Fig. 10. A model showing the multiple actions of PKC activators (PMA/bryostatin) and neurotrophins (BDNF/NT3) on intracellular signalling pathways that lead to protection and neuritogenesis of SGNs after deafferentation in vitro. Upon activation of PKCßI and TrkB/TrkC, both the PI3K/Akt and MAPK/ERK pathways are required for protection and neurite extension of SGNs, as demonstrated by using specific inhibitors of PKC (GF109203X, Gö6976, LY333531), PI3K (LY294002) and MEK (U0126). The combination of neurotrophins with PMA treatment leads to a synergistic action on SGN survival. PYK2 represents an intermediary kinase, which could be involved in the signal pathway linking PKCßI activity to PI3K signalling (see Discussion for details).