Regional distribution of putative amino acid neurotransmitters in the CNS of spiders (Arachnida: Araneida).

The regional occurrence of five amino acid neurotransmitters (GABA, taurine, glycine, glutamate, aspartate) was studied in the CNS of five spider families, using a fluorescence microchromatogram method. Clear differences in transmitter distribution were obvious in relation to the phylogenetic standard of the spider families and the CNS regions investigated. For example, high relative amounts of taurine and GABA were typically confined to the protocerebral brain parts, particularly in the Araneidae and Salticidae. Remarkable amounts of glutamate were shown to exist in the lower CNS parts of the Agelenidae and, especially, the Theraphosidae. The results obtained confirm the dominant functional role of the protocerebrum in arthropods.