MAPK8 and brain ischemia: Among the three MAPK signaling pathways, the p38 MAPK and c-Jun N-terminal protein kinase (JNK) signaling pathways have been implicated in apoptosis in response to stress or some pathological conditions, such as cerebral ischemia.14 Modulation of the MAPK signaling pathway by TRPV4 activation has been previously reported.7, 18Figures 2a and b show that an increase in phosphorylated p38 MAPK (p-p38 MAPK) protein level was found in the GSK-injected mice, whereas the protein level of phosphorylated JNK1/2 (p-JNK1/2) was nearly unchanged.