The implantation of puromycin into the neurosecretory nuclei of the rat

Summary Following the bilateral implantation of puromycin into the paraventricular nuclei of rats, the neurosecretory cells became atrophic and the amount of aldehyde-fuchsin (AF) positive material in the neural lobe decreased. In these rats, urine excretion and water intake increased remarkably. The supraoptic nuclei of the rats were not affected by this treatment. After the unilateral implantation of puromycin in the paraventricular nucleus, the neurosecretory cells of the implanted side became atrophic, while those of the unimplanted side hypertrophied. The neural lobe contained similar amounts of AF-positive material to those of the control rats with unilateral cholesterol implants. In the rats implanted bilaterally with puromycin immediately above the supraoptic nucleus, the neurosecretory cells of this nucleus contained little or no AF-positive material, and urine excretion and water intake increased greatly. The cells of the paraventricular nucleus remained unchanged in these rats.     

Effect of progesterone and estrogens on the state of the hypothalamo-hypophyseal neurosecretory system in pregnancy and labor

Morphofunctional state of the hypothalamo-hypophyseal neurosecretory system was studied in rats at late stages of pregnancy. No special differences both in function of the supraoptical and praventricular nuclei, and in the hypophysis of intact and pregnant rats at administration of progesterone were noted. When estrogenes were administered to pregnant animals, a sharp increase in functioning of the supraoptic and especially of the paraventricular nuclei was noted. The greatest activity of the supraoptic nucleus was observed at delivery that could be resulted from a stress reaction to pain.     

CHANGES IN THE HYPOTHALAMO-NEUROHYPOPHYSICAL NEURO-SECRETORY MATERIALS OF RATS DURING DIFFERENT PHASES OF MORPHINE ADMINISTRATION

Abstract—

• 1 Acute morphine treatment of rats increased the concentration of neuro-secretory material in the posterior pituitary. These changes were accompanied by the presence of more neurosecretory materials in the axons of the hypothalamic supraoptic and paraventricular neurons and in the hypothalamic capillaries and sinuses. In the perikarya of the hypothalamic supraoptic and paraventricular neurons, the neurosecretory material is in a dispersed state.
• 2 Following chronic morphine treatment, neurosecretory material was almost absent from the posterior pituitary, whereas in the perikarya of the supraoptic and paraventricular neurons, congestion of neurosecretory material is observed which is accompanied by the absence of the neurosecretory material from the axons arising from the supraoptic and paraventricular nuclei and from the hypothalamic capillaries and sinuses.
• 3 During nalorphine-induced abstinence, there was sudden reappearance of the neurosecretory material in the posterior pituitary along with the appearance of neurosecretory material in the hypothalamic neurosecretory neuronal tracts, blood capillaries and sinuses together with the dispersion of the neurosecretory materials from the hypothalamic neurosecretory neurons.

     

State of the hypothalamo-hypophyseal neurocirculatory system of the gerbil, Rhombomys opimus, during dehydration

Big gerbils, inhabitants of desert, were found to have indices of an increased functional activity of HHNS: low content of neurosecretory material all over the system, relatively large volumes of neurosecretory cell nuclei and nucleoli, hyperemia. Under the condition of a seven-day dehydration, the neurosecretory material reduction in all links of HHNS, enlargement of neurosecretory cell nuclei and nucleoli, intensification of hyperemia were found. With the increase in dehydration time to 23 days a progressive reduction of neurosecretory material in cell processes and hypophysis are seen. However, the decrease in nuclear size takes place under the condition of continuing increase in nucleolar size both in supraoptic and paraventricular nuclei. Extremely intensive hyperemia of all regions of HHNS is seen. The activation of HHNS under the water-salt regime change, seen in big gerbils, is not as pronounced as in albino rats. This is, evidently, due to a specificity of the function and their osmoregulating system.     

