A critical role for astrocytes in hypercapnic vasodilation in brain by Howarth, C, Sutherland, B, Choi, H, Martin, C, Lind, B, Khennouf, L, LeDue, J, Pakan, J, Ko, R, Ellis-Davies, G, Lauritzen, M, Sibson, N, Buchan, A, MacVicar, B