Pharmacological Dissection of the Crosstalk between Na V and Ca V Channels in GH3b6 Cells.

Thanks to the crosstalk between Na + and Ca 2+ channels, Na + and Ca 2+ homeostasis interplay in so-called excitable cells enables the generation of action potential in response to electrical stimulation. Here, we investigated the impact of persistent activation of voltage-gated Na + (Na V ) channels by neurotoxins, such as veratridine (VTD), on intracellular Ca 2+ concentration ([Ca 2+ ] i ) in a model of excitable cells, the rat pituitary GH3b6 cells, in order to identify the molecular actors involved in Na + -Ca 2+ homeostasis crosstalk. By combining RT-qPCR, immunoblotting, immunocytochemistry, and patch-clamp techniques, we showed that GH3b6 cells predominantly express the Na V 1.3 channel subtype, which likely endorses their voltage-activated Na + currents. Notably, these Na + currents were blocked by ICA-121431 and activated by the β-scorpion toxin Tf2, two selective Na V 1.3 channel ligands. Using Fura-2, we showed that VTD induced a [Ca 2+ ] i increase. This effect was suppressed by the selective Na V channel blocker tetrodotoxin, as well by the selective L-type Ca V channel (LTCC) blocker nifedipine. We also evidenced that crobenetine, a Na V channel blocker, abolished VTD-induced [Ca 2+ ] i elevation, while it had no effects on LTCC. Altogether, our findings highlight a crosstalk between Na V and LTCC in GH3b6 cells, providing a new insight into the mode of action of neurotoxins.