Differential vulnerability of hippocampus, basal ganglia, and prefrontal cortex to long-term NMDA excitotoxicity

In human brain, nonartherosclerotic calcification is associated with normal aging and several pathological conditions without any clear significance. In all situations, calcification appears predominantly in the basal ganglia , but is also frequent in the hippocampus and cerebral cortex, alpha-Amino- (3-hydroxi-5-methyl-4-isoxazol-4-il)-propionic acid-induced lesion of the g lobus pallidus is associated in rats with the formation of calcium deposits similar to those observed in the human brain. To determine whether direct neuronal activation may induce calcification, N-methyl-D-aspartate (NMDA) w as microinjected in rat hippocampus, globus pallidus, and lateral prefronta l cortex. Two months later, neuronal death was associated with calcium depo sits that were characterized in terms of distribution and size. A unique po pulation of deposits was present in the hippocampus and prefrontal cortex, whereas in the globus pallidus two main groups could be differentiated. Cal cification was always associated with a significant microglial reaction as shown by the peripheral benzodiazepine receptor autoradiography. Monoamine oxidase B autoradiography, reflecting the astroglial reaction, was also sig nificantly increased. Our results provide evidence that acute NMDA neuronal activation leads with time to calcification associated with a glial reacti on and indicate that nonartherosclerotic calcification in the human brain m ay develop from an acute NMDA receptor activation. A key role of the metabo tropic mGluR1 receptor is also suggested. (C) 2000 Academic Press.