PREGNENOLONE SULFATE EXACERBATES NMDA-INDUCED DEATH OF HIPPOCAMPAL-NEURONS

Excessive stimulation of the N-methyl-D-aspartate (NMDA)-type glutamat e receptor has been implicated in the neuronal death resulting from fo cal hypoxia-ischemia. Certain neurosteroids, steroids synthesized de n ovo in the central nervous system (CNS), have been shown to modulate t he action of neurotransmitters at their cellular receptors. Pregnenolo ne sulfate (PS) is an abundant neurosteroid that enhances the current evoked by NMDA. Using the Ca2+-sensitive fluorescent dye, Fluo-3, AM, and a trypan blue exclusion assay, we evaluated the ability of PS to m odulate NMDA-induced changes in intracellular free calcium concentrati on ([Ca2+](i)) and neuronal death in primary cultures of rat hippocamp al neurons. The results demonstrate that PS potentiates NMDA-induced i ncreases in [Ca2+](i) by 150%. Further, PS exacerbates the MK-801-sens itive neuronal death produced by acute (PS EC50 = 37 mu M) or chronic NMDA exposure, reducing the EC50 of NMDA from 13 to 4 mu M under chron ic exposure conditions, whereas pregnenolone is ineffective. Our resul ts show that PS, or related sulfated neurosteroids, may play a role in the onset of excitotoxic neuronal death in vivo. (C) 1998 Elsevier Sc ience B.V. All rights reserved.