Correlations (indicated by regression lines) between basal striatal DA efflux and nigral DA cell electrophysiological activity measured simultaneously in drug-naive (triangles) and HAL-treated (circles) rats. Top, Inset, Population firing rate in drug-naive (open bar) and HAL-treated (solid bar) rats (*p < 0.05, relative to drug-naive group). Main, Correlation between striatal DA efflux and population firing rate in all animals. DA efflux was significantly correlated with population firing rate (Pearson’sr = 0.50; p < 0.05).Bottom, Inset, Population burst firing in drug-naive (open bar) and HAL-treated (solid bar) rats. Main, Correlations between striatal DA efflux and population burst firing in drug-naive (triangles and dotted regression line) and HAL-treated (circles and solid regression line) rats. The correlation in drug-naive rats was not significant (Pearson’s r = 0.30; p= 0.31), whereas it was significant (Pearson’s r = 0.64; p < 0.05) for the HAL-treated rats. Thus, basal striatal DA efflux appeared to depend on firing rate in both untreated and HAL-treated rats; however, only in HAL-treated rats did basal DA efflux appear also to depend on burst-firing activity.