Neurovascular uncoupling under mild hypoxic hypoxia: an EEG-fMRI study in rats.

The effects of oxygen availability on neurovascular coupling were investigated using simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI), in addition to the monitoring of physiological parameters, in 16 α-chloralose-anesthetized rats. Mild hypoxic hypoxia (oxygen saturation=83.6±12.1%) induced significant reductions in fMRI responses (P<0.05) to electrical stimulation in the forepaw, but EEG responses remained unchanged. In addition, the changes in oxygen saturation were linearly correlated with the changes in the fMRI responses. These data further emphasize the importance of oxygen availability, which may regulate neurovascular coupling via the oxygen-dependent enzymatic synthesis of messenger molecules.