The development of the corticoliberin- and vasopressinergic elements of the rat hypothalamus during postnatal ontogeny

In 10--81-day and adult Wistar rats, neurosecretory cells were revealed which react with antisera to corticoliberin and vasopressin. Morphometric analysis of these cells in the supraoptic, paraventricular and anterior commissural nuclei shows that in the latter vasopressinergic cells develop somewhat later than in the supraoptic and paraventricular nuclei. Complete differentiation of neurosecretory cells in all the centres investigated is observed in 2-month animals. Studies were also made on the amount of corticoliberin- and vasopressinergic terminals in the external zone of the median eminence. Vasopressin-immunoreactive fibers are more numerous in young rats than in adult ones. Corticoliberin-positive neurosecretory fibers are more abundant in adult animals. Earlier development of vasopressinergic elements corresponds to a hypothesis of a more ancient origin of nonapeptidergic structures as compared to those producing liberins and statins.     

Changes in metabolic activity of neurons in the anterior hypothalamus nuclei during hyperthermia, fever, and hypothermia

Differently directed changes in metabolic activity of anterior hypothalamic nuclei's neurons in rats during hyperthermia, fever, and hypothermia were revealed with histochemical methods. During hyperthermia, the activity of energy metabolism enzymes increased as well as RNA content in the neurons of supraoptic, paraventricular and median preoptic anterior hypothalamic nuclei. This is shown by an increase in the metabolic activity of neurons of these nuclei. Metabolic activity in neurons of median preoptic nuclei decreased and was not changed considerably in neurons of supraoptic and paraventricular nuclei during endotoxin-induced fever. The development of hypothermia was characterised by a decrease in metabolic activity of neurons of supraoptic, paraventricular and medium preoptic nuclei. It is supposed that differently directed metabolic activity changes in neurons of anterior hypothalamic nuclei during hyperthermia are connected with the mechanisms of body temperature regulation (median preoptic nuclei) and neurosecretory processes (supraoptic and paraventricular nuclei).     

Studies of the hypothalamo-hypophyseal corticoliberin system. VII. Effect of ether stress and dexamethasone on the hypothalamo-hypophyseal-adrenal axis]

The effect of ether stress and dexamethasone on hypothalamo-hypophyseal-adrenal axis was investigated in sexually mature male Wistar rats. Separate group of rats was subjected to ether stress during 2 minutes. The remaining animals were treated with dexamethasone during 7 days. CRF-immunoreactive and vasopressin-immunoreactive neurons were detected within paraventricular nuclei and median eminence by using specific antibodies. Body weight of the rats as well as the weights of pituitary and adrenal glands were also measured. The levels of ACTH and corticosterone were determined in blood serum. It was found that the ether stress caused a considerable decrease in the amount of CRF-immunopositive substances in the outer layer of median eminence and a decrease in the amount of vasopressin-immunoreactive neurocytes in the parvocellular fragment of paraventricular nuclei. Dexamethasone administration caused an increase in the amount of CRF-immunopositive perikaryons within paraventricular nuclei and also an increase in vasopressin-immunopositive nerve fibers in median eminence.     

The influence of the antimitotic drug CCNU on the neurosecretion of rat hypothalamo-hypophyseal system

The purpose of this investigation was to evaluate the influence of the antimitotic drug CCNU on the morphology of the hypothalamo-hypophyseal neurosecretory system of rat. Adult Wistar rats were treated intragastrically with 2.5 mg CCNU once a week during 3 consecutive weeks and 5 mg at the end of the 4th week. The brains and hypophyses were fixed in Zenker-formol solution. Paraffin slices were stained with chromhematoxylin to demonstrate neurosecretory material and with cresyl violet. PAS reaction was also performed. The experiment resulted in disturbances of the neurosecretory function of the hypothalamo-hypophyseal system in form of alteration in the content of neurosecretion in the neuronal cytoplasm and processes within supraoptic and paraventricular nuclei as well as in the neurohypophysis. The morphometric measurements showed enlargement of the cell nuclei and cytoplasm volumes in the nucleus supraopticus of hypothalamus.     

Morphometric and electron microscopic studies of the secretory granules of neurosecretory cells of the supraoptic and paraventricular nuclei of white rats and mice]

The morphometrical and electron microscopic analysis of secretory granules in the perikaryons of neurosecretory cells of the supraoptic and paraventricular nuclei in male rats and mice has shown than in the cells of these nuclei in both species of animals there occur secretory granules of the same kind and size. Therefore this method fails to determine which of them contain oxytocin and which of them contain vasorpressin. The neurosecretory granules located in the Golgi apparatus zone are of a less size and have more osmiophilic cnetral material than the granules localized on the periphery which mainly have granular central material and are of a greater size. The distinctions in the size and type of secretory granules are associated with certain stages of their "maturation". Granular particles appear to be "swallen", more active forms of storing neurohormones. The presence of larger granular particles in the supraoptic nucleus of mice allows to suggest greater reactivity of this nucleus than in rats which is likely to be associated with a higher ability of mice, as compared with rats, to adaptate to disturbances in water-salt metabolism.     

