EFFECT OF KINURENIC ACID ON THE ACQUISITION OF INTRAVENOUS MORPHINE SELF-ADMINISTRATION HABIT BY RATS

Male Wistar rats with a silicone cannula implanted into a jugular vein were each placed, for 6 h daily on 5 successive days, in a standard Skinner box where they were trained to self-administer morphine intravenously by pressing a bar. Kynurenic acid, an endogenous nonselective antagonist of excitatory amino acids, injected into rats before their placement in the Skinner box inhibited in a dose-dependent manner the acquisition by them of the morphone self-administration habit, as assessed by the number of times the bar was pressed.