Cellular plasticity in the supraoptic and paraventricular nuclei after prolonged dehydration in the desert rodent Meriones shawi: Vasopressin and GFAP immunohistochemical study.

Supraoptic (SON) and paraventricular (PVN) nuclei are part of the hypothalamic-neurohypophysial system, they constitute the main source for vasopressin and they represent also obvious examples of activity-dependent neuroglial plasticity. Certain physiological conditions such as dehydration are accompanied by a structural remodeling of the neurons, their synaptic inputs and their surrounding glia. In the present work, an adult Meriones shawi (a rodent adapted to desert life) is used as an animal model. Using GFAP and vasopressin expressions as indicators successively of astrocytes and neuronal activations, the effect of a prolonged episode of water deprivation on the SON and PVN, hypothalamus nuclei were examined. We studied the immunoreactivity of GFAP and vasopressin in various hydration states (total deprivation of drinking water for 1 and 2months compared to hydrated animals). Prolonged dehydration produces an important decrease of GFAP immunoreactivity in both SON and PVN after 1 and 2months of water restriction. This decrease is accompanied by increased vasopressin immunoreactivity following the same periods of water deprivation. These findings may explain a real communication between vasopressin neurons and their surrounding astrocytes, thus the retraction of astrocytes and their processes is accompanied by an enhancement of vasopressin neuron density and their projecting fibers in response to this osmotic stress situation. Furthermore, these data could open further investigations concerning the possible involvement of the communication between astrocytes and vasopressin neurons in both PVN and SON in the regulation of Meriones hydrous balance and resistance to dehydration.