Local anaesthetics do not affect protein kinase C function in intact neuroblastoma cells

The effects of local anaesthetics on protein kinase C function in vitro were examined in two model systems: differentiation in mouse Neuro-2a neuroblastoma cells and muscarine M1-receptor mediated phosphoinositide breakdown in human SK-N-MC neuroblastoma cells. Staurosporin, a protein kinase C inhibitor, induced marked neuritogenesis in Neuro-2a cells after incubation for 5 h, whereas no effect could be seen after exposure to the local anaesthetics ropivacaine, lidocaine or bupivacaine. In the other model, protein kinase C-mediated regulation of phospholipase C was demonstrated for SK-N-MC cells. Phorbol 12-myristate 13-acetate, a protein kinase C activator, produced a dose-dependent decrease in both basal and carbachol-stimulated phosphoinositide breakdown. Staurosporin blocked this phorbol ester-induced subsensitivity completely, while ropivacaine, lidocaine or bupivacaine did not, suggesting that no functional protein kinase C antagonism is mediated by local anaesthetics. The present study suggests that unlike the reported inhibiting effects of local anaesthetics on purified protein kinase C isoforms, no such modulation is found in intact neuroblastoma cells.