Sexual differences in the effect of serotonin on LH secretion in rats

1985 ◽  
Vol 109 (3) ◽  
pp. 320-325 ◽  
Author(s):  
Jaime A. Moguilevsky ◽  
María R. Faigón ◽  
Modesto C. Rubio ◽  
Pablo Scacchi ◽  
Berta Szwarcfarb
Keyword(s):  
Sexual Differences ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Adult Rats ◽  
Serotoninergic Neurons ◽  
Male And Female Rats ◽  
Lh Release ◽  
Prepubertal Rats ◽  
Lh Secretion ◽  
The Brain

Abstract. The effect of 5-hydroxytryptophan (5-HTP), a serotonin (5-HT) precursor, on luteinizing hormone (LH) secretion was studied in prepubertal male and female rats of different ages. In females 5-HTP stimulated LH release on days 16, 18 and 20 but not in older rats (26, 30, 35 days of age). No effects of 5-HTP on LH levels were observed in males. The positive feed-back mechanism of oestrogen-progesterone (E-P), that normally matures in the female between 20 and 26 days, was inhibited by 5-HTP in all the ages studied during prepuberty (26, 30 and 35 days old). On the other hand, in adult ovariectomized rats, 5-HTP administration not only decreased the high LH levels induced by ovariectomy, but the LH release response to E-P as well. These results indicate that there are sexual differences in the effect of 5-HT on LH in prepubertal rats younger than 26 days old. Administration of p-chloroamphetamine (PCA) a serotonin neurotoxin selective for serotoninergic neurons that depletes 5-HT levels in the brain, induced a significant increase in the LH release response to LRH in females, but had no effect in males. These results, besides suggesting a probable pituitary participation in the 5-HT action on LH secretion in the female, appear to indicate the existence of sexual differences in the effect of 5-HT in adult rats.

EFFECTS OF NALOXONE ON LUTEINIZING HORMONE AND PROLACTIN IN SERUM OF RATS

1980 ◽  
Vol 85 (2) ◽  
pp. 307-315 ◽  
Author(s):  
M. S. BLANK ◽  
A. E. PANERAI ◽  
H. G. FRIESEN
Keyword(s):  
Female Rats ◽  
Male Rats ◽  
Ovariectomized Rats ◽  
Serum Prolactin ◽  
Immature Female ◽  
Subcutaneous Injections ◽  
Serum Lh ◽  
Opiate Peptides ◽  
Lh Release ◽  
Lh Secretion

The effects of subcutaneous injections of the opiate antagonist naloxone on the tonic and phasic secretion of prolactin and LH were studied in rats. During development, resting levels of prolactin in serum were decreased by naloxone (2·5 mg/kg body wt) on days 24,45 and 50 in female rats and on days 28,45 and 50 in male rats. In the adult, naloxone (2·5 mg/kg body wt) decreased basal levels of serum prolactin in male rats and levels during oestrus in female rats. In 25-day-old female rats, serum LH rose from resting levels within 7·5 min of naloxone administration (2·5 mg/kg body wt) and returned to pretreatment levels by 30 min, while prolactin fell by 7·5 min and remained low for as long as 60 min after treatment. Furthermore, a tenfold lower dose of naloxone (0·25 mg/kg body wt) did not raise basal levels of serum LH but still decreased resting levels of serum prolactin in immature female rats (24 days old). The effect of naloxone (2·5 mg/kg body wt) on phasic LH release was studied in 29-day-old immature female rats primed on day 27 with pregnant mare serum gonadotrophin (PMSG). In these PMSG-treated rats the onset of the prolactin surge was blunted by naloxone while it had no effect on phasic LH release. Naloxone (5 mg/kg body wt) also induced a rise in levels of serum LH in ovariectomized rats and, if administered with morphine, it reversed the short-term inhibition of LH secretion caused by morphine. However, naloxone was ineffective after pretreatment with oestradiol benzoate. These findings suggest that the responses of serum LH and prolactin to naloxone were dissociated and that oestrogens and opiate peptides may have interacted to regulate secretion of LH.

