DISTRIBUTION OF NEUROFILAMENT PROTEIN AND CALCIUM-BINDING PROTEINS PARVALBUMIN, CALBINDIN, AND CALRETININ IN THE CANINE HIPPOCAMPUS

Neurofilament protein and calcium-binding proteins parvalbumin, calbin din, and calretinin are present in morphologically distinct neuronal s ubpopulations in the mammalian cerebral cortex. Immunohistochemical st udies of the hippocampal formation and neocortex have demonstrated tha t while neurofilament protein and calbindin are localized in subsets o f pyramidal neurons, the three calcium-binding proteins are useful mar kers to differentiate non-overlapping populations of interneurons. To date, most studies have been performed in rodents and primates, In the present analysis, we analyzed the distribution of these proteins in t he canine hippocampus. Neurofilament protein was present in large mult ipolar neurons in the hilus and in pyramidal neurons in the CA3 field, whereas pyramidal neurons in the CA1 field and subiculum were less in tensely immunoreactive. Parvalbumin immunoreactivity was observed in l arge multipolar neurons in the hilus and throughout the CA3-CA1 fields , in a few pyramidal-shaped neurons in the CA1 field and subiculum, an d had a distinct neuropil staining pattern in the granule cell layer a nd stratum pyramidale of the Ammon's horn, Calbindin immunoreactivity displayed a strong labeling of the granule cells and messy fibers and was also observed in a population of moderately immunoreactive neurons in the CAI field and subiculum. Calretinin immunoreactivity was relat ively weaker overall. The inner molecular layer in the dentate gyrus h ad a distinct band of labeling, the stratum lacunosum/moleculare conta ined a punctate neuropil staining, and there were a few small multipol ar neurons in the hilus, CA3-CA1 fields, and subiculum. Comparison of the staining patterns observed in the dog hippocampus with those in hu man, macaque monkeys and rats revealed that although there are some su bregional differences among these taxa, the dog may constitute a valua ble large animal model for the study of certain neurological condition s that affect humans, in spite of the phylogenetic distance between ca rnivores and primates.