Neuronal subpopulations of developing rat hippocampus containing different calcium-binding proteins behave distinctively in trimethyltin-induced neurodegeneration

The present study investigates, by immunocytochemistry, the behavior of different neuronal subpopulations of the developing rat hippocampus, selectively labeled by the calcium-binding proteins calbindin D28-k (CB), parvalbumin (PV), and calretinin (CR), in neurodegenerative processes induced by the neurotoxicant trimethyltin (TMT). Previous studies on adult rats indicated that CB-immunoreactive (IR) neurons were affected by TMT, while PV- and CR-IR neurons were selectively spared. The present findings show that only CR-IR neurons are spared in developing rats, and in addition the number of CR-IR neurons are significantly higher in the DG of treated animals. On the contrary, PV-IR neurons, spared in adult rats, were affected by TMT during development. CB-IR neurons were affected also in developing rats, as in adults. The different postnatal time-courses of calcium-binding protein expression in relationship to the time of TMT administration (presence of CR but absence of PV) could have a role in the different behavior of CR- and PV-IR cells in developing rats.