Showing papers on "Hypothalamus published in 1969"

Glucose and Osmosensitive Neurones of the Rat Hypothalamus

Abstract: THE lateral hypothalamic region (LH) is generally referred to as the feeding centre of the brain in the regulation of food intake, and many authors consider the ventromedial hypothalamic nucleus (VMH) to be the satiety centre1. Various hypotheses have been put forward to explain how the cells of these centres are activated, and one of these is the glucostat theory1. The existence of hypothalamic chemoreceptors, such as those sensitive to the concentration of blood glucose, can be inferred from studies of single unit discharges induced by intravenous or intracarotid administration of various solutions2–4 and from work on selective gold thioglucose lesions5. It has, however, been impossible to determine which centre is activated or inhibited first or whether both centres are modulated directly by a change in the concentration of blood glucose, because of the reciprocal relations which exist between the activities of the VMH and the LH2,6. We report here the direct effects of glucose on individual cells of the VMH and LH, which we studied by means of electro-osmotic applications of glucose from micropipettes—the method used by Krnjevic and Whittaker7 in other regions in the brain.

Control of body temperature in the unanaesthetized monkey by cholinergic and aminergic systems in the hypothalamus

Abstract: 1. In the unanaesthetized rhesus monkey, 5-hydroxytryptamine (5-HT), catecholamines, acetylcholine or carbachol were micro-injected in a volume of 1·0 μl. or less through chronically implanted cannulae at eighty-six sites in the hypothalamus. 2. 5-HT in doses of 2-10 μg caused a long-lasting elevation in temperature which was dose-dependent. An anatomical `mapping' of the hypothalamus revealed that the hyperthermic action of 5-HT was localized to the anterior, pre-optic area directly ventral to the anterior commissure. 3. Noradrenaline in doses of 1-12 μg produced a dose-dependent fall in temperature of short duration. An anatomical `mapping' showed that the hypothermic action of this and other catecholamines was again localized to the anterior, pre-optic region. 4. Acetylcholine, alone or in a mixture with eserine, or carbachol caused a dose-dependent hyperthermia which was characterized by an intense rise of short duration and vigorous shivering. A `mapping' of this response revealed a diffuse patterning of sites throughout the hypothalamus which were sensitive to the application of acetylcholine and carbachol. However, in one circumscribed region at the junction between the posterior hypothalamus and mesencephalon, the two cholinomimetic substances caused a marked fall in temperature. 5. We conclude that 5-HT activates a cholinergic heat production pathway which projects from the anterior to posterior hypothalamus. Noradrenaline, on the other hand, blocks the hyperthermic action of 5-HT rather than activates the heat loss system. A chemically mediated heat loss pathway apparently does not exist in the hypothalamus.

Autoradiographic analysis of estradiol uptake in the brain and pituitary of the female rat.

Abstract: The localization of 6,7-3H-estradiol in the brain and pituitary of the ovariectomized rat was studied by autoradiography. Estradiol was incorporated into cells of the dorsal part of the posterior third of the medial amygdaloid nucleus and the nucleus interstitialis stria terminalis and the lateral septal nucleus. The medial preoptic area had labeled cells along with periventricular and suprachiasmatic nuclei of the preoptic region. In the hypothalamus, the labeled cells were found in the arcuate nucleus and the pars lateralis of the ventral medial nucleus as well as the periventricular nucleus. In a time study, animals were killed at 2, 4, 6 and 8 hr after 3H-estradiol injection. The number of labeled cells at 2 hr was maximal. In each subsequent 2-hr interval, the number decreased by about one third. Thus, by 8 hr post injection there were essentially no labeled cells. Unlabeled estradiol (2 μg) given 1 hr before the injection of 3H-estradiol significantly decreased the accumulation of labeled estradiol ...

