High Gonadotropin Levels Research Articles

Testicular involvement in peripubertal gonadotropin levels and accessory sex organ weight of male hamsters.

This study evaluates the influence of testicular secretions during development in male hamsters on peripubertal gonadotropin levels. Castration or sham operations were performed on the day of birth (Day 1), Day 5, 10, or 20 of life. Repeated plasma samples on Days 20-60 at 10-day intervals were taken via orbital sinus puncture. Castrated animals received a subcutaneous testosterone capsule on Day 60 and were killed on Day 70. In addition, seminal vesicles and ventral prostate weights were taken in all animals at Day 70. Castrated animals, regardless of day of castration, had higher gonadotropin levels and suppressed sexual accessory organ weights. Animals castrated on the day of birth had lower luteinizing hormone (LH) levels than animals castrated on other days. Castration on Day 10 resulted in lower follicle stimulating hormone (FSH) levels. Males castrated on Day 20 were most sensitive to the negative feedback effect of testosterone on LH secretion, while Day 10 castrates had elevated FSH levels after testosterone exposure. Sexual accessory weights also differed depending upon the day of castration. Results point out the importance of testicular secretions on the developmental processes as well as the differing ages at which various systems may be influenced.

Hormonal characterization of female SL/Ni mice: a small thymus gland strain exhibiting ovarian dysgenesis

Female SL/Ni mice have a small thymus gland and show accelerated aging of the reproductive system characterized by an early loss of the follicular apparatus and early onset of ovarian tumors. At 9 months of age, circulating levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were higher in the SL/Ni animals than in controls while prolactin (PRL) was lower in the SL/Ni mice. The trends of these hormones are consistent with the loss of the follicular apparatus which is responsible for estradiol production. The high levels of gonadotropins which precede the onset of the tumors confirm the hypothesis that prolonged stimulation by gonadotropins can be a cause of ovarian tumorigenesis. Further, these data suggest that aging of the reproductive system may be a thymus-dependent phenomenon.

Immunohistochemical and Electron Microscopic Study of Nonfunctioning Pituitary Adenomas

Immunohistochemical techniques and electron microscopy were employed in a study of nine surgical patients with nonfunctioning pituitary adenomas and no clinical or biochemical evidence of increased hormone secretion. Six of the patients were found to have gonadotroph adenomas, which exhibited extensive immunostaining for gonadotropins, and the remaining three appeared to have null cell adenomas, which showed no reactivity for any pituitary hormone. Clinically, it was difficult to distinguish these two groups of patients. Gonadotroph adenomas are likely to have low secretory activity, resulting in normal or slightly high serum gonadotropin levels. In addition, some common histopathological features were observed in the two groups: a predominantly papillary, sinusoidal pattern; rather poorly developed cell organelles, with the exception of an abundance of mitochondria; and small, round secretory granules dispersed throughout the cytoplasm. It is possible that null cell adenoma produces so little gonadotropin that it is not detectable by immunohistochemistry. In this study, two thirds of the nonfunctioning adenomas were, in fact, gonadotroph adenomas. The authors speculate that there is a common cytogenesis of gonadotroph adenomas and some, if not all, null cell adenomas.

Bone mass and its relationship to age and the menopause.

To examine the influence of age and the menopause on bone loss we studied 178 healthy women, aged 29-78 yr. Bone mass was measured at 2 forearm sites, in the total spine, in the lumbar spine, and in the whole body by single and dual photon absorptiometry. Women of the same age but different menopausal status had significantly different bone masses, whereas a 5-yr difference in age had no effect on bone mass in women with the same menopausal status. At the menopause the hormone changes (low serum estrogen and high serum gonadotropin levels) occurred simultaneously with the appearance of biochemical indices of increased bone turnover. Neither biochemical values nor bone measurements indicated significant bone loss before the menopause. We conclude that the menopause has a greater effect on bone loss than does chronological age.

