Percentage of intrinsic and relay cells in a thalamic nucleus projecting to general cortex in reptiles, Caiman crocodilus.

Small injections of horseradish peroxidase (HRP) restricted solely to the general cortex in reptiles, Caiman crocodilus, resulted in retrogradely labeled cells located bilaterally in the nucleus dorsolateralis anterior of the thalamus. Larger cortical injections of HRP labeled greater numbers of nucleus dorsolateralis anterior cells. HRP injections designed to label as much cortex as possible resulted in very few unlabeled ipsilateral neurons in the nucleus dorsolateralis anterior. The percentage of these unlabeled cells was less than 1%. These data indicate that the nucleus dorsolateralis anterior contains few, if any, intrinsic or local circuit neurons.