Role of DSC1 in Drosophila melanogaster synaptic activities in response to haedoxan A

Drosophila sodium channel 1 (DSC1) encodes a voltage-gated divalent cation channel that mediates neuronal excitability in insects. Previous research revealed that DSC1 knockout Drosophila melanogaster conferred different susceptibility to insecticides, which indicated the vital regulation role of DSC1 under insecticide stress. Haedoxan A (HA) is a lignan compound isolated from Phryma leptostachya, and we found that HA has excellent insecticidal activity and is worthy of further study as a botanical insecticide. Herein, we performed bioassay and electrophysiological experiments to test the biological and neural changes in the larval Drosophila with/without DSC1 knockout in response to HA. Bioassay results showed that knockout of DSC1 reduced the sensitivity to HA in both w¹¹¹⁸ (a common wild-type strain in the laboratory) and para^ts1 (a pyrethroid-resistant strain) larvae. Except for para^ts1 /DSC1^-/- , electrophysiology results implicated that HA delayed the decay rate and increased the frequency of miniature excitatory junctional potentials of Drosophila from w¹¹¹⁸ , para^ts1 , and DSC1^-/- strains. Moreover, the neuromuscular synapse excitatory activities of para^ts1 /DSC1^-/- larvae were more sensitive to HA than DSC1^-/- larvae, which further confirmed the functional contribution of DSC1 to neuronal excitability. Collectively, these results indicated that the DSC1 channel not only regulated the insecticidal activity of HA, but also maintained the stability of neural circuits through functional interaction with voltage-gated sodium channels. Therefore, our study provides useful information for elucidating the regulatory mechanism of DSC1 in the neural system of insects involving the action of HA derived from P. leptostachya.