Effects of dehydration on the rate of proliferation of hypothalamic neuroglia cells

doi:10.1016/0014-4886(68)90087-3

Experimental Neurology

Volume 20, Issue 3, March 1968, Pages 460-468

https://doi.org/10.1016/0014-4886(68)90087-3 Get rights and content

Abstract

Radioautographic techniques were used to study the effects of osmotic stimuli on the rate of proliferation of neuroglia cells in the hypothalamus of the rat. Five animals served as controls and four rats were dehydrated by drinking a 1% saline solution for 14 days. The animals were injected with ³H-thymidine each day during the 14 days of treatment. Significant increases in the numbers of labeled neuroglia cells occurred in the supraoptic nucleus and posterior pituitary of dehydrated rats while there were no significant differences between control and dehydrated animals in the percentages of labeled cells in the median eminence and infundibular stem, the optic nerve, or the trigeminal nerve and ganglion. Dehydration thus appears to act as a stimulus to glial proliferation in the supraoptic nucleus and posterior pituitary.

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Cited by (28)

Structural plasticity of nonneuronal cells in the hypothalamo-neurohypophyseal system: in the right place at the right time
2003, Advances in Molecular and Cell Biology
Citation Excerpt :
The breakdown of extracellular matrix may be one such factor. It is tempting to speculate that at least some of the proliferation of nonneuronal cells previously reported in the SON (Murray, 1968; Paterson and LeBlond, 1977) includes microglia. However, we have only seen the occasional microglial cell in the SON in the act of dividing.
This chapter reviews that structural plasticity of astrocytes in the normally functioning brain is widespread. Two of the best-studied regions where structural plasticity occurs are the supraoptic nucleus (SON) and posterior pituitary. It discusses the recent developments in understanding of how this structural remodelling, including new finding that show microglia also participate in structural plasticity of the SON. The chapter also introduces other brain areas, where structural plasticity of astrocytes has been demonstrated. Structural plasticity of glia, predominantly that of astrocytes, occurs throughout the nervous system. Sites, where structural plasticity of astrocytes has been documented in normal brains include the hippocampus with long term potentiation induction in the suprachiasmatic nucleus across the diurnal cycle, in the cerebellar cortex with motor learning in the arcuate nucleus of the rat and monkey, across changing estrogen levels, and extensively, in the hypothalamo-neurohypophyseal system (HNS) in response to diverse conditions leading to the synthesis and release of the peptides oxytocin (OX) and vasopressin (VP). The chapter concludes that the factors that are investigated in the SON of the hypothalamus include reorientation of astrocytes, reentry of glial cells into the cell cycle, downregulation of morphoregulatory molecules, dissolution of the basal lamina, changes in the GFAP, concomitant changes in expression of GFAP message, and changes in the population of resident microglia.
Neuronal-glial interactions and behaviour
2000, Neuroscience and Biobehavioral Reviews
Citation Excerpt :
In the SON alone, data indicate that SON-VGL astrocytes are a different population to those in the nucleus proper. First, SON astrocytes proliferate readily when the nucleus is activated [307,337], whereas SON-VGL astrocytes do not (Salm and Moats, unpublished observations). In addition, SON-VGL astrocytes express relatively high levels of vimentin [32] and tenascin [434] and taurine [86] whereas SON astrocytes do not.
Both neurons and glia interact dynamically to enable information processing and behaviour. They have had increasingly intimate, numerous and differentiated associations during brain evolution. Radial glia form a scaffold for neuronal developmental migration and astrocytes enable later synapse elimination. Functionally syncytial glial cells are depolarised by elevated potassium to generate slow potential shifts that are quantitatively related to arousal, levels of motivation and accompany learning. Potassium stimulates astrocytic glycogenolysis and neuronal oxidative metabolism, the former of which is necessary for passive avoidance learning in chicks. Neurons oxidatively metabolise lactate/pyruvate derived from astrocytic glycolysis as their major energy source, stimulated by elevated glutamate. In astrocytes, noradrenaline activates both glycogenolysis and oxidative metabolism. Neuronal glutamate depends crucially on the supply of astrocytically derived glutamine. Released glutamate depolarises astrocytes and their handling of potassium and induces waves of elevated intracellular calcium. Serotonin causes astrocytic hyperpolarisation. Astrocytes alter their physical relationships with neurons to regulate neuronal communication in the hypothalamus during lactation, parturition and dehydration and in response to steroid hormones. There is also structural plasticity of astrocytes during learning in cortex and cerebellum.
Astroglia proliferate in response to oxytocin and vasopressin
1995, Brain Research
The effects of the peptides oxytocin and vasopressin on the proliferation of cultured cortical and hypothalamic astroglia were assessed by two corroborative methods. Both hemocytometer cell counts, and immunocytochemistry for bromodeoxyuridine (BrdU) incorporation and glial fibrillary acidic protein (GFAP) expression indicate that oxytocin increases the rate of proliferation of both cortical and hypothalamic astroglia. While vasopressin also had an effect on cortical cells, no conclusive evidence for vasopressin affecting proliferation of hypothalamic astroglia was found.
Microglial responses to physiological change: Osmotic stress elevates DNA synthesis of neurohypophyseal microglia
1993, Neuroscience
We were interested to discover whether microglia could play a role in the remodelling of the adult CNS or participate in adaptations to physiological rather than pathological changes. We have studied microglia in the neurohypophysis of adult mice since microglia normally interact with neurons in this tissue and the biochemical and anatomical consequences of osmotic stress on the neurohypophysis are well known. In this study, we have examined microglial immuno-phenotype and numbers synthesizing DNA in the neurohypophysis of adult mice to establish whether these cells respond to progressive osmotic stress.
Neurohypophyseal F4/80⁺ microglia underwent a large synchronous burst of DNA synthesis 48 h after initiation of osmotic stress (drinking 2.5% saline). The labelling index (percentage of F4/80⁺ cells labelled by [³⁺H]thymidine) l h after injection the isotope rose to 17% from a control value of less than 1%. On the third day of treatment the labelling index had returned to control levels. In contrast, non-microglia cells in the neurohypophysis and microglial cells elsewhere in the brain did not show this response. The increase in DNA synthesis was not accompanied by signs of microglia activation commonly observed in inflammatory models. They did not acquire an “activated” or “hypertrophic” morphology, nor was their staining with a panel of antibodies greatly altered. A small up-regulation of CD45 expression was the only phenotypic change detected.
Thus, neurohypophyseal microglia respond to increased neurosecretory activity during the adaptation to osmotic stress in a distinctive way which differs from microglia reactions to inflammatory stimuli elsewhere in the CNS.
A role for glial cells in activity-dependent central nervous plasticity? review and hypothesis
1992, International Review of Neurobiology
This chapter presents the experimental evidence that long-term plastic changes in a variety of model systems of activity-dependent plasticity are indeed parallelled by, and probably based on, structural changes in neuronal connectivity. This fact calls for an extended view of possible mechanisms of CNS plasticity going beyond the assumption of sole changes in the efficacy of synaptic transmission at a constant number of synapses. The chapter foscuses on plasticity manifested in synapse elimination and synapse formation. Evidence is presented that glial cells may be involved in such changes in neuronal connectivity underlying long-term manifestation of CNS plasticity. In addition, possible mechanisms of glial participation in changes of synaptic efficacy are summarized. The understanding of glial contributions in the control of regeneration is reviewed briefly and compared with a possible involvement of glial cells in plasticity of the undamaged CNS. Activity-dependent plasticity relies on changes in neuronal transmission that are controlled by coincidence or noncoincidence of presynaptic and postsynaptic activity. These changes may rely on modulation of neural transmission or on structural changes in neuronal circuitry.
Alterations in supraoptic nucleus ultrastructure of maternally behaving virgin rats
1988, Brain Research Bulletin
Adult, nulliparous female rats were induced to behave maternally via constant cohousing with rat pups. After exhibiting maternal behaviors for 3 days, the animals were transcardially perfused, the supraoptic nuclei (SON) excised and examined quantitatively by transmission electron microscopy. Relative to virgin controls, the animals behaving maternally were found to have significant increases in:
- 1.
  a) mean number of dendrites in large (9–12) dendritic bundles,
- 2.
  b) mean area per single dendritic profile,
- 3.
  c) area of the dendritic zone occupied by dendritic profiles and
- 4.
  d) size of the dendritic zone. No significant changes were observed in the cell body zone or in the number of double synapses in the dendritic region. The observed changes are likely to be at least in part associated with the oxytocin-containing cells of the SON. These observations suggest a role for the SON in promoting maternal behaviors and constitute a novel demonstration of a neural modification in the mammalian central nervous system that appears conjointly with a complex set of behaviors.

