Sepulveda M J, Hernandez L, Rada P, Tucci S, Contreras E
Department of Physiology, Medical School, Los Andes University, Merida, Venezuela.
Pharmacol Biochem Behav. 1998 May;60(1):255-62. doi: 10.1016/s0091-3057(97)00550-9.
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.
