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Published on: March 23, 2011
Neuronal cell death in hippocampus induced by homocysteic acid in immature rats
Milos Langmeier1, Jaroslava Folbergrová, Renata Haugvicová
1Institute of Physiology, First Medical School, Charles University, Prague, Czech Republic. mlangm@lfl.cuni.cz
Insights
Immature rats exposed to homocysteic acid (HCA) seizures showed significant hippocampal damage, including cell loss and apoptosis, highlighting brain vulnerability. The cerebral cortex remained unaffected, suggesting region-specific neurotoxicity.
Area of Science:
- Neuroscience
- Developmental Neuroscience
- Neurotoxicology
Background:
- Immature brains exhibit unique vulnerabilities to insults.
- Seizure activity can lead to neuronal damage and long-term consequences.
- Homocysteic acid (HCA) is an excitotoxic agent that can induce seizures.
Purpose of the Study:
- To investigate the morphologic changes in the cerebral cortex and hippocampus of immature rats 6 days after induced generalized clonic-tonic seizures.
- To assess the neurotoxic effects of homocysteic acid (HCA) on the developing brain.
Main Methods:
- Generalized clonic-tonic seizures were induced in 12-day-old rats via bilateral intracerebroventricular infusion of homocysteic acid (HCA).
- Histological analysis using Nissl stain and bis-benzimide (Hoechst 33342) was performed on brain tissue 6 days post-seizure.
- Light and electron microscopy were employed to examine morphologic alterations in the cerebral cortex and hippocampus.
Main Results:
- No significant pathologic changes were observed in the cerebral cortex.
- Severe alterations were found in the hippocampus, including complete loss of CA3 pyramidal cells and marked changes in CA1 and the dentate gyrus.
- Apoptotic neuronal death, characterized by nuclear fragmentation, was evident in the dentate gyrus granule cell layer, accompanied by a prominent glial reaction.
Conclusions:
- The immature rat brain is highly vulnerable to homocysteic acid (HCA)-induced seizures.
- Neurotoxicity likely results from a combination of HCA's direct effects and prolonged seizure activity.
- Further research is needed to delineate the specific contributions of excitotoxicity and seizure duration to observed brain damage.
Purpose:
To examine the morphologic alterations in the cerebral cortex and hippocampus of immature rats 6 days after the generalized clonic-tonic seizures induced by homocysteic acid (HCA).
Methods:
Seizures were induced by bilateral intracerebroventricular infusion of HCA (600 nmol per each side) in 12-day-old rats. After 6 days, rat pups were transcardially perfused under deep ether anesthesia with heparinized normal saline and subsequently with the fixation solution (4% paraformaldehyde in phosphate buffer, pH 7.4, for light microscopy) or with Karnovsky's solution (4% paraformaldehyde and 2% glutaraldehyde in phosphate buffer, pH 7.4, for electron microscopic analysis). Nissl stain and the DNA-specific dye bis-benzimide (Hoechst 33342) were used.
Results:
No pathologic changes were found in the cerebral cortex, whereas serious alterations occurred in the hippocampus. A total loss of CA3 pyramidal cells was observed, with marked changes in the CA1 region and dentate gyrus. A prominent glial reaction was seen in many regions of the hippocampal formation. A slight dilatation of the cerebral ventricles was noticed in some experimental as well as control animals. In the granule cell layer of the dentate gyrus, neurons with segmented or fragmented nuclei in various stages of degeneration were detected, displaying the features of apoptotic death.
Conclusions:
These findings demonstrate the vulnerability of the immature rat brain, which most likely reflects both the direct neurotoxic effect of HCA and prolonged seizure activity. The relative contribution of these two factors still remains to be assessed.