Developmental processes in early adolescence: Relationships between adolescent adjustment problems and chronologic age, pubertal stage, and puberty-related serum hormone levels

Relations between adolescent psychosocial adjustment problems and markers of biologic development, including chronologic age, pubertal status, and serum hormone levels, were examined in 56 normal boys and 52 normal girls, ages 9 to 14 years. Adolescent psychosocial adjustment was assessed by adolescent self-ratings of various aspects of self-image (Offer Self-Image Questionnaire for Adolescents) and parent ratings of adolescent behavior problems (Child Behavior Checklist). The pubertal status measure used in the analyses was Tanner genital stage for boys and Tanner breast stage for girls. The hormone measures, determined by radioimmunoassay, were serum levels of gonadotropins (luteinizing hormone and follicle stimulating hormone), sex steroids (testosterone and estradiol), and adrenal androgens (dehydroepiandrosterone and its sulfate, and androstenedione). The testosterone/estradiol ratio also was computed. Overall, findings were stronger, more consistent, and more generalized for boys than for girls. For boys, adjustment problems typically were associated with a multivariate profile that may be characteristic for later maturers: relatively low sex steroid levels, or lower pubertal stage, and relatively high adrenal androgen (androstenedione) levels, frequently in conjunction with higher chronologic age. Univariate relations predominated for girls; that is, associated with adjustment problems for girls were relatively high levels of gonadotropins, relatively low levels of dehydroepiandrosterone sulfate, and relatively high levels of androstenedione on their own or in conjunction with lower pubertal stage. Higher levels of androstenedione, a steroid particularly responsive to stress, were associated with adjustment problems in both boys and girls. This relation may reflect the stress of later maturation, which could result from environmental factors, such as adolescent self-comparisons with same-age peers, or endogenous effects of hormones.

Neonatal release of gonadotropins is essential for development of ovarian follicle-stimulating hormone receptors.

In the rat, ovarian follicle-stimulating hormone (FSH) receptors increase markedly during the first two postnatal weeks, when serum gonadotropin levels are most elevated. This study was conducted to evaluate the hypothesis that these high gonadotropin levels, and in particular FSH, are involved in the acquisition of FSH receptors by the developing ovary. Gonadotropin release was suppressed by administration of several non-aromatizable androgens, among which dihydrotestosterone propionate (DHTP) was the most effective. In one series of experiments the steroids were administered from Days 5 to 11, and serum FSH and luteinizing hormone (LH) were measured on Day 12. Surprisingly, FSH receptor content was greater in rats with suppressed serum gonadotropins than in controls. The greatest increase in available receptors was observed in DHTP-treated rats in which serum FSH was reduced to 20% of control values and LH suppressed to undetectable values. DHTP failed to directly increase available FSH receptors in hypophysectomized immature rats. Magnesium chloride (MgCl2) treatment of ovarian membranes removed bound 125I-hFSH by 87% without affecting receptor viability. Exposure of control 12-day-old ovaries to MgCl2 increased available FSH receptors to a level similar to that of ovaries from DHTP-treated rats not exposed to MgCl2, suggesting that more receptors were available in DHTP-treated rats because serum FSH was suppressed. Earlier initation of DHTP treatment (postnatal Day 1) suppressed serum FSH and LH to undetectable values by Day 5 and decreased FSH receptor content below control values by Day 12. MgCl2 treatment only slightly increased available receptors in these DHTP-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

The human gonadotropic adenoma: pathologic diagnosis and hormonal correlations in 26 tumors.

Twenty-six out of 400 surgically removed pituitary tumors were identified as gonadotropic adenomas (frequency 6.25%). Morphologic, immunocytochemical, and hormonal characteristics of the gonadotropic adenoma are described. The following morphologic characteristics may suggest the diagnosis: arrangement in cords of cells showing signs of cellular activity, secretory granules, which vary in electron density, form, and size (mean diameter 150 nm) and which are numerous in the extensions near the capillaries, and a rough endoplasmic reticulum arranged in short cisternae. However, owing to the morphofunctional variations from one adenoma to another, we consider that only immunoreactivity with gonadotropin antisera proves the diagnosis. Because the material used to generate the gonadotropin antisera was purified but not pure, for precise characterization of the immunoreactivity, absorption tests with various antigens have to be performed. FSH-LH adenomas (n = 14), FSH adenomas (n = 7), and alpha-subunit adenomas (n = 5) but no LH adenomas were identified in our series. No evident morphologic difference related to the type of immunoreactivity and to the sex was found. Almost all the tumors were large with visual signs caused by suprasellar extension. A recurrence following adenomectomy was noted with a frequency of 12%. The diagnosis of gonadotropic adenoma was considered preoperatively in six out of 26 patients only, on the basis of increased serum gonadotropin levels. Correlations between hormonal levels and pathologic data were established in 17 patients. Seven tumors were associated with high serum gonadotropin levels (FSH and LH: three patients and FSH alone: four patients). In ten cases, the serum gonadotropin levels were normal but serum alpha-subunit assay had not been performed. For the pathologist systematically testing the adenomas with many antisera, gonadotropic adenomas are not as rare as for the clinician. Immunocytochemical studies with gonadotropin antisera and serum gonadotropic determination must be performed in all tumors, especially in those pituitary adenomas that appear nonfunctional.

