The effects of
AMG-1 [6(5-hydroxy-2-methylpyridylamino)-9 ribofranosylpurine], an
adenosine analogue, and
adenosine on Ca2+-dependent and independent release of
glutamate from rat synaptosomes induced by KCl 30 mmol.L-1 were studied with an
enzyme-linked fluorometric assay. The synaptosomes were prepared and preincubated for 30 min at 37 degrees C. Two ml of incubation mixture containing synaptosomes (1.27 mg
protein), NADP+ 1 mmol.L-1, L-glutamic
dehydrogenase 50 U, CaCl2 1.3 mmol.L-1 (or
EGTA 1.3 mmol.L-1) was transferred to the stirred cuvette in the fluorometer at 37 degrees C for 5 min. Then,
AMG-1 (or
adenosine) was added. Released
glutamate (eg. fluorescent intensity) was monitored following the addition of 30 mmol.L-1 KCl. The results indicate that Ca2+-dependent
glutamate release from depolarized synaptosomes is inhibited by
AMG-1 (0.1 mmol.L-1) or
adenosine (0.3 mmol.L-1). The action of
AMG-1 seems to be similar to that of
adenosine. However, no change was found on Ca2+-independent release of
glutamate. This implies that the protective effect of
AMG-1 against
cerebral ischemia may be partially due to inhibiting
glutamate release from nerve terminal via the activation of
adenosine A1 receptor.