Effects of perinatal stroke on striatal amino acid efflux in rats studied with in vivo microdialysis.
We used in vivo microdialysis to determine the impact of a focal hypoxic-ischemic insult on striatal amino acid efflux in the immature brain. Microdialysis probes were inserted into the right striatum of postnatal day 7 rats. To induce hypoxic-ischemic injury, the right carotid artery was ligated and the animals were exposed to 8% oxygen for 2.5 hours (n = 22). Rats exposed to ligation alone (n = 10) or hypoxia alone (n = 8) and untreated controls (n = 17) were also studied. Two hours after probe insertion, a 30-minute baseline microdialysis sample was obtained. After arterial ligation, two additional baseline samples were collected. Five more samples were collected over the next 2.5 hours (in 8% oxygen or room air). Eight amino acids (glutamate, aspartate, taurine, glutamine, alanine, serine, glycine, and asparagine) were consistently detected in dialysates using a high-performance liquid chromatography assay with electrochemical detection. In untreated controls, amino acid efflux did not change over 4 hours. During hypoxia-ischemia, efflux values fluctuated widely, with marked intra-animal and interanimal variability. Efflux peaks for each amino acid were defined as values greater than the highest control mean value plus two standard deviations. Glutamate efflux peaks (greater than 7 pmol/min compared with 2 pmol/min at baseline) were detected in no controls and in eight hypoxic-ischemic rats (p = 0.006, Fisher's two-tailed exact test). Taurine efflux peaks (greater than 75 pmol/min compared with 10 pmol/min for controls at baseline) were detected in 10 hypoxic-ischemic rats and one control (p = 0.01) and in seven of the eight animals in which glutamate efflux peaks occurred (p = 0.006).(ABSTRACT TRUNCATED AT 250 WORDS)
Gordon
K E
KE
Department of Pediatrics, University of Michigan, Ann Arbor 48109-0570.
Simpson
J
J
Statman
D
D
Silverstein
F S
FS
D000409:Alanine / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D002561:Cerebrovascular Disorders / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003342:Corpus Striatum / Q000378:metabolism*; D003956:Dialysis / Q000379:methods; D005973:Glutamine / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013654:Taurine / Q000378:metabolism
D000596:Amino Acids; D005973:Glutamine; D013654:Taurine; D000409:Alanine