Induction of aquaporin-4 water channel mRNA after focal cerebral ischemia in rat

Aquaporin-4 (AQP4) is a member of a water-selective channel aquaporin-famil y and mainly expressed in the several structures of the brain and in the co llecting duct of the kidney. Here we show its functional involvement in the water homeostasis of the ischemic brain. The expression of AQP4-mRNA is in creased in the peri-infarcted cortex during the observation period (similar to 7 days) after MCA-occlusion, maximally on day 3. The change corresponds to the generation and resolution of brain edema monitored by MRI. The sign als for the mRNA are predominantly observed in glial cells in the molecular and outer granular layer of the peri-infarcted cortex. These results indic ate that AQP4 plays a role in post-ischemic edema formation. (C) 2000 Elsev ier Science B.V. All rights reserved.