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Effect of seizures on cerebral hypoxic-ischemic lesions in immature rats
J Towfighi1, C Housman, D Mauger
1Department of Pathology (Anatomic Pathology), The Milton S. Hershey Medical Center, The Pennsylvania State University College of Medicine, P.O. Box 850, Hershey, PA 17033-0850, USA. jtowfighi@psghs.edu
Insights
Chemically induced seizures before hypoxic-ischemic (HI) brain injury protected immature rats against damage. Seizures after HI did not alter injury severity, suggesting seizures can confer tolerance.
Area of Science:
- Neuroscience
- Developmental Neuroscience
- Neuroprotection
Background:
- Cerebral hypoxic-ischemic (HI) injury is a significant cause of neurological damage in immature individuals.
- The impact of seizures on HI brain damage in early development is not fully understood.
- Understanding seizure effects is crucial for developing therapeutic strategies against neonatal brain injury.
Purpose of the Study:
- To investigate the effect of chemically induced seizures on cerebral HI damage in immature rats.
- To determine if seizures occurring before or after HI influence the extent of brain injury.
- To assess the potential of seizures to confer neuroprotection or exacerbate existing damage.
Main Methods:
- Hypoxic-ischemic (HI) brain injury was induced in 7-day (p7) and 13-day (p13) postnatal rats.
- Seizures were chemically induced using kainic acid (KA) or flurothyl vapor.
- Seizures were administered at different time points: 24h and 6h prior to HI, or 2h and 24h post-HI.
Main Results:
- Seizures induced prior to HI significantly reduced the duration of subsequent seizures and conferred protection against cerebral damage, particularly in the hippocampus and cerebral cortex.
- The protective effect of pre-HI seizures varied between seizure types (flurothyl vs. KA) and age groups (p7 vs. p13 rats).
- Seizures induced 2h or 24h after HI showed no significant difference in brain lesion severity compared to HI-only controls.
Conclusions:
- Chemically induced seizures prior to HI do not aggravate, but rather protect against, cerebral damage in immature rats.
- Seizures occurring after HI do not significantly alter the extent of brain injury.
- These findings suggest that seizures can confer tolerance to HI insults when timed appropriately, offering potential therapeutic insights.
Abstract:
The present investigation was designed to study the effect of chemically induced seizures on cerebral hypoxic-ischemic (HI) damage in immature animals. Accordingly, cerebral HI was produced in 7-day postnatal (p7) rats and p13 rats by combined unilateral common carotid artery ligation and hypoxia with 8% oxygen. Seizures were induced chemically by the subcutaneous injection of kainic acid (KA) or inhalation of flurothyl vapor. Three types of experiments were conducted in each age group and for each convulsant. In some animals (group 1), seizures were produced at 24 h and again at 6 h prior to HI. In groups 2 and 3, seizures were induced 2 h or 24 h post HI, respectively. The results indicate that in group 1 animals, the first seizure significantly reduced duration of the second seizure challenge 18 h later at both p7 and p13 (p=0.001). Histologic examination of brains of animals in group 1 subjected to seizures prior to HI and their HI-only controls showed that seizures prior to HI conferred protection against cerebral damage. This effect was significant for flurothyl seizures in p13 rats for all cerebral regions, especially hippocampal CA1 (p=0.0004), and in p7 rats for hippocampus (p=0.04) and particularly cerebral cortex (p=0.007). For KA seizures, the protective effect was only significant in p13 rats and was limited to hippocampal CA regions and subiculum (p=0.0009). Histologic assessment of cerebral lesions of p7 and p13 rats in the other two groups showed no significant difference between the animals subjected to seizures 2 h or 24 h post HI and their HI-only controls (p>0.05). In conclusion, the results of the present study provide no evidence that seizures in early postnatal development aggravate pre-existing cerebral HI damage. They do suggest that seizures prior to HI or prior to a second seizure confer tolerance to both conditions.