Comparison of the superfused efflux of preaccumulated D-[3H]aspartate and endogenous L-aspartate and L-glutamate from rat cerebrocortical minislices.
Because the validity of the use of preaccumulated isotopic excitatory amino acids (EAAs) to index the depolarization-evoked release of endogenous EAAs has been questioned, we compared the K(+)-evoked efflux of preaccumulated D-[3H]aspartate from rat cerebrocortical minislices with that of endogenous L-aspartate and L-glutamate. Release of all EAAs increased with the rate of superfusion. Using the most rapid rate (1.6 ml/min), transient elevations in [K+] caused a concentration-dependent increase, with 50 mM K+ evoking a 33-, 23- and 93-fold increase in the efflux of D-[3H]aspartate, L-aspartate and L-glutamate, respectively; this efflux was Ca(2+)-dependent and tetrodotoxin insensitive. Under polarized conditions (5 mM K+), 1 mM kainic acid increased the efflux of preaccumulated and endogenous EAAs. These elevations were not blocked by the competitive kainate receptor antagonist 6,7-dinitroquinoxaline-2-3-dione (DNQX) and were not affected by removing Ca2+ ions. We conclude that in superfused cortical minislices, the efflux of preaccumulated D-[3H]aspartate provides a robust and reliable index of the release of endogenous L-aspartate and L-glutamate.
Department of Psychiatry, University of Pittsburgh School of Medicine, PA.
A M
AM
Palmer
C T
CT
Reiter
D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism*; D066298:In Vitro Techniques; D007608:Kainic Acid / Q000494:pharmacology; D008297:Male; D011188:Potassium / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013237:Stereoisomerism; D013779:Tetrodotoxin / Q000494:pharmacology
D011810:Quinoxalines; D001224:Aspartic Acid; D018698:Glutamic Acid; D013779:Tetrodotoxin; C056723:FG 9041; D011188:Potassium; D007608:Kainic Acid; D002118:Calcium