Glutamic acid decarboxylase immunoreactivity in some dorsal thalamic nuclei in Crocodilia

Glutamic acid decarboxylase (GAD) immunocytochemical properties of thalamic nuclei known to project to the telencephalon were investigated in reptiles, Caiman crocodilus and Alligator mississippiensis, by monoclonal antibodies to GAD epitopes designated as GAD-1, GAD-2 and GAD-5. GAD-immunoreactive puncta were observed with all three monoclonal antibodies in the following dorsal thalamic nuclei by avidin-biotin complex methodology: dorsolateralis anterior, dorsomedialis anterior, diagonalis, rotundus, reuniens pars centralis and pars diffusa, and the medialis complex. In general, immunoreactivity to GAD was more robust in Alligator than in Caiman. GAD-2 immunoreactivity was more intense than immunoreactivity to GAD-1 or GAD-5 at similar antibody concentrations in both species. Thalamic nuclei varied in the pattern and intensity of GAD (+)puncta staining in Caiman and Alligator. No GAD-immunoreactive neurons were observed in any of these seven thalamic nuclei with any GAD antibody in either species.