Electrically induced release of labelled taurine, alpha- and beta-alanine, glycine, glutamate and other amino acids from rat neocortical slices in vitro.
The electrically induced release of labelled alpha-aminoisobutyrate, L-alpha-alanine, beta-alanine, glycine, histidine, serine, glutamate, aspartate and taurine, from superfused thin slices of the rat neocortex, held on quick-transfer electrodes was studied. In no instance did the release of these substances resemble that of (3H)-labelled noradrenaline, acetylcholine or 5-hydroxytryptamine, which can be released by 0.5-3 V stimuli and whose release shows an absolute dependency on calcium ions. Small amounts of alpha-aminoisobutyrate, beta-alanine, serine, glutamate and aspartate were released with 4 V stimuli, but the release was statistically significant for the first two substances only. Following incubation with (3H)-histidine, substantial labelling of homocarnosine was found, but no electrically induced release of this dipeptide could be detected. With (14C)-taurine, however, small but significant release was found with sinewave stimuli of 1.5 V or higher. Such release was significantly increased in the absence of calcium ions. Biphasic pulses of frequencies ranging between 10 and 100 Hz. (1 V, 3 ms duration) did not evoke the release of (14C)-taurine, although this type of stimulation readily induced the release of (3H)-noradrenaline studied simultaneously. Differences in threshold, calcium dependency and shape of the taurine efflux peak, relative to that seen with (3H)-noradrenaline and other transmitters, suggest that taurine release occurs by mechanisms unrelated to those that mediate transmitter secretion. The release of all the above amino acids can readily be elicited, however, if stimuli that are too intense, prolonged or damaging are utilized. The occurrence of these artifacts in the present and in previous work is discussed.
Orrego
F
F
Department of Biochemistry, Instituto Nacional de Cardiología, México 7, D.F.
Miranda
R
R
Saldate
C
C
D000409:Alanine / Q000378:metabolism* / Q000493:pharmacokinetics; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism / Q000493:pharmacokinetics; D002336:Carnosine / Q000378:metabolism / Q000493:pharmacokinetics; D004558:Electric Stimulation; D018698:Glutamic Acid / Q000378:metabolism* / Q000493:pharmacokinetics; D005998:Glycine / Q000378:metabolism* / Q000493:pharmacokinetics; D006639:Histidine / Q000378:metabolism / Q000493:pharmacokinetics; D019579:Neocortex / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D009924:Organ Culture Techniques; D051381:Rats; D012694:Serine / Q000378:metabolism / Q000493:pharmacokinetics; D013654:Taurine / Q000378:metabolism* / Q000493:pharmacokinetics; D014316:Tritium / Q000493:pharmacokinetics
D014316:Tritium; D013654:Taurine; D001224:Aspartic Acid; D018698:Glutamic Acid; D012694:Serine; D006639:Histidine; D002336:Carnosine; D000409:Alanine; D005998:Glycine