Quantitative histoenzymatic analysis of the hypothalamic neurosecretory system in rat ontogeny

In experiments on 6 and 16 days old rats cytophotometric studies have been made of histochemical reactions for succinate, lactate and glutamate dehydrogenases, alpha-glycerophosphate dehydrogenase and glucose-6-phosphate dehydrogenase in the supraoptic nucleus, paraventricular hypothalamic nucleus and the posterior hypophysis. It was found that heterochronous development of the neurones in the supraoptic and paraventricular nuclei, as well as the development of their axons in the posterior hypothalamus depend on the rate of maturation of the enzymic systems in postnatal life. In consolidation of the unique structure of the hypothalamic neurosecretory system, the key role is played by afferent influences, succinic dehydrogenase being involved into their realization. The data obtained indicate the importance of heterochronous development of the enzymic activities in the formation of bifunctional properties of neurosecretory hypothalamic neurones and reveal the primary development of neurotransmittery function as compared to the excretory one.     

Functional changes in neurosecretory cells of the anterior hypothalamic nuclei after stimulation of the midbrain reticular formation

The functional activity of the neurosecretory cells in the supraoptic and paraventricular nuclei was studied in male Wistar albino rats at various intervals after electric stimulation of the midbrain reticular formation. These studies showed that such stimulation elicits higher functional activity of the neurosecretory cells in the anterior hypothalamic nuclei, characterized by increased secretory synthesis by these cells and rapid transport of the neurosecretion. These changes were most pronounced 1 h after stimulation of the reticular formation. The changes observed were unidirectional in both neurosecretory centers, but their manifestation was different: in the supraoptic nucleus the reaction was more intense but short lived, in the paraventricular it was less intense but lasted longer.A. A. Bogomolets Institute of Physiology, Academy of Sciences, Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 3, No. 4, pp. 394–400, July–August, 1971.     

Ultrastructural aspects of the inhibition of neurosecretion by puromycin

Summary The supraoptic nuclei and the infundibular process of the neurohypophysis were studied under the electron microscope in rats fed on dried food for 1 to 3 days and in similarly dehydrated animals but injected subarachnoidally with puromycin 4 to 24 hours prior to fixation. With 4 to 8 hours of puromycin the intracisternal filamentous material found in the control is greatly diminished. After 24 hours this inhibitory effect disappears in the perikaryon but the neurotubular material of the neuronal processes within the supraoptic nucleus and the neurosecretion in the infundibular process are greatly reduced. These results are discussed taking into consideration the inhibition of protein synthesis caused by puromycin and the neurosecretory cycle which characterizes the supraoptic neurons.Supported by grants from the Consejo Nacional de Investigaciones Cientificas y Técnicas and by the Air Force Office of Scientific Research (963–65).     

The effect of adrenaline and acetylcholine on the hypothalamic-hypophysial neurosecretion in the rat

Summary The present investigation was undertaken to study the effects of adrenaline and acetylcholine on the hypothalamic-hypophysial neurosecretory system in rats.The drugs were injected intraperitoneally and into the lateral brain ventricle. The water diuresis was measured (I group). The animals were killed 45 min after intraperitoneal and 20 min after intraventricular administration of the drugs for the histological observations on the neurosecretory system and the histochemical studies of catecholamines in this area (II group).The antidiuretic effect of adrenaline and acetylcholine was established. The antidiuresis was more remarkable following intraventricular treatment.There was no direct relationship between the amount of neurosecretory substance and ADH activity in the posterior pituitary in the short term experiment after intraperitoneal administration of these drugs.The rapid release of ADH from the posterior pituitary was accompanied with a remarkable output of neurosecretory substance from the neurosecretory cell bodies into the axons and these effects were considerable after intraventricular introduction of the drugs. Some neurosecretory cells in the state of the initial hyperfunction were observed. In the posterior pituitary the initial mobilisation of the neurosecretory material from the neurosecretory terminals following intraventricular introduction of the drugs was observed.The supraoptic nucleus seems to be more sensitive to acetylcholine and the paraventricular nucleus to adrenaline treatment.The significant vasodilatation in the posterior pituitary and in the area of the supraoptic nucleus following intraventricular acetylcholine introduction was established.According to the data described it is possible to expect the existence of control of the hypothalamic neurosecretory activity by means of adrenergic and cholinergic structures.I am very obliged to Prof. W. Bargmann for his stimulating interest in this Study. I am grateful to Dr. G. Leontieva and Dr. V. Govyrin for the possibility to use the fluorescence catecholamine method, to Dr. E. Zeimal and Prof. M. Michelson for using the method for intraventricular injections.     