MATURATION OF THE HYPOTHALAMO-PITUITARYGONADAL AXIS IN PRETERM GIRLS

We found oestradiol producing ovarian cysts and high serum concentrations of oestradiol in four very pre-term infants at a postconceptional age that slightly preceded the expected time of delivery.To determine the maturation of the hypothalamo-pituitary-gonadal axis in these infants measurements of serum concentration of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were made before and after an i.v. injection of luteinizing hormone releasing hormone (LHRH). At the time when the girls developed cysts, they had a postpubertal type of response to LHRH, i.e. the increase in LH was more marked than the increase in FSH. Some months later they had a prepubertal type of response and a low preinjection serum concentration of LH as expected at that age.We then made a series of LHRH tests in all consecutive preterm girls born at a gestational age of less than 30 weeks at a postconceptional age of 32-33 weeks. All these girls had a postpubertal type of response to an LHRH injection, and the preinjection concentrations of LH and FSH were very high. When the tests were repeated at a date later than the calculated time of birth they all had a prepubertal type of response with low basal concentrations of FSH and LH. The oestradiol concentration was low on both occasions. Two girls developed very small ovarian cysts. The strong stimulation of the ovaries after birth may be a consequence of withdrawal of placental steroids.The feed-back system may be too immature in preterm girls to respond to low levels of oestradiol, resulting in high levels of gonadotrophins and an “ovarian hyperstimulation syndrome”.

Lack of relationship of hypogonadism to muscle wasting in myotonic dystrophy.

Myotonic dystrophy is frequently associated with testicular atrophy. Since androgens may play a role in the maintenance of muscle mass, we have studied the levels of plasma testosterone and gonadotropins and of urinary 17-ketosteroids in 22 men with myotonic dystrophy, 36 normal men, and 16 men (control group) with muscle wasting. Results were correlated with muscle mass as estimated by creatinine excretion and total body potassium. Patients with myotonic dystrophy had significantly lower testosterone and higher gonadotropin levels than normal, and these changes were progressive in longitudinal studies. Testosterone levels were also lower than normal in disease control subjects. There was no correlation between low testosterone levels and diminished muscle mass in either myotonic dystrophy or disease control patients. The low plasma concentration of testosterone in men with myotonic dystrophy and other neuromuscular diseases does not appear to be directly related to their muscle wasting. This study does not exclude the possibility that an alteration in testosterone receptor or tissue effects may contribute to a loss of muscle tissue.

Manic depression: A multiple hormone disorder?

The finding by Paschalis et al. (1977) that the sweat of manics has an abnormally high K +/Na + ratio, whereas that of depressives has an abnormally low one, is an important clue to the causes of manic depression, which seems to have been completely ignored. It strongly suggests that there is an adrenal component in this disorder and it implicates aldosterone. Hendler (1975) has shown that aldosterone levels are elevated in mania and that lithium will lower them and alleviate the manic symptoms, but only after natriuresis has occurred. It has been known for some time that doparnine has natriuretic properties because it inhibits the output of aldosterone (Noth et al. 1980). What has been difficult to understand is at what point dopamine acted. However, it has just been reported (Franco-Saenz et al. 1984) that there appears to be atrophic hormone for aldosterone secreted by the intermediate lobe of the pituitary. This hormone does not raise cortisol levels, nor will glucocorticoids suppress it; dopamine, however, will do so. Dopamine also inhibits the release of thyroid-stimulating hormone (TSH) (Kaptein et al. 1980) and gonadotrophin-releasing factor (GnRF) (Husemarm et al. 1980). Hence, low dopamine levels/activity should lead to high sweat K+/Na + ratios because of the high levels of aldosterone and also to hyperactive behavior and hypersexuality because of the high levels of thyroid hormone and gonadotropins, respectively. All of these are manic features. It may also be significant that hyperthyroid patients have, like manics, elevated potassium sweat levels (Gibinski 1972), suggesting that mania and hyperthyroidism have more than one feature in common. Depressives have low sweat K÷/Na + ratios (Paschalis et al. 1977), so perhaps their aldosterone levels are too low, suggesting that dopamine activity might be too high. This last hypothesis would explain why depressives have a blunted response of TSH to thyrotropin-releasing hormone (TRH) stimulation (Maeda et al. 1975), as dopamine inhibits the release of TSH. It is well known that depression and hypothyroidism have features in common, e.g., weight and appetite abnormalities, anergy, and constipation. Moreover, Prange et al. (1969) have shown that thyroid treatment will improve depression. Finally, high dopamine activity would also explain the lack of sexual interest shown by depressives, as dopamine lowers gonadotrophin-releasing factor levels (Husemann et al. 1980). It has long been known that depression is often associated with raised serum cortisol

