Functional architecture of the mammalian striatum: Mouse vascular and striosome organization and their anatomic relationships

To determine whether the general architecture of striatal vessels and mu opioid receptor-rich striosomes is similar, we investigated 3D reconstructions of coronal sections in 10 FVB mice. The sections were stained for striosomes using a mu opioid receptor antibody (MOR1). We used computerized procedures to detect striosomes and vessels and to calculate volume, number and colocalization of striosomes and vessels. The results showed a lattice-like pattern of striosomes similar to, and often surrounding, blood vessels. Furthermore, co-localization calculations suggested that the striosomes are more vascular than the matrix. Vessel volume was 5.0 ± 1.3% per μm³ in striosomes versus 3.6 ± 0.9% μm³ in matrix (p = 0.01). The findings emphasize the probable importance of a grid- or lattice-like structure as an organizing principle of striatal anatomy and function. In addition, the greater vascularity of the striosomes compared to the matrix suggests a unique function of this compartment in relation to humoral signals and neurotropic drugs.