COMPARTMENTAL ORGANIZATION OF THE PEPTIDE NETWORK IN THE HUMAN CAUDATE-NUCLEUS

The mammalian striatum may be divided into a striosomal compartment an d a surrounding matrix region. We have examined the distribution of le ucine enkephalin (LENK) and substance P (SP) immunoreactivity in relat ion to striosomes defined by calbindin-D (CABD) staining in alternate 70 mu m serial sections from the human caudate nucleus. The distributi on of LENK immunoreactivity showed a transition from dorsal to ventral striatum: dorsally, LENK-rich patches were present in a lightly stain ed matrix; mid-ventrally, annular patches of LENK staining with a ligh ter core were seen. These patches corresponded to striosomal regions d efined by CABD-poor zones. In contrast, in the ventral caudate and nuc leus accumbens, LENK-poor zones matched CABD-defined striosomes. CABD staining in the matrix was intense in the dorsal caudate, diminishing ventrally. SP-rich zones in dorsal caudate and SP-poor areas in the mi d-ventral region overlapped striosomes. In the ventromedial sector, th e SP staining pattern was complex and did not consistently correlate w ith striosomes. Computer-assisted three-dimensional reconstruction of the striosomal system in the human, based on regions of either high LE NK or low CABD immunoreactivity, revealed the existence of considerabl e long-range order. Patches appeared aligned over several millimeters to form long, horizontal structures in the caudate nucleus, with occas ional orthogonal interconnecting crossbridges. Our results are in acco rd with previous work in the human and in other species. These three-d imensional networks are strikingly similar across individuals and may relate to the segregation of and interactions between striatal circuit s.