REDUCED NMDA RECEPTOR SENSITIVITY MAY UNDERLIE THE RESISTANCE OF SUBPOPULATIONS OF PVN NEURONS TO EXCITOTOXICITY

MAGNOCELLULAR neurons in the paraventricular nucleus are resistant to excitotoxic cell damage. We tested the hypothesis that a modified post -synaptic response following NMDA receptor activation may underlie thi s resistance. Whole-cell recordings from hypothalamic slices showed th at NMDA receptor activation caused dose-dependent depolarizations in b oth Type I (putative magnocellular) and Type II (putative parvocellula r) neurons. Type II cells, however, were an order of magnitude more se nsitive (10 nM) than Type I neurons (100 nM). The depolarizations reco rded in Type II cells were also significantly greater (> 35% resulting in sodium channel inactivation) than those recorded in Type I neurons . This differential sensitivity of neurons to NMDA receptor activation may explain the selective resistance of magnocellular PVN neurons to excitatory neurotoxins.