Cytologie du lobe anterieur de l'hypophyse du chien

Summary Detailed histochemical studies have been made on the distribution of various enzymes such as phosphatases, cholinesterases, glycolytic enzymes and respiratory enzymes in various components of the hypothalamus with special reference to the supraoptic and paraventricular nuclei of the Squirrel Monkey. Cytological studies have also been made by the McManus, Einarson, Gomori and Bargmann methods.A few neurons of these nuclei showed scanty Gomori-positive material in the cytoplasm for the Gomori and Bargmann methods. Nissl granules were located in the peripheral cytoplasm of most neurons. No glycogen granules were observed in these neurons. For these reasons, the Squirrel Monkey, like the rat, may not be a suitable species for the study of neurosecretory phenomena.The axons of these neurons were negative for the specific cholinesterase test, though the perikaryon and some parts of the processes gave a moderately positive reaction. These neurons may be non-cholinergic and the cholinergic fibers from an unknown nucleus may end in synapses on their cell bodies. Blood vessels and glial cells in the neurosecretory nuclei showed non-specific cholinesterase activity. This enzyme may hydrolyze the acetylcholine which has escaped splitting by specific cholinesterase. Alkaline phosphatase and acid phosphatase in these neurons may be involved in the metabolism concerned with the production of neurosecretory material. The neurons may be physicochemical receptors and may get enough energy and raw material to synthesize the neurosecretory material from the rich blood supply. Neurons of the supraoptic and paraventricular nuclei as well as other hypothalamic neurons, like neurons of other regions of the brain, are well equipped with the enzymes of the glycolytic pathways and the tricarboxylic acid cycle. Since the glial cells of these nuclei have amylophosphorylase activity and glycolytic pathways, they may work as energy donators to the neurons of the neurosecretory nuclei. T. R. Shanthaveerappa in previous publications.     

Gene expression and chemical diversity in hypothalamic neurosecretory neurons

Hypothalamic neurosecretory neurons transcribe, translate, store, and secrete a large number of chemical messengers. The neurons contain hypothalamic signal substances that regulate the secretion of anterior pituitary hormones as well as the neurohypophysial peptides vasopressin and oxytocin. In addition to the classical hypophysiotropic hormones, a large number of neuropeptides and classical transmitters of amine and amino acid nature are present in the same cells. This is particularly evident in the magnocellular neurons of the supraoptic and paraventricular nuclei, and in parvocellular neurons of the arcuate and paraventricular nuclei. The changes in gene expression induced by experimental manipulations and the colocalization chemical messengers in hypothalamic neurosecretory neurons and its possible significance is summarized in this review.     

The kinetics of 35S-labelled cysteine in the hypothalamic-neurohypophyseal neurosecretory system of the dehydrated rat

Thirst stimulation of the supraoptic nucleus (SON) and paraventricular nucleus (PVN) was induced in rats by withholding all fluids during three days. 35S-cysteine was then intraperitoneally administered and the rats were killed at predetermined times and examined by autoradiography, applying the authors' previously described method. This experimental series totalling 51 animals was compared with a control series of 70 rats, similarly treated, who had had free access to water. The kinetic phenomena in SON and PVN were analysed in terms of the two-compartment model previously used, which gives an estimate of the neurosecretory material (NSM) secretion parameters and of those of the lumped structural cell protein turnover in the nuclei. The kinetics of the precursor amino acids after administration of labelled cysteine were also assessed. Determinations of the label uptake at two specific times in the experiment, in the infundibular nucleus, ventromedial nucleus and optic nerve tissue in both series served as a check on the specifity of the structural protein turnover changes observed. Compared with the controls, the turnover rate of the slow compartment was more than tripled in the dehydrated rats, while that of the fast compartment had gone down to about one-third; both effects very nearly equal in SON and PVN. These results are compatible with the concept according to which thirst stimulates the SON and PVN equally. A distinct, and strikingly equal, hump was observed (2 hours after label administration) in all specific activity curves, also in the precursor serum concentration, and it is probably due to recycling of 35s from cysteine to methionine. This and other circumstances render the phenomena rather too complex for a straight-forward evaluation by the two-compartment model. Even so, the observations are believed to furnish good evidence of the biological verity of this model as well as the thirst-induced changes elicited.     