Differential effects of gonadectomy on sensitivity to testosterone of brain centres associated with gonadotrophin negative feedback and with mating behaviour in rams.

Castrated sheep were used to study the effects of gonadectomy on sensitivity to testosterone of brain centres associated with gonadotrophin negative feedback and with mating behaviour. In the first experiment serum LH and FSH concentrations were determined in intact rams, recently castrated (2 days and 3 weeks) and long-term castrated animals (greater than 2 years, wethers) during intravenous testosterone infusion at physiological and supraphysiological levels. In intact rams, testosterone infusions effectively suppressed serum LH whilst FSH levels were suppressed only after prolonged infusion at the supraphysiological dose. Recently castrated sheep, which had higher gonadotrophin levels than intact rams, were less sensitive to testosterone feedback. Neither rate of testosterone infusion had any effect on the raised gonadotrophin levels in wethers. In a second experiment gonadotrophin concentrations and mating behaviour were determined in wethers bearing subdermal polydimethylsiloxane implants of testosterone, dihydrotestosterone and oestradiol. Testosterone implants stimulated mating behaviour in all wethers but suppressed gonadotrophins in only a proportion (three out of seven) of the animals. Both oestradiol and dihydrotestosterone suppressed LH and FSH in all wethers, whilst oestradiol, but not dihydrotestosterone, also stimulated mating behaviour. The present findings indicate that testosterone imposes continuing negative feedback on gonadotrophin secretion and that changes in the gonadotrophin regulatory system, which lead eventually to a loss in sensitivity to testosterone feedback, develop soon after gonadectomy. The results also provide the first direct evidence that longterm gonadectomy in male sheep has differential effects on sensitivity to testosterone of brain centres associated with gonadotrophin negative feedback and with mating behaviour.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of gonadotrophins on early follicle cell development and early oocyte growth in the immature rat.

Ovaries of neonatal rats were transplanted on the day after birth into ovariectomized (high gonadotrophin levels) or ovariectomized-hypophysectomized adult female rats (extremely low gonadotrophin levels). Although transplantation caused a reduction of the number of growing follicles in all transplants, it did not seem to induce a clearly abnormal course of follicle development. After 15 days of development, the hormone-rich transplants contained a greater number of follicles larger than type 4 and a smaller number of oocytes with diameters less than 21 micrometers, than did the hormone-poor transplants. In the transplants with high hormone levels, the smallest follicles (types 2--3a) showed advanced transition of flattened into cuboidal follicle cells and oocyte growth. It is concluded that in these experimental conditions gonadotrophins, presumably especially FSH, seem to have a stimulatory effect on early follicle cell development and early oocyte growth.

Role of the subcommissural organ in the control of gonadotrophin secretion in the female rat.

Thermal lesions were placed in the subcommissural organ (SCO) of female rats with normal cycles and long-term ovariectomized rats. In normal female rats SCO lesions disrupted the oestrous cycle in more than half of the animals, the majority of which entered a state of prolonged dioestrus. In these animals, serum gonadotrophin levels were similar to those of rats with regular cycles on day 2 of dioestrus. In animals in which the oestrous cycle was maintained, a delayed LH surge occurred on the day of pro-oestrus and the pro-oestrous FSH surge was absent. The usual increase in FSH on the day of oestrus was present. Lesions in the SCO did not change the high gonadotrophin levels typical of ovariectomized animals. These results suggested that the SCO may play a role in the control of the cyclic but not the tonic release of the gonadotrophins. In particular, it appears that the SCO might be involved in the regulation of the hypersecretion of FSH during the day of pro-oestrus.

