Fig. 3.

Jun kinase is activated in sympathetic neurons after NGF withdrawal. A, Jun kinase assays were performed with extracts prepared from sympathetic neurons that had been withdrawn from NGF for 4, 8, or 16 hr (−NGF) or that had been refed with fresh NGF-containing medium (4 hr, +NGF), as described in Materials and Methods. Fifty micrograms of extract were used per immunoprecipitation. Relative Jun kinase activity was determined by scanning autoradiographs on a densitometer. The level of Jun kinase activity at time 0was set as 100%. The results shown are the average of three independent experiments. Error bars indicate SE. B,Survival agents prevent the NGF withdrawal-induced activation of Jun kinase in sympathetic neurons. Sympathetic neurons were refed with fresh NGF-containing medium (+NGF) or were deprived of NGF in the absence (−NGF) or presence of 100 μm CPTcAMP (−NGF +100 μm CPTcAMP) or 30 mmN-acetylcysteine (−NGF + 30 mm NAC). Four hours later, extracts were prepared, and immune complex kinase assays were performed using 50 μg of extract/immunoprecipitation. The results shown are the average of three independent experiments. Error bars indicate SE.