HYPOTHALAMIC CONTROL OF PITUITARY GONADOTROPHINS

1961 ◽  
Vol 22 (1) ◽  
pp. 107-117 ◽  
Author(s):  
C. C. GALE ◽  
S. M. McCANN
Keyword(s):  
Diabetes Insipidus ◽  
Median Eminence ◽  
Oestrogen Therapy ◽  
Milk Ejection ◽  
Pregnant Rats ◽  
Tuber Cinereum ◽  
Severe Diabetes ◽  
Hypothalamic Control ◽  
Electrolytic Lesions ◽  
Experienced Difficulty

SUMMARY Impairments in gestation, parturition, and milk ejection were produced when electrolytic lesions were placed in the median eminence of the tuber cinereum of pregnant rats at various stages of gestation. Thus, uterine implantation of ova was blocked in 65% of rats following placement of lesions on day 1 of gestation, and implantation of ova was induced in these animals by administration of oestrogen. When lesions localized to the caudal median eminence were placed on days 4–9, implantation was not blocked but abortion-resorption resulted in 90% of cases. Replacement studies during pregnancy in rats with lesions in the caudal median eminence suggest that (1) all aborting rats were deficient in gonadotrophins necessary for secretion of oestrogen, and (2) half of them were deficient in luteotrophin as well. (That is, luteotrophin had no replacement value, while oestrogen therapy permitted maintenance of gestation in 54% of cases, and oestrogen plus progesterone allowed 100% to remain pregnant.) In rats receiving lesions on days 7–9 and maintaining gestation to term, 32% of those with severe diabetes insipidus experienced difficulty during delivery. Placement of lesions after day 13 impaired neither gestation nor parturition. The observation that most rats with lesions were able to deliver their litters normally but were unable to eject milk following suckling stimuli suggests that oxytocin is not essential for parturition in this species. Most of the rats with lesions failed to resume oestrous cycles; of the few showing return of normal or irregular cycles, the majority failed to mate.

PERMANENT ISOLATION OF THE ADENOHYPOPHYSIS FROM HYPOTHALAMIC CONTROL IN RATS WITH DIABETES INSIPIDUS

1964 ◽  
Vol 30 (3) ◽  
pp. 377-NP
Author(s):  
G. C. KENNEDY ◽  
R. A. PARKER
Keyword(s):  
Diabetes Insipidus ◽  
Median Eminence ◽  
Posterior Part ◽  
Normal Weight ◽  
Aldehyde Fuchsin ◽  
Thyroid Uptake ◽  
Electrolytic Lesions ◽  
Cytological Changes ◽  
The Difference ◽  
Portal Veins

SUMMARY Electrolytic lesions in the posterior part of the median eminence of rats caused diabetes insipidus, and aldehyde-fuchsin-positive material disappeared from the infundibular process but not from the hypothalamus. The lesions were consistently followed by infarction of the central pars distalis and depression of the thyroid uptake of radioactive iodine, but the effects on the gonads and adrenal cortex were very variable. Chronic adrenal atrophy occurred in some females in association with recurrent pseudopregnancy, atrophic but hyperluteinized ovaries, and cytological changes in the pituitary similar to those in ectopic grafts. After a short post-operative period of pseudopregnancy other rats recovered normal cycles and had, in general, adrenals of normal weight; their pituitaries resembled ectopic grafts returned to the median eminence. It is suggested that the difference between the two groups of rats with chronic lesions depended on the permanence or otherwise of the damage to the long portal veins. No evidence could be found of a separate corticotrophin-releasing mechanism in the median eminence, nor of any dependence of the secretion of corticotrophin on the release of vasopressin.

