BackgroundBacterial meningitis is known to cause neurodegenerations in the hippocampus, motor cortex and cerebellum. Aim of the present study was to investigate quantitatively the effect of pneumococcal meningitis on hippocampal sub regions in Wistar rats.Method  Thirty days old rats were divided into normal control (NC) and meningitis (M) groups. Rats in the meningitis group were infected with Streptococcus pneumoniae intracisternally on postnatal day 31. The concentration of the bacterial suspension in phosphate-buffered saline (PBS) was 1×10⁶ cfu/ml (colony forming units/ml). The rats were kept under observation for 18 hrs for clinical symptoms of meningitis to develop. After 18-24 hrs of incubation, 10-50µl of the CSF sample was collected. Gram's staining of the CSF smear
was done and observed under oil immersion objective (100X) for Gram positive, lanceolate diplococci. The rats were perfused transcardially with saline followed by 10% formalin. Brains were removed, processed for paraffin sectioning and stained with cresyl violet stain. Neurodegeneration in the hippocampal CA1, CA3 and dentate hilus were quantified. ResultsThe hippocampal sub-regions showed neurodegeneration. Significant fractions of neurons in the above regions were darkly stained and were irregular in shape. There was 56-81% neuronal loss in these regions. The surviving neurons showed 34-45% decrease in cell diameter and 28-29%  decrease in the cross-sectional area in the hippocampal sub regions. ConclusionMeningitis affects the hippocampal subregions equally and may be the neural basis of cognitive deficit. The mechanism of such neurodegeneration could have been due to necrosis or apoptosis.  Word count: [Abstract: 243; Full text: 3597]Figures and Tables: [6]