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¹: This investigation was supported in part by a United States Public Health Service Training grant 2T01 GM00721-06 and in part by a grant of the Medical Research Council of Canada to Dr. C. P. Leblond. The technical assistance of Miss Ritha Paradis is gratefully acknowledged.

View full text

Effects of dehydration on the rate of proliferation of hypothalamic neuroglia cells

Abstract

Exptl. Neurol.

Progr. Brain Res.

Exptl. Neurol.

Autoradiographic examination of the effects of enriched environment on the rate of glial multiplication in the adult rat brain

Nature

Morphologische und experimentelle Untersuchungen über das hypothalamisch-hypophysäre System

Acta Neuroveg.

Juxtavascular karyokinesis and microglia cell proliferation during retrograde reaction in the mouse facial nucleus

Ergeb. Anat. Entwicklungsgeschichte

Numerical estimates of neurons and glia in lateral geniculate body during retrograde degeneration

J. Comp. Neurol.

The effect of an enriched environment on the histology of the rat cerebral cortex

J. Comp. Neurol.

Increases in cortical depth and glia numbers in rats subjected to enriched environment

J. Comp. Neurol.

Quantitative Ribonukleinsäure-untersuchungen an den Ganglienzellen des Nucleus Supraopticus der Albino-ratte unter experimentellen Bedingungen

Z. Zellforsch. Mikroskop. Anat. Abt. Histochem.