Abstract
The effects of dobutamine on the diameters of rat pial vessels were investigated in vivo using a closed cranial window technique. Dobutamine (10-7-10-3 M) was dissolved in artificial cerebrospinal fluid (CSF). Arterioles (17-78 μm in diameter) and venules (20-97 μm in diameter) were observed through the cranial window over the left parietal cortex. Superfusion of the brain surface with only artificial CSF had no effect on vessel diameter. Dobutamine, even at a high concentration of 10-4 M, did not induce significant diameter changes in the pial vessels, compared with control animals. The arterioles showed marked dilatation (+73%) during superfusion with 10-3 M dobutamine (p < 0.01 vs. control). The venules were also dilated (+12%), although the increased diameter was not statistically different from controls. Therefore, dobutamine did not induce a dose-dependent dilation. The results strongly suggest that dobutamine at clinical dosages does not have a direct vasomotor effect on brain microvessels.
