Effects of an adenosine A2A receptor blockade in the nucleus accumbens on locomotion, feeding, and prepulse inhibition in rats

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Abstract
The nucleus accumbens (NAc) subserves behaviors governed by natural rewards, i.e., feeding or exploration, and has been implicated in control of prepulse inhibition (PPI), a measure of sensorimotor gating. The present study sought to determine whether a tonic stimulation of adenosine A2A receptors in the rat NAc is involved in control of spontaneous locomotor activity, feeding behavior, and PPI. To this end, bilateral microinfusions of a prodrug (MSX-3) (3 μg and 5 μg in 1 μl per side) of the selective A2A receptor antagonist MSX-2 or vehicle (1 μl per side) were administered into the NAc. Results show that blockade of intra-NAc adenosine A2A receptors by a high (5 μg), but not by a low (3 μg), dose of MSX-3 increased locomotor activity in an open field, reduced food intake, and delayed intake onset in food-deprived rats examined in a test cage with standard laboratory chow. Furthermore, PPI was significantly disrupted after intra-NAc infusion of 5 μg, but not 3 μg, MSX-3. These findings suggest that locomotor activity as well as intact PPI and feeding behavior rely on tonic activation of intra-NAc A2A receptors. The data add further support to the view that adenosine is a tonically active modulator of striatal function through actions on A2A receptors. Synapse 49:279–286, 2003.
Funding Information
  • Deutsche Forschungsgemeinschaft (Ha2340/1-4)