SENSITIVITY OF ANTERIOR HYPOTHALAMIC AREAS TO GONADAL STEROID IMPLANTATION IN ANDROGENIZED FEMALE RATS

1977 ◽  
Vol 74 (2) ◽  
pp. 315-NP ◽  
Author(s):  
A. DANGUY ◽  
J. L. PASTEELS ◽  
F. ECTORS
Keyword(s):  
Single Injection ◽  
Mammary Glands ◽  
Prolactin Secretion ◽  
Female Rats ◽  
Male Rats ◽  
Control Synthesis ◽  
Normal Female ◽  
Immunofluorescence Studies ◽  
Oestradiol Benzoate ◽  
Stimulation Of

A single injection of 1 mg of a complex of testosterone esters on day 5 of life was used to prepare constantly oestrous rats. Such androgenized female rats were then ovariectomized and submitted to stereotaxical implantation of 1 μg oestradiol benzoate, 5 μg testosterone isobutyrate or, as a control, 10 μg cholesterol in the anterior hypothalamic areas. The effects of the steroids on plasma and pituitary FSH and LH were assessed by radioimmunoassay. As reported previously by us in normal female and male rats, the preoptic–suprachiasmatic area (POA) was able to control synthesis and secretion of both gonadotrophins and did not lose its sensitivity to oestradiol and testosterone in androgenized rats. Evidence for enhanced prolactin secretion in androgenized rats was derived from immunofluorescence studies of the pituitary gland and from histology of the mammary glands. In this respect the condition of the androgenized females was opposite to that of the males. The present work demonstrated that stimulation of prolactin secretion in androgenized female rats resulted from oestrogen action due to permanent oestrus rather than from impairment of hypothalamo-hypophysial relationships. Indeed, prolactin stimulation was suppressed when the androgenized rats were ovariectomized and restored when they were subsequently implanted with oestradiol in the POA.

RELATIONSHIP BETWEEN THE PITUITARY GLAND AND GONADAL STEROIDS: INVOLVEMENT OF A HYPOPHYSIAL FACTOR IN REDUCED α2u-GLOBULIN AND INCREASED TRANSCORTIN CONCENTRATIONS IN RAT SERUM

1978 ◽  
Vol 78 (1) ◽  
pp. 31-38 ◽  
Author(s):  
G. VANDOREN ◽  
H. VAN BAELEN ◽  
G. VERHOEVEN ◽  
P. DE MOOR
Keyword(s):  
Pituitary Gland ◽  
Testosterone Propionate ◽  
Single Injection ◽  
Prolactin Secretion ◽  
Female Rats ◽  
Male Rats ◽  
Rat Serum ◽  
Mediated Effects ◽  
Male And Female Rats ◽  
Oestradiol Benzoate

Evidence is presented that the level of α2u-globulin in the serum of male rats depends, at least in part, on neonatal androgens. After castration of adult animals the concentration of this protein falls but remains measurable, whereas in intact or ovariectomized female rats α2u-globulin cannot be detected. Moreover, α2u-globulin is found in adult male and female rats gonadectomized at birth and treated with a single injection of testosterone propionate immediately thereafter. The mechanism by which neonatal androgens increase the concentration of α2u-globulin has been investigated. Transplantation of a supplementary pituitary gland under the renal capsule of male rats resulted in reduced levels of α2u-globulin and increased levels of transcortin. The changes discussed here were observed only in those animals in which the transplant was functional and they were amplified or reversed by modulators of prolactin secretion such as oestrogens or bromocriptine respectively. The hypothesis is advanced that neonatal androgens stimulate the production of a hypothalamic inhibitory factor that controls the secretion of prolactin, or another hypophysial hormone subjected to similar neuroendocrine control. Measurements in gonadectomized animals and in rats receiving both oestradiol benzoate and bromocriptine indicate that, besides these pituitary-mediated effects, both oestrogens and androgens exert direct effects on the level of α2u-globulin.

