Organization of the Projections of the Lateral Midbrain Tegmental Nuclei to the Basal Ganglia in the Dog Brain

Abstract

The organization of the projections of the lateral nuclei of the midbrain tegmentum (the peripeduncular and perilemniscal nuclei, the nucleus of the brachium of the posterior colliculus) to the functionally diverse nuclei of the basal ganglia system of the brain was studied in dogs (n = 34) using a method based on the retrograde axonal transport of horseradish peroxidase. The study nuclei of the midbrain were found to be involved in functionally diverse circuits whose components include the basal ganglia. These nuclei innervate the area of the putamen, globus pallidus, cuneate nucleus, and subcuneate nucleus, which on the basis of their predominant connections with the motor or limbic nuclei of the brain are classified as motor or limbic nuclei, as well as the area of the caudate and accumbens nuclei and the compact zone of the pedunculopontine nucleus, which receive projections from functionally diverse structures. Analysis of Nissl-stained frontal sections allowed the topographical anatomy of the individual lateral nuclei of the midbrain tegmentum to be refined. Histochemical reactions for NADPH diaphorase was used to determine the cholinergic nature of their neurons.