Ontogenetic Features of Audiogenic Seizure Susceptibility Induced in Immature Rats by Noise

Abstract

Although numerous models are currently used for systematic study of the mechanisms of epileptogenesis in mature brain, few animal models have been developed that allow similar explorations in the developing nervous system. One experimental model of epilepsy supports a premise that perinatal experience can lead to eventual seizure susceptibility, however. Audiogenic seizure (AGS) susceptibility can be induced during a critical developmental period in normal mice by auditory deprivation and therefore by cochlear trauma. We studied the developmental parameters that affect success of both induction and testing of AGS-susceptibility in the rat. Intense high-frequency noise exposure was used as the traumatizing agent. The Wistar rat strain used is inherently seizure-resistant because in greater than 400 trials, untreated rats have never exhibited susceptibility at any age. Although single prolonged exposures to high-intensity noise were administered to groups of rats at ages between postnatal days (PNDs) 12 and 36, PND 14 was the age when exposure was most likely to result in eventual seizure susceptibility. Furthermore, duration of initial exposure on PND 14 determined the rate of susceptibility when measured 2 weeks later. Accordingly, we noted that single noise exposures at an intensity of 125 dB and ranging between 6 and 10 min in duration induced susceptibility in 100% of rats tested on PND 28; nonetheless, seizures among the rats exposed for 8 min were the most severe. Typically, these seizures began as wild running attacks and were followed by tonic/clonic convulsions.(ABSTRACT TRUNCATED AT 250 WORDS)

Audiogenic seizures in the developmentally primed Long-Evans rat

“…Studies of AGS induction in rodents have determined optimal days for introduction of a priming stimulus, in which initial auditory exposure leads to enhanced excitability in the auditory system Coleman, Ross, Mullaney, & Cooper, 1999;Henry et al, 1971;Pierson & Liebmann, 1992;Pierson & Swann, 1991;Reid & Collins, 1989). Later in life, this excitability may manifest as AGS.…”

“…For the Wistar and Sprague-Dawley rat strains, the optimal acoustic priming day is approximately postnatal Day 14 or 15 (Pierson & Liebmann, 1992;Pierson & Swann, 1991). For mice, the optimal priming period varies, from postnatal Day 16 for C57BL/6J mice (Henry et al, 1971) to postnatal Day 21 for BALB/c mice and SJL/J mice (Reid & Collins, 1986).…”

“…Later in life, this excitability may manifest as AGS. Acoustic priming must occur during a critical developmental period in order to be effective Pierson & Liebmann, 1992;Pierson & Swann, 1991;Reid & Collins, 1986), when the outer ear canals are newly opened and the subject is vulnerable to auditory overstimulation. Auditory priming is believed to cause hearing loss, which is manifested by increased auditory thresholds at the round window in primed mice (Saunders, Bock, Chen, & Gates, 1972).…”

“…One outcome of postnatal sound ma-In these studies, AGS susceptibility was induced by intense sound exposure or deprivation during a vulnerable period of postnatal development, followed by testing at some later date. For example, Pierson and Swann (1991) exposed Wistar rat pups to intense sound on postnatal Day 14 and observed AGS behaviors in all subjects tested on postnatal Day 28. The percentage of subjects displaying AGS behaviors when tested on other days was reduced.…”

Audiogenic Seizures - Biological Phenomenon and Experimental Model of Human Epilepsies

“…GEPRs cochleas hair cell and electrocochleographic alterations, particularly, were investigated (Faingold et al, 1990) being in accordance with mouse data. Furthermore, several neonatal manipulations such as acoustic trauma (Pierson & Snyder-Keller, 1994) or kanamycin (Pierson & Swann, 1991), perinatal antithyroid treatment (Middlesworth & Norris, 1980) induced audiogenic seizure susceptibility in normal rats. The detailed reviews of AE after the priming procedure were presented by Ross & Coleman (2000) and Garcia-Cairasco, (2002).…”