Effect of precipitated withdrawal on extracellular glutamate and aspartate in the nucleus accumbens of chronically morphine-treated rats: an in vivo microdialysis study.
Excitatory amino acids release during morphine or naloxone administration was studied in rats. Microdialysis in freely moving animals and capillary electrophoresis with laser-induced fluorescence detection were used to measure several amino acids including glutamate and aspartate in the extracellular fluid at the nucleus accumbens. Perfusion with a calcium-free Ringer's solution decreased glutamate and aspartate in nucleus accumbens dialysates to 35% of its baseline levels, suggesting partial synaptic origin of these amino acids. The first morphine injection decreased glutamate and aspartate to 50% of its baseline level. After repeated morphine injections this effect disappeared, suggesting tolerance. Naloxone injections to morphine-dependent rats increased 300% glutamate and aspartate release; these experiments suggest that excitatory amino acid release in the nucleus accumbens might play a role in morphine withdrawal.
Sepulveda
M J
MJ
Department of Physiology, Medical School, Los Andes University, Merida, Venezuela.
Hernandez
L
L
Rada
P
P
Tucci
S
S
Contreras
E
E
D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D008297:Male; D017551:Microdialysis; D009020:Morphine / Q000008:administration & dosage / Q000633:toxicity*; D009270:Naloxone / Q000008:administration & dosage; D009292:Narcotic Antagonists / Q000008:administration & dosage; D009714:Nucleus Accumbens / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013375:Substance Withdrawal Syndrome / Q000209:etiology / Q000378:metabolism*
D009292:Narcotic Antagonists; D001224:Aspartic Acid; D009270:Naloxone; D018698:Glutamic Acid; D009020:Morphine; D002118:Calcium