Quantitative image analysis study of the cerebral vasodilatory activity of nicardipine in spontaneously hypertensive rats

The effect of the Ca²⁺ channel blocker nicardipine on the circle of Willis and the different sized pial arteries was assessed in 20-week- old spontaneously hypertensive rats (SHR) using quantitative image analysis techniques. Normotensive Wistar Kyoto (WKY) rats were also used as a normotensive reference group. In SHR a significant increase of systolic blood pressure (SBP) is noticeable in comparison with WKY rats. The media-to-lumen ratio was increased in the circle of Willis arteries, large sized (diameter > than 150 μm), medium sized (diameter between 150 and 50 μm) and small sized (diameter < than 50 μm), pial artery branches. An increase in the thickness of the tunica media and a luminal narrowing was also seen in medium and small sized pial arteries of SHR in comparison with WKY rats. Treatment with an oral dose of 10 mg/Kg of nicardipine 3 h before the sacrifice significantly reduced SBP in SHR. The drug was without effect on circle of Willis and on large sized pial arteries. Moreover, treatment with nicardipine reduced the thickness of the tunica