NOS3 and migraine disorder: For example, the C allele of the NOS3 locus — a polymorphism 786T>C (rs2070744) — results in a decrease in eNOS expression and, thus, in a decrease in NO production, which in turn may be accompanied by an increased risk of hypertension [6], preeclampsia [7], diabetic nephropathy [8], and migraine [9].