HOC does not change the total amount of AQP4 in the SON, albeit it transiently increases molecular association of AQP4 with GFAP. A, A lack of effect by 10 min HOC in vivo on total AQP4 levels in the SON when compared to iso-osmotic (IO) control. B, Co-immunoprecipitation (IP) of GFAP with AQP4 in the SON after HOC in vivo at different time points. C, Comparison of co-immunoprecipitation of GFAP with AQP4 in the SON 10 min after in vivo HOC with control IO treatment. *P < .05 when compared to IO control. In A and C, panels show representative Western blots (a) and summary graph (b), expressed as a percentage of the AQP4 level in matching controls; n, sample size. Arrows indicate estimated molecular weight of the proteins. Actin was used as a loading control. IgG and total lysate (TL): negative and positive controls respectively