Relative Resilience of Cerebellar Purkinje Cells in a Cardiac Arrest/Resuscitation Rat Model

In studies on cardiac arrest (CA)/resuscitation (R) injury, Purkinje cell degeneration was described, however, with inconsistent data concerning severity and time point of manifestation. Moreover, CA/R studies paid only limited attention to inhibitory stellate interneurons. To this aim, the hypothesis that cerebellar could be relatively resilient toward CA/R because of diverse cellular defense mechanisms including interaction with stellate cells was tested.

We examined rats with survival times of 6, 24, and 48 h, and 7 and 21 days in comparison with sham- and nonoperated animals. Thereby, we focused on the immunohistochemical expression of cfos, MnSOD, Bcl2, caspase 3, parvalbumin, calbindin D28 k, MAP2, IBA1, and GFAP, especially in the particular sensitivity to CA/R cerebellar lobule IX. Hippocampal CA1 degeneration was demonstrated by expression patterns of MAP2 and NeuN in combination with IBA1 and GFAP.

Comparative analysis of hippocampal CA1 pyramidal cells and cerebellar Purkinje cells confirmed a relative resil-ience of Purkinje cells to CA/R. We found only a notable degeneration of Purkinje cell neuronal fiber network, which, however, not necessarily led to neuronal cell death. To induce significant Purkinje cell loss, a stronger ischemic trigger seems to be needed. As possible Purkinje cell-protecting mechanisms, we would propose: (1) activation of inhibitory stellate cells, shown by cfos, MnSOD, and Bcl2 expression, balancing out ischemia-induced excitation and inhibition of Purkinje cells; (2) translocation of the calcium-buffering system, shown by parvalbumin and calbindin D28 k expression, protecting Purkinje cells from detrimental calcium overload; (3) activation of the neuron-astrocyte cross talk, protecting Purkinje cells from over-excitation by removing potassium and neurotransmitters from the extracellular space; (4) activation of the effective and long-lasting MnSOD defense system; and (5) of the anti-apoptotic protein Bcl2 in Purkinje cells itself. Moreover, the results emphasize the limited comparability of animal CA/R studies because of the heterogeneity of the used experimental regimes.