Cardiovascular responses and nitric oxide production in cerebral ischemic rats.
We investigated that the role of nitric oxide (NO) on ischemic rats in brain and heart. Ischemia was induced by both common carotid arteries (CCA) occlusion for 24h following reperfusion. Then tissue samples were removed and measured NOx. In brain, NOx was increased by about 40% vs. normal and it was significantly inhibited by aminoguanidine, selective iNOS inhibitor. This result showed that NOx concentration was increased by iNOS. We investigated the role of Ca2+ during ischemia. Nimodipine, L-type calcium channel blocker, didn't inhibit the increases of NOx concentration during ischemia. It suggested that increased NOx was due to calcium-independent NOS. MK-801, which N-methyl-D-aspartate (NMDA) receptor antagonist, didn't significantly prevent the increases of NOx. In heart, ischemia caused NOx decrease and it is inconsistent with NOx increase in brain. Aminoguanidine and nimodipine didnt affect on NOx decrease. But MK-801 more lowered NOx concentration than those of ischemia control group. It seemed that Ca2+ influx in heart partially occurred via NMDA receptor and inhibited by NMDA receptor antagonist. The mean arterial pressure (MAP) in ischemic rats after 24h of CCA occlusion was decreased when compared to normal value, whereas the heart rates (HR) was not different between two groups. Aminoguanidine or MK801 had no effect on MAP or HR, but nimodipine reduced MAP. There was no difference the effects of aminoguanidine, nimodipine, or MK-801, on MAP and HR between normal rats and ischemic rats. In summary, ischemic model caused an increase of NOx concentration, suggesting that this may be produced via iNOS, which is calcium independent in brain. However in heart, ischemia decreased NOx concentration and NMDA receptor was partially involved. The basal MAP was decreased in ischemic rats but HR was not different from normal control, suggesting that increased NOx in brain of ischemic rat may result in the hypotension.
Shin
Chang Yell
CY
Department of Pharmacology, College of Pharmacy, Chung Ang University, Seoul, Korea.
Lee
Nam In
NI
Je
Hyun Dong
HD
Kim
Jeong Soo
JS
Sung
Ji Hyun
JH
Kim
Dong Seok
DS
Lee
Doo Won
DW
Bae
Ki Lyong
KL
Sohn
Uy Dong
UD
D000818:Animals; D002545:Brain Ischemia / Q000378:metabolism*; D002319:Cardiovascular System / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley
D009569:Nitric Oxide