MAPK8 and retinal degeneration: The molecular mechanisms for chemical proteasome inhibition-induced retinal degeneration were further characterized using the NMDA antagonist memantine (100 nmol/eye), the calcium channel blocker lomerizine (50 nmol/eye), the serine protease inhibitor nafamostat (10 nmol/eye), MAP kinase inhibitors (the JNK inhibitor AS601245, 10.5 nmol/eye; the p38 inhibitor SB239063, 20 nmol/eye; the ERK inhibitor U0126, 50 nmol/eye), and the ER stress inhibitor salubrinal (12.5 or 50 nmol/eye) and PBA (100 nmol/eye).