The role of dopamine in the conditioned place preference formed by the aftereffect of high-plate stress

Abstract

When experimental animals under stress, an immediate and robust releasing of dopamine appears in the prefrontal cortex, amygdala, nucleus accumbens, or striatum. In contrast to these neurochemical findings, the behavioral effects under or following stress are rarely studied and remained uncertain. The purpose of this study was to establish an animal model for measuring the alteration of conditioned behavior after the stress. Experiment 1 found that the conditioned place preference (CPP) was formed by the aftereffect of a single trial of high-plate stressor. Experiment 2 investigated the time course of this stressor on dopamine, serotonin, and their metabolies in the prefrontal cortex, hippocampus, amygdala, nucleus accumbens, and striatum. The results showed that all the areas, except hippocampus, contained distinct patterns of changes on dopamine, serotonin and their metabolies during 120 min after stress. The neurochemical alterations are more profound in the nucleus accumbens than the prefrontal cortex. The 3rd and 4th experiments examined the effects of dopamine D1 or D2 receptor antagonists, administered respectively via intraperitoneal or local infusion into the prefrontal cortex, on the CPP formed by the aftereffect of high-plate stress. The results showed that either drug administration of dopamine receptor blockade can inhibit stress-induced CPP. Taken together, these results indicated the CPP formed after high-plate stressor is developed on the immediate increase of dopamine release in the central dopamine system. However, both D1 and D2 receptors in the prefrontal cortex are equally important.