Figure 1. Proposed model for astrocyte TrkB-T1 induced neurodegeneration. (1) Astrocytes upregulate TrkB-T1 in MS and EAE and become responsive to neurotrophins (yellow, blue, green dots for BDNF, NT3, NT4 respectively). TrkB signaling in astrocytes results in enhanced iNOS expression (2) and, consequently, NO synthesis and release (3). Astrocyte NO triggers a secondary NO boost in neurons (4), leading to protein nitrosylation (5), neuronal fragmentation (6) and apoptosis (7).