Effect of pneumolysin on rat brain ciliary function: Comparison of brain slices with cultured ependymal cells

This study compares two models for examining ependymal ciliary function: ra t brain slices cut from the fourth ventricle and primary ependymal cells in culture. The cilia from both preparations were very reproducible; each pre paration had cilia beating at a constant frequency of between 38 and 44 Hz. With the brain slices, ciliary stasis occurred after 5 d in culture. Howev er, ependymal cells had fully functional cilia for up to 48 d in culture. T he pneumococcal toxin, pneumolysin, caused a dose-dependent inhibition of c ilia beat frequency within 15 min in both models. There were no significant differences in the mean log 50% inhibitory concentration (pIC(50)) slice = 0.65 +/- 0.05, equivalent to 4.4 hemolytic units (HU)/mL; cells = 0.57 +/- 0.14, equivalent to 3.7 HU/mL. There were also no significant differences in the mean Hill slope factors for the curves (slice = 1.4 +/- 0.05; cells = 1.6 +/- 0.4). These data demonstrate that both models can be used to exam ine the acute (15-min) effects of pneumolysin on cilia beat frequency. The main advantage of the primary ependymal culture model is that considerably more cultured ependymal cells (similar to 70%) are available, compared with the number of ependymal cells on the brain slices (similar to 2%), thus re ducing the number of animals used. A pure ependymal culture was not achieve d (similar to 30% of the cells were not ciliated). The increased survival t ime of the ependymal cells compared with the brain slices make cultured epe ndymal cells more useful for examining long-term ciliary function, whereas brain slices may be more useful for examining the interactions between epen dymal and other nearby cells.