PLASMA CORTICOSTERONE IN RATS WITH EXPERIMENTAL DIABETES INSIPIDUS

1963 ◽  
Vol 27 (3) ◽  
pp. 345-353 ◽  
Author(s):  
G. C. KENNEDY ◽  
H. S. LIPSCOMB ◽  
P. HAGUE
Keyword(s):  
Diabetes Insipidus ◽  
Median Eminence ◽  
Experimental Diabetes ◽  
Plasma Corticosterone ◽  
Normal Range ◽  
Mean Values ◽  
Ether Anaesthesia ◽  
Electrolytic Lesions ◽  
The Mean

SUMMARY Electrolytic lesions were produced in the median eminence in a series of rats; the resultant diabetes insipidus varied in severity over the whole range expected from this type of operation, and no part of the median eminence was spared. Plasma corticosterone was estimated both under resting conditions and after ether anaesthesia, and at different intervals after the induction of polyuria. Although the levels under both conditions were variable, the variability was not correlated with the severity of the polyuria, and the mean values were in the normal range.

HORMONAL BASIS FOR IMPAIRMENTS IN MILK SYNTHESIS AND MILK EJECTION FOLLOWING HYPOTHALAMIC LESIONS

1961 ◽  
Vol 23 (3) ◽  
pp. 303-316 ◽  
Author(s):  
C. C. GALE ◽  
S. TALEISNIK ◽  
H. M. FRIEDMAN ◽  
S. M. McCANN
Keyword(s):  
Median Eminence ◽  
Adrenal Glands ◽  
Regulatory Mechanisms ◽  
Adrenocorticotrophic Hormone ◽  
Milk Ejection ◽  
Hypothalamic Lesions ◽  
Severe Impairment ◽  
Electrolytic Lesions ◽  
Hypophysectomized Rats ◽  
Pituitary Secretion

SUMMARY The placing of electrolytic lesions in the median eminence of the hypothalamic tuber cinereum induces severe impairment of lactation in rats by causing deficiencies in pituitary secretion of adrenocorticotrophic hormone (ACTH; essential for milk synthesis) and of oxytocin (necessary for milk ejection). Thus, in rats with lesions given oxytocin × 2/day to permit milk ejection, it was observed that: (1) the severity of impairment in lactation correlated significantly with the degree of atrophy of the dams' adrenal glands; (2) administration of luteotrophin (LTH) failed to repair this defect in lactation; (3) when cortisol was administered milk production was markedly improved—to about 70–80% of normal for days 5–10—(a further slight increase in milk yield resulted when oxytocin injections were given every 4 hr. 'around the clock' to rats receiving cortisol therapy); and (4) administration of regimens consisting of either LTH and cortisol, or LTH, growth hormone (GH), and cortisol failed to improve lactation beyond levels attained with cortisol therapy alone. In hypophysectomized rats replacement with cortisol and LTH, plus oxytocin × 2/day, permitted substantial synthesis which was not significantly improved further when GH was added to the regimen, and which promptly declined when LTH therapy was withdrawn. Since no deficiency in secretion of LTH could be demonstrated in lactating rats with lesions given hormonal replacement, these data provide evidence that elimination of hypothalamic regulatory mechanisms by hypothalamic lesions is compatible with secretion of large amounts of LTH. This demonstration that lesions in the median eminence block release of ACTH while permitting continued secretion of LTH indicates that the hypothalamic mechanisms regulating their release are not identical.

THE EFFECT OF HYPOTHALAMIC LESIONS ON REPRODUCTIVE ACTIVITY IN SHEEP

1967 ◽  
Vol 39 (3) ◽  
pp. 415-NP ◽  
Author(s):  
H. M. RADFORD
Keyword(s):  
Median Eminence ◽  
Reproductive Activity ◽  
Mammillary Body ◽  
Optic Chiasma ◽  
Hypothalamic Lesions ◽  
Apparent Change ◽  
Electrolytic Lesions ◽  
Releasing Factors ◽  
Bilateral Lesions ◽  
Made In

SUMMARY Electrolytic lesions were made in the hypothalamus of 41 Merino ewes which were subsequently observed for 2–16 months. Ovarian inactivity resulted from bilateral medial and ventral lesions placed immediately posterior to the optic chiasma (four ewes) or immediately anterior to the mammillary body (five ewes). Failure to show oestrus while apparently still ovulating regularly was a feature in another four ewes in which bilateral medial and ventral lesions were placed between the sites already described. Small bilateral lesions in these ventral regions led initially to ovarian inactivity, but final re-establishment of apparently normal reproductive activity in three ewes. Bilateral lesions in regions other than those described above resulted in no apparent change in reproductive activity (eight ewes). Similarly, unilateral or asymmetrical lesions in the remaining 17 ewes failed to affect their reproductive activity. The results are consistent with the hypothesis that in sheep a region of the median eminence responsible for the production of gonadotrophin-releasing factors requires neural inputs traversing both anterior and posterior hypothalamic areas.

