Region-specific effects on brain metabolites of hypoxia and hyperoxia overlaid on cerebral ischemia in young and old rats: a quantitative proton magnetic resonance spectroscopy study.
BACKGROUND
Both hypoxia and hyperoxia, deregulating the oxidative balance, may play a role in the pathology of neurodegenerative disorders underlain by cerebral ischemia. In the present study, quantitative proton magnetic resonance spectroscopy was used to evaluate regional metabolic alterations, following a 24-hour hypoxic or hyperoxic exposure on the background of ischemic brain insult, in two contrasting age-groups of rats: young--3 months old and aged--24 months old.


METHODS
Cerebral ischemia was induced by ligation of the right common carotid artery. Concentrations of eight metabolites (alanine, choline-containing compounds, total creatine, gamma-aminobutyric acid, glutamate, lactate, myo-inositol and N-acetylaspartate) were quantified from extracts in three different brain regions (fronto-parietal and occipital cortices and the hippocampus) from both hemispheres.


RESULTS
In the control normoxic condition, there were significant increases in lactate and myo-inositol concentrations in the hippocampus of the aged rats, compared with the respective values in the young ones. In the ischemia-hypoxia condition, the most prevalent changes in the brain metabolites were found in the hippocampal regions of both young and aged rats; but the effects were more evident in the aged animals. The ischemia-hyperoxia procedure caused less dedicated changes in the brain metabolites, which may reflect more limited tissue damage.


CONCLUSIONS
We conclude that the hippocampus turns out to be particularly susceptible to hypoxia overlaid on cerebral ischemia and that old age further increases this susceptibility.
Macri
Maria A
MA
Department of Respiratory Research, Medical Research Center, Polish Academy of Sciences, Warsaw, Poland.
D'Alessandro
Nicola
N
Di Giulio
Camillo
C
Di Iorio
Patrizia
P
Di Luzio
Silvano
S
Giuliani
Patricia
P
Esposito
Ennio
E
Pokorski
Mieczyslaw
M
D000375:Aging / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000378:metabolism*; D002545:Brain Ischemia / Q000150:complications / Q000378:metabolism*; D005260:Female; D018496:Hyperoxia / Q000150:complications / Q000378:metabolism*; D020925:Hypoxia-Ischemia, Brain / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D011522:Protons; D051381:Rats; D017207:Rats, Sprague-Dawley
D011522:Protons