5'-nucleotidase in the rodent ventral striatum: relation to the distribution of leu-enkephalin, cell clusters, and infralimbic cortical innervation.

The goal of this study was to determine the compartmental organization of 5'-nucleotidase within the rodent ventral striatum and to compare the distribution of 5'-nucleotidase with that of leu-enkephalin, cell clusters, and infralimbic cortical innervation. In the core, 5'-nucleotidase is present in several contiguous patchy structures that are in register with leu-enkephalin compartments. In the shell, 5'-nucleotidase is concentrated in a longitudinal band along the septal border. This "medial band" extends from the rostral pole of the ventral striatum to the bed nucleus of stria terminalis. The ventral portion of the medial band is in register with a cluster of cells, located medial to the most dorsal island of Cajella. A second 5'-nucleotidase compartment along the border of the core and shell is in register with a cell cluster and is most evident at caudal levels of the ventral striatum. The innervation of the ventral striatum by the infralimbic cortex is denser in the shell than in the core. In the shell, fibers from the superficial layers of the infralimbic cortex tend to avoid the 5'-nucleotidase-rich cell clusters and terminate in areas of moderate 5'-nucleotidase density. By contrast, fibers from the deep layers terminate in the ventral striatum without regard to the 5'-nucleotidase-rich cell clusters. Overall, the compartmental structure of 5'-nucleotidase in the ventral striatum segregates projections from different layers of the infralimbic cortex. Dense 5'-nucleotidase compartments are innervated by neurons in the deep layers of the infralimbic cortex. The area of moderate 5'-nucleotidase density surrounding the 5'-nucleotidase compartments is innervated by neurons in both the superficial and deep layers.