INDUCTION OF PROLACTIN AND LUTEINIZING HORMONE RELEASE BY HISTAMINE IN MALE AND FEMALE RATS AND THE INFLUENCE OF BRAIN TRANSMITTER ANTAGONISTS

1978 ◽  
Vol 76 (2) ◽  
pp. 193-202 ◽  
Author(s):  
A. O. DONOSO
Keyword(s):  
Prolactin Secretion ◽  
Oestrous Cycle ◽  
Female Rats ◽  
Male Rats ◽  
Intraventricular Injection ◽  
Hormone Release ◽  
Stimulatory Action ◽  
Male And Female Rats ◽  
Oestradiol Benzoate ◽  
Lh Release

The levels of prolactin and LH in the plasma of rats were determined at various times after intraventricular injection of histamine. Doses of 5 and 60 μg histamine (free base) in male rats, anaesthetized with ether, induced an increase in the level of prolactin in the plasma, whilst producing a slight decrease in the concentration of LH. Injection of 5 μg histamine at 14.00 h into female rats at all stages of the oestrous cycle caused prolactin to be released; the effect was greatest at oestrus and at day 1 of dioestrus. Histamine also gave rise to a marked increase in the level of LH in the plasma when administered to pro-oestrous rats, but had no effect when injected at the other stages of the oestrous cycle. The effect of histamine on the release of prolactin in ovariectomized, oestradiol benzoate: progesterone-primed (OVX,OB:P) rats was found to be dose-related, and the level of LH in the plasma was increased by as little as 1·25 μg. Pretreatment with adrenergic (phenoxybenzamine and propranolol) and cholinergic (atropine) antagonists failed to block the stimulatory effects of histamine on prolactin secretion, but pretreatment with methysergide (serotonin antagonist) increased the histamine-induced release of prolactin in male rats. Antagonists did not modify the response of prolactin to histamine in OVX,OB:P-primed rats. The histamine-induced release of LH in OVX,OB:P-primed rats was slightly reduced by pretreatment with phenoxybenzamine, propranolol and atropine, but not by methysergide. These results indicate that histamine facilitates the release of prolactin. The stimulatory action of histamine on both pro-oestrous and OVX,OB:P-primed but not male rats suggests that histamine may be involved in LH release in the rat. Results obtained in animals pretreated with transmitter antagonists, which were unable to prevent histamine-induced hormone release, suggest that the actions of this amine are not mediated by cholinergic, noradrenergic or serotonergic mechanisms.

ROLE OF OESTROGENS AND GONADOTROPHINS IN PERPHENAZINE-INDUCED MAMMOGENESIS

1970 ◽  
Vol 48 (3) ◽  
pp. 365-371 ◽  
Author(s):  
A. DANON ◽  
C. P. WELLER ◽  
F. G. SULMAN
Keyword(s):  
Median Eminence ◽  
Mammary Glands ◽  
Prolactin Secretion ◽  
Female Rats ◽  
Male Rats ◽  
Ovariectomized Rats ◽  
Gonadotrophin Secretion

SUMMARY Treatment of intact or recently (1 day) ovariectomized female rats with 5 mg perphenazine (Trilafon)/kg/day for 5 days resulted in marked lobulo—alveolar differentiation of the mammary glands. Perphenazine failed to stimulate mammogenesis in chronically (12 days) ovariectomized rats, unless they had been primed with oestradiol. However, mammogenic effects in chronically ovariectomized rats were obtained after implantation of minute amounts (2 μg) of oestradiol into the median eminence, or after treatment for 16 days with the non-steroid pituitary gonadotrophin-inhibitor methallibure (ICI 33828; 20 mg/kg/day). Since these latter procedures counteract the gonadotrophin surge after ovariectomy, it would appear that inhibition of gonadotrophin secretion is necessary before prolactin secretion can be stimulated by perphenazine. Castrated male rats responded to perphenazine with lobulo—alveolar differentiation similar to that in intact males. The implications of this difference with regard to the mechanism of pituitary response to gonadectomy are discussed.

INHIBITION OF PROLACTIN SECRETION BY ERGOT ALKALOIDS

1975 ◽  
Vol 80 (3) ◽  
pp. 429-443 ◽  
Author(s):  
H. Nasr ◽  
O. H. Pearson
Keyword(s):  
Ergot Alkaloids ◽  
Prolactin Secretion ◽  
Female Rats ◽  
Function Evaluation ◽  
Inhibiting Effect ◽  
Oestradiol Benzoate ◽  
Ovine Prolactin ◽  
Medical Therapeutics ◽  
Stimulation Of ◽  
Intact Rats

