BASAL AMYGDALOID COMPLEX AFFERENTS TO THE RAT NUCLEUS-ACCUMBENS ARE COMPARTMENTALLY ORGANIZED

The basal amygdaloid complex (BAG) topographically projects to the nuc leus accumbens (Acb) in patchy, inhomogeneous patterns. These terminat ion patterns may be related to the histological features of the Acb th at define the shell, core, and adjacent ventral caudate-putamen (CPv), and the ventral striatal compartments providing output to different a utonomic, motor, and endocrine targets. Knowledge of the relationships of BAC afferents with these compartments is essential for understandi ng the activities of amygdalostriatal circuits. Therefore, anterograde tracing experiments were performed, combined with calbindin-D-28K (Ca B) immunohistochemistry or Nissl staining. The results demonstrated th at the caudal parvicellular basal amygdala (Bpc) projected primarily t o cell clusters in the dorsal shell of the medial Acb, and to patches in the core/CPv. Fibers from the caudal accessory basal nucleus (AB) s electively reached CaB-immunoreactive cell clusters in the ventral she ll, avoiding the core/CPv. The rostral AB projected to the same ventra l shell compartments as the caudal AB; in addition, dense terminations were found in the matrix of the core/CPv, avoiding the patches. Cauda l magnocellular basal amygdala (Bmg) fibers reached ventral parts of t he shell, including the CaB-immunoreactive cell clusters. The caudal B mg projected strongly to the patches of the core/CPv, evading the matr ix. Finally, the rostral Bmg densely innervated the moderately CaB-imm unoreactive lateral shell and the patches of the core/CPv, largely avo iding the matrix. These results indicate the specific compartmental re lationships of the patchy BAC terminations and suggest that BAC subreg ions differentially influence particular ventral striatal outputs.