Dopamine and hippocampal input to the nucleus accumbens play an essential role in the search for food in an unpredictable environment

Abstract

The role of D1 and D2 receptors in the nucleus accumbens, and their interaction with hippocampal afferents in mediating exploration, was assessed during a foraging task on a radial-arm maze. In Experiment 1, bilateral infusions into the nucleus accumbens of the D1 antagonist SCH 23390 (50, 100, or 500 ng), but not the D2 antagonist sulpiride (125, 250, or 500 ng), disrupted foraging for four pellets placed at random on an eight-arm radial maze. In Experiment 2, we examined the effects on foraging of blockade of dopamine receptors in the nucleus accumbens in combination with temporary disruption of information relayed by hippocampal afferents to the ventral striatum. Specifically, we employed an asymmetrical infusion procedure that consisted of a unilateral infusion of SCH 23390 (500 ng) into the nucleus accumbens in combination with a contralateral lidocaine-induced inactivation of the ventral CA1/subiculum, and this asymmetrical infusion procedure disrupted choice of unexplored arms on the radial-arm maze. These data suggest that mesoaccumbens dopamine transmission selectively modulates hippocampal inputs to the nucleus accumbens via an action at D1 receptors when an animal is searching for food in the absence of stimuli that predict where food is located in a complex environment.