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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Activation of certain neurosecretory systems of the mammalian hypothalamus induces remodelling of the conformation of their neurons and glial cells. During stimulation of the hypothalamo-neurohypophysial system, astrocytic coverage of oxytocinergic somata and dendrites diminishes and their surfaces become extensively juxtaposed. In the neurohypophysis and median eminence, stimulation evokes a retraction of glial processes and an increase in the contact area between neurosecretory terminals and the perivascular space. These changes are reversible and glial coverage returns to normal upon cessation of stimulation. Neuronal-astrocytic rearrangements also occur in the arcuate nucleus in response to changes in sex steroid levels. The significance of such modifications is a matter of speculation. In the hypothalamic nuclei they may permit synaptic remodelling that takes place concurrently; in the neurohaemal structures they may facilitate neuropeptide release. We know little about the cellular mechanisms involved but glia and neurons of these systems express certain molecules implicated in cell-cell interactions in the developing central nervous system, such as the polysialylated isoform of the neural cell adhesion molecule; this may allow them to manifest their capacity for morphological plasticity in adulthood. The factors inducing the changes vary in the different structures: while oxytocin, in synergy with steroids, appears essential to the induction of the changes in the oxytocinergic system, oestrogen alone is critical in the arcuate nucleus; in the neurohypophysis noradrenaline appears important.
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PMID:Neuronal-glial and synaptic remodelling in the adult hypothalamus in response to physiological stimuli. 142 25

Intracellular recording and labeling were combined with neurophysin immunohistochemistry to study neurons in the paraventricular nucleus region of the rat hypothalamus. Neuronal membrane properties were examined in hypothalamic slices, and cells were labeled by injecting biocytin or Lucifer yellow. Slices were then embedded, sectioned, and immunohistochemically processed for neurophysin. Immunoreactivity patterns, and in some cases counterstaining, enabled determinations of the cytoarchitectonic positions of recorded cells to be made. Recorded cells were divided into three types according to their electrophysiological characteristics. The first type lacked low-threshold Ca2+ spikes and displayed linear current-voltage relations, a short time constant, and evidence for an A current. These were relatively large cells that were typically immunoreactive for neurophysin and were situated near other neurophysin-positive neurons. The second type had relatively small low-threshold potentials that did not generate bursts of Na+ spikes. These cells had heterogeneous current-voltage relations and intermediate time constants. They did not label for neurophysin, and most were located in the parvicellular subregion of the paraventricular nucleus. The third type had large low-threshold Ca2- spikes that generated bursts of Na+ spikes, and these cells had nonlinear current-voltage relations and long time constants. These neurons were dorsal or dorsolateral to the paraventricular nucleus and were not immunoreactive for neurophysin. These results indicate that paraventricular magnocellular neurons lack low-threshold potentials, whereas paraventricular parvicellular neurons display low-threshold potentials that generate one or two action potentials. Neurons that fire spike bursts from low-threshold potentials are adjacent to the paraventricular nucleus, confirming earlier reports.
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PMID:Immunohistochemical differentiation of electrophysiologically defined neuronal populations in the region of the rat hypothalamic paraventricular nucleus. 185 30

Neuronal mRNA is thought to be restricted to perikaryal and dendritic compartments containing rough endoplasmic reticulum. We have used both in situ hybridization and DNA polymerase chain reaction methods to determine the precise intracellular distribution of oxytocin mRNA. Using light- and electron-microscopic detection of in situ hybridization with 5'-bromo-2'-deoxyuridine-labeled oligonucleotide probes, we found oxytocin mRNA in axons and Herring bodies in the lateral and ventral hypothalamus, the median eminence, and the posterior lobe of the pituitary in postpartum lactating rats. Southern blot analysis of the amplification products confirmed the presence of oxytocin mRNA in all three tissue samples. The present findings indicate that oxytocin mRNA can be transported axonally. Such transport could reflect an adventitious compartmentalization or a functional storage in Herring bodies for subsequent secretion.
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PMID:mRNA coding for oxytocin is present in axons of the hypothalamo-neurohypophysial tract. 226 84