Structural Changes, Related to Reproduction, in the Hypothalamus and in the Pars Tuberalis of the Rhesus Monkey. Part I. The Hypothalamus. Part II. The Pars Tuberalis

Abstract: Certain cells lining a circumscribed area of the III ventricle of the rhesus monkey differ from those cells which constitute the characteristic ependymal lining of the brain. The specialized cells studied comprise a number of types which differ in their structure, ultrastructure and staining affinities; all demonstrate features which are generally associated with active secretion and/or absorption. A group of such cells, which form a limited area of the latero-ventral walls of the anterior hypothalamus, have long processes which extend to the walls of the blood vessels in the median eminence. The evidence indicates that many of these cells, here described as Type B or tanycyte cells, secrete their products into the primary capillary network of the pituitary portal system. Another group of cells, here described as Type C and $C'$ cells are found in a slightly more posterior position lining the floor of the ventricle; as yet there are no indications that these may secrete into blood vessels in the median eminence. Some of the specialized cells lining the III ventricle (Types B and C') showed changes in relation to reproductive activity: No such changes were observed in Type C cells nor in the characteristic ependymal cells (Type A) found elsewhere. Studies on normal and experimental male and female monkeys showed that Type B tanycyte cells differed in males and females and altered during the menstrual cycle in the female. Following ovariectomy these cells showed regressive changes but returned to a normal appearance after a single injection of oestradiol. In view of the close spatial relationship of the tanycyte ependyma to cells of the pars tuberalis it was interesting to note that pars tuberalis cells also altered in relation to the menstrual cycle. The evidence presented accords with the view that certain cells which line the III ventricle of the brain and have prolongations extending to pituitary blood vessels, thus linking the cerebrospinal fluid and the blood system in the region of the pituitary, may play a role in the regulation of pituitary function and thereby constitute an important neuro-endocrine system.

4 - Thyroid Function and Its Control in Fishes

Abstract: This chapter discusses the exhaustive review of thyroidal function in fishes. Much of the research on piscine thyroid physiology has merely established that in the broad sense it is not too different from thyroid function in other vertebrates. The chapter also discusses the four components of thyroid, such as (1) the brain, a complex of nervous afferents to a center, presumably in the hypothalamus, regulates pituitary thyrotropic secretion. (2) the pars distalis of the pituitary gland, and more precisely the thyroid-stimulating hormone (TSH) secreting cells in it, (3) the characteristic thyroid function is accumulation of iodine and the formation of the tyrosine derived hormone, thyroxine, and (4) the peripheral tissues of vertebrates, particularly in growing and differentiating animals, respond in a variety of ways to circulate thyroxine levels. These responses are basic metabolic phenomena; in part, they are structural and secretory responses.

Effects of Hypothalamic Stimulation, Hormones, and Drugs on Ovarian Function in Old Female Rats

Abstract: SummaryOld female rats in constant estrus were given different treatments in an attempt to induce ovulation. Subcutaneous injections of progesterone for 3 days or epinephrine for 10 days, induced ovulation in 6 out of 10 and 11 out of 22 rats respectively, with normal appearing estrous cycles observed in many epinephrine-treated rats. Electrical stimulation of the preoptic area of the hypothalamus produced ovulation in 3 out of 5 old rats. Injections of reserpine, thyroxine or cyproterone acetate, and cervical stimulation, failed to induce ovulation, whereas ovariectomy resulted in anestrus. These observations suggest that changes in hypothalamic function account for constant estrus in old female rats.

Influence of amphetamines on plasma corticosteroid and growth hormone levels in man

Abstract: Plasma fluorogenic corticosteroid and immunoreactive growth hormone levels rose significantly after the intravenous administration of methylamphetamine to healthy young men at various times of the day. The rise in corticosteroids was most pronounced in the evening and was accompanied by an increase in circulating levels of immunoreactive corticotrophin. Oral dexamphetamine also resulted in significant rises in plasma corticosteroids but not in growth hormone. These hormonal changes were accompanied by evidence of mild central stimulation. Though they may be part of an associated and non-specific response, it is more likely that they represent specific effects of amphetamines on centres in the hypothalamus or midbrain controlling secretion of corticotrophin and growth hormone releasing factors.