Dissociation between the ovarian factors controlling sexual receptivity and preovulatory secretion of LH in cyclic female rats

1987 ◽  
Vol 112 (1) ◽  
pp. 133-138 ◽  
Author(s):  
P. Södersten ◽  
P. Eneroth
Keyword(s):  
Sexual Behaviour ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Sexual Receptivity ◽  
Serum Progesterone ◽  
Lh Surge ◽  
Oestradiol Benzoate ◽  
Lh Release ◽  
Lh Secretion ◽  
Intact Rats

ABSTRACT Ovariectomy and treatment with oestradiol benzoate (10 μg OB) on the day before behavioural oestrus eliminated the preovulatory surge of LH and reduced the level of sexual receptivity on the following day. Sexual behaviour, but not the LH surge, was restored by progesterone (0·5 mg) given 18 h later. Injection of OB on the day after behavioural oestrus induced a small release of LH and normal sexual behaviour on the following day. Ovariectomy on the day after behavioural oestrus reduced the stimulatory effect of OB on sexual behaviour and eliminated its weakly stimulatory effect on LH release. Sexual behaviour, but not the small LH surge, was restored in these animals by progesterone (0·5 mg) given 18 h later. Treatment of rats ovariectomized 2 days before the day of the LH surge with implants containing oestradiol or injections of oestradiol (1 μg) induced LH surges but the amplitudes of these LH surges were much smaller than those of the normal LH surge. Treatment of intact rats with OB increased serum progesterone levels 24 h later, an effect which was eliminated by ovariectomy. Injections of LH (20 μg) into intact rats on the day after behavioural oestrus also increased serum progesterone concentrations but failed to stimulate sexual behaviour. It is suggested that OB treatment of intact rats on the day after behavioural oestrus stimulates sexual behaviour by inducing a surge of LH secretion which activates ovarian secretion of progesterone. Thus, oestrogen and progesterone but not the LH surge are essential for sexual behaviour. Whereas oestradiol and progesterone restore normal sexual behaviour in ovariectomized rats, additional ovarian factors may be required for induction of normal LH surges. J. Endocr. (1987) 112, 133–138

Neuropharmacological analysis of the control of LH secretion in gonadectomized male and female rats: altered hypothalamic responses to inhibitory neurotransmitters in long-term castrated rats

1988 ◽  
Vol 119 (1) ◽  
pp. 15-21 ◽  
Author(s):  
O. F. X. Almeida ◽  
K. E. Nikolarakis ◽  
A. Herz
Keyword(s):  
Opioid Receptor ◽  
Female Rats ◽  
Male Rats ◽  
Dopaminergic Agonists ◽  
Male And Female ◽  
Opioid Agonists ◽  
Male And Female Rats ◽  
Lh Release ◽  
Lh Secretion

ABSTRACT The control of LHRH and LH by neurotransmitters and neuromodulators such as the endogenous opioid peptides is essentially the same in intact adult male and female rats: adrenergic and dopaminergic agonists stimulate LH release and opioid agonists inhibit it. Several weeks after gonadectomy, however, the contribution of the endogenous ligands of adrenergic, dopaminergic and opioidergic receptors to the control of LHRH is altered. A detailed pharmacological analysis in long-term ovariectomized females confirmed previous reports that adrenergic and dopaminergic agonists still enhance secretion of LHRH and LH and opioid receptor agonists still suppress it. A similar investigation in long-term castrated males also confirmed previous reports that opioid agonists fail to block LH secretion. In addition, we have found that while adrenergic and dopaminergic agonists cause increases in serum concentrations of LH, adrenoreceptor and dopamine receptor antagonists do not inhibit LH release in long-term castrates. Furthermore, the opioid antagonist naloxone does not raise serum LH levels in either sex after long-term gonadectomy. These observations therefore imply reduced opioidergic, dopaminergic and adrenergic transmission, in relation to LHRH release, after longterm castration. In addition, opioid receptor activity (assessed by responsiveness to an opioid receptor agonist) of female rats is maintained, whereas that of male rats is lost, after long-term gonadectomy. J. Endocr. (1988) 119, 15–21

