Study of projections from the entopeduncular nucleus to the thalamus of the rat

Abstract

The entopeduncular nucleus (EP) is a major outflow nucleus of the basal ganglia and innervates the lateral habenula, parafascicular, pedunculopontine, ventrolateral (VL), ventromedial (VM), and mediodorsal thalamic nuclei. This study investigated the morphology of single axons of entopeduncular neurons projecting to the motor thalamus by placing small injections of dextran biotin into the EP and reconstructing drawings of single axons from serial sections. There were two populations of entopeduncular-thalamic projection axons: those that projected only to the motor thalamus (VL and VM) and those that projected to both the motor thalamus and other nuclei (e.g., the habenula). The neurochemist..