Electrical activity in the supraoptic and paraventricular nuclei associated with neurohypophysial hormone release

Abstract: 1. Unit recordings were made from the hypothalamus in anaesthetized male rats using steel or glass micro-electrodes. 2. Stimuli which are known to release vasopressin and oxytocin (electrical stimulation of the central end of the severed right vagus nerve and intracarotid injection of CaCl2 solution) also excite units in the supraoptic and paraventricular nuclei. In addition, these units are excited by intracarotid injections of carbachol, acetylcholine and NaCl (5%) which are less effective stimuli for vasopressin release. 3. These stimuli also excite units from which potentials can be evoked by stimulation of the pituitary stalk and which are likely to be neurosecretory neurones. Neurosecretory neurones can conduct electrical impulses like other less specialized nerve cells. Estimations of conduction velocity range between 0·4 and 1·3 m/sec. 4. The proportion of units in the supraoptic and paraventricular nuclei which are excited and the degree of excitation corresponds approximately to the amount of vasopressin released by the stimuli. In addition, excitation of the supraoptic nucleus seems to be more directly associated with vasopressin release and excitation of the paraventricular nucleus with oxytocin release.

Hyperphagia in Rats with Cuts between the Ventromedial and Lateral Hypothalamus

Abstract: Bilateral cuts between the ventromedial and lateral hypothalamus in female rats consistently produced hyperphagia. Hyperphagia occurred slightly less reliably when one of the cuts entered the ventromedial hypothalamus and only infrequently if one entered the lateral hypothalamus. The results are consistent with other evidence that suggests that fibers originating medially stop eating by inhibiting cells in the lateral hypothalamus.

Evidence for a Diurnal Rhythm of Corticotrophin-Releasing Factor (CRF) in the Hypothalamus

Abstract: Although diurnal rhythms in pituitary ACTH, blood ACTH and plasma corticosterone levels have been described, such changes in CRF activity in nonstressed animals have not heretofore been detected. In this study, a rhythm of hypothalamic CRF activity was observed in nonstressed male rats during controlled 24-hr light-dark cycles. Hypothalamic tissue was obtained from donor rats at 3-hr intervals. For CRF assay, acid extracts were administered to recipient rats which were either steroid-treated or lesioned in the ventral hypothalamus and CRF activity was estimated by the observed increase in plasma corticosterone. When hypothalamic extract was injected into lesioned rats, large increments in plasma corticosterone were observed and a good dose-response curve was obtained. In contrast, dexamethasone-treated, Diabutalized recipients showed a decreased sensitivity to the extract and a rather flat dose-response curve.When lesioned recipient rats were employed for CRF assay, detectable CRF activity was observed in...

Feeding and drinking following stimulation of the diencephalon of the monkey with amines and other substances

Abstract: In over 400 micro-injection experiments involving 70 loci within the brain stem of the conscious rhesus monkey (M. mulatta), the diencephalon was mapped in relation to changes in ingestive and other responses to chemical stimulation. Norepinephrine, in a wide range of doses, elicited eating and drinking in the satiated monkey when injected into the anterior-preoptic region, lateral hypothalamus, zona incerta, rostral tegmentum and the periventricular gray region medial to the ventromedial hypothalamus. Other compounds, in order of their potency, which produced ingestive responses were epinephrine, dopamine and serotonin (5-HT).

Influence of Estrogen on the Pituitary-Thyroid System of the Female Rat: Mechanisms and Loci of Action

Abstract: The influence of estrogen on the pituitary-thyroid system of the adult rat was determined after sc administration of small daily doses of estradiol benzoate (EB: .004, .016, .064 and .246 μg; 9–11 days) to 26–28 day ovariectomized animals and after pituitary implantation of 17β-estradiol in rats bearing median eminence lesions (18–39 days). It was demonstrated that estradiol has a biphasic action on TSH secretion and thyroid gland activity. Chronic administration of the .064 μg dose of EB produced thyroid hyperplasia. Lower doses of the steroid had no significant effect on thyroid histology, whereas a 4-fold increase in dose (.256 μg) induced histological regression in the gland (accumulation of colloid with reduction in acinar cell height). TSH blood titers and thyroid activity were markedly diminished in spayed ratswith hypothalamic lesions. Intrahypophysial estradiol implants in such animals stimulated thyroid function and significantly elevated TSH levels. Cholesterol implants were ineffective. The im...

