MECHANISM OF ANALGESIC ACTION OF HYPERIN

In previous works, we reported that Hyp (hyperin) showed strong analgesic effect, and inhibited discharges induced by multialgesics, 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 markly 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 algesics, EGTA markly elevated while cacl₂ lowered the effect of Hyp. It was also found that A₂₃₁₈₇, which promote influx of Ca~(2+), could antagonize the effect of Hyp. In the frog sciatic nerves, we fouud 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.