Varying sensitivity to the negative oestrogen feedback during the ovarian cycle of female rats: evidence for the involvement of oestrogen and the medial preoptic area

1984 ◽  
Vol 102 (3) ◽  
pp. 287-294 ◽  
Author(s):  
F. Döcke ◽  
W. Rohde ◽  
P. Gerber ◽  
R. Chaoui ◽  
G. Dörner
Keyword(s):  
Preoptic Area ◽  
Medial Preoptic Area ◽  
Ovarian Cycle ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Adult Rats ◽  
Gonadotrophin Secretion ◽  
Arcuate Region ◽  
Lh Secretion ◽  
Follicle Maturation

ABSTRACT The gonadotrophic response to a single injection of oestradiol benzoate (OB) was studied in acutely ovariectomized adult rats during the different stages of a 4-day ovarian cycle. The results showed a sudden decline of the sensitivity to the gonadotrophin-inhibiting effect of OB between metoestrus and dioestrus. This desensitization to the negative oestrogen feedback was probably caused by an oestrogen action on the medial preoptic area (MPOA). In rats ovariectomized and implanted with OB in the MPOA in metoestrus, an s.c. injection of OB on the presumptive day of pro-oestrus did not lower the circulating LH and FSH levels, whereas a clear suppression of gonadotrophin secretion was seen in females implanted with cholesterol in the MPOA or implanted with OB in the hypothalamic ventromedial–arcuate region. Similar findings were obtained in rats which had been ovariectomized 3–4 weeks before implantation. A final experiment demonstrated that bilateral lesioning of the MPOA also reduced the sensitivity to the negative feedback action of oestrogen in long-term ovariectomized rats. In all experiments performed, diminution of the oestrogen-induced inhibition of LH secretion was more marked than that of suppression of FSH secretion. It is proposed that desensitization to the negative oestrogen feedback, probably resulting from an inhibitory oestrogen action on medial preoptic neurones, is a prerequisite for adequate gonadotrophic support of preovulatory follicle maturation in the presence of a continuously rising oestrogen concentration in the blood. J. Endocr. (1984) 102, 287–294

EFFECT OF NEONATAL ADMINISTRATION OF STEROIDS OR GONADECTOMY UPON OESTRADIOL-INDUCED LUTEINIZING HORMONE RELEASE IN RATS OF BOTH SEXES

1980 ◽  
Vol 85 (1) ◽  
pp. 69-74 ◽  
Author(s):  
F. GOGAN ◽  
I. A. BEATTIE ◽  
M. HERY ◽  
E. LAPLANTE ◽  
C. KORDON
Keyword(s):  
Luteinizing Hormone ◽  
Sexual Differentiation ◽  
Female Rats ◽  
Male Rats ◽  
Ovariectomized Rats ◽  
Hormone Release ◽  
Adult Rats ◽  
Luteinizing Hormone Release ◽  
Neonatal Administration ◽  
Lh Secretion

SUMMARY Implantation of oestradiol into adult rats of both sexes induced different patterns of LH secretion depending on the time at which gonadectomy or testosterone injection were performed. Castration 2 h after birth allowed an LH peak to occur daily at 18.00 h, but its amplitude was lower than that of adult gonadectomized female rats treated with oestradiol. Castration 24 h after birth elicited two kinds of response; a circadian discharge of LH lower than that of male rats gonadectomized 2 h after birth or a steady low level of LH. The LH rhythmicity induced by implantation of oestradiol was not seen after castration at 8 weeks of age. Neonatal administration of testosterone to female rats prevented the LH peak induced by oestradiol that was seen in adult ovariectomized rats. Neonatal or adult ovariectomy did not interfere with the rhythmical response of LH after implantation of oestradiol. Thus, it is concluded that sexual differentiation of the hypothalamus is primarily of masculine origin.