ABSTRACT The effect of various ergot alkaloids on prolactin (Pr) secretion in adult female rats was determined by radioimmunoassay. Ergocornine (ECO) and ergocristine (ECR) in doses of 0.25 to 1.0 mg lowered serum Pr markedly by 1 h with the effect persisting for 24 h at the larger doses. Several other ergots had similar effects while the dihydro derivatives had diverse responses. The pro-oestrous surge of Pr could be blocked by ECR or ECO without interfering with the oestrous cycle. ECO or ECR could suppress the rise in serum Pr induced by oestradiol benzoate (OeB) (5–50 μg) in oophorectomized rats. Perphenazine (PE) stimulation of Pr could be partially antagonized by ECO depending on dose and timing of injections. ECO 2 mg produced an abrupt cessation of lactation with concomitant fall in serum Pr, and ovine prolactin restored this function. Evaluation of pituitary Pr concentration in lactating and intact rats receiving ECO leads to the conclusion that release of Pr from the pituitary is affected. ECO 1 or 2 mg produced a regression of dimethylbenz(a)anthracene (DMBA) induced rat mammary tumours which could not be reversed by OeB 5 μg, with persisting low serum Pr. PE 1 mg was able to raise serum Pr and stimulated tumour growth. Several of the ergot alkaloids have a profound inhibiting effect on Pr secretion and may be used for studies on Pr action, as well as in medical therapeutics.

LORDOSIS BEHAVIOUR IN MALE, FEMALE AND ANDROGENIZED FEMALE RATS

1976 ◽  
Vol 70 (3) ◽  
pp. 409-420 ◽  
Author(s):  
P. SÖDERSTEN
Keyword(s):  
Testosterone Propionate ◽  
Female Rats ◽  
Male Rats ◽  
High Dose ◽  
Normal Female ◽  
Adult Rats ◽  
Oestradiol Benzoate ◽  
Series Of Experiments ◽  
Lordosis Behaviour ◽  
Dose Dependent

SUMMARY Sex differences in the lordosis response of adult rats to ovarian hormones were studied in a series of experiments. Male rats were less sensitive to oestradiol benzoate (OB, a single injection of 10, 100 or 1000 μg/kg or seven daily injections of 2, 10 or 50 μg/kg) than were female rats. Oestradiol benzoate-primed (10 μg/kg) female, but not male, rats showed dose-dependent responses to progesterone (0·4, 2·0 or 10·0 mg/kg). Male rats responded clearly to progesterone (2 mg/rat) only when primed with a high dose of OB (100 μg/rat). Display of the whole pattern of female sexual behaviour was induced in male rats by treatment with 100 μg OB and 2 mg progesterone. Female rats treated with 1 mg testosterone propionate (TP) on day 4 of life, ovariectomized as adults and tested under the same endocrine conditions as the rats described above, retained behavioural OB sensitivity but responded poorly to progesterone. Evidence is presented that ovarian secretions during development significantly modify the response of neonatally TP-treated and normal female rats to OB in adulthood.

EFFECT OF OVARIAN STEROIDS ON PREPUTIAL GLAND ODOURS IN THE FEMALE RAT

1978 ◽  
Vol 77 (3) ◽  
pp. 397-403 ◽  
Author(s):  
A. J. THODY ◽  
H. DIJKSTRA
Keyword(s):  
Single Injection ◽  
Female Rats ◽  
Male Rats ◽  
Ovariectomized Rats ◽  
Whole Body ◽  
Female Rat ◽  
Preputial Gland ◽  
Intact Female ◽  
Oestradiol Benzoate ◽  
Experienced Male

Sexually experienced male rats were used to test for whole body and preputial gland odours of female rats. The male rats clearly preferred whole body odours of intact female rats to those of preputialectomized female rats. The male rats also preferred the odour of preputial gland tissue of intact female rats to that of ovariectomized female rats and were especially attracted to the preputial gland odours of female rats in pro-oestrus and oestrus. The preputial gland odours of ovariectomized rats that had received oestradiol benzoate for 7 days were attractive to male rats, although similar treatment with progesterone was ineffective. However, a single injection of progesterone given 72 h after a single injection of oestradiol benzoate not only made ovariectomized rats receptive, but also made their preputial gland odours attractive to male rats. The results suggest that the preputial gland of the female rat is responsible for odours that serve to attract sexually experienced male rats. Ovarian steroids, as well as controlling receptivity in the female rat, would also appear to control the production of sex attractants in the preputial gland. There was no relationship between the size of the preputial glands and their ability to attract male rats which suggests that preputial gland growth and production of sex attractants are not under the same hormonal control.

