Neuronal subpopulations in a reptilian thalamic reticular nucleus.

In reptiles, Caiman crocodilus, some neurons in the thalamic reticular nucleus are immunoreactive for parvalbumin. Utilizing double-labeling experiments with fluorescent tracers and indirect fluorescence immunocytochemistry, some of these parvalbumin immunoreactive neurons were found to project to the dorsal thalamus. Other thalamic reticular neurons not immunoreactive for parvalbumin were also found to terminate in the dorsal thalamus. These findings suggest that the thalamic reticular nucleus in Caiman contains at least two chemically, and perhaps functionally, distinct neuronal subpopulations.