All of the assays were performed with samples dissected from 20 µm freeze dried coronal microtome sections; the size of utilized sample and preparation for assay varied with the substance to be measured. All of the methods employed were based on the conversion of NAD+ to NADPH, NADH to NAD+, or NADPH to NADP+. The amount of pyridine product formed varied from about 1x10^-12 mole in the aspartate assays to about 200x10^-12 mole in the pyruvate kinase assays. It was therefore necessary in all cases to increase the sensitivity 1,000 to 10,000-fold by enzymatic cycling.

Results:

Glucose-6-P dehydrogenase and especially aspartate aminotransferase varied least among the different regions. Glutaminase, associated with the role of glutamate as a transmitter, showed a wider range of activities than any of the six purely metabolic enzymes; moreover, the distribution did not resemble any of these. Both glutamate and aspartate varied over about a 30% range among the twelve subdivisions of the hippocampal formation analyzed. GABA data were somewhat more consistent than GAD data, with relatively high levels for both found in the fascia dentate and the pyramidal cell and molecular layers. While major differences were observed in the normal distribution patterns of each enzyme and amino acid, no substantive effects of either microgravity or tail suspension on these patterns were clearly demonstrated.