Heterogeneity of evoked dopamine overflow within the striatal and striatoamygdaloid regions

The heterogeneity of evoked dopamine overflow in vivo was examined and compared in striatal and striatoamygdaloid regions of the rat. The characteristics of appearance and disappearance rates and the maximum concentration elicited were determined from overflow curves measured by fast-scan cyclic voltammetry. Overall, the characteristics of evoked dopamine overflow were quite variable in the striatum compared to the relative uniformity of overflow in the basolateral amygdaloid nucleus. In addition, there was a significant decrease in the extracellular disappearance rate of evoked dopamine with depth in the striatum. This gradient did not alter with passage from the caudate-putamen to the nucleus accumbens and no change was observed for the appearance rate or maximum concentration. In contrast, differences in evoked dopamine overflow within the striatoamygdaloid region were sharply defined dorsoventrally and appeared to be region-specific. Dopamine terminal fields in the striatum are not clearly demarcated into the caudate-putamen and nucleus accumbens, but may exist as a continuum. The uptake of dopamine appears to be the distinguishing characteristic for the regulation of extracellular dopamine levels in the striatum and the basolateral amygdaloid nucleus.