Effects of nifedipine of pial arteriolar calibre: an in vivo study.
In cats the response of individual pial arterioles to perivascular microapplication of the Ca++-antagonistic drug nifedipine was studied using the image-splitting technique developed by Baez. It has previously been shown that the coefficient of variation for repeated measurements of pial vessel diameter using this system is 1%, under conditions of steady arterial pressure and blood gas tensions. All investigated pial arterioles invariably responded with a dilatation at an injected nifedipine concentration of 10 microM. The dilatatory response was inversely proportional to the resting vessel calibre, i.e., arterioles less tham 70 microns responded with a significantly stronger dilatation as compared with arterioles greater than 100 microns in diameter. In experiments where a minor subarachnoid hemorrhage was made by the injection micropipette injuring capillaries just before the perivascular microapplication of nifedipine, a dilatatory response invariably ensued in spite of the perivascular blood which in itself constricted the arterioles under examination.
D000818:Animals; D002415:Cats; D002536:Cerebral Arteries / Q000187:drug effects*; D005260:Female; D008297:Male; D009543:Nifedipine / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D011725:Pyridines / Q000494:pharmacology*; D013345:Subarachnoid Hemorrhage / Q000188:drug therapy; D014664:Vasodilation / Q000187:drug effects*
D011725:Pyridines; D009543:Nifedipine