The hypothalamic suprachiasmatic nucleus (SCh) is the principal brain structure involved in the generation of circadian rhythms. In the present study, we have employed immunohistochemical techniques to evaluate the development of the fetal SCh following its transplantation to the brain of adult host animals. Donor hypothalami were obtained from normal Long-Evans fetuses and transplanted to the lateral, third, or fourth ventricle of Brattleboro rats. Neuronal aggregations exhibiting the organotypic features of the SCh were present in over 90% of the grafts recovered at each transplantation site. Like the normal endogenous SCh, SCh-like cell groups identified within the transplants contained a prominent population of parvicellular (9-13 micron), neurophysin-containing neurons that were immunopositive for vasopressin (VP) but not oxytocin. These SCh-like cell groups also invariably contained similar small neurons that were immunoreactive for vasoactive intestinal polypeptide (VIP). Typically, VP and VIP immunoreactive perikarya were concentrated in contiguous, complementary parts of the grafted SCh, but fibers immunoreactive for either peptide were distributed throughout the extent of the nucleus. Because the brain of the Brattleboro rat is deficient in vasopressin, it was possible to evaluate the projection of the vasopressinergic component of the transplanted SCh to the host brain. Although SCh were identified in grafts recovered from each intraventricular transplantation site, an appreciable input to the host brain could be identified only when the fetal tissue was grafted to the third ventricle. Here, grafted SCh established efferent connections with periventricular diencephalic structures which ordinarily receive a projection from the in situ SCh. Specifically, VP immunoreactive fibers originating from transplanted SCh were identified in the medial preoptic area, the periventricular and dorsomedial hypothalamic nuclei, the paraventricular nuclei of the thalamus and hypothalamus, and in the retrochiasmatic area, arcuate nucleus, and suprachiasmatic nucleus of the host brain. These results demonstrate that the fetal SCh not only survives transplantation but also retains its distinguishing cytological features and the capacity to form an appropriately restricted set of efferent connections with the brain of adult host animals.
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PMID:Organization and efferent connections of transplanted suprachiasmatic nuclei. 334 77

The preganglionic sympathetic neurons in the intermediolateral cell column of the thoracic and upper lumbar segments of the spinal cord which innervate the chromaffin cells in the adrenal medulla, sympathoadrenal preganglionic neurons, were identified by the method of retrograde axonal transport of the fluorescent dyes Fast Blue and True Blue. In rats, Fast Blue or True Blue was injected into the medulla of the left adrenal gland. After a survival period of 5 days, the animals were perfusion fixed, the thoracic and lumbar spinal cord sectioned and processed for the immunofluorescent localization of met-enkephalin, neurophysin, oxytocin, serotonin, somatostatin and substance P immunoreactivity. Neuronal perikarya which were retrogradedly-labeled with Fast Blue or True Blue were observed in the intermediolateral cell column from the T1 to the L2 spinal cord segments. The distribution of the sympathoadrenal neurons was determined by counting the number of retrogradedly-labeled neurons per spinal cord segment. In the five animals used for quantifying the sympathoadrenal preganglionic neurons, the majority (72.3%) of the retrogradely-labeled neurons counted per spinal cord were located within the T7-T12 segments. The T9 segment contained the largest average number (20.1%) of retrogradely-labeled cells in a single segment. Met-enkephalin, serotonin and substance P immunoreactive fibers were prominent in the intermediolateral cell column, whereas oxytocin, neurophysin and somatostatin immunoreactive fibers were sparse. The met-enkephalin, serotonin and substance P fibers were seen surrounding both unlabeled and retrogradely-labeled neurons; somatostatin fibers appeared to preferentially contact retrogradely-labeled neurons; whereas, the neurophysin and oxytocin fibers were not found in proximity to retrogradely-labeled neurons. Met-enkephalin, neurophysin, oxytocin, somatostatin and substance P immunoreactivity were depleted in the intermediolateral cell column below the level of a spinal cord transection. Serotonin immunoreactivity was depleted in the intermediolateral cell column below the level of the transection for five to six segments, but sparse networks of immunoreactive fibers were observed in both the intermediolateral cell column and the ventral horn in more caudal segments. Met-enkephalin, serotonin, somatostatin and substance P immunoreactivity were decreased in both the contralateral and ipsilateral intermediolateral cell column below the level of a spinal cord hemisection, suggesting that both crossed and uncrossed descending pathways exist. Neurophysin and oxytocin immunoreactivity were depleted below the level of the hemisection in the ipsilateral intermediolateral cell column without noticeable decrease in the level of immunoreactivity in the contralateral intermediolateral cell column, suggesting that a decussation does not occur at the level of the spinal cord, but may exist above the level of the hemisection...
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PMID:The differential distribution and relationship of serotoninergic and peptidergic fibers to sympathoadrenal neurons in the intermediolateral cell column of the rat: a combined retrograde axonal transport and immunofluorescence study. 618 Mar 52

Neuronal discharges of the anterior hypothalamus were studied in acute experiments on rats anesthetized with nembutal. Intravenous injection of oxytocin exerted a pronounced effect on the background activity, which became more rapid in the majority of cases and was sometimes reconstructed. A dose-dependent action of the peptide as well as the different latent periods of the neuronal responses were noted. In several cases, the drug induced bundle formation, making the impulsation rhythm more regular in some of the cells. The data obtained are discussed from the standpoint of oxytocin involvement in the activity of the cells forming the hypothalamic cyclic center in rats.
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PMID:[Action of oxytocin on the cellular activity of the hypothalamic cyclic center in rats]. 647 16

