Assessment of the seizure susceptibility of Wistar Audiogenic rat to electroshock, pentyleneterazole and pilocarpine

Abstract

This work evaluates the seizure susceptibility of naı̈ve female Wistar Audiogenic rats (WARs), a genetic model of reflex epilepsy in which seizures are induced by high-intensity sound stimulation (120 dB SPL), to other pro-convulsive stimuli: transauricular electroshock (ES), pentylenetetrazole (PTZ) and pilocarpine (PILO). Normal Wistar rats from the main breeding stock of the Institute of Biological Sciences, UFMG were taken as controls. Electroshock seizures were induced through a pair of ear-clip electrodes (10 mA, at a frequency of 60 Hz, applied for 1 s). In order to test WAR susceptibility to chemically induced seizures, animals were treated either with PTZ (37.5 mg/kg i.p.) or PILO (200, 270 and 300 mg/kg i.p.). Seizure severity was evaluated by appropriate behavioral severity index scales (SI) specific to each epilepsy model and tested for statistical significance using the non-parametric Mann–Whitney Rank Sum test. Results show a significantly greater susceptibility of WARs for ES (SI WAR=3±3/3, SI Wistar=1±1/1; median±interquartile range 25%/75%, P<0.01) and PTZ (SI WAR=4±4/4, SI Wistar=1±1/4; median±interquartile range 25%/75%, P<0.02), as indicated by significantly higher SI scores and shorter latencies for seizure onset ( T WAR=71±7 s, T Wistar=94±8 s; P<0.05 Student t-test, mean±S.E.M.). Although PILO also caused higher SI scores in WARs (WAR 200 mg=1±1/1, Wistar 200 mg=1±1/1; WAR 270 mg=1.5±1/2, Wistar 270 mg=1±1/1.25; WAR 300 mg=9±1/9, Wistar 300 mg=4±1.5/7.5; median±interquartile range 25%/75%), statistically significant differences were not observed. In conclusion, our results show that WARs have an inherited broader predisposition for seizures.