Functional variations in cerebral cortical activity are accompanied
by local changes in blood flow, but the mechanisms underlying this physiological
coupling are not well understood. Here we report that dopamine, a neurotransmitter
normally associated with neuromodulatory actions, may directly affect local
cortical blood flow. Using light and electron-microscopic immunocytochemistry,
we show that dopaminergic axons innervate the intraparenchymal microvessels.
We also provide evidence in an in vitro slice preparation that dopamine
produces vasomotor responses in the cortical vasculature. These anatomical
and physiological observations reveal a previously unknown source of regulation
of the microvasculature by dopamine. The findings may be relevant to the mechanisms
underlying changes in blood flow observed in circulatory and neuropsychiatric
disorders.
