support the view that the oestrogen-induced afternoon increase of noradrenaline turnover in the POAH represents a pre-requisite for the induction of LH surges. The stimulatory effect of oestradiol on hypothalamic noradrenaline turnover seems to be mediated by a classical oestrogen receptor mechanism. J. Endocr. (1985) 106, 37–42

RESTORATION BY OESTRADIOL BENZOATE OF A NEURAL AND HORMONAL RHYTHM IN THE OVARIECTOMIZED RAT

1975 ◽  
Vol 64 (1) ◽  
pp. 27-35 ◽  
Author(s):  
F. R. BURNET ◽  
P. C. B. MACKINNON
Keyword(s):  
Single Injection ◽  
Time Of Day ◽  
Ovariectomized Rats ◽  
Female Rat ◽  
Functional Link ◽  
Initial Injection ◽  
Oestradiol Benzoate ◽  
Before And After ◽  
Lh Release ◽  
The Brain

SUMMARY The rate of [35S]methionine incorporation into protein in discrete cerebral areas was measured before and after the administration of oestradiol benzoate (OB) to chronically ovariectomized rats. The circadian rhythm of incorporation which is normally seen in the intact cyclic female rat was deleted by ovariectomy. A daily rhythm of incorporation reappeared, however, in all the brain areas studied 30 h after a single injection of OB (20 μg), and was still present 12 days later. The release of luteinizing hormone (LH) after administration of 20 μg OB was measured in chronically ovariectomized animals and was found to be biphasic. High levels of LH after ovariectomy were initially reduced by negative feedback, but this phase was followed 52 h later by a facilitation of LH release between 15.00 and 18.00 h. The facilitation of LH release at this time of day was still detectable 12 days after the initial injection. The evidence for a functional link between the rhythm of neural activity which is reflected by [35S]methionine incorporation, and the ability to 'time' the facilitation of LH release is discussed.

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