GLUTAMATE PRODUCTION BY CULTURED MICROGLIA - DIFFERENCES BETWEEN RAT AND MOUSE, ENHANCEMENT BY LIPOPOLYSACCHARIDE AND LACK EFFECT OF HIV COAT PROTEIN GP120 AND DEPOLARIZING AGENTS

Glutamate release from rat and mouse microglia subcultures grown in a serum-free medium was substantially greater in the presence than in th e absence of a physiological concentration of glutamine (0.5 mM). Mous e microglia produced and released more glutamate than rat microglia. G lutamate accumulation in the medium increased with time and cell densi ty, which is consistent with the virtual absence of glutamate reuptake . Lipopolysaccharide (LPS; 10-100 ng/ml), HIV coat protein gp120 (0.1- 10 nM), high K+ (35 mM) or ATP (150 mu M), did not affect glutamate re lease from cells maintained in serum-free medium. In the presence of 1 % dialyzed serum, however, LPS induced a dose- and time-dependent incr ease in the accumulation of glutamate in the medium, suggesting that, as in other cell types, serum factors are required for LPS binding to its receptors.