Effects Of Hypothalamic Lesions Research Articles

Evaporative cooling in the rat: effects of hypothalamic lesions and chorda tympani damage.

Previous studies have demonstrated the importance of saliva spreading for evaporative cooling by rats in the heat. In particular, submaxillary–sublingual salivary gland function must be unimpaired for the rat to regulate its body temperature at ambient temperatures above 38 °C. The present study investigated some of the neural components of this thermoregulatory effector system. Bilateral destruction of the chorda tympani, the parasympathetic innervation of the submaxillary–sublingual glands, severely impaired the rat's tolerance of high ambient temperatures. Rats with bilateral electrolytic lesions in the anterior or lateral hypothalamus, placed without chorda tympani damage, also showed pronounced deficits in salivary evaporative water loss and impaired thermal tolerances during heat stress. Other heat loss mechanisms, such as peripheral vasodilatation, may also have been disrupted. These results support previous reports of thermoregulatory deficits in rats following hypothalamic lesions.

The effect of hypothalamic lesions on the melanocyte-stimulating hormone content and histology of the pars intermedia of the rat pituitary gland.

1. The effect of bilateral lesions in the anterior hypothalamus on the histology and content of melanocyte-stimulating hormone (MSH) of the pars intermedia has been studied in the adult male rat.2. By 7-15 days striking histological changes, suggestive of hyperactivity, were evident. These changes were accompanied by an elevated MSH content, which was particularly noticeable at 7 days.3. By 7 days there was an increase in the acid phosphatase activity of pars intermedia cells, as demonstrated histochemically.4. It was concluded that a hypothalamic control system exists for the mammalian pars intermedia and may involve both inhibitory and excitatory components.

Effect of hypothalamic lesions on the time course of corticosterone secretion.

Effect of hypothalamic lesions on the time course of corticosterone secretion.

Effects of hypothalamic lesions on incidence and growth of mammary tumors in carcinogen-treated rats.

SummaryIntact and ovariectomized Sprague-Dawley rats with ME lesions placed prior to treatment with DMBA, showed a 30 and 0% mammary tumor incidence, respectively, in contrast to a 95 and 54% mammary tumor incidence in the respective nonlesioned control groups. Intact and ovariectomized rats lesioned 75 days after DMBA treatment showed a 120 and 80% increase, respectively, in number of palpable mammary tumors 10 days after treatment. In contrast the non-lesioned intact and ovariectomized control groups showed a 19% increase and a 27% decrease in number of palpable mammary tumors, respectively. After 25 days, stimulation of mammary tumor growth was still marked in the intact-lesioned group but regression occurred in the ovariectomized-lesioned group. These results indicate that ME lesions placed before DMBA treatment inhibit mammary tumorigenesis, presumably by increasing prolactin secretion and stimulating mammary growth, thereby leaving the mammary glands refractory to DMBA; ME lesions placed 75 days aft...

The effect of hypothalamic lesions on sexual maturation and growth in female rats

生後2週令の幼若雌ラットの視床下部を電気的に破壊し,以後の性成熟および成長過程を観察し,以下の成績を得た。先端を1mm露出させたステンレス製電極を視床下部破壊に用いたとき,処理により,1)成長はやや抑制され,腟開口時の体重は全体的に低くなったが,腟開口日令と開口時の体重の分布の傾斜は無処置のものと大差なかった。2)腟開口の早められるものが現われた(平均30.3日,同腹の対照:平均40.1日)。3)肥満を伴ない性腺が未成熟の状態に留まるものが生じた。切断面のみを露出させた白金電極を用いたとき,処理により,1)成長は無処理のものと大差なかった。2)前部視床下部を破壊したものは,無処理のものと変らない成長で,腟開口を早めた(平均30.4日,対照:平均36.7日)。

The effect of hypothalamic lesions on sexual maturation and growth in male rats

The effect of hypothalamic lesions on sexual maturation and growth in male rats

Effect of Hypothalamic Lesions on Pituitary-Adrenocortical Responses to Histamine and Methopyrapone

A study to determine the effect of destructive hypothalamic lesions on pituitaryadrenocortical responses following the administration of histamine and methopyrapone (metyrapone) has been carried out in dogs. Adrenocortical responses were evaluated by an increase in the secretory rate of 17-OHCS in adrenal venous blood collected by the retention cannula method. The responses to histamine and to methopyrapone were both suppressed by anterior hypothalamic lesions. In dogs with posterior hypothalamic lesions, the response to histamine was normal, while that to methopyrapone was suppressed. On the basis of these findings, a functional dichotomy of the hypothalamus concerning the regulatory mechanism of ACTH secretion is proposed. (Endocrinology 81: 941, 1967)

Effect of hypothalamic lesions on MSH content of the intermediate lobe of the pituitary gland in the rat.

