Pharmacological manipulations of the nucleus accumbens: effects on classically conditioned responses and locomotor activity in the cat.

Agonists and antagonists of dopamine, acetylcholine, and glutamate were injected bilaterally into the nucleus accumbens in 5 adult cats, and their effects on classically conditioned responses and locomotor activity were observed. Dopamine reduced conditioned consummatory responses (leg flexion and vocalization) and conditioned changes in respiration rate, but did not affect other conditioned preparatory responses (changes in heart rate and respiration amplitude). The cholinergic agonist oxotremorine reduced both conditioned and unconditioned leg flexion. The glutamatergic agonist and antagonist had no effect on any of the conditioned responses. All drugs except haloperidol increased the cats locomotor activity in an open field setting. The results suggest that dopaminergic input to the nucleus accumbens is involved in the inhibition of consummatory conditioned responses, and that the behavioral effect of dopamine in the nucleus accumbens might be dependent on the emotional state of the animal.