T. Nishikawa et al., NITRIC-OXIDE SYNTHASE INHIBITION REDUCES CAUDATE INJURY FOLLOWING TRANSIENT FOCAL ISCHEMIA IN CATS, Stroke, 25(4), 1994, pp. 877-885
Background and Purpose We tested the hypothesis that inhibiting nitric
oxide production either before or during transient focal ischemia aff
ects early postischemic brain injury. Methods Halothane-anesthetized c
ats underwent 1 hour of left middle cerebral artery occlusion plus 3 h
ours of reperfusion. Pretreatment groups received either intravenous N
(omega)-nitro-L-arginine methyl ester (L-NAME; 10 mg/kg, n = 10) or an
equal volume of diluent (10 mL saline, n = 10) over 30 minutes before
ischemia. Posttreatment groups received intravenous L-NAME (10 mg/kg)
over 30 minutes from 45 minutes of ischemia to 15 minutes of reperfus
ion (n = 10) or intravenous L-NAME (10 mg/kg) plus L-arginine (200 mg/
kg) over the same period followed by continuous L-arginine infusion (2
00 mg/kg per hour) for the remainder of reperfusion (n = 10). Results
Microsphere-determined blood flow to ipsilateral caudate nucleus and i
nferior temporal cortex decreased to the same extent during ischemia a
nd recovered to the same extent during reperfusion in the four groups.
Triphenyltetrazolium-determined injury volume of ipsilateral caudate
nucleus in cats treated with L-NAME before or during ischemia (42 +/-
7% and 42 +/- 3% of caudate nucleus, respectively; mean +/- SE) was le
ss (P<.05) compared with that in cats pretreated with saline (72 +/- 5
%) or cats treated with L-NAME plus L-arginine (68 +/- 5%). Ipsilatera
l cerebral hemispheric injury volume was similar among the four groups
(23 +/- 5%, 13 +/- 3%, 18 +/- 5%, and 29 +/- 5% of hemisphere in grou
ps treated with L-NAME before ischemia and during ischemia, the saline
-treated group, and the group treated with L-NAME plus L-arginine, res
pectively). Conclusions Inhibition of nitric oxide synthase decreases
caudate injury volume from transient focal cerebral ischemia in cats.
The beneficial effect is reversed by L-arginine and is not caused by f
avorable redistribution of blood flow during ischemia and reperfusion.
Because L-NAME was efficacious when administered at reperfusion, nitr
ic oxide generated during reperfusion appears to contribute to caudate
injury.