F. Masi et al., Dopamine output in the nucleus accumbens shell is related to the acquisition and the retention of a motivated appetitive behavior in rats, BRAIN RES, 903(1-2), 2001, pp. 102-109
Chronic stress exposure consistently impairs the reactivity to aversive and
pleasurable stimuli in rats: these behavioral modifications are associated
with a decrease in dopamine output in the nucleus accumbens shell (NAcS).
However, when rats that have already acquired an appetitive behavior are ex
posed to chronic stress, they develop an impaired reactivity to avoidable a
versive stimuli while retaining the appetitive behavior. The dissociation b
etween these two behavioral traits was used to study whether the decreased
dopaminergic activity in the NAcS was connected to either of the two defici
ts. Dopamine output was studied through microdialysis as dopamine accumulat
ion following re-uptake inhibition by cocaine. When rats that had previousl
y acquired the appetitive behavior were exposed to chronic stress, they sho
wed a dopaminergic transmission in the NAcS similar to that of controls and
significantly higher than that of chronically stressed animals. Thus, dopa
mine output in the NAcS was consistently associated to the acquisition and
maintenance of appetitive behavior, while the expression of a deficit in av
oidance appeared to be independent of it. (C) 2001 Elsevier Science B.V. Al
l rights reserved.