NOS3 and Hyponatremia: This suggestion is legitimate on the basis of the observation that removal of the endothelium eliminates dilation of the MCA in response to hyponatremia, whereas inhibition of NOS-dependent signaling with a nonselective NOS inhibitor (L-NAME blocks both constitutive NO synthases, endothelial eNOS and neuronal nNOS) or blockade of cGMP synthesis leads to MCA constriction in hyponatremia.