Figure 1.
Overexpression of ΔFosB in the nucleus accumbens increases instrumental responding for food in mice and rats: new insights for the gating hypothesis of dopamine? A, Experimental model. Control animals (left) were bitransgenic NSE-tTA-TetOP-ΔFosB mice given doxycycline (Dox) or rats injected with LacZ-cDNA containing herpes virus. Both did not express ΔFosB. Right, Bitransgenic NSE-tTA-TetOP-ΔFosB mice deprived from doxycycline expressed ΔFosB in the striatal complex, whereas rats injected in the core of the NAc with ΔFosB -cDNA containing herpes virus expressed ΔFosB specifically in this structure. B, Summary of the results. When challenged to acquire an instrumental conditioning (IC) (i.e., pressing a lever to obtain food) or during a PR, animals overexpressing ΔFosB displayed an increased instrumental responding compared with control animals. BP, Breaking point. C, Theoretical perspective. Under normal conditions (left), the behavior displayed by an animal facing a challenge to obtain a reward is controlled both by the contingency between its action and the outcome, and the motivational value of the reward. Within the NAc, dopamine could control a functional window through which the appropriate behavioral response to the motivational cues would be selected. When ΔFosB is overexpressed (right), this window would be widened, and this would contribute to a stronger behavioral response to the same motivational stimuli.