In this study, the effect of the scorpion alpha-like toxin BmK M1 was investigated on isolated DUM neurons from Locusta migratoria and compared with the effect on para/tipE voltage-gated Na(+) channels (VGSC), cloned from Drosophila melanogaster. The two insects display different pharmacological properties regarding alpha-like toxins. Moreover, with the aid of the alpha-like toxin BmK M1 and 5 of its mutants, the importance of aromatic residues for the interaction of the toxin with the VGSC in L. migratoria and D. melanogaster, is shown.