G-proteins are involved in riluzole inhibition of high voltage-activated calcium channels in rat dorsal root ganglion neurons

Effects of riluzole on high voltage-activated (HVA) calcium channels of rat dorsal root ganglion neurons were studied using the whole cell patch- clamp technique. Riluzole at 30 μM inhibited the HVA currents. The onset and offset of riluzole inhibitory effect were slow usually taking more than 3 min. Riluzole inhibition of the HVA currents was abolished and partially reduced by addition of 500 μM GDP-β-S and 1 mM N-ethylmaleimide, respectively, to the pipette solution. Pre-treatment with pertussis toxin or application of depolarizing pre-pulses did not affect riluzole's inhibitory effect on the HVA currents. Riluzole inhibition of the HVA currents was also blocked by internal application of 50 μg/ml protein kinase A inhibitory peptide. It was concluded that pertussis toxin-insensitive G-proteins and protein kinase A may be involved in riluzole inhibition of the HVA currents.