Permethrin modulates cholinergic mini-synaptic currents by partially blocking the calcium channel

Pyrethroid insecticide modulation of the voltage-gated sodium channel (VGSC) is proposed to underlie their effects on neuronal excitability by inhibiting channel inactivation and increasing channel open time. However, some in vitro evidences indicate that target sites other than VGSCs could contribute to pyrethroid disruption of neuronal activity. Cholinergic excitability in Drosophila, as in other insects and mammals, is important for activity in the central nervous system. The effects of permethrin, a putative calcium antagonist, on calcium current and cholinergic mini-synaptic transmission were investigated in the Drosophila brain. At concentration of 2.5 μM, permethrin significantly decreased the calcium current and cholinergic mini-synaptic current. However, the permethrin could not antagonize the calcium current completely. Removal of calcium from the external solution produced a significant decrease of cholinergic mini-synaptic transmission. The results are consistent with the hypothesis that permethrin may modulate cholinergic mini-synaptic currents by partially blocking the calcium channel.