Changes in Electrical Activity in the Rat Hypothalamus Related to Electrochemical Stimulation of Adenohypophyseal Function

Abstract: In the median eminence-arcuate nuclear region of the rat hypothalamus, a study has been made of the effects on multiple unit activity evoked by the application of ovulationinducing anodal DC electrochemical stimuli to the medial preoptic area. During the critical period of proestrus, with spontaneous ovulation blocked by pentobarbital, electrochemical stimulation (30 μA DC, 1–3 min) which was effective in releasing an ovulating amount of pituitary gonadotrophin (presumably largely LH) always caused an elevation in integrated multiple unit activity. The rise in activity started immediately, reached a peak around 9 min and lasted about 30 min. No elevation in multiunit activity appeared in a group of 4 rats which failed to ovulate in response to the electrochemical stimulus. Positive responses were also observed before and after the pentobarbital-blocked critical period, invariably related to induction of ovulation, and failure to respond to the stimulus with a rise in multiunit activity was again generally...

A quantitative analysis of the normal neuron population of the hypothalamic magnocellular nuclei in man and of their projections to the neurohypophysis.

Abstract: The supraoptic nucleus in man extends throughout the greater length of the hypothalamus and most of it is retrochiasmatic in location. It contains an average of 75,500 neurons, of which about two-thirds are in its dorsolateral portion (SON-dl) and one-third in its combined dorsomedial and ventromedial portions. The average density of neurons in SON-dl is 15,300 per mm3 and, unlike neuron frequency, is remarkably constant from specimen to specimen. The paraventricular nucleus has an average of 55,500 magnocellular neurons. In patients surviving one year or longer after hypophysectomy, there is retrograde loss of over 80% of neurons in both the supraoptic and paraventricular nuclei. Neuron loss occurs uniformly thrughout the length of each nucleus. Density decrease in SON-dl is almost exactly proportional to decrease in neuron frequency. It is concluded from these observations that most of the neurons throughout the entire extent of both the supraoptic and paraventricular nuclei in man project to the posterior lobe of the neurohypophysis and that there are over 200,000 fibers in the hypophysial stalk.

The role of the median eminence in control of photoperiodically induced testicular growth in the white-crowned sparrow. Zonotrichia leucophrys gambelii.

Abstract: Midline electrolytic lesions were created in the basal hypothalamus of adult white-crowned sparrows, Zonotrichia leucophrys gambelii, in order to explore further the neuroendocrine basis of photoperiodic control of testicular growth. Lesions that destroyed the anterior and posterior divisions of the median eminence (AME and PME) prevented photoperiodically induced testicular growth, confirming the previously reported experiments of Wilson (1967) on this species. Destruction of the PME alone also abolished photoperiodic testicular growth. Destruction of the AME usually had no inhibitory effect. Moreover, extraeminential lesions that interrupted a majority of the fibers of the supraoptico-hypophysial tract thereby causing a marked depletion of stainable neurosecretory material from the AME had, in all but two birds, no noticeable effect on testicular growth. On the other hand, destruction of selected regions of the infundibular nucleus, without involvement of the median eminence, suppressed the photoperiodic testicular response. Destruction of the posterior region of the infundibular nucleus, causing antegrade degeneration of tubero-hypophysial fibers into the PME, also suppressed the testicular response. These results suggest that the infundibular nucleus may be composed of separate cellular populations functioning in the control of photoperiodically induced testicular growth and that only one of these may contribute neuronal elements to the neurohemal organs of the PME.

Inhibition by Dexamethasone of the in Vivo Pituitary Response to Corticotropin-Releasing Factor (CRF)1

Abstract: Dexamethasone phosphate in doses ranging from 0 (vehicle control) to 2 μg/rat was injected into both lobes of the anterior pituitary, or into the median eminence or septa region of the brain. Endogenous CRF release was provoked by scald. Dexamethasone bilaterally in the anterior pituitary inhibited ACTH release after scald in doses of 100 ng/lobe or greater. These doses of dexamethasone were ineffective against scald when given intravenously. These results indicated that endogenous CRF-induced ACTH secretion is a corticosteroid-sensitive process, and that the anterior pituitary may be a corticosteroid feedback point. To test this conclusion further, we studied the effect of intrapituitary dexamethasone on the ACTH release induced by exogenous ovine CRF. Intrapituitary dexamethasone was again effective in preventing ACTH release. When similar small doses of dexamethasone were placed in the anterior medial basal hypothalamus, they were effective in stopping the adrenocortical response both to scald and to e...

