Abstract
The experiments were performed using 2 groups of male albino rats with the monopolar electrodes implanted in medial forebrain bundle. Animals were trained to press a bar in a standard Skinner box to obtain the electrical stimulation. All animals received 7 daily injections of morphine 5 mg/kg (s.c) followed 50 min later by i.p. administration of either vehicle (2% Tween-80; group 1, n=8) or 6,7-dinitroquinoxaline-2,3-dione (DNQX, 100 mg/kg; group 2, n=7). Each self-stimulation session began 30 min after morphine injection. On day 7 morphine-induced increase in response rate, but not decrease of threshold current was more pronounced in group 1 than in group 2. Two weeks later the rats were exposed to the test injection of the same dose of morphine. The “sensitization” to morphine-induced alterations in response rate and threshold current intensity was observed in group 1, but not group 2. Additional control experiments failed to find any effect of both acute and chronic administration of DNQX on responding in the rats received either acute saline or acute morphine.
These results indicate that the chronic administration of morphine elicits long-term changes in the reward pathways which may be prevented by the concomitant administration of the antagonist of non-NMDA subtypes of glutamate receptors DNQX.
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Bespalov, A., Dumpis, M., Piotrovsky, L. et al. Sensitization to Morphine-Induced Potentiation of Brain Stimulation Reward: Reversal by DNQX. Neuropsychopharmacol 11, 290 (1994). https://doi.org/10.1038/sj.npp.1380232
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DOI: https://doi.org/10.1038/sj.npp.1380232