Brain Research 960 (2003) 184–189 www.elsevier.com / locate / brainres Research report Assessment of the seizure susceptibility of Wistar Audiogenic rat to electroshock, pentyleneterazole and pilocarpine * ˜ A.V. Scarlatelli-Lima, L.H.M. Magalhaes, M.C. Doretto, M.F.D. Moraes Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Av. Antonio Carlos 6627, Campus Pampulha, CEP 31270-901 Belo Horizonte, MG, Brazil Accepted 16 October 2002 Abstract ¨ This work evaluates the seizure susceptibility of naıve 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 5363/3, SI 5161/1; median6interquartile range 25% / 75%, WAR Wistar P,0.01) and PTZ (SI 5464/4, SI 5161/4; median6interquartile range 25% / 75%, P,0.02), as indicated by significantly WAR Wistar higher SI scores and shorter latencies for seizure onset ( T 57167 s, T 59468 s; P,0.05 Student t -test, mean6S.E.M.). Although WAR Wistar PILO also caused higher SI scores in WARs (WAR 5161/1, Wistar 5161/1; WAR 51.561/2, Wistar 5161/ 200 mg 200 mg 270 mg 270 mg 1.25; WAR 5961 / 9, Wistar 5461.5 / 7.5; median6interquartile range 25% / 75%), statistically significant differences were not 300 mg 300 mg observed. In conclusion, our results show that WARs have an inherited broader predisposition for seizures.  2002 Elsevier Science B.V. All rights reserved. Theme: Neurological and psychiatric conditions Topic: Epilepsy: human studies and animal models Keywords: Auditory stimulus; Electrical stimulus; Pilocarpine; Pentylenetetrazole; Seizure; Wistar Audiogenic rat 1. Introduction from brainstem circuitry. A partial list of stimuli that might induce forebrain convulsions includes systemic low doses Experimental models of epilepsy might be generally of chemical convulsants (e.g. pentylenetetrazole (PTZ), classified as having a forebrain or a brainstem origin [2]. pilocarpine (PILO)), low currents of transcorneal elec- Convulsions mediated by the forebrain involve clonic troshock or discrete stimulation of forebrain nuclei [2]. In spasms [30] behavioral immobility [10], myoclonic jerks contrast, convulsions mediated by the brainstem involve [25], as well as face and forelimb clonus that may progress tonic–clonic convulsions that may or may not be preceded to rearing and falling. Such ictal behavior is referred to as by wild-running [2]. Brainstem seizures also may occur limbic seizures [31]. Forebrain involvement may occur in independently of forebrain neural substrates once general- the absence of brainstem circuitry, as evidenced by epi- ized tonic–clonic convulsions are induced by transauricu- leptiform electroencephalographic recordings after total lar electroshock (ES) in rats even after surgically decou- midbrain transection [3], completely separating forebrain pling forebrain from brainstem neural networks [1]. Genetic models of generalized seizures have played a critical role in elucidating the pharmacological, electro- *Corresponding author. Tel.: 155-31-3499-2930; fax: 155-31-3499- physiological and neuroethological aspects of generalized 2924. E-mail address: mfdm@icb.ufmg.br (M.F.D. Moraes). seizures. Of particular interest here is the genetically 0006-8993 / 02 / $ – see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0006-8993(02)03831-3