Nuclear distribution of glutamate, gamma-aminobutyrate and aspartate within the normal human thalamus

Detailed mapping of amino acid neurotransmitter candidates, glutamate, gamma-aminobutyrate and aspartate within the human thalamus, was performed with a grid microdissection method using two horizontal slices of the right thalamus from four neurologically normal cases. Although the fine distribution of these amino acids varied considerably from case to case, characteristic patterns of distribution for each amino acid could be demonstrated by superimposing maps of each case. Glutamate was high around a caudal part of nucleus medialis and a rostral part of nucleus pulvinaris. Interestingly enough, gamma-aminobutyrate distributed in a similar manner to glutamate, suggesting the possible interaction between glutamate and gamma-aminobutyrate in these areas of the thalamus. The distribution of aspartate was different from the former two amino acids and highly concentrated areas were patchy and scattered in the middle part of the thalamus. The results were discussed in relation to the recently accumulated evidence obtained from animal brains for neurotransmitter roles of these amino acids in the thalamus.