EFFECT OF VARIOUS ABLATIONS IN THE HYPOTHALAMUS ON ESTABLISHED PREGNANCY IN THE RAT

1967 ◽  
Vol 45 (6) ◽  
pp. 1081-1091 ◽  
Author(s):  
S. A. Holloway ◽  
J. A. F. Stevenson
Keyword(s):  
Anterior Pituitary ◽  
Hypothalamic Control ◽  
Fetal Birth Weight ◽  
The Face ◽  
Electrolytic Lesions ◽  
Ad Libitum ◽  
Maternal Resources ◽  
Made In ◽  
Length Of Gestation

To investigate the role of the hypothalamus in the maintenance of established pregnancy, bilateral electrolytic lesions were made in various regions of the hypothalamus in Wistar rats on day 10 of gestation. These lesioned rats were compared with pair-fed controls, and controls fed ad libitum. No significant differences were noted between lesioned and pair-fed control rats in litter and fetal weights, length of gestation, or stillbirth rates. Lesioned rats were able to complete their pregnancies to term. Fetal birth weight was normal or slightly subnormal in the face of significant decreases, and in one group an increase, in maternal food intake. After lesions in some regions of the hypothalamus, there were changes in maternal endocrine weights, suggesting a disturbance of hypothalamic control of the anterior pituitary. These results show that pregnancy can be maintained successfully in the presence of large symmetrical lesions in several regions of the hypothalamus and support the concept that the fetus is nourished at the expense of maternal resources.

ADIPSIA PRODUCED BY HYPOTHALAMIC LESIONS IN THE RAT

1957 ◽  
Vol 35 (1) ◽  
pp. 31-37 ◽  
Author(s):  
D. G. Montemurro ◽  
J. A. F. Stevenson
Keyword(s):  
Body Weight ◽  
Food Intake ◽  
Tap Water ◽  
Frontal Plane ◽  
Sprague Dawley ◽  
Stomach Tube ◽  
Tuber Cinereum ◽  
Lateral Hypothalamic ◽  
Electrolytic Lesions ◽  
General Improvement

With the use of the Horsley–Clarke stereotaxic instrument, bilateral electrolytic lesions were placed in the lateral hypothalamic areas of female Sprague–Dawley rats. Changes in food and water intake and body weight were correlated with the histological localization of the lesions. Rats with large lesions in the frontal plane of the middle of the tuber cinereum died within a week of the operation. Food and water administered by stomach tube did not prevent weight loss and death.Two rats developed adipsia which lasted 13 and 16 days respectively; 10 ml. of tap water per day by stomach tube resulted in increases in food intake and body weight during the period of adipsia. These rats had lesions in the lateral hypothalamic areas in the frontal plane of the middle of the tuber cinereum, but these were small and relatively asymmetrical.Another rat refused water from the time of operation until sacrifice (55 days). Administration of 20 ml. per day of tap water caused an increase in food intake and body weight, and a general improvement. Whenever intake of water was not imposed by stomach tube, however, the food intake dropped and body weight was lost. This animal failed to drink spontaneously. The lesions in this animal were more symmetrical, slightly more dorsal, and about 0.75 mm. more posterior than those which produced temporary adipsia. In the rat, an area essential to the regulation of voluntary consumption of water appears to be located in the lateral hypothalamic areas at about the plane of the posterior ventromedial nuclei and the anterior border of the premammillary nuclei.

