Astrocytes tell vessels when to dilate

The brain increases blood flow to specific areas when neurons are in a highly activated state – an event known as functional hyperaemia. This process is fundamental to brain function, but the signaling pathways involved have been poorly understood. In November 25 Nature Neuroscience, Micaela Zonta and colleagues from Università di Padova, Italy, show that neuron-to-astrocyte signaling is central to the dynamic control of brain microcirculation (Nature Neuroscience, doi:10.1038/nn980, November 25, 2002).

Zonta et al. examined acute cortical slices of rats and observed that dilation of arterioles triggered by neuronal activity is dependent on glutamate-mediated [Ca2⁺]_i oscillations in astrocytes. Inhibition of these Ca2⁺ responses resulted in the impairment of activity dependent vasodilation, whereas selective activation of single astrocytes in contact with arterioles triggered vessel relaxation. In addition, they showed that a cyclooxygenase product is centrally involved in this astrocyte-mediated control of arterioles.

"While our data do not exclude the possibility ...