Summary
Sodium nitroprusside (SNP) and 3-morpholinosydnonimine (SIN-1), are known to liberate
nitric oxide (NO). In this study the effects of SNP and SIN-1 on thrombus formation
in rat cerebral arterioles and venules in vivo were assessed using a helium-neon (He-Ne)
laser. SNP infused at doses from 10 Μg/kg/h significantly inhibited thrombus formation
in a dose dependent manner. This inhibition of thrombus formation was suppressed by
methylene blue. SIN-1 at a dose of 100 Μg/kg/h also demonstrated a significant antithrombotic
effect. Moreover, treatment with SNP increased vessel diameter in a dose dependent
manner and enhanced the mean red cell velocity measured with a fiber-optic laser-Doppler
anemometer microscope (FLDAM). Blood flow, calculated from the mean red cell velocity
and vessel diameters was increased significantly during infusion. In contrast, mean
wall shear rates in the arterioles and venules were not changed by SNP infusion. The
results indicated that SNP and SIN-1 possessed potent antithrombotic activities, whilst
SNP increased cerebral blood flow without changing wall shear rate. The findings suggest
that the NO released by SNP and SIN-1 may be beneficial for the treatment and protection
of cerebral infarction
