NEUROCHEMICAL COMPARTMENTALIZATION OF THE GLOBUS-PALLIDUS IN THE RAT - AN IMMUNOCYTOCHEMICAL STUDY OF CALCIUM-BINDING PROTEINS

The globus pallidus external segment forms a major target center of th e mammalian striatum which is characterized by neurochemically distinc t compartments. The present study was undertaken to determine if a cor responding compartmentalization exists within the globus pallidus exte rnal segment in the rat. Immunocytochemical examination of the calcium -binding proteins parvalbumin and calbindin D-28kDa, which are present in neurons of the striatal matrix compartment, was employed. The resu lts indicate three neurochemically distinct compartments within the gl obus pallidus external segment: 1) an area in the medial aspect of the entire length of the globus pallidus that contains dense immunoreacti vity for calbindin D-28kDa; 2) a narrow rim at the striatopallidal jun ction in the rostral two-thirds of the globus palidus that contains ca lbindin D-28kDa immunoreactivity designated as the ''border zone'' of the globus pallidus; and 3) an area between these two zones showing ve ry poor immunoreactivity for calbindin D-28kDa but containing parvalbu min immunoreactive neurons. The calbindin D-28kDa immunoreactive borde r zone corresponds to the area of the globus pallidus where striatal i nputs converge extensively, whereas the rest of the nucleus is involve d in segregated, topographically organized pathways. Parvalbumin-conta ining neurons are involved in the propagation of striatal output relat ed to striosomal and sensorimotor aspects of basal ganglia function. T he present results also indicate that calbindin D-28kDa immunoreactivi ty is completely absent from striosomal neurons and is therefore a use ful marker for striatal compartments. (C) 1994 Wiley-Liss, Inc.