Extracellular electrical recordings were taken from twenty antidromically identified paraventricular neurones in unanaesthetized, unrestrained rabbits. Neuronal activity was correlated with nursing behaviour of the doe and responses of the young during suckling. Magnocellular neurones were divided into two groups on the basis of their activity in suckling. Group 1 (n = 14) showed several discrete bursts of high-frequency activity whilst neurones in group 2 (n = 6) did not. Neurones in group 1 showed 5-9 bursts of high-frequency activity in suckling. Each burst lasted 1-4 s and represented a 3-10-fold rise in the discharge of the cell. These units were classified as oxytocinergic, as their stereotyped activation preceded bouts of sucking behaviour of the young indicative of milk ejection. All fourteen cells continued to show intermittent bursts of neurosecretory activity for up to 20 min after nursing terminated. This pattern of discharge followed grooming behaviour of the doe. In contrast, neurones in group 2 (n = 6) showed no high-frequency activity in suckling. They showed a significant fall in their discharge frequency compared with pre-suckling values (P less than 0.05; Student's t test) and a significant (P less than 0.05) lengthening of the modal interspike interval. They were classed as potential vasopressin-producing cells. Control recordings were taken from thirty-two neurones which could not be antidromically driven. The recording sites were shown histologically to be in the lateral hypothalamic area. These cells showed a significant fall in their discharge frequency (P less than 0.05) and a significant increase (P less than 0.01) in the modal interval during suckling. Cross-correlation studies of the activity, recorded from one electrode, of groups of neurones clustered around a single hypothalamic neurone suggest that bursting discharge from the putative oxytocin neurones in suckling is accompanied by the synchronous activation of some of the surrounding magnocellular units.
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PMID:Activity of putative oxytocin neurones during reflex milk ejection in conscious rabbits. 670 64

Localization of enkephalins and opiate binding sites in the central nervous system of rats has been reported by several authors. These studies did not reveal an extensive enkephalinergic system in the hypothalamo-hypophyseal axis of rats. The present paper reports on an extensive enkephalinergic system in the cat hypothalamo-hypophyseal system. Sections of paraformaldehyde fixed cat hypothalami were incubated with anti-methionine enkephalin serum, anti-vasopressin serum, and anti-oxytocin serum. Immunohistochemical localization of methionine enkephalin fibers and terminals in the median eminence, hypophyseal stalk, and pars nervosa was similar, but not identical to the distribution of vasopressin and oxytocin in these structures. Neuronal perikarya localized with the three antisera in the nucleus supraopticus and nucleus paraventricularis were of a similar size and morphology. In cats treated with colchicine prior to sacrifice, the anti-methionine enkephalin serum revealed a group of periventricular cell bodies. Cell bodies were not localized in this area with anti-vasopressin or anti-oxytocin sera. The functional significance of such an extensive enkephalinergic system in the cat hypothalamo-hypophyseal axis is discussed.
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PMID:Relationship between enkephalinergic neurons and the vasopressin-oxytocin neuroendocrine system of the cat: an immunohistochemical study. 699 53

Neuronal peptides exert neurohormonal and neurotransmitter (neuromodulator) functions in the central nervous system (CNS). Besides these functions, a group of neuropeptides may have a capacity to create cell proliferation, growth, and survival. Axotomy induces transient (1-21 d) upregulation of synthesis and gene expression of neuropeptides, such as galanin, corticotropin releasing factor, dynorphin, calcitonin gene-related peptide, vasoactive intestinal polypeptide, cholecystokinin, angiotensin II, and neuropeptide Y. These neuropeptides are colocalized with "classic" neurotransmitters (acetylcholine, aspartate, glutamate) or neurohormones (vasopressin, oxytocin) that are downregulated by axotomy in the same neuronal cells. It is more likely that neuronal cells, in response to axotomy, increase expression of neuropeptides that promote their survival and regeneration, and may downregulate substances related to their transmitter or secretory activities.
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PMID:Neuropeptide messenger plasticity in the CNS neurons following axotomy. 757 12

Osmotically stimulated vasopressin and oxytocin release were measured in pinealectomized and sham operated male rats infused with hypertonic sodium chloride. Neuronal activation in the hypothalamic regions associated with oxytocin and vasopressin release was investigated by quantitative assessment of Fos protein production. The osmotically stimulated release of both vasopressin and oxytocin was significantly lower in pinealectomized animals as compared to sham operated controls. The slope of regression lines between plasma osmolality and hormone concentrations in the sham animals showed a 1.0 +/- 0.1 pmol per mosm/kg rise in vasopressin and 2.0 +/- 0.4 pmol per mosm/kg rise in oxytocin whilst in the pinealectomized animals these values were significantly lower at 0.4 +/- 0.1 pmol vasopressin per mosm/kg and 0.8 +/- 0.2pmol oxytocin per mosm/kg. The osmotic thresholds for hormone release were unaffected by pinealectomy. Fos production was also significantly lower in the supraoptic nucleus and organ vasculosum of the lamina terminalis in the pinealectomized rat at 62 +/- 20 and 59 +/- 9 Fos immunoreactive cells/section as compared to corresponding values of 202 +/- 31 and 123 +/- 20 Fos immunoreactive cells/section in the shams. These observations suggest that reduced hormone release in the pinealectomized animal is due to lowered responsiveness of central osmoregulatory mechanisms and that melatonin may therefore influence the activation of the magnocellular system.
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PMID:The effect of pinealectomy on osmotically stimulated vasopressin and oxytocin release and Fos protein production within the hypothalamus of the rat. 891 Aug 3


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