DISTRIBUTION OF LIMBIC SYSTEM-ASSOCIATED MEMBRANE-PROTEIN IMMUNOREACTIVITY IN PRIMATE BASAL GANGLIA

The limbic system-associated membrane protein is a 64,000-68,000 mol.w t molecule known to be preferentially expressed by neurons in limbic s tructures of rats and cats. The present immunohistochemical study desc ribes the distribution of this protein in the basal ganglia of Macaca fascicularis. The ventral striatum of the cynomolgus monkey displays a very intense immunostaining, whereas the dorsal striatum is much more weakly stained, except for some small zones scattered in the caudate nucleus and, to a lesser extent, in the putamen. These protein-rich zo nes are in register with striosomes, as visualized on adjacent section s immunostained for calbindin. At pallidal levels, immunostaining for the protein is observed only in the subcommissural region, at the vent romedial tip of the internal pallidum, and in the caudoventral portion of the external pallidum. At nigral levels, the immunostaining is hig hly heterogeneous with a marked decreasing rostrocaudal gradient. The staining is most intense in nigral regions that receive striatal input s and are enriched with calbindin. Nigral sectors populated by dopamin ergic neurons, as visualized on adjacent sections immunostained for ty rosine hydroxylase, are largely devoid of immunoreactivity. In contras t, the immunostaining is uniformly intense in the ventral tegmental ar ea. This study provides the first neuroanatomical evidence for the exi stence of the limbic system-associated membrane protein in primate bra in. It reveals that this glycoprotein is distributed in a highly heter ogeneous manner in primate basal ganglia, where it preferentially labe ls regions that are anatomically and functionally linked to the limbic system.