Effect of High Temperature on Electrical Seizure-induced Neuronal Damage in Explant Culture of Rat Hippocampus

Chae, Soo Ahn; Park, Yong Min; Yoo, Byoung Hoon; Kim, Dong Wook

Abstract

PURPOSE: Epileptic patients have a increasing tendency to develop seizure attack in high temperature. This finding suggests that high temperature may have an effect on neuronal hyperexcitability and injury of epileptic brain. Therefore, the influence of high temperature on normal and epileptic brain was studied in organotypic explant cultures of rat.
METHODS
Fourteen days-in-vitro cultures from 8 day-old rat pups were perfused with standard aCSF bubbled with 95%/5% O2/CO2 in a microchamber. Stimulus train(0.3 sec, 60 Hz) was applied to Schaffer collaterals in CA3 and extracellular field potential was recorded in the CA1 pyramidal layer. At 36degrees C initially, AD was evoked. In high temperature(HT) group, the cultures were subjected to 39degrees C for a period of 8 min before the second stimulus train was applied. They were then restored to 36degrees C for 10 min. In normal temperature group, temperature was maintained at 36degrees C for the second stimulus train. The cultures were returned to the incubator and observed serially for neuronal damage. Intensity of propidium iodide fluorescence indicative of neuronal injury was quantitated by digital image analysis. The cultures on the same insert that were not stimulated served as the unstimulated groups.
RESULTS
There was not a statistically significant difference in neuronal damage between the unstimulated high-temperature(HT) and normal-temperature(NT) group. In CA1 sector, % damage(mean+/-SEM) was 0.42+/-0.20 vs 0.27+/-0.05 at 24 hrs(HT vs NT group, n=16 each, P>0.05, Student t-test); 1.81+/-0.79 vs 1.43+/-0.27 at 48 hrs(P>0.05); 3.50+/-1.32 vs 3.35+/-0.56 at 72 hrs(P>0.05). In CA3 sector, % damage was 0.34+/-0.10 vs 0.20+/-0.03 at 24 hrs(P>0.05); 0.99+/-0.20 vs 0.83+/-0.23 at 48 hrs(P>0.05); 2.00+/-0.38% vs 2.26+/-0.35% at 72 hrs(P>0.05). Neuronal damage on AD induced cultures during febrile setting(n=16) was significantly higher than in nonfebrile setting(n=16). In CA1 sector, % damage was 6.63+/-2.56 vs 0.92+/-0.45 at 24 hrs(febrile setting vs nonfebrile setting, P= 0.036); 26.37+/-7.44 vs 4.99+/-2.23 at 48 hrs(P=0.010); 38.59+/-9.63 vs 6.48+/-2.30 at 72 hrs (P=0.003). In CA3 sector, % damage was 1.23+/-0.48 vs 3.91+/-2.37 at 24 hrs(P=0.277); 13.09+/-5.75 vs 5.93+/-3.27 at 48 hrs(P=0.288); 27.86+/-8.68 vs 7.54+/-3.74 at 72 hrs(P=0.04).
CONCLUSION
At high temperature, seizures in epileptic brain may be more injurious than seizures in normal temperature.