Schematic representation of procedures.

(A) Diagrams of coronal brain plates modified from a rat brain atlas [26] depicting the sites where the stereotaxic injections were made. (B) Template obtained from a MOR immunolabeled brain section showing the distribution of the striosomes (s) into the dorsal striatum. The template is applied over the photomicrography of a section immunolabeled for TH, DAT or VMAT-2 (in this figure illustrated by TH) to quantify the optical density of each marker in the striosomal (s) and matrix (m) compartments. Abbreviations: AP: anteroposterior; L: lateral; V: ventral. Scale bar is 1 mm.