Increased turnover of 3H-norepinephrine in rat brain following castration or treatment with ovine follicle-stimulating hormone.

Abstract: Castration or treatment with exogenous follicle-stimulating hormone (FSH) both increase the turnover of 3H-norepinephrine in rat brain. The effect of castration is greatest in the hypothalamus and midbrain, and is probably mediated by endogenous FSH. The action of FSH is independent of the gonads, and is not shared by luteinizing hormone. (Endocrinology 84: 1489, 1969)

Effects of hypothalamic and amygdaloid lesions on development and growth of carcinogen-induced mammary tumors in the female rat.

Abstract: The effects of median eminence and preoptic and amygdaloid lesions on normal and 7,12-dimethylbenzanthracene-induced neoplastic mammary tissue growth were investigated in female Sprague-Dawley rats. Marked stimulation of normal and neoplastic mammary tissue growth was observed in intact rats 10 and 25 days after placement of median eminence lesions. When median eminence lesions and ovariectomy were combined, a striking stimulation of normal and neoplastic tissue was noted 10 days but not 25 days later. If ovariectomy preceded the median eminence lesions by 10 days, no effect was observed on neoplastic mammary growth, and only a slight stimulation of normal mammary growth was observed 10 days after lesion placement. Since lesions in the median eminence result in enhanced prolactin secretion and reduced secretion of all other anterior pituitary hormones, these observations indicate that prolactin is the principal hormone responsible for growth of the 7,12-dimethylbenzanthracene-induced mammary tumors. Lesions in the preoptic or amygdaloid complex of intact rats induced marked tumor regression 10 or 25 days after lesion placement, but they apparently had no effect on normal mammary development 10 days after lesion placement. The reduction in mammary tumor growth was accompanied by decreased ovarian and uterine weights, suggesting that estrogen secretion was lowered. Since the latter can result in diminished prolactin secretion, it is possible that reduced secretion of estrogen and prolactin was responsible for the mammary regression observed in the le-sioned rats.

Efferent projections of the anterior olfactory nucleus.

Abstract: The efferent projection fibers from the rostral and the medial segments of the anterior olfactory nucleus have been studied using the Nauta or the Fink modification of the Nauta method for degenrating axons. Lesions were suitably placed by electrocoagulation. From the rostral segment of the anterior olfactory nucleus efferent fibers by way of the bulbar part of the anterior commissure were traced to the internal granular and the mitral cell layer of the normal side. Preterminal and terminal degeneration were traced by way of the homolateral lateral olfactory tract and these fibers ended in the lateral two-thirds of the olfactory tubercle, the prepiriform, the piriform and the periamygdalar cortices and into the corticomedial segment of the amygdaloid complex. Degenerating fibers were also noted in the dorsomedial nucleus, the lateral habenular nucleus, the lateral hypothalamic area and in the supraoptic area of the same side where the lesion was made. In animals where the lesion was placed in the medial segment of the anterior olfactory nucleus the same fiber distribution was observed as reported when the lesion was placed in the rostral segment of the anterior olfactory nucleus. However, other areas were observed receiving fibers from the medial segment of the nucleus. These areas were the basolateral segment of the amygdaloid complex and the mammillary areas.

Fine structure of the paraventricular organ of Xenopus laevis tadpoles.

Abstract: The ultrastructure of the Paraventricular organ in the hypothalamus of Xenopus laevis tadpoles is described. It appeares that the Paraventricular organ of this anuran species is homologous with the Organon vasculosum hypothalami or the Paraventricular organ of other vertebrates. The Paraventricular organ of Xenopus laevis is characterized by an ependymal lining with only few cilia and by two types of nerve cells. Both types of nerve cells have ventricular processes, protruding into the lumen of the third ventricle and forming a network. The protrusions bear cilia of the 8+1 pattern. It has been possible to distinguish both types of nerve cells on account of their dense-core vesicles. A secretory function of both cell types is suggested. In a region close to the Paraventricular organ, another granulated type of nerve cell has been observed. A relationship between these cells and the preoptic nucleus is discussed.