Abstracts

Rationale: It is known that status epilepticus (SE) induces an increase in cell proliferation and neurogenesis as well as neuronal cell death in the developing rat hippocampus. Evidence shows that the cerebellum is a highly neurogenic brain region, but it is still controversial if this region exhibits neuronal injury after SE in immature rats. The goal of this study was to determine whether SE increases cell proliferation and/or neuronal cell death in the cerebellar vermis after lithium-pilocarpine-induced SE in fourteen-days-old (P14) rat pups. Methods: Wistar rats were given 3 mEq/kg lithium chloride i.p. on the day before the induction of SE, which was carried out at P14 by subcutaneous injection of 60 mg/kg pilocarpine hydrochloride; control animals were given an equal volume of saline subcutaneously. Twenty four h (for detecting neuronal cell death with Fluoro-Jade B (F-JB) and Tunel staining, n=6) or 7 days (for detecting cell proliferation after 6 daily injections of 50 mg/kg 5-Bromo-2 -deoxyuridine (BrdU) i.p., n=6) following SE rats were anesthetized and transcardially perfused with 4% phosphate-buffered paraformaldehyde; control rats (n=6 per group) were processed similarly. Subsequently, the cerebellum was removed in order to perform peroxidative immunohistochemistry to detect BrdU (40- m-thick sagittal floating sections from medial vermis) or F-JB and Tunel staining (10- m-thick sagittal paraffin sections from medial vermis) in cerebellum.Results: SE increased the number of BrdU-immunoreactive cells at the granular layer (1701.8 74.9) when compared to control rats (1350.7 98.7) (p=0.01). This increment was observed in lobules I (117 7.3), IIIb (118.5 8.1), IV (113.5 5.2), V (137.8 11.5), VIa (117.7 6.6), VIb (127.3 14) and IXa (146.7 11.2) from SE group when compared to the control group (82.7 5.9, 78 7.1, 74.8 5.7, 100.5 5, 94.3 7, 105.7 5.7 y 98.8 9.2, respectively; (p<0.05). F-JB or Tunel positive cells were not detected in vermis from control or SE groups.Conclusions: SE augments cell proliferation in medial vermis from the developing rat in absence of neuronal cell death. Supported by a CONACYT grant (CB-2008-106402 to MLLM).