EFFECT OF AMG-1 AND ADENOSINE ON GLUTAMATE RELEASE FROM SYNAPTOSOMES IN RATS

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 KC1 30 mmol · L^-1 were studied with an enzyme-linked fluorometric assay. The synaptosomes were prepared and preincubated for 30 min at 37℃. 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℃ 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.