<b>BmK AS, an active scorpion polypeptide, enhances [<sup>3</sup>H]noradrenaline release from rat hippocampal </b><b>slices </b>

Abstract

Slices of rat hippocampus were preincubated with [3H]noradrenaline ([3H]NA) and superfused with a medium containing desipramine (1 mM) to prevent the reuptake of NA. Addition of BmK AS (0.4 mM), a polypeptide activator of skeletal muscle ryanodine receptor isolated from Chinese scorpion Butlztzs martensi Karsch, to the superfusion medium significantly increased [3H]NA release. The response curve showed a bell-shaped dose-response relationship (0.05-l mM) with the maximal response at 0.4 mM. Further experiments showed that the increase of [3H]NA release was dependent on the presence of extracellular Ca", and inhibited completely by tetrodotoxin (0.3 mM) and strongly by cu-conotoxin GVIA (0.1 mM). The results observed in this study suggest that BmK AS may induce noradrenaline release by increasing Na+ influx.