THE INFLUENCE OF A SINGLE HIGH DOSE OF OESTRADIOL BENZOATE ON THE ICSH-CONTENT IN THE SERUM OF GONADECTOMIZED MALE AND FEMALE RATS

1965 ◽  
Vol 49 (2) ◽  
pp. 231-238 ◽  
Author(s):  
T. Swelheim
Keyword(s):  
Anterior Pituitary ◽  
Single Injection ◽  
Female Rats ◽  
Male Rats ◽  
Ventral Prostate ◽  
High Dose ◽  
Male And Female ◽  
Single High Dose ◽  
Male And Female Rats ◽  
Oestradiol Benzoate

ABSTRACT A single injection of 50 μg oestradiol benzoate, administered at 11 a.m. to adult female rats which had been spayed 14 days previously and had since been treated with 0.5 μg oestradiol benzoate daily, led to an increase in the ICSH-content of the serum, which was determined 29 hours after the injection. In an identical experimental design a decrease in the ICSH-content of the serum was found in adult male rats. ICSH-determinations were carried out by the ventral prostate assay. A stimulating effect upon the ventral prostate of oestrogen present in the serum used for the above determinations was excluded. At the time when the changes in the serum were established, there were no demonstrable changes in the ICSH-content of the anterior pituitary gland in both sexes. The existence of a fundamental sex difference in the response to a single high dose of oestrogen is suggested.

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.

LORDOSIS BEHAVIOUR IN IMMATURE MALE RATS

1978 ◽  
Vol 76 (2) ◽  
pp. 233-240 ◽  
Author(s):  
P. SÖDERSTEN
Keyword(s):  
Normal Development ◽  
Single Injection ◽  
Inhibitory Effect ◽  
Female Rats ◽  
Male Rats ◽  
Intact Male ◽  
Tb Treatment ◽  
Oestradiol Benzoate ◽  
Lordosis Behaviour ◽  
The Brain

Lordosis behaviour was induced in immature 20-day-old male rats by sequential treatment with oestradiol benzoate (OB) and progesterone, but prepubertal male rats were behaviourally less sensitive to the OB and progesterone treatment than were female rats. Thus, the sex difference in the lordosis response was present early during development. Castration at various times after birth showed that the capacity of immature rats to show lordosis is normally inhibited by an action of testicular secretions exerted during the first 10 days of life. Treatment of day 0 castrated rats with OB, either as a single injection given on the day of birth or as daily injections given on the first 10 days after birth, was much more effective in inhibiting the display of lordosis behaviour at 30 and 37 days of age than was treatment with testosterone benzoate (TB). Treatment with dihydrotestosterone benzoate neonatally had no inhibitory effect. Treatment of intact male rats or day 0 castrated OB-or TB-treated rats with the anti-oestrogen ethamoxytriphetol (MER-25) during the first 10 days of life antagonized the inhibitory effect of the testes and of the OB or TB treatment on the development of the lordosis response. It is suggested that during normal development oestradiol formed in the brain from testosterone in the circulation acts during the first 10 days of life to inhibit the capacity of male rats to show lordosis when adult.

OESTROGEN AND PROGESTERONE INFLUENCE ON THE RELEASE OF PROLACTIN IN OVARIECTOMIZED RATS

1974 ◽  
Vol 60 (2) ◽  
pp. 205-215 ◽  
Author(s):  
L. CALIGARIS ◽  
J. J. ASTRADA ◽  
S. TALEISNIK
Keyword(s):  
Single Injection ◽  
Prolactin Secretion ◽  
Male Rats ◽  
Ovariectomized Rats ◽  
Serum Prolactin ◽  
Inhibitory Effects ◽  
Oestradiol Benzoate ◽  
Close Relationship ◽  
Dose Dependent

SUMMARY The concentration of prolactin in serum after oestrogen and progesterone injection into spayed rats was measured by radioimmunoassay. After a single injection of 5 μg oestradiol benzoate (OB) into long-term ovariectomized rats, serum prolactin concentrations showed a circadian rhythm with high levels in the afternoon and almost no changes in the morning. Peaks of prolactin occurred 2, 3 and 4 days after the injection. Below a dose of 1 μg OB, the response was dose-dependent, but the response was then maximal. In spayed rats primed with 5 μg OB, the injection of 2 mg progesterone 2, 3 or 4 days later resulted in a significant increase in serum prolactin. This response, in contrast to that of oestrogen, occurred in the morning and in the evening and was found to be dose-dependent. The rise in serum prolactin after injection of 1 mg progesterone also showed a close relationship to the priming dose of OB. Progesterone had no effect in spayed, untreated animals. Maximal levels of prolactin were attained 3–4 h after the s.c. injection of progesterone. The release of prolactin which can be induced either by OB or by progesterone was blocked by the administration of progesterone injected 1 day before the expected release would occur. These results indicate that progesterone exerts both facilitatory and inhibitory effects on prolactin secretion. Male rats were found to be less sensitive to the ovarian steroid treatment. It is suggested that oestrogen could be responsible for the rise in prolactin observed at pro-oestrus and progesterone for the increase in prolactin in pseudopregnancy and pregnancy.

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