['Palytoxin (PLT) is a potent toxin that binds to the Na,K-ATPase. Palytoxin is highly neurotoxic and increases the cytosolic calcium concentration ([Ca(2+)](c)) while decreasing intracellular pH (pH(i)) in neurons (Vale et al., 2006; Vale-Gonzalez et al., 2007). It is also a tumour promoter that activates several protein kinases.', 'The role of different protein kinases in the effects of palytoxin on [Ca(2+)](c), pH(i) and cytoxicity was investigated in cultured neurons.', 'Palytoxin-induced calcium load was not affected by inhibition of calcium-dependent protein kinase C (PKC) isoforms but it was partially ameliorated by blockade of calcium-independent PKC isozymes. Inhibition of the extracellular signal-regulated kinase (ERK) 2 eliminated the palytoxin-induced rise in calcium and intracellular acidification, whereas inhibition of MEK greatly attenuated the palytoxin effect on calcium without modifying the PLT-evoked intracellular acidification. Blockade of c-Jun N-terminal protein kinases (JNK) somewhat decreased the palytoxin-effect on calcium, whereas inhibition of the p38 mitogen activated protein kinases (MAPKs) delayed the onset of the palytoxin-evoked rise in calcium and acidification. Furthermore, the cytotoxicity of palytoxin was completely blocked by inhibition of ERK 2 and partially prevented by inhibition of MEK. PLT increased phosphorylated ERK immunoreactivity in a concentration-dependent manner.'] Do mitogen-activated protein kinases regulate palytoxin-induced calcium influx and cytotoxicity in cultured neurons?