Residual neurogenesis in chronically epileptic hippocampus of mice

Abstract

Abnormal hippocampal neurogenesis after acute seizures has been well addressed. However, whether newly generated cells continued to be disturbed even they were born in the chronic stage after pilocarpine-induce status epilepticus has remained elusive. Labeling dividing progenitors and their progeny with retroviral vector expressing green fluorescent protein or proliferation marker 5-bromo-2′-deoxyuridine at 3 months post pilocarpine-induced status epilepticus in mice, a spot of newly born neurons exhibiting hilar ectopic location (4.57±2.3%), aberrant basal dendrites (8.09±1.5%) and abnormal axon sprouting into inner molecular layer of dentate gyrus was identified when examined 6 weeks later. No significant difference on the amount of mossy fiber sprouting was found when cohorts of newborn cells were eliminated by methylazoxymethanol acetate injection initiated at 3 months after SE, suggesting that adult generated neurons in the chronically epileptic hippocampus don’t contribute a lot to the mossy fiber sprouting. These results indicated that the aberrant neurogenesis in the chronically epileptic hippocampus occurs only in a small population of newly generated granule cells.