The Effects Of Cold And Freezing Temperatures On The Blood Brain Barrier And Aquaporin 1, 4, And 9 Expression In Cope’S Gray Treefrog, Hyla Chrysoscelis

Abstract

Felemban, Dalal. M.S. Department of Biological Sciences, Wright State University, 2016. The Effects of Cold and Freezing Temperatures on The Blood Brain Barrier and Aquaporin 1, 4, and 9 Expression in Cope’s Gray Treefrog, Hyla chrysoscelis. In sub-freezing temperatures, cerebrospinal fluid (CSF) and blood plasma within the brain of freeze-tolerant gray treefrogs, Hyla chrysoscelis, are likely to freeze. We hypothesized that this would challenge blood-brain barrier (BBB) integrity and volume regulation for cells in the brain. Our first hypothesis, tested as cerebral Evans blue permeability, was not supported; BBB integrity appeared uncompromised by cold. Our second hypothesis, tested as changing expression of aquaporin (AQP) proteins, was partially supported. Whole-brain expression (Western blot) of AQP1 and AQP4 were unchanged by cold conditions, but AQP9 expression increased in thawed animals. AQP1 was found (immunohistochemistry) in ependymal cells, endothelial cells, neurons, and astrocytes, AQP4 and AQP9 in neurons and astrocytes. Cell localizations of AQPs were not changed by thermal conditions, but cold conditions did enhance immunofluorescence intensity. The brain of gray treefrogs is protected from damage during freezing. Changing expression of AQPs may protect cells during cold-induced osmotic challenges.