Rapid expression of neuronal and inducible nitric oxide synthases during post-ischemic reperfusion in rat brain.
OBJECTIVE
To determine whether neuronal and inducible nitric oxide synthase (nNOS and iNOS) isoforms are expressed within cortical neurons during early reperfusion after focal cerebral ischemia.


METHODS
Male spontaneously hypertensive rats underwent occlusion of the left middle cerebral artery for 2 h. Coronal brain sections with normal and ischemic cortex were obtained after 15 min or 1, 6 or 24 h of reperfusion. Immunohistochemical and double-label immunofluorescent techniques were used to confirm cellular identity and localize nNOS and iNOS.


RESULTS
Immunoreactive nNOS was identified within isolated neurons in layer V of normal cortex. However, the number of nNOS-immunoreactive neurons in ischemic cortex rose markedly at 15 min and persisted for 24 h (P< or =0.001 at each time point when compared to normal cortex). Cells that were immunoreactive for nNOS appeared in perivascular clusters within ischemic brain at all sampling times. Immunoreactive iNOS was also expressed within neurons in ischemic cortex, peaking after 15 min of reperfusion (P< or =0.01). Although nNOS-immunoreactive neurons were observed in random numbers within normal tissue throughout reperfusion, iNOS-immunoreactive neurons increased steadily in the same region (P< or =0.05).


CONCLUSIONS
Ischemic neurons become immunoreactive for both nNOS and iNOS during early reperfusion. Expression of iNOS immunoreactivity in unaffected neurons may reflect transcription of immediate early genes in response to stimulatory neurotransmission from ischemic cortex.
Holtz
M L
ML
The Paul G. Blazer, Jr. Stroke Research Laboratory, Sanders-Brown Center on Aging, University of Kentucky College of Medicine, 101 Sanders-Brown Building, 800 South Limestone Street, 40536-0230, Lexington, KY, USA.
Craddock
S D
SD
Pettigrew
L C
LC
D000818:Animals; D001921:Brain / Q000201:enzymology* / Q000473:pathology; D002545:Brain Ischemia / Q000201:enzymology*; D005455:Fluorescent Antibody Technique; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000201:enzymology; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D051381:Rats; D011918:Rats, Inbred SHR; D012016:Reference Values; D015427:Reperfusion Injury / Q000201:enzymology*; D013997:Time Factors
D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; C496322:Nos1 protein, rat; C496318:Nos2 protein, rat