Es wird gezeigt, dass Elektrokoagulation in verschiedenen Teilen des basalen Hypothalamus einen Einfluss auf den Melanophorenhormongehalt im Hypophysenzwischenlappen der Ratte hat.

The effect of hypothalamic lesions on adrenal function in intact and adenohypophysectomized cockerels

Electrolytic lesions in the ventral tuberal area of the hypothalamus had contrary effects upon adrenal function of intact and adenohypophysectomized cockerels, as measured by corticosterone concentration in adrenal vein plasma: adrenal function decreased in intact birds, while it increased in adenohypophysectomized birds. Lesions in any other area of the hypothalamus had no influence upon adrenal function. Interrenal tissue atrophied in adrenals of adenohypophysectomized cockerels, and there was loss of differentiation between interrenal and chromaffin tissue. The interrenal tissue at the periphery appeared stimulated and exhausted of its granulation. Adrenals of adenohypophysectomized birds which were also lesioned showed little change from those in adenohypophysectomized birds. Interrenal cells in the periphery of adrenals of intact birds which were lesioned showed a decrease in activity, and an increase in amount proportional to chromaffin tissue. The histology of adrenal interrenal cells lying between the periphery and the center of the gland appeared to reflect the levels of corticosterone concentration in adrenal vein plasma. While adenohypophysectomy caused a decrease in adrenal weight, hypothalamic lesions had no effect. While the data appears to support the current view of the role of the hypothalamo-hypophyseal axis in regulation of adrenal function in intact cockerels, there is no indication from this study that the extrahypophyseal support for adrenal function in adenohypophysectomized cockerels resides in the hypothalamus.

Effect of hypothalamic lesions on histamine toxicity in the guinea pig.

Effect of hypothalamic lesions on histamine toxicity in the guinea pig.

Effects of hypothalamic lesions and testosterone on aortic oxygen uptake in rats

Effects of hypothalamic lesions and testosterone on aortic oxygen uptake in rats

Hypothalamic regulation of growth hormone secretion.

To investigate neural control of growth hormone (GH) secretion, the effect of hypothalamic lesions on resting GH plasma concentrations and GH response to insulininduced hypoglycemia was studied in squirrel monkeys. Plasma GH was determined by radioimmunoassay using a human growth hormone system. In 9 control animals with small lesions in the frontal cortex, hypoglycemia induced by the intravenous injection of insulin, 0.15 U/kg body wt, led to an acute rise in GH. Of 16 animals with lesions in various basilar brain structures, 8 had either markedly reduced or completely blocked GH responses to hypoglycemia. Anatomical analysis of the site of the lesions suggests that the anterior median eminence, central median eminence and pituitary stalk mediate reflex GH discharge. Resting levels of GH were not altered by hypothalamic lesions, a finding which is indicative of a reasonable degree of autonomy of basal GH secretion. During the first hr of the insulin tolerance test, blood sugar changes had a similar time ...

5-HYDROXYTRYPTOPHAN DECARBOXYLASE IN RAT BRAIN: EFFECT OF HYPOTHALAMIC LESIONS.

Section of the medial forebrain bundle within the lateral hypothalamus of the rat reduces the serotonin content and the 5-hydroxytryptophan decarboxylase activity in the brain. The integrity of this fiber tract appears necessary for the maintenance of normal concentrations of the amine and enzyme in the telencephalon.

EFFECT OF HYPOTHALAMIC LESIONS ON RAT ANAPHYLAXIS.

