The decreases in calcium binding proteins and neurofilament immunoreactivities in the Purkinje cell of the Seizure Sensitive Gerbils

Abstract

In previous studies, it has been reported that Purkinje cell degeneration during seizure is evoked by excitotoxicity due to an increase in the intracellular Ca 2+ level, though calbindin D-28k (CB) and parvalbumin (PV), intracellular free calcium buffers, are abundantly colocalized in these cells. In the present study, we investigated the expressions of CB, PV, neurofilament (NF) 68, 150, 200, and polyphosphorylated epitope in NF (RT 97), in the cerebellum of gerbils to identify the mechanism of Purkinje cell damages induced by seizure. In seizure resistant gerbils, nearly all the Purkinje cells showed CB, PA, NF 150, NF 200 and RT 97 immunoreactivity. In SS gerbils, however, a clear decrease in the number of CB + and PV + Purkinje cells was observed. The NF and RT 97 immunoreactivities, in the Purkinje cells was also lower (except NF 68), but not absent. These results suggest several points. First, the decrease in the concentrations of CB and PV may render the Purkinje cells more susceptible to intermittent Ca 2+ fluctuations and more prone to accumulating intolerable quantities of Ca 2+. Second, during the Ca 2+-PV interaction PV plays an important role in facilitating donations of Mg 2+, which is a potent enzyme activator in phosphorylation. Thus the decline in PV concentration also implicated the defects of phosphorylation in the NF. Third, increases in both the intracellular Ca 2+ level and dephosphorylation trigger the degradation of the NF, particularly NF 200. Finally, these degradations in the NF induce the functional defects in Purkinje cell, which then cause Purkinje cell degeneration.