Fig. 6.

ATP and BzATP induce an efflux of preloaded¹⁴C glutamate and ³H d-aspartate.A, ¹⁴C glutamate release induced by 6 min incubations in standard BSS (left) or Ca²⁺/Mg²⁺-free BSS (right). BzATP produced a greater response than ATP under both conditions (p < 0.05), and the effects of both agonists were amplified in the Ca²⁺/Mg²⁺-free BSS. Cultures used for ¹⁴C glutamate studies were pretreated with methionine sulfoximine and amino-oxyacetic acid to inhibit the metabolism of glutamate to other ¹⁴C-labeled compounds (see Materials and Methods). B, ³H d-aspartate release induced by 6 min incubations in standard BSS (left) or Ca²⁺/Mg²⁺-free BSS (right). The dose–response curves indicate that BzATP is a more potent agonist than ATP and that the effects of both agonists are amplified in Ca²⁺/Mg²⁺-free medium. C, The effect of ATP on ³Hd-aspartate release was amplified by the removal of both Mg²⁺ and Ca²⁺ but not by the removal of either cation alone. Values in each panel are means ± SE; n ≥ 6. +, With; −, without. **p < 0.01.