Preferential small arteriolar vasodilatation by the potassium channel opener, BRL 38227, in conscious spontaneously hypertensive rats.

The microvascular effects of the potassium channel opener, BRL 38227 (the active enantiomer of cromakalim), were investigated in conscious spontaneously hypertensive rats (SHR) provided with a chronic dorsal microcirculatory chamber. BRL 38227 decreased blood pressure and increased heart rate in a dose-dependent manner. It dilated arterioles of different sizes, with the most pronounced effect on the smallest precapillary arterioles. Venule diameters were not significantly affected by BRL 38227. The data show a preferential sensitivity of small precapillary arterioles for potassium channel opening.