Neuron Glia Interactions in the Hypothalamus and the Pituitary

Although the close anatomical association of glia and neurons is a familiar notion, we are only beginning to appreciate that this association is dynamic and modifiable. A neuronal system, which well exemplifies this is the hypothalamoneurohypophysial system, in which neurons and glial cells undergo physiologically linked morphological changes throughout life. Thus, during conditions that enhance neurohormone secretion

(parturition, lactation, and prolonged osmotic stimulation), glial coverage of oxytocinergic neurons markedly diminishes and their surfaces are left in extensive juxtaposition. Concurrently, there is formation of new synapses, which are predominantly GABAergic and which couple two or more oxytocinergic neurons simultaneously; glutamatergic synapse numbers also increase significantly. The same stimuli induce similar changes in the posterior pituitary, in which retraction of pituicyte processes from posterior pituitary neurons and growth and multiplication of neurosecretory axon terminals lead to an increase neurohemal contact. These structural changes do not permanently modify the anatomy of the system since upon cessation of stimulation neuronal juxtapositions and shared synapses disappear, and they reappear upon new stimulation. Activity-related changes in the conformation of glia, neurons, and synaptic inputs also occur in other hypothalamic-neurosecretory systems, such as the arcuate nucleus in relation to varying estrogen level.

Conquering Fear In The 21th Century

Conquering Fear In The 21th Century

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