Role of the subfornical organ (SFO) in the control of gonadotropin secretion

Radiofrequency lesions have been placed in the subfornical organ (SFO) or normally cycling and of long-term castrated female rats. The data have shown that, in normal female rats, SFO lesions bring about a disruption of estrous cyclicity in a large number of animals, the majority of which enter a state of prolonged diestrus. In these animals, serum gonadotropin levels are similar to those of regularly cycling animals in the second day of diestrus. In the animals in which estrous cyclicity was still present, an LH surge occurred which was regular in timing and magnitude. On the contrary the proestrous FSH surge was absent, but the usual FSH elevation of the day of estrus was present. SFO lesions were not able to change the high gonadotropin levels typical of the post-castration situation. These results suggest that the SFO may play a role in the control of the "cyclic" but not of the "tonic" release of the two gonadotropins. In particular, it appears from the results that the SFO might be involved in the regulation of the hypersecretion of FSH which occurs during the day of proestrus.

CLASSIFICATION OF MENSTRUAL CYCLES IN PRE- AND PERIMENOPAUSAL WOMEN

Urine for the analysis of pregnanediol, oestrogens, FSH and LH, was collected weekly from 50 normal menstruant women. Twenty of these women were aged ≥ 40 years and had a history of regular menstrual cycles; they are termed premenopausal. The other 30 reported a recent break in regular cyclicity and are termed perimenopausal. All menstrual cycles observed in the premenopausal women were ovulatory in type and 25–30 days in length. The 124 cycles observed in the perimenopausal women were 18–260 days in length (median, 29 days), with 52% of the ovulatory type. To describe this diversity, a systematic classification is proposed based on (1) the excretion of pregnanediol in the 12 days preceding menstruation (classes I–IV), (2) gonadotrophin output (categories A–E, and L), and (3) the length of the menstrual cycle in days. The premenstrual surge of pregnanediol was greatest in class I cycles and diminished progressively until it became undetectable in class IV. Gonadotrophin excretion was lowest in category A cycles and increased progressively until all levels were within the postmenopausal range by category E. In cycles of category L only LH (and not FSH) was raised. In the perimenopausal women 37 cycles included episodes of high gonadotrophin excretion (categories C–L), a phenomenon which was not seen in the premenopausal women. These cycles were usually longer than 50 days and were often anovulatory in type (classes II—IV). Typically they began with the high gonadotrophin levels and the low oestrogens which characterize the postmenopausal state, and ended after a rise in oestrogen output to levels ≥ 70 nmol/24 h. It is concluded that 'anovulatory' cycles and cycles in which there are 'postmenopausal' levels of FSH and LH are common in the perimenopause and that they are rare in premenopausal women.

16 GONADOTROPIN SECRETION IN GONADAL PATHOLOGY IN CHILDREN

Top of pageAbstract Gonadal insuficiency was previously diagnosed because of lack of sexual development at puberty. The gonadotropic response to Gn-RH was studied in pre and post pubertal patients with anorchia and ovarian dysgenesis. In 16 patients with anorchia, aged 1 to 16 years, basal and post stimulation FSH and LH, were significantly higher than in cryptorchid patients, but comparable to anorchid adult men. Twenty three pre and post pubertal girls with Turner's syndrome and chromosomal constitutions XO; XO/XX; XO/Xr; XXqi and XO/Xqi were also studied. In the XO group, values were always significantly elevated, however, in the others, normal and high gonadotropin levels, specially FSH were observed in prepubertal patients. These findings demonstrate that prepubertal gonadotropin increase would indicate absence of functional testicular tissue in the male and in girls with Turner's syndrome and mosaicism or structural abnormalities of X chromosome the existence of ovarian agenesis like in the XO syndrome. On the contrary, normal levels would indicate the presence of functional ovarian tissue.

Large solitary luteinized follicle cyst of pregnancy and puerperium: A clinicopathological analysis of eight cases.

Eight cases of a rare type of ovarian cyst with distinctive clinical and pathologic features are reported. The patients presented with a palpable adnexal mass during pregnancy or the puerperium, or with a unilateral ovarian cyst during cesarean section at term. There were no associated endocrine disturbances. The cysts were large, solitary and unilocular and had a median diameter of 25 cm. On microscopical examination they were lined by luteinized cells that exhibited focal marked nuclear atypicality. All six patients who were followed postoperatively were alive and well at intervals of 5--68 months, suggesting that the cysts were luteinized follicle cysts related to the high gonadotropin levels of pregnancy rather than cystic neoplasms.

