Direct striatothalamic projections in the neonatal rat

Employing anterograde axonal transport of wheat germ agglutinin conjugated to horseradish peroxidase and retrograde axonal transport of fluorescent tracers, we provided evidence for the existence of direct striatothalamic projections in the neonatal rat. The major terminal sites included the ventromedial, centrolateral and parafascicular thalamic nuclei. Cells of origin of these projections were aggregated in a mosaic fashion. The fact that such pathways do not exist in the adult suggests that they might play a transient role in the development of basal ganglia-related circuitry. These transient projections may also serve as an ideal model system to study the mechanisms underlying neuronal cell death and/or axon collateral retraction naturally occurring during the development of the nervous system.