Effects of chronic thyroid hormone administration on pregnancy, lactogenesis and lactation in the rat

1992 ◽  
Vol 127 (6) ◽  
pp. 547-554 ◽  
Author(s):  
Roberto R Rosato ◽  
Maria S Gimenez ◽  
Graciela A Jahn
Keyword(s):  
Mammary Gland ◽  
Maternal Behavior ◽  
Elevated Serum ◽  
Fatty Acid Synthetase ◽  
Milk Ejection ◽  
Serum Progesterone ◽  
Pregnant Rats ◽  
Severe Reduction ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Gland Content

We studied the effects of daily administration of 1 mg/kg thyroxine (T4) starting 10–15 days before mating, on parturition, maternal behavior and lactation in rats. Treated rats had elevated serum titers of T3 and T4, a greater number of fetuses and parturition was advanced approximately 12 h and lasted longer than in controls. None of the treated rats were able to lactate because of defects in maternal behavior and milk ejection; the litters died usually within 48 h postpartum. In rats sacrificed at 10.00 on day 21 of pregnancy, mammary gland content of total protein, phospholipids, casein and lactose were significantly increased, but total lipid was markedly reduced. Lipogenesis was also significantly increased, as well as the activity of the lipogenic enzymes glucose-6-phosphate dehydrogenase, fatty acid synthetase and isocytrate dehydrogenase. These results are indicative of normal albeit premature lactogenesis. The T4-treated rats also had advances in the prepartum fall in serum progesterone and the increase in prolactin as well as in the increase in mammary casein and lactose concentrations of approximately 12 h with respect to control pregnant rats. These results show that chronic T4 treatment induces an advance of approximately 12 h in luteolysis, which in turn advances lactogenesis and parturition in rats. Although the mammary gland was able to produce milk, lactation failed due to abnormal maternal behavior and milk ejection, the causes of which are still unknown. Other effects of hyperthyroidism were also present, such as a severe reduction in lipid content of the gland. The observed increases in lipogenesis and lipogenic enzyme activities could be due to a combination of the effects of hyperthyroidism per se as well as to the increase in lipogenesis that occurs during lactogenesis.

Prenatal exposure to ethanol causes partial diabetes insipidus in adult rats

2004 ◽  
Vol 287 (2) ◽  
pp. R277-R283 ◽  
Author(s):  
Daniel S. Knee ◽  
Aileen K. Sato ◽  
Catherine F. T. Uyehara ◽  
John R. Claybaugh
Keyword(s):  
Diabetes Insipidus ◽  
Water Intake ◽  
Plasma Osmolality ◽  
Liquid Diet ◽  
Female Rats ◽  
Adult Rats ◽  
Pregnant Rats ◽  
Adult Rat ◽  
Mrna Content ◽  
The Right

Chronic consumption of ethanol in adult rats and humans leads to reduced AVP-producing neurons, and prenatal ethanol (PE) exposure has been reported to cause changes in the morphology of AVP-producing cells in the suprachiasmatic nucleus of young rats. The present studies further characterize the effects of PE exposure on AVP in the young adult rat, its hypothalamic synthesis, pituitary storage, and osmotically stimulated release. Pregnant rats were fed a liquid diet with 35% of the calories from ethanol or a control liquid diet for days 7–22 of pregnancy. Water consumption and urine excretion rate were measured in the offspring at 60–68 days of age. Subsequently, the offspring were infused with 5% NaCl at 0.05 ml·kg−1·min−1 with plasma samples taken before and at three 40-min intervals during infusion for measurement of AVP and osmolality. Urine output and water intake were ∼20% greater in PE-exposed rats than in rats with no PE exposure, and female rats had a greater water intake than males. The relationship between plasma osmolality and AVP in PE-exposed rats was parallel to, but shifted to the right of, the control rats, indicating an increase in osmotic threshold for AVP release. Pituitary AVP was reduced by 13% and hypothalamic AVP mRNA content was reduced by 35% in PE-exposed rats. Our data suggest that PE exposure can cause a permanent condition of a mild partial central diabetes insipidus.

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