AQP4 and amyotrophic lateral sclerosis: Quantitative IHC analysis revealed a significant (p < 0.001) increase of AQP4 in the ALS mice SC at the presymptomatic stage (P80) (YFP mice = 541.6 +/- 131.5 a.u. vs YFP, G93A-SOD1 mice = 5403 +/-176 a.u.)(1-2 fold increase) predominantly in the extra-axonal compartment (Fig. 5b and c).