Role of dopaminergic neuronal system in dizocilpine-induced acetylcholine release in the rat brain

The effects of dopaminergic receptor antagonists on dizocilpine-induced increase in extracellular acetylcholine (ACh) levels in the rat parietal cortex were examined in freely-moving rats, using an in vivo brain microdialysis method. Dizocilpine (0.5mg/kg) significantly increased extracellular ACh levels in the rat parietal cortex and hippocampus, but not in the striatum. Pretreatment with α-methyl-p-tyrosine methyl ester (αMpT) delayed the onset but prolonged the duration of the dizocilpine-induced increases in extracellular ACh levels. The dopamine D₂ receptor antagonist, haloperidol, showed dual effects similarly to αMpT, while the dopamine D₁ receptor antagonist, SCH23390, prolonged, but did not delay, the onset of the dizocilpine-induced increases in ACh levels. These results suggest that the dopaminergic system is involved in the dizocilpine-induced increase in the extracellular ACh level in the parietal cortex in two ways, through both dopamine D₁ and D₂ receptors.