'Priming' enhances the relationship of striatal L-dopa concentration to behavior

Rats with unilateral 6-hydroxydopamine (6-OHDA) lesions were exposed to L-DOPA treatments, 25 mg kg-1 L-DOPA methyl ester/2 mg kg-1 carbidopa, or to saline. Fourteen days later, both sets of animals were tested with the L-DOPA/carbidopa treatment. The L-DOPA pre-exposed animals exhibited behavioral sensitization as indexed by a higher frequency of contralateral rotations. Although striatal L-DOPA and HVA concentrations were equivalent in the two groups, the L-DOPA treatment induced a 10 fold variation in the range of L-DOPA concentrations in the 6-OHDA striatum in both sets of animals. Importantly, significant correlations between striatal L-DOPA concentration and behavior were obtained only for the L-DOPA pre-exposed animals.