INCREASED HYPOTHALAMIC GLUTAMATE RECEPTORS INDUCED BY WATER-DEPRIVATION

To examine the role of receptor changes in the adaptive response to ph ysiological stimulation, the density and distribution of excitatory am ino acid receptors within the hypothalamus and other brain regions wer e examined in rats deprived of water for 2 days. Membrane binding assa y revealed an increase in glutamate receptor density and a small shift in the affinity of glutamate for the receptor. Regional analysis of t hese changes by receptor autoradiography specific for NMDA, non-NMDA o r metabotropic glutamate receptor binding indicated that NMDA and meta botropic receptor densities are increased in the brain. Regional incre ases were found principally for the NMDA receptor binding within the s upraoptic nucleus, anterior hypothalamus, caudate-putamen and globus p allidus with no significant changes in 24 other brain regions. No sign ificant changes were found in any brain regions for AMPA receptors. Me tabotropic and kainate receptors tended to parallel the NMDA receptor changes, although few regions reached statistical significance. These changes indicate that brain regions associated with water balance regu lation show selective adaptive increases in NMDA receptors during wate r deprivation which may facilitate prolonged activation of these cells .