Treatment of single rat hippocampal neurons with 200 pM recombinant HIV-1 envelope glycoprotein, gp 120, resulted in large increases in the intracellular free calcium concentration ([Ca2+]i) as measured with indo-1-based microfluorimetry. Three patterns of [Ca2+]i increases were observed: in one pattern the [Ca2+]i rose rapidly and transiently as a single peak, in a second pattern gp120 induced [Ca2+]i oscillations that subsided when the protein was removed, and in a third pattern the oscillations continued long after washout of gp120. Both single peak and oscillatory [Ca2+]i increases were completely blocked by the Ca2+ channel blocker nitrendipine (1 μM). The sustained oscillatory responses were also blocked completely and reversibly by the N-methyl-d-aspartate (NMDA) receptor antagonist CGS19755 (10 μM) and the Na+ channel blocker tetrodotoxin (1 μM). Complete block by antagonists of Ca2+, Na+, and NMDA-gated ion channels suggests that at least two cells are required to maintain the [Ca2+]i oscillations. We hypothesize that gp120 acts as an excitotoxin by increasing synaptic activity in the network of neurons established in primary culture.
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Acknowledgements. This work was supported by grants from the USPHS (DA06781 and DA07304), the NSF (BNS9010486) and the Graduate School of the University of Minnesota (S.A.T.). S.A.T. is a University of MinnesOa McKnight-Land Grant Professor T.P. was supported by NIi-I training Grant GM07994.
- Hippocampal neurons
- Intracellular calcium