Effect of fixation on the demonstration of neurophysin and "Gomori-positive" substances in neurosecretory granules of the rat hypothalamus.

Proteins reacting with neurophysin antibodies and "Gomori-positive" substances were demonstrated histochemically in hypothalamic neurosecretory material of normal and bilaterally adrenalectomized rats after two different fixations: a) picric acid-formalin (PAF) for 7 days at 37 degrees C; b) Bouin's fluid for 20 h at 4 degrees C. After PAF-fixation anti-neurophysin reactive neurosecretory granules are found in all parts of the supraoptico-hypophysial system and in the suprachiasmatic nucleus of normal and adrenalectomized animals. In the latter they can additionally be demonstrated in the outer layer of the median eminence. Amount and distribution of "Gomori-positive" substances correspond to those described for the immunoreactive material, except for the suprachiasmatic nucleus, in which the substances can not be detected; Following fixation in Bouin's fluid the immunohistochemical reactions are unchanged whereas the staining of "Gomori-positive" substances is remarkably impaired. The amounts of the substances demonstrable in the neural lobe are diminished and in the cells of the supraoptic and paraventricular nuclei as well as in both median eminence layers only traces of the substances are to be seen. The findings indicate that negative results in demonstrating "Gomori-positive" substances may be caused by inappropriate fixation and need to be controlled by immunohistochemical techniques.     

Changes in histones and transcription in the nuclei of sympathetic neurons in rats of various ages under the action of testosterone

A study of chromatin in KSTG neurocytes revealed the most remarkable changes of template activity after testosterone administration in 9 days old rats and less significant changes in adult rats. No changes were detected in 19 days old rats. The pattern of silver staining of the nuclei did not differ from the control in all age groups. The possible role of testosterone in differentiation of KSTG neurocytes in early postnatal period as well as the stage-related differences in mechanisms of the hormone action during ontogenesis are discussed.     

Coexistence of NADPH-diaphorase with vasopressin and oxytocin in the hypothalamic magnocellular neurosecretory nuclei of the rat

Coexistence of NADPH-diaphorase with vasopressin and oxytocin was studied in the magnocellular neurosecretory nuclei of the rat hypothalamus by use of sequential histochemical and immunocytochemical techniques in the same sections. Coexistence was found in all the nuclei examined (supraoptic, paraventricular, circular, fornical, and in some isolated neurons located in the hypothalamic area between the paraventricular and supraoptic nuclei). The ratios of neurons expressing both markers (NADPH-diaphorase and vasopressin, NADPH-diaphorase and oxytocin) in each of the nuclei were very similar. Although further studies must be carried out, the partial coexistence found in all nuclei suggests that NADPH-diaphorase is probably not related to general mechanisms involving vasopressin and oxytocin, but rather in specific functions shared by certain hypothalamic neuronal cell populations.     

Selective specificity of calcium-binding proteins calbindin and calretinin expression in the magnocellular neurosecretory hypothalamic nuclei of tortoises and turtles

We have studied the distribution of calcium-binding proteins in the magnocellular neurosecretory nuclei of nonapeptidergic neurosecretory nuclei of the preoptic–hypothalamic complex in a tortoise (Testudo horsfieldi) and a pond turtle (Emys orbicularis) using immunohistochemistry. We have found that different types of cells in the paraventricular and supraoptic nuclei predominantly express calbindin and, to a lesser extent, calretinin, but not parvalbumin. The selective calbindin/calretinin control of the neurohormone secretion in these hypothalamic nuclei is an evolutionary conservative feature typical of reptiles and mammals.