A comparison between the stimulated and paroxysmal release of endogenous amino acids from rat cerebellar, striatal and hippocampal slices: a manifestation of spreading depression?
Spreading depression, which can be evoked by a variety of stimuli both in vitro and in vivo, is associated with profound changes in extracellular ion concentrations and enhanced release of neurotransmitter amino acids. We have observed a transient spontaneous release of amino acids in slice preparations obtained from rat cerebellum, striatum and hippocampus; this phenomenon has similar properties to stimulus-evoked spreading depression. Aspartate, glutamate, glutamine, serine, glycine and gamma-aminobutyric acid (GABA) release were potentiated during these episodes in all three brain regions, with a variable effect upon taurine release. When compared to glutamate release, a consistently high release of aspartate, glycine and serine was observed. Amino acid release, evoked by whole slice depolarization using veratridine (10-25 microM) or elevated potassium (35-60 mM) consistently enhanced glutamate release, and to a lesser extent aspartate release, but had negligible effect upon the other amino acids. Thus, the release profiles for spontaneous and depolarization-evoked release are markedly different. We suggest that the spontaneous release observed in brain slices represents a spreading depression-like phenomenon; the putative roles of the amino acids are discussed.
Davies
J A
JA
Department of Pharmacology and Therapeutics, University of Wales College of Medicine, Health Park, Cardiff, UK.
Annels
S J
SJ
Dickie
B G
BG
Ellis
Y
Y
Knott
N J
NJ
D000818:Animals; D002531:Cerebellum / Q000187:drug effects / Q000378:metabolism*; D013181:Cortical Spreading Depression / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D017072:Neostriatum / Q000187:drug effects / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014701:Veratridine / Q000494:pharmacology
D018377:Neurotransmitter Agents; D011189:Potassium Chloride; D014701:Veratridine