, Volume 25, Issue 5, pp 329-338

In situ measurements of enzyme activities in the brain

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access

Summary

The present review focusses on enzymes involved in the metabolism of amino acid neurotransmitters and the microphotometric determinations of their activities in various layers of the rat hippocampus. The enzymes are NAD-linked isocitrate dehydrogenase (NAD-ICDH), glutamate dehydrogenase (GDH), and GABA transaminase (GABAT), all of which are localized in mitochondria. GDH seems to be restricted to astrocytes, whereas NAD-ICDH and GABAT are localized in neurons as well as in astrocytes. NAD-ICDH is an important enzyme of the tricarboxylic acid cycle and may deliver α-ketoglutarate for the formation of glutamate and GABA, which serve as neurotransmitters in the hippocampus. GDH catalyses the interconversion of α-ketoglutarate and glutamate, whereas GABAT is the important GABA-degrading enzyme and requires α-ketoglutarate for its activity. While differing in their cellular distribution and activity levels, NAD-ICDH, GDH and GABAT are significantly correlated in their hippocampal distribution. Furthermore, developmental and pharmacohistochemical studies suggest that the distribution and activity of astrocytic GDH is correlated with amino-acidergic neurotransmission in the hippocampus. The data reported give further evidence for a metabolic relationship between neurons and astrocytes in the turnover and metabolism of glutamate and GABA.