The present study was aimed to investigate the ability of free radical scavenger(hydroxyl radical scavenger, dimethyl sulfoxide, DMSO) to change the release of 5-hydroxytryptamine(5-HT)from the hypoxia-sensitive rat hippocampal slices.

The hippocampus was obtained from the rat brain and sliced 400µm thickness with the manual chopper. After 30min's preincubation in the normal buffer, the slices were incubated for 20min in a buffer containing[³H]-5-HT(0.1µM, 74µCi/8ml) 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 hypoxia(gassing it with 95% N₂, 5% CO₂) was done in 6th and 7th tube, and DMSO was added 10 minutes prior to these manipulations. 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 hypoxia for 20min, [³H]-5-HT release was decreased and a rebound release of [³H]-5-HT was observed on the post-hypoxic period. Administration of DMSO(10mM) increased the spontaneous release of [³H]-5-HT in the control group. And DMSO also prevented hypoxia-induced decrease of [³H]-5-HT release. But the rebound release of [³H]-5-HT during post-hypoxic period was not affected by DMSO.

In addition to the hydroxyl radical scavenging effect, DMSO has direct stimulation effect on the firing of 5-HT neuron.