Vol. 58, Issue 1, 18-26, July 2000

Sarco-Endoplasmic ATPase Blocker 2,5-Di(tert-butyl)-1,4-benzohydroquinone Inhibits N-, P-, and Q- but Not T-, L-, or R-Type Calcium Currents in Central and Peripheral Neurons

Frédérique Scamps, Stéphan Vigues, Sophie Restituito, Brice Campo, Anne Roig, Pierre Charnet, and Jean Valmier

Institut National de la Santé et de la Recherche Médicale, Montpellier Université II, place Eugène Bataillon, Montpellier (F.S., S.V., B.C., A.R., J.V.); and Centre de Recherche de Biologie Moléculaire, Unité Propre de Recherche, Montpellier, France (S.R., P.C.)

The effects of 2,5-di(tert-butyl)-1,4-benzohydroquinone (tBHQ), a synthetic phenolic antioxidant and a blocker of the sarco-endoplasmic ATPase, were evaluated on low and high voltage-activated Ca²⁺ currents (ICas) with rodent dorsal root ganglion, hippocampal, and motor neurons. In all cell types tested, tBHQ (IC₅₀ = 35 µM) blocked ICa at concentrations used to inhibit sarco-endoplasmic ATPase. This effect was specific to tBHQ because the other sarco-endoplasmic reticulum calcium ATPase pump inhibitors (thapsigargin and cyclopiazonic acid) had no effect. Selective blockade of the N-type current with -conotoxin GVIA and of P- (motoneuron) or Q-type currents (hippocampal neuron) with -agatoxin IVA indicated that tBHQ inhibited N, P, and Q types of ICa. tBHQ had no effect on nitrendipine-sensitive (L-type) and residual drug-resistant (R-type) ICa, nor on the low voltage-activated T-type ICa. Contrary to neuronal cells, the L-type ICa was inhibited by tBHQ in a differentiated mouse neuroblastoma and rat glioma hybrid cell line. Injection of cDNAs encoding the 1A, 1B, 1C, and 1E subunits into oocytes showed that tBHQ blocked ICas at the level of the pore-forming protein. This effect of tBHQ on ICa should be considered when interpreting results obtained with tBHQ used on neuronal preparations. It also may be useful for developing new strategies for the generation of more potent intracellular calcium transient inhibitors.