SIR: Blood vessels respond to transmural pressure elevation with constriction and to pressure reduction with dilation. This behavior, which is called myogenic response, is believed to play a central role in the maintenance of constant blood flow and capillary hydrostatic pressure (Pc) during variations in systemic arterial pressure.1
Kitamura and Yamazaki2 have postulated that stretching the vessel wall by increased blood pressure activates the volume regulated Cl− channels. This probably causes the membrane to become depolarized and consequently to activate -type Ca2+ channels and reduce the arterial diameter.
On the other hand, the autoregulation of cerebral hydrostatic pressure is completely different in migraine patients compared with healthy subjects and it seems that myogenic cerebrovascular autoregulation is disturbed in some kinds of migraines.3,4
It may be possible that Cl− channels contribute to migraine disease. We propose that some of the symptoms of migraine headaches may be cured by enhancing Cl− channel currents. In accordance with our hypothesis, Smith et al.5 mentioned that BTS 72664, which enhances chloride currents through picrotoxin-sensitive chloride channels, is likely to have antimigraine activity. Surely, experimental and clinical research is needed to verify this hypothesis.