The role that NO plays in control of regional blood flow with increased neural activity in the brain is controversial. We have shown from direct electrochemical measurements with microelectrodes that there are transient decreases in tissue pO2 (Ances et al. Neurosci. Lett. 306:106–110, 2001) and increases in tissue NO (Buerk et al. NeuroImage 18:1–9, 2003) that precede increases in blood flow during functional activation of the rat somatosensory cortex with electrical stimulation of the forepaw. More recent NO measurements have been made in mouse olfactory cortex in response to different odors. These observations prompt many other questions: Does inhibition of oxidative metabolism by NO play a role in mediating blood flow responses? Is there an increase in O2 used by NO synthases to produce NO? Are there different sensitivities of nNOS and eNOS to O2? What role do astrocytes play in the control of blood flow? Does NO interact with cyclooxygenase and epoxygenase pathways? Can predictive dynamic mathematical models for coupled NO and O2 transport incorporating nonlinear coupling of blood flow and metabolism with neural activity be developed based on experimental observations?
Footnotes
Acknowledgements
(Supported in part by NIH 068164)