Epileptic patients commonly describe sensory events preceding their seizures, which are called auras. One type of aura involves the perception of odors and there are reports of patients who can prevent the occurrence of seizures through olfactory stimuli (Efron, 1956). Similar findings were reported in animal models. In the animal model of Temporal Lobe Epilepsy by electrical kindling of the amygdala, olfactory stimulation with toluene suppressed seizures in most rats. This effect was maintained even when the animals receive an electrical stimulus 20% higher than the seizure threshold (Ebert and Löscher, 2000). Olfactory stimulation with toluene also decreased the severity of behavioral seizures in Wistar Audiogenic Rats (WAR strain), a model of tonic-clonic seizures by auditory stimulation and also acute limbic seizures by repeated stimulation (audiogenic kindling) (Bertti et al., 2011; Bertti et al., 2010). The aim of this project is to evaluate the effect of olfactory stimulation on the expression of behavioral and electroencephalographic seizures in the WAR strain. For this, male rats will be exposed to olfactory stimulation for 15 seconds prior to acoustic stimulