IMPAIRED ACQUISITION AND OPERANT RESPONDING AFTER NEONATAL DOPAMINE DEPLETION IN RATS

The effect of neonatal dopamine depletion in rats was examined using o perant conditioning. Rat pups were given 6-hydroxydopamine (6-OHDA) or sham lesions at 3 days of age. When tested as adults, 6-OHDA treated subjects were impaired in the acquisition of lever pressing for reward and displayed stereotyped sniffing patterns not observed in the contr ol subjects. In addition, significantly lower rates of responding were measured for the lesion group during continuous reinforcement (CRF), dilution of reinforcer efficacy, and with progressively increasing fix ed ratio requirements. Alpha-methyl-p-tyrosine (AMPT), given before on e CRF session, attenuated responding in over half the lesion animals a nd in none of the controls. Dopamine content in caudate nucleus was fo und to significantly correlate with number of trials to acquisition an d rates of responding following AMPT in the lesion group, but not in t he control group. Overall, the results of this experiment showed that neonatal dopamine depletion does not lead to severe motor impairment o r the inability to learn, but does disrupt the normal patterns of beha vior associated with operant conditioning.