Effect of acute immunoneutralization of endogenous leptin on prolactin and LH secretion during the afternoon of pro-oestrus or in steroid-treated ovariectomized female rats

Reproduction ◽  
2000 ◽  
pp. 39-45 ◽  
Author(s):  
LC Gonzalez ◽  
L Pinilla ◽  
M Tena-Sempere ◽  
C Dieguez ◽  
FF Casanueva ◽  
...  
Keyword(s):  
Prolactin Secretion ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Rabbit Serum ◽  
Normal Rabbit Serum ◽  
Blood Samples ◽  
Lh Release ◽  
Lh Secretion

Recent data indicate that leptin is involved in the control of reproductive function. Experiments were carried out to analyse the role of endogenous leptin in the regulation of LH and prolactin secretion during the afternoon of pro-oestrus and that induced by ovarian steroids in ovariectomized rats. In the first experiment, cyclic female rats were implanted with intra-auricular and intracerebroventricular (i.c.v.) cannulae and, at pro-oestrus, were injected (i.c.v.) with 10 microliters normal rabbit serum or leptin antiserum (at 13:00 and 14:00 h). Blood samples were obtained at 10:00 h and at intervals of 1 h between 13:00 and 20:00 h. In the second experiment, female rats in pro-oestrus were injected with normal rabbit serum or leptin antiserum at 16:00 and 18:00 h and blood samples were taken every 10 min between 18:00 and 20:00 h. In the third experiment, adult female rats that had been ovariectomized 2 weeks before were implanted with intra-auricular and i.c.v. cannulae and treated with oestradiol benzoate (30 micrograms s.c.) at 10:00 h and progesterone (2 mg s.c.) 48 h later. Normal rabbit serum (10 microliters) or leptin antiserum (10 microliters) were injected (i.c.v.) at 13:00 and 14:00 h, and blood samples were obtained at 10:00 h and at intervals of 1 h between 13:00 and 20:00 h. In the fourth experiment, hemipituitaries from ovariectomized steroid-treated female rats were incubated in the presence of leptin116-130 (an active fragment of the native molecule), GnRH or leptin + GnRH. Prolactin and LH secretion during the afternoon of pro-oestrus in females treated with leptin antiserum was similar to that observed in animals injected with normal rabbit serum. In ovariectomized female rats, the steroid-induced LH surge increased slightly after administration of leptin antiserum, whereas the prolactin surge remained unchanged. In vitro, leptin116-130 (10(-5) to 10(-8) mol l-1) inhibited LH secretion and modulated the effect of GnRH on LH release, depending on the concentration of GnRH: leptin116-130 (10(-6) mol l-1) reduced the effectiveness of 10(-7) mol GnRH l-1 and increased that of 10(-9) mol GnRH l-1. In conclusion, these experiments indicate that acute immunoneutralization of endogenous leptin does not interfere with spontaneous or steroid-induced LH and prolactin surges. In addition, the finding that leptin116-130 inhibited LH release and modulated the effectiveness of GnRH in vitro provides evidence of the direct modulatory role of leptin on LH secretion acting at the pituitary.

Age, gender, and vasopressin affect survival and brain adaptation in rats with metabolic encephalopathy

1995 ◽  
Vol 268 (5) ◽  
pp. R1143-R1152 ◽  
Author(s):  
A. I. Arieff ◽  
E. Kozniewska ◽  
T. P. Roberts ◽  
Z. S. Vexler ◽  
J. C. Ayus ◽  
...  
Keyword(s):  
Cerebral Perfusion ◽  
Female Rats ◽  
Adult Males ◽  
Adult Rats ◽  
Metabolic Encephalopathy ◽  
Adult Females ◽  
Male And Female Rats ◽  
Chronic Hyponatremia ◽  
Prepubertal Rats ◽  
Acute Hyponatremia

Children and menstruant women are far more likely than men to develop metabolic brain damage from hyponatremia. We evaluated brain adaptation and mortality from hyponatremia in male and female rats of three different age groups. With acute hyponatremia, the mortality was 84% in prepubertal rats vs. 15% in adults and 0% in elderly rats. With chronic hyponatremia, mortality was 13% in adult males vs. 62% in females. Testosterone pretreatment significantly decreased mortality (from 62 to 9% in adult females, and from 100% to zero in prepubertal rats), but estrogen significantly increased mortality (from 13 to 44% in adult males). With acute hyponatremia in adult rats, brain sodium was significantly decreased (-17%), but in prepubertal rats it was actually increased (+ 37%). Cerebral perfusion during chronic hyponatremia was significantly impaired in adult females vs. males or controls (P < 0.01). Neither vasopressin administration nor chronic hyponatremia induced with desmopressin resulted in any mortality or decrement of cerebral perfusion. Thus age, gender, and the cerebral effects of vasopressin are major determinants of mortality in experimental metabolic encephalopathy.

