AFFERENT CONNECTIONS OF THE ANTERIOR THALAMUS IN RABBITS

This study was designed to determine whether axons of cholinergic dors al tegmental neurons terminate on cells in the anterior thalamus in ra bbits as in other species, and to localize projecting tegmental cells for future studies of their contributions to anterior thalamic learnin g-relevant neuronal activity. The distribution of retrogradely labeled neurons was examined following injections of wheat germ agglutinin ho rseradish peroxidase (WGA-HRP) centered in the anterior ventral (AV) t halamic nucleus. Tle results confirm past findings in rabbits indicati ng projections to anterior thalamus from the mammillary nuclei, the po sterior cingulate cortex, presubiculum and postsubiculum. Demonstrated for the first time in rabbits were projections from the lateral dorsa l and the pedunculopontine tegmental nuclei, locus coeruleus, dorsal r aphe nucleus, Gudden's dorsal tegmental nucleus, pretectum and reticul ar thalamic nucleus.