The effects of pinacidil and tolbutamide in feline pial arteries in situ.

The vasomotor effect of the K+ channel opener pinacidil was investigated in feline pial arteries of the parietal cortex. Perivascular microapplication (5 microliters in 40 sex) and an image splitting method for the measurement of vascular diameter were employed. Pinacidil (10(-11) - 10(-7) M) induced concentration-dependent dilatations at 10(-9) M and higher concentrations. A maximal dilatation of about 42% was achieved at 10(-8) M, the dilatation at 10(-7) M was reduced to 22%. The sulphonylurea tolbutamide exerted per se no effect in pial arteries but it blocked concentration-dependently the pinacidil induced dilatation. This is consistent with the presence of ATP-sensitive K+ channels in pial arteries which are closed under resting conditions.