The effects of adenosine, adenosine A1 receptor antagonist (DPCPX), or NMDA receptor antagonist (APV) on the spontaneous release of [3H]-5-hydroxytryptamine ([3H]-5-HT) during normoxic/normoglycemic or hypoxic/hypoglycemic period were studied in the rat hippocampal slices. The hippocampus was obtained from the rat brain and sliced 400 Ռm thickness with the tissue slicer. After 30 min's preincubation in the normal buffer, the slices were incubated for 30 min in a buffer containing [3H]-5-HT (0.1 ㄍM, 74 ㄍCi/8 ml) for uptake, and washed. To measure the release of [3H]-5-HT into the buffer, the incubation medium was drained off and refilled every ten minutes through sequence of 14 tubes. Induction of glucose/oxygen deprivation (GOD; medium depleting glucose and gassed with 95% N2/5% CO2) was done in 6th and 7th tube. The radioactivities in each buffer and the tissue were counted using liquid scintillation counter and the results were expressed as a percentage of the total radioactivities. When slices were exposed to GOD for 20 mins, the spontaneous release of [3H]-5-HT was markedly increased and this increase of [3H]-5-HT release was blocked by adenosine (10 ㄍM) or DL-2-amino-5-phosphonovaleric acid (APV; 30 ㄍM). Adenosine A1 receptor specific antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) exacerbate GOD-induced increase of spontaneous release of [3H]-5-HT. These results suggest that Adenosine may play a role in the GOD-induced spontaneous release of [3H]-5-HT through adenosine A1 receptor activity.