The present study investigated the effect of anterior and posterior hypothalamic lesions on lethal anaphylaxis in the rat. Three groups of animals—control, posterior hypothalamic lesioned, and anterior hypothalamic lesioned—were sensitized to ovalbumin and subsequently challenged with various doses of the antigen. Dose-mortality curves were plotted for the control and two experimental groups. The three curves were demonstrated to be parallel. Ovalbumin was significantly less potent in the animals with anterior hypothalamic lesions than in both the control rats and those with posterior lesions. The protective action of anterior hypothalamic lesions against lethal anaphylaxis in the rat is discussed in terms of neuroendocrine processes, parasympathetic-sympathetic effects and antibody formation.

EFFECTS OF HYPOTHALAMIC LESIONS ON THE ERYTHROPOIETIC RESPONSE TO HYPOXIA IN RABBITS.

AbstractPrevious studies have indicated that electrical stimulation of the hypothalamus increases erythropoiesis (Seip et al. 1961) and erythropoietin production (Halvorsen 1961). The effects of hypothalamic lesions on the erythropoietic response to hypoxia have been investigated in the present study. The lesioned rabbits were exposed to low oxygen and the erythropoietic response evaluated by means of reticulocyte counts. Eleven out of 26 rabbits showed a normal response to hypoxia while 15 showed a reduced response. Of these 15 rabbits, 6 showed a normal response when ACTH was given prior to the hypoxic test indicating that the reduced response to hypoxia in these rabbits was due to ACTH deficiency following the hypothalamic lesion. The lesions in these 6 rabbits were in the ventral and median part of hypothalamus. Seven out of the 15 rabbits neither responded normally to hypoxia alone nor to hypoxia following ACTH injections. The lesions in these 7 rabbits were in the posterior part of the hypothalamus. It is concluded that an extra‐pituitary influence on erythropoiesis may be exerted from this region.

EFFECT OF HYPOTHALAMIC LESIONS ON PITUITARY PROLACTIN CONTENT IN THE RABBIT.

Hypothalamic lesions have been shown to induce lactation, but their mechanisms of action have not been understood. In the present study the effects of lactation-inducing hypothalamic lesions on pituitary prolactin were assessed in mature New Zealand female rabbits. The rabbits were ovariectomized and primed 10 days with estradiol benzoate. On day 12 an electrolytic lesion was placed in the basal hypothalamus, and autopsy was performed on day 15. Mammary gland activation was classified both grossly and by histologic examination. Pituitary prolactin was assayed by an intradermal crop sac method employing White King squabs. In rabbits which failed to show mammary gland activation, the lesions lay outside the posterior tuberal area, and pituitary prolactin content was high. Conversely, the mammary glands were markedly activated in rabbits with lesions involving the posterior tuber, and pituitary prolactin was low. Results indicate that the activation of mammary glands by hypothalamic lesions is an effect exer...

THE EFFECT OF HYPOTHALAMIC LESIONS ON GROWTH

THE EFFECT OF HYPOTHALAMIC LESIONS ON GROWTH

Clinical use of a new diagnostic agent, methopyrapone (SU-4885), in pituitary and adrenocortical disorders.

Excerpt Disorders involving the adrenocortical secretion of cortisol have become more precisely characterized within recent years as knowledge concerning pituitary-adrenal physiology has increased ...

The effect of hypothalamic lesions on the testes and prostate of male dogs.

The effects of hypothalamic lesions on testicular function were studied in 21 mature male dogs. Destruction of the posterior median eminence (S dogs) resulted in testicular and prostatic atrophy without evidence of adrenocortieiil or thyroid inhibition. In these dogs, seminiferous tubule diameter and testicular and prostatic weight and histology were similar to those of hypophyscctomized dogs. One animal with a lesion involving the most caudal part of the posterior median eminence had atrophic seminiferous tubules and normal interstitial tissue. In 12 animals lesions did not involve the posterior median eminence, and testicular weight and histology were normal. Serial evaluation of sperm count and motility in 13 of the dogs with lesions revealed a prompt disappearance of motile sperms in four of the six animals with posterior median eminence lesions. In the other two dogs, spermatogenesis persisted for eight and 21 days respectively before declining to negligible levels. Four dogs with lesions in the anterior and middle median eminence showed a moderate decline in the number and motility of spermatozoa ejaculated, without atrophy of the gonads. Sperm count and motility remained normal in two of three dogs with normal testes and lesions sparing the median eminence. The significance of these findings is discussed.

The effects of hypothalamic lesions on conditioned avoidance learning.

The effects of hypothalamic lesions on conditioned avoidance learning.