title: Characterisation of extracellular amino acids in striatum of freely moving rats by in vivo microdialysis.
abstract: To investigate the characteristics of extracellular amino acids released from the striatum, we performed in vivo microdialysis in non-anaesthetised, freely moving rats. Amino acids were determined after precolumn derivatisation with o-phthalaldehyde by high-performance liquid chromatography and fluorescence detection. The omission of Ca2+ in the perfusion medium partially decreased the basal concentration of aspartate and glutamate. This shows that a small fraction of basal concentration of aspartate and glutamate is of neuronal origin. The effect of high K+ and veratrine stimulation was evaluated in the presence or absence of Ca2+ or tetrodotoxin (1 microM). High K+ and veratrine caused a remarkable increase in the aspartate and glutamate efflux. The omission of Ca2+ only partially decreased K(+)-stimulated aspartate and glutamate efflux. Tetrodotoxin completely antagonised veratrine-stimulated aspartate and glutamate efflux. Although glycine and taurine releases were stimulated by high K+ and veratrine, their release was not always antagonised with Ca2+ omission or tetrodotoxin inclusion. Thus, the neuronal origin of stimulated release of glycine and taurine is unclear. Although tetrodotoxin sensitivity and Ca2(+)-dependency are regarded as a basic criterion for classical neurotransmitters in microdialysis experiments, they should not be adapted to the physiological characteristics of the release of amino acids.
authors: Division of Health Sciences, University of the Air, Chiba, Japan.
authors: J
authors: J
authors: Semba
authors: S
authors: S
authors: Kito
authors: M
authors: M
authors: Toru
mesh_terms: D000596:Amino Acids / Q000032:analysis*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D003342:Corpus Striatum / Q000378:metabolism*; D008297:Male; D017551:Microdialysis; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015222:Sodium Channels / Q000187:drug effects; D013779:Tetrodotoxin / Q000494:pharmacology; D014702:Veratrine / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D015222:Sodium Channels; D013779:Tetrodotoxin; D014702:Veratrine; D011188:Potassium; D002118:Calcium