The source of physiologically stimulated glutamate efflux from the striatum of conscious rats.
1. Glutamate in the extracellular compartment of the striatum of freely moving rats was monitored at 5 min intervals using microdialysis and an enzyme-based assay. 2. Basal levels of dialysate glutamate were 3.6 +/- 0.5 microM. Local infusion through the dialysis probe of tetrodotoxin (TTX), cadmium chloride or magnesium chloride produced no reduction in basal levels of glutamate; with the latter two there was, instead, an increase. 3. Neuronal activation stimulated by induced grooming was accompanied by an increase in total glutamate efflux of 47.5 +/- 25.0% above basal level; this increase was not reduced by local infusion of TTX. 4. We propose that the TTX-insensitive release of glutamate in response to physiological stimulation is derived from glial cells and is a Ca(2+)-dependent mechanism triggered by a receptor-mediated release of Ca2+ from internal stores that spreads through the network of astrocytes.
Miele
M
M
University Laboratory of Physiology, Oxford, UK.
Boutelle
M G
MG
Fillenz
M
M
D000818:Animals; D019256:Cadmium Chloride / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism*; D006120:Grooming / Q000502:physiology; D015636:Magnesium Chloride / Q000494:pharmacology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013239:Stereotyped Behavior / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology
D015636:Magnesium Chloride; D018698:Glutamic Acid; D013779:Tetrodotoxin; D019256:Cadmium Chloride; D002118:Calcium