[Mechanism of analgesic action of hyperin]

In previous works, we reported that Hyp (hyperin) showed strong analgesic effect, and inhibited discharges induced by multianalgesics, but without anesthetic action. In this study, the analgesic mechanism of Hyp was further investigated. In the tail-flick test in mice, EGTA was shown to markedly enhance the analgesic effect of Hyp and shift the dose-effect curve to the upper-left. CaCl2 significantly antagonized the effect of Hyp and shifted the dose-effect curve to the lower-right. In the afferent discharges induced by analgesics, EGTA markly elevated while cacl2 lowered the effect of Hyp. It was also found that A23187, which promote influx of Ca2+, could antagonize the effect of Hyp. In the frog sciatic nerves, we found that Hyp could significantly inhibit influx of Ca2+. This finding suggests that the analgesic effect of Hyp may have close relationship with the reduction of calcium in afferent nerve endings.