Dopamine-NO Interactions in the Nucleus Accumbens during Stress-Induced Inhibition of Exploratory Behavior

Abstract

Experiments on Sprague–Dawley rats using vital intracerebral microdialysis showed that stress accompanied by the acquisition of a conditioned reflex fear reaction leads, at one day, to inhibition of exploratory activity and reductions in exploratory activity-induced increases in extracellular citrulline level (citrulline is a coproduct of NO synthesis) in the nucleus accumbens). Administration of the D2 dopamine receptor antagonist raclopride (10 μM) after acquisition of the conditioned reflex fear reaction led, one day after administration, to recovery of the parameters of exploratory behavior and reversal o the increase in the extracellular citrulline level in the nucleus accumbens accompanying this behavior. These data provide the first evidence that inhibition of exploratory behavior by previously experienced stress may be mediated by a stress-induced decrease the activity of the nitrergic system of the nucleus accumbens formed with the involvement of dopamine D2 receptors in this structure.