摘要:

Electrical stimulation of the hypothalamus in 181 mature female Holtzman rats with monopolar electrodes, using 1.0 mA intensity square wave pulses of 5 msec duration and 50 cps, showed that plasma growth hormone rises occurred only when the stimulation sites were located in the ventromedial hypothalamic nuclei, their border zones, and the median eminence. Equivocal growth hormone changes were observed in several anterior and posterior hypothalamic areas and are attributed to a spread of current via intrahypothalamic fiber systems. The results suggest that the hypothalamic control of growth hormone secretion is localized in the immediate vicinity of the ventromedial nuclei.

ISSN:0028-3835    

DOI:10.1159/000121967

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

The amount of endogenous dopamine available for release was reduced by the ‘false transmitter’-forming precursor α-methyl-dopa in immature female rats during the ‘critical period’ of the day of pro- estrus. The drug was microinjected into various parts of the hypo- thalamus and into the pituitary, in order to block dopaminergic transmission at discrete, well-determined levels of the LH-release controlling structures of the brain; the dosage of the drug was kept very low. Microinjections of α-methyl-dopa resulted in ovulation blockade only when applied to the medio-basal part of the infundibulum; microinjections into other hypo-thalamic sites, or directly into the pituitary, were ineffective in our experimental conditions. It is concluded that dopamine release from terminals of the tubero-infundibular tract is stimulatory to the discharge of pituitary ovulating hormone, and that it plays an essential role in the control of ovulation during the ‘criti

ISSN:0028-3835    

DOI:10.1159/000121968

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

Removal of eyes from young male rats led to slight retardation in body weight gain, tibial length, and tail length compared with respective parameters measured in normal rats. Young rats lacking eyes and pineal glands presented body weights, tibial lengths, and tail lengths that approached normal. Pituitary levels of radio-immunoassayable growth hormone (GH) were significantly lower in blinded rats with intact pineal glands compared with levels in normal or blinded-pinealectomized rats. Plasma levels of GH tended to be lower in blinded and blinded- pinealectomized rats relative to normal levels; however, due to the wide range of GH levels in all groups, no statistically significant differences were observed. Blindness and anosmia in young male rats severely retarded body weight gain, tibial length, and tail length relative to respective parameters of normal, blinded, blinded-pinealectomized, and blinded-anosmic-pinealectomized rats. Blinded-anosmic-pineal-ectomized rats grew subnormally, with body weights equal to those of blinded rats. Plasma GH concentrations were low in blinded-anosmic rats, but due to the overlapping values, statistical significance was not attained. In general, the size of reproductive organs correlated well with inhibition of body growth, being moderately smaller in blinded rats and markedly so in blinded-anosmic rats. These differences in the size of the reproductive organs were not observed if pinealectomy was performed simultaneously with blinding and olfactory bulb removal. It is concluded that, in young male rats that are deprived of light by blinding, there is a dramatic inhibition of GH production and release by the pituitary gland. This response, like the response of the reproductive organs, is enhanced when rats are deprived of both smell and light. These phenomena only occur in the presence of the pineal gland. Therefore, the pineal gland plays an important role in these processes. It is further concluded that anosmia or perhaps non-specific surgical stress may alter GH synthesis and/or release from the pituitary gland.

ISSN:0028-3835    

DOI:10.1159/000121969

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

The influence of alterations in blood volume on osmotically-induced vasopressin release has been determined in normal subjects. The plasma osmolality at which vasopressin release was initiated (osmotic threshold) in hydrated subjects receiving a maintained water load was determined by inducing hypertonicity either by infusion of 5% saline or by water deprivation. The osmotic threshold obtained by saline infusion was 286.6 ± 0.9 (SD) mOsm/kg, while that obtained by water deprivation was 282.2 ±2.0. These differences were significant and, together with previously reported data on the influence of plasma volume expansion with dextran, lend support to the concept that relatively small changes in plasma volume have a modifying effect on osmotically-induced release of vasopressin. A decrease in plasma volume lowers the osmotic threshold, while an increase in plasma volume increases the osmotic threshold for vasopressin releas

ISSN:0028-3835    

DOI:10.1159/000121970

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

Subcutaneous administration of crude rat hypothalamic extracts containing FSH-RF and devoid of any FSH and sex steroid contamination gives rise to a considerable reduction of FSH- RF stores in the hypothalamus of castrated-hypophysectomized rats. It is suggested that the brain contains receptors sensitive to circulating levels of FSH-RF and, possibly, of other releasing factors; it is also postulated that FSH-RF might directly regulate its own production, through what might be called an ‘ultrashort’ feedback eff

ISSN:0028-3835    

DOI:10.1159/000121971

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

Prepuberal patterns of pituitary luteinizing hormone (LH) con-tent in male and female rats were studied using the ovarian ascorbic acid-depletion bioassay technique. Pituitary LH content increases in both sexes until 26 days of age; however, the con-tent in the female is greater than in the male. After 26 days, pituitary LH content in the female reaches a plateau until the onset of puberty, at which time a significant fall in LH is observed coincident with vaginal opening and ovulation. Pituitary LH content in the male continues to rise beyond 26 days of age, surpassing the level in the female. A peak pituitary LH content is observed in males at 60 days with a fall to final adult levels by 75 days. Although puberty (defined as the time of appearance of sperm in penile smears) occurs later in the male than in the female rat, an increase in accessory sex organ weights, suggestive of increased gonadal steroid secretions, precedes the puberal fall of LH in both sexes. Testosterone administration to 1-day-old female rats inhibits the development of cyclicity and initially produces a prepuberal pattern of pituitary LH content similar to that of the male. However, after the appearance of the polycystic ovary syndrome at 40 days of age, a plateau is reached in pituitary LH content, and puberal changes characteristic of either the normal male or female are never observed.

ISSN:0028-3835    

DOI:10.1159/000121972

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

Hypothalamic and pituitary functions of 21-month-old rats in constant estrus were compared with those of 3-month-old cycling rats on the day of estrus. FSH-RF in the hypothalamus and pituitary FSH were significantly higher in the old than in the young rats. Pituitary LH was significantly lower in the old than in the young rats. Hypothalamic PIF was similar in both groups, but pituitary prolactin concentration was significantly greater in the old rats. The old constant-estrous rats showed well-developed ovarian follicles but no corpora lutea, increased uterine weight, hyperplastic mammary glands, and increased pituitary weight. It is suggested that the constant estrus observed in many old female rats is the result of a fundamental change in hypothalamic control of pituitary FSH, LH, and prolactin secretion.

ISSN:0028-3835    

DOI:10.1159/000121973

出版商:S. Karger AG    

年代:1971

数据来源: Karger