Is the Incubation Patch Required for the Construction of a Normal Nest?

-New methods are presented for examining the function of the incubation patch in the nest-building process. These involve direct interference with the tactile sensitivity of the brood patch and hence its ability to assess nest size and texture. The patch may be covered with a pliable plastic apron or rendered completely insensitive to touch by surgical denervation. Data from several experiments employing such methods indicate that the incubation patch is not required for construction of a nest of normal size and composition by Canaries. In addition, its absence does not affect the birds' disinterest in nest-building as egg-laying approaches. The results suggest that receptors in places other than the incubation patch may be used in its absence to assess nest quality and size. More than two decades ago, Robert Hinde (1958) published his classic monograph on the nest-building behavior of Canaries (Serinus canaria). In this and later papers (e.g., Warren and Hinde 1959, Hinde and Steel 1962, 1975, Steel and Hinde 1963, 1966, 1972a, b, Hinde 1965, 1967), he and his associates catalogued the Canary's stereotypic nest-building behaviors, demonstrated that estrogen and long daily photoperiods evoke them, and showed that certain characteristics of the nest modify them. In brief, when female Canaries are given grass and feathers as nest material and then photostimulated or treated with estrogen, they build a nest that consists of two discrete layers: an outer grassy one and an inner feather-rich one. The bird's early preference for material of coarse texture and later preference for feathers depends on the size and the texture of the nest. Increased interest in feathers as building material occurs whenever the nest cavity is small or has a rough, grassy texture. In addition, building activity declines before the bird lays its clutch because the nest cavity is small and has a rough texture (Hinde 1958, 1965, Steel and Hinde 1977). Photostimulated Canaries exhibit high endogenous levels of gonadotrophins and estrogen which induce the formation of an incubation patch in the ventral apterium near the time when the nest is being constructed (Steel and Hinde 1963, Hutchison et al. 1967, Follett et al. 1973). The incubation patch is well endowed with superficial nonmyelinated nerve fibers (Kern and Coruzzi 1979) and is highly sensitive to touch (Hinde et al. 1963). Several nestbuilding b haviors (scrabbling, turning, weaving, and pressing down) bring it into intimate contact with the forming nest. Apparently, this area of skin provides the central n rvous system with information about nest quality and size during such contact and in this way brings about modifications and cessation of building activities. Hinde proposed these functions for the incubation patch on the basis of experiments in which he altered the Canary's nest-building activities by modifying the nest. In this paper, we reexamine the role of the incubation patch in the nest-building process by using different methods that directly affect the sensitivity of the skin. In some cases, we monitor building behavior directly, as did Hinde, but more often we use the structure of the nest to tell us about the bird's building behavior. Because the nest is built from the outside in, differences in the composition of its outer and inner layers reflect differences in the Canary's preference for materials such as grass and feath-

A Gonadotrophin Responsive Testosterone Producing Adrenocortical Adenoma and High Gonadotrophin Levels in an Elderly Woman

SUMMARY A gonadotrophin responsive testosterone producing adrenal cortical adenoma in a 61–year-old woman is described. Oophorectomy was performed before adrenalectomy as at first an ovarian origin of excess androgen production was suspected. The hypophyseal gonadal feedback system was studied after oophorectomy using LHRH before and after administration of ethinyloestradiol. After adrenalectomy this study was repeated using ethinyloestradiol at two dose levels and after premedication with testosterone. In this patient the LH feedback system behaved similarly to that observed in Klinefelter's syndrome and in patients with anorchia.

Photoperiodic control of seasonal breeding in the ram: participation of the cranial sympathetic nervous system.

Four mature Soay rams, cranially sympathectomized by removal of the superior cervical ganglia, were housed alongside four normal rams controlled lighting conditions of alternating 16 week periods of short days of 8 h light: 16 h darkness (8L : 16D) and long days (16L : 8D). The changes in the concentration of FSH, LH, prolactin and testosterone in the plasma, the size of the testes, the intensity of the sexual flush and the sexual and aggressive behaviour of the animals were recorded. While the control rams were able to respond to the artificial lighting conditions with synchronized cycles of reproductive activity, the ganglionectomized animals failed to respond. The treated rams had well-developed testes and relatively high levels of gonadotrophins and testosterone in the blood throughout the experiment. It is concluded that the cranial sympathetic nervous system is involved in the photoperiodic control of seasonal breeding in the ram, probably through its role in the innervation of the pineal gland.