EDNRA and obstructive sleep apnea syndrome: As with dilations involving stimulation of endothelial receptors, neurovascular coupling could be restored by inhibition of NADPH oxidase signaling (Figure 6), reduction of the oxidative state, or blocking of endothelin type A receptors.112 Attenuation of neurovascular coupling implicates dysfunction in cell types other than the endothelium because it involves communications among neurons, astrocytes, and vascular smooth muscle.86 Thus, OSA, or at least intermittent hypoxia, affects not only the endothelium but also the entire neurovascular unit.