THE SHORT
AND LONG TERM EFFECT OF EARLY-LIFE SEIZURES ON RAT'S BRAIN
Jiang YW,
Zhang GJ, Wu XR
Department
of Pediatrics, Peking University First Hospital, Beijing 100034
Objective: To study the short and
long term effect of early-life seizures on rat's brain.
Methods: We use a ¡°two hit¡± rat
seizure model, in which systemic kainate or hot water bath was used to
induce seizures on 15 postnatal day (P15) and systemic kainate again on 55
postnatal day (P55). We recorded the latent period of seizures during
developmental period and adulthood. After the second time seizure, we
observe behavior of the rats in all groups, and test memory by Morris water
maze; meanwhile we also examine the mossy fiber sprouting in the
hippocampus by Timm staining and apoptosis of neurons in the hippocampus
and cortex by TUNEL staining.
Results: The latent period of
kainate-induced seizure during development is markedly shorter than that of
seizures during adulthood, but the mossy fiber sprouting and neuron
apoptosis were more severe in latter group. After seizure, there was no
difference between rats with seizure on P15 and normal rats without seizure
in the average searching platform latencies (SPL) in Morris water maze, but
the SPL was significantly longer in rats with seizure on P55 than that in
rats with seizure on P15. Compared the rats with and without seizure during
early development after the second time seizure, the mossy fiber sprouting
and apoptosis of neurons were significantly more severe in the former
without reference to seizure type, as well as SPL in water maze. The rats
in the former group also presented markedly more severe behavioral problem
than that of the rats in the latter group.
Conclusion: Although seizure
susceptibility was higher during development than that in adulthood, but
the brain injury after seizure was milder in the former. No detectable
histologic evidence of brain injury had been found after first
kainate-induced seizure or febrile seizure during development, but brain
injury, such as neurons apoptosis and mossy fibers sprouting, was
significantly more severe in adult rats with seizures during development.
It indicated that seizures during development may induce subtle neuron
pathological injury to increase susceptibility of the neuron to the harmful
effects of seizures later during adulthood.