The accessory nucleus of Luys in the rat.

The morphology and connections of the accessory nucleus of Luys were examined in male Wistar strain rats using normal materials stained for Nissl or myelin sheath, and employing the horseradish peroxidase (HRP) method. This nucleus is situated ventrocaudally to the subthalamic nucleus and rostrally to the substantia nigra. The cells of the nucleus were stained more faintly than those of the subthalamic nucleus, zona incerta and substantia nigra. They were embedded in less myelinated fibers of the cerebral peduncle. HRP experiments showed that the accessory nucleus of Luys projects to the anterior portions of the thalamus, probably to the ventral lateral nucleus.