Role of serotoninergic neurones in the control of gonadotrophin and prolactin secretion in the rat

1982 ◽  
Vol 94 (1) ◽  
pp. 83-89 ◽  
Author(s):  
Csilla Ruzsas ◽  
Patrizia Limonta ◽  
L. Martini
Keyword(s):  
Combined Treatment ◽  
Prolactin Secretion ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Serum Prolactin ◽  
Intact Male ◽  
Prolactin Release ◽  
Lh Secretion ◽  
The Brain

The role of brain serotonin (5-hydroxytryptamine, 5-HT) in the control of LH, FSH and prolactin secretion was studied in two groups of experimental animals: intact adult male rats and ovariectomized adult female rats. 5-Hydroxytryptophan (5-HTP), a precursor of serotonin synthesis, and fluoxetine, a specific inhibitor of 5-HT uptake, were given either alone or together. 5-Hydroxytryptophan (50 mg/kg) was administered intraperitoneally and fluoxetine (20 μg/rat) was given into one of the lateral ventricles of the brain. Neither 5-HTP nor fluoxetine given alone affected LH secretion but combined treatment with the two drugs elicited a significant increase in serum LH levels in both intact male and ovariectomized female rats. Fluoxetine and 5-HTP, alone or together, did not modify FSH secretion in either kind of animal. In intact males and in ovariectomized females, 5-HTP induced a significant increase in prolactin release; fluoxetine alone was ineffective. In male animals treated with fluoxetine plus 5-HTP, serum prolactin levels increased but such an increase was lower than that found in the animals treated only with 5-HTP. In ovariectomized rats, the combined treatment induced an increase in serum prolactin levels similar to that found in animals treated with 5-HTP alone. These data suggested that brain serotonin exerts a stimulating effect on LH secretion in both intact male and ovariectomized rats, but that it does not play any role in the control of FSH release in either kind of animal and that central serotoninergic pathways participate in the stimulating control of prolactin release from the anterior pituitary gland. However, some of the data also suggested the possibility of the existence in the brain of serotoninergic systems inhibiting prolactin secretion.

Are catechol oestrogens obligatory mediators of oestrogen action in the central nervous system? II. Potencies of natural and synthetic oestrogens for induction of gonadotrophin release and female sexual behaviour in the rat

1986 ◽  
Vol 110 (3) ◽  
pp. 499-505 ◽  
Author(s):  
N. J. MacLusky ◽  
L. C. Krey ◽  
B. Parsons ◽  
G. R. Merriam ◽  
D. L. Loriaux ◽  
...  
Keyword(s):  
Pituitary Gland ◽  
Sexual Behaviour ◽  
Female Rats ◽  
Oestrogen Receptors ◽  
Ability To Act ◽  
The Central Nervous System ◽  
Lh Release ◽  
Lh Secretion ◽  
The Brain

