Acute restraint stress prevents nicotine-induced mesolimbic dopaminergic activation via a corticosterone-mediated mechanism: A microdialysis study in the rat

Background: Stress affects the responsiveness to nicotine (NIC), by increasing drug use, facilitating relapse and reinstating NIC self administration even after prolonged abstinence. In turn, high corticosterone (CURT) blood levels induced by stress may alter the neurobiological properties of NIC by acting on the dopamine (DA) mesolimbic system. Methods: In this study, we evaluated the effect of exposure to acute restraint stress on NIC-induced stimulation of the mesolimbic DA system of the rat, by studying extracellular DA levels in the nucleus accumbens shell (NAccs) with microdialysis. Results: NIC intravenous administration (130 mu g/kg) increased DA levels in the NAccs in control rats but not in subjects exposed to stress; this latter phenomenon was prevented by blockade of CURT effects with the inhibitor of corticosterone synthesis metirapone (100 mg/Kg) or the glucorticoid receptor antagonist mifepristone (150 mu mol/kg). Conclusions: These observations show that exposure to acute stress inhibits the stimulatory response of the mesolimbic DA system to NIC and suggest that this effect is mediated by circulating CURT acting on its receptors. These results may bear relevance in explaining the role played by stressful stimuli in NIC-seeking and taking behavior.