Serum and depolarizing agents cause acute neurotoxicity in cultured cerebellar granule cells: role of the glutamate receptor responsive to N-methyl-D-aspartate.

The life span of neonatal rat cerebellar granule cells, grown in basal minimal Eagle's medium containing 10% (vol/vol) fetal calf serum, was extended to 21-30 days by weekly supplementation with glucose. Addition of 1% fetal calf serum to the culture at 14 days killed 85% of the cells within 1 hr. This lethal effect could be prevented by the N-methyl-D-aspartate (NMDA) receptor antagonists dibenzocyclohepteneimine (MK-801) and 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonate (CPP). These findings suggested that the glutamate in the serum caused the dramatic neuronal death through action on the NMDA receptor. Indeed, a 5-min incubation in a Locke physiological salt solution containing 20 microM glutamate and 5 microM glycine killed 55-90% of the cells. This acute toxicity could be prevented by a lyso-GM1 ganglioside with N-acetylated sphingosine. The relatively low glutamate content of the sera analyzed suggests that factors in addition to glycine potentiate serum neurotoxicity. The above noted antagonists of the NMDA receptor also greatly reduced the lethal effect of depolarization by 90 mM KCl or 10 microM veratridine. Therefore, it is likely that the toxicity of the depolarizing agents is mediated by glutamate released from the cells. It is concluded that survival of cerebellar neurons in primary culture may be strongly affected by unsuspected neurotoxic phenomena elicited by brief action of a rather low glutamate concentration.