Spatial and temporal evolution of neuronal activation, stress and injury in lithium–pilocarpine seizures in adult rats

Abstract

In order to follow the spatial and temporal evolution of neuronal damage, cellular activation and stress responses subsequent to lithium-pilocarpine seizures of various durations in the adult rat, we analyzed the expression of Fos protein and local cerebral glucose utilization as markers of cellular activation, HSP72 immunoreactivity and acid fuchsin staining as indicators of cellular stress and injury, and Cresyl violet staining for the assessment of neuronal damage. The expression of Fos appeared very early, 2-30 min after the onset of polyspikes and intensified during the following 4 h. Fos immunoreactivity was especially high in the hippocampus, cerebral cortex, amygdala and anterior olfactory nuclei. Local cerebral glucose utilization measured during the second hour of seizures was largely increased (350-580%) over control levels in cortical areas, amygdala, dentate gyrus, caudate nucleus and mediodorsal thalamus. HSP72 immunoreactivity never appeared earlier than 40-50 min after the onset of polyspikes, and was most prominent in hippocampal CA3 area, cerebral cortex (except the piriform cortex) and anterior olfactory nuclei. Acid fuchsin staining was maximal in the piriform cortex and the polymorphic layer of the dentate gyrus. Staining was moderate in the sensorimotor cortex and the amygdala. Neuronal damage was extensive in the piriform and entorhinal cortices, the hippocampal CA3 area and the polymorphic layer of the dentate gyrus, basal amygdala, mediodorsal thalamus and anterior olfactory nuclei. In conclusion, the present study shows that brain regions with the highest expression of Fos and the largest metabolic activation were also highly stained with acid fuchsin and most heavily damaged. Conversely, there is no clear relationship between HSP72 expression, cellular activation and neuronal damage.

Magnetic Resonance Imaging in the Study of the Lithium–Pilocarpine Model of Temporal Lobe Epilepsy in Adult Rats

“…Lesions in the hippocampus (CA1, CA3, and the hilus), amygdala, and piriform and entorhinal cortices begin to appear as soon as the first hour of SE and worsen or extend thereafter (7). During SE, brain areas where most damage occurs are those with highest expression of Fos (marker of cellular hyperactivation), acid fuchsin staining (marker of dying neurons), and largest metabolic activation (8)(9)(10)). …”

Treatment Strategies for the NMDA Component of Organophosphorus Convulsions

“…Alternatively, the 1 h SE duration used in this study may not have been of sufficient duration to generate either superoxide or neuronal damage in these areas. Negligible neuronal damage occurs unless SE lasts at least 1 h in Li-pilo (Motte et al, 1998) or 40 min in pilocarpine seizures (Fujikawa, 1996;Lemos and Cavalheiro, 1995). The 1 h SE used in this study may not have been sufficient to induce significant superoxide production in all brain regions.…”

“…A 5 jiM section was taken every 150 jiM through the brain tissue 0.8 to 4.8 mm posterior to bregma. This area was chosen for the histopathological analysis for efficiency and because it contains critical brain nuclei that exhibit the greatest degree of damage fi-om soman (McDonough et al, 1998) and Li-pilo convulsions Motte et al, 1998;Fujikawa et al, 1999;Peredery et al, 2000). The sections were prepared with hematoxylin and eosin (H&E) staining and sent to the coinvestigator.…”

“…In addition, hthium-pilocarpine (Li-pilo)-induced SE results in well-characterized neuropathology in cortex, thalamus, hippocampus and amygdala regions (Honchar et al, 1983;Motte et al, 1998;Peredery et al, 2000;Dube et al, , 2001, without which spontaneous seizures do not develop (Lemos and Cavalheiro, 1995). The mechanism of Li-pilo-induced SE and the resultant neuronal damage are unclear.…”

“…This was compared by ratio to the luminosity of identical electronically defined regions within the hypothalamus of the same section. Because the hypothalamus receives little or no damage in Lipilo convulsions Motte et al, 1998), the optical density m rats without SE was approximately 1 as the light intensity or luminosity in the cortical areas was similar to that in the hypothalamus. In rats with SE the optical density ratio was greater than 1.0 as the necrotic and malacic tissue in the piriform and perirhinal cortex allowed a greater transmission of light.…”