Extracellular overflow of glutamate, aspartate, GABA and taurine in the cortex and basal ganglia of fetal lambs during hypoxia-ischemia.

• Extracellular levels of excitatory and inhibitory amino acids were measured in the cortex and striatum of asphyxiated fetal lambs. The fetus was exteriorized from the anesthetized ewe and dialysis probes were placed in the parietal cortex and caudate nucleus. Cerebral blood flow was measured with Xe-clearance. Cortical somatosensory-evoked potentials and electroencephalogram (EEG) were continuously recorded. Asphyxia was induced by clamping the umbilical cord or by graded compression of the maternal aorta. Asphyxia accompanied by elevated cerebral blood flow resulted in a moderate rise in extracellular amino acid levels. During extreme asphyxia, i.e. abolished evoked potentials and reduced cerebral blood flow, marked extracellular elevations of glutamate (3- to 11-fold), aspartate (3- to 7-fold), gamma-aminobutyric acid (GABA) (3- to 5-fold) and taurine (3- to 18-fold) occurred, the higher values representing striatum. Excessive levels of excitatory amino acids may exert injurious effects on immature neurons during such hypoxic-ischemic states.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine (hsv//eng)

Keyword

Amino Acids

metabolism

Animals

Aspartic Acid

metabolism

Asphyxia

metabolism

Brain Ischemia

metabolism

Cerebrovascular Circulation

Evoked Potentials

Somatosensory

Fetus

metabolism

Glutamates

metabolism

Glutamic Acid

Hypoxia

Brain

metabolism

Sheep

Taurine

metabolism

Telencephalon

metabolism

physiopathology

gamma-Aminobutyric Acid

metabolism

Publication and Content Type

ref (subject category)

art (subject category)