ABSTRACT The role of catechol oestrogen formation in the mechanism by which circulating oestrogens facilitate gonadotrophin release and female sexual behaviour was explored in adult female rats. The effects of oestradiol-17β were compared with those of a group of oestrogens with either a reduced affinity for oestrogen receptors (oestradiol-17α) or a reduced ability to act as substrates for catechol oestrogen formation (2-fluoro-oestradiol, 4-fluoro-oestradiol and moxestrol (11β-methoxy-17α-ethynyloestradiol)). Rats were ovariectomized on the evening of dioestrus day 1 of the 4-day oestrous cycle and implanted s.c. 12 h later with infusion pumps containing either one of the test oestrogens or vehicle alone. Infusion rates for oestradiol-17β, moxestrol, 2-fluoro-oestradiol and 4-fluoro-oestradiol were adjusted to give concentrations of nuclear oestrogen receptors in the brain and pituitary gland within the range of those found in intact female rats during pro-oestrus. Oestradiol-17α was infused at the same and at a tenfold higher rate than that of oestradiol-17β; neither of these treatments with oestradiol-17α significantly increased brain or pituitary gland nuclear oestrogen receptor levels. On the day after the pump was implanted, samples of tail vein blood were withdrawn at 12.00, 14.00, 16.00 and 18.00 h for LH assay. All animals were then injected s.c. with 1 mg progesterone in propylene glycol, and tested for feminine sexual behaviour 5 h later. Oestradiol-17β, moxestrol, 2-fluoro-oestradiol and 4-fluoro-oestradiol all elicited pronounced LH surges and facilitated progesterone-triggered proceptive and lordosis behaviours. In contrast, oestradiol-17α was without effect on LH secretion and sexual behaviours. These results are consistent with the hypothesis that catechol oestrogen biosynthesis is not an obligatory step in the mechanism by which circulating oestrogens induce LH release and feminine sexual behaviour in the rat. J. Endocr. (1986) 110, 499–505

INDUCTION OF GOITRE BY PTU OR KClO4 IN MALE AND FEMALE RATS. EFFECT OF GONADECTOMY

1973 ◽  
Vol 74 (1) ◽  
pp. 88-104 ◽  
Author(s):  
T. Jolín ◽  
M. J. Tarin ◽  
M. D. Garcia
Keyword(s):  
Iodine Content ◽  
High Plasma ◽  
Disc Electrophoresis ◽  
Female Rats ◽  
Male Rats ◽  
Adult Rats ◽  
Male And Female ◽  
Glucose Levels ◽  
Male And Female Rats ◽  
Tsh Levels

ABSTRACT Male and female rats of varying ages were placad on a low iodine diet (LID) plus KClO4 or 6-propyl-2-thiouracil (PTU) or on the same diet supplemented with I (control rats). Goitrogenesis was also induced with LID plus PTU in gonadectomized animals of both sexes. The weight of the control and goitrogen treated animals, and the weight and iodine content of their thyroids were determined, as well as the plasma PBI, TSH, insulin and glucose levels. The pituitary GH-like protein content was assessed by disc electrophoresis on polyacrylamide gels. If goitrogenesis was induced in young rats of both sexes starting with rats of the same age, body weight (B.W.) and pituitary growth hormone (GH) content, it was found that both the males and females developed goitres of the same size. On the contrary, when goitrogenesis was induced in adult animals, it was found that male rats, that had larger B.W. and pituitary GH content than age-paired females, developed larger goitres. However, both male and female rats were in a hypothyroid condition of comparable degree as judged by the thyroidal iodine content and the plasma PBI and TSH levels. When all the data on the PTU or KClO4-treated male and female rats of varying age and B.W. were considered together, it was observed that the weights of the thyroids increased proportionally to B.W. However, a difference in the slope of the regression of the thyroid weight over B.W. was found between male and female rats, due to the fact that adult male rats develop larger goitres than female animals. In addition, in the male rats treated with PTU, gonadectomy decreased the B.W., pituitary content of GH-like protein and, concomitantly, the size of the goitre decreased; an opposite effect was induced by ovariectomy on the female animals. However, when goitrogenesis was induced in weight-paired adult rats of both sexes, the male animals still developed larger goitres than the females. Among all the parameters studied here, the only ones which appeared to bear a consistent relationship with the size of the goitres in rats of different sexes, treated with a given goitrogen, were the rate of body growth and the amount of a pituitary GH-like protein found before the onset of the goitrogen treatment. Moreover, though the pituitary content of the GH-like protein decreased as a consequence of goitrogen treatment, it was still somewhat higher in male that in female animals. The present results suggest that GH may somehow be involved in the mechanism by which male and female rats on goitrogens develop goitres of different sizes, despite equally high plasma TSH levels.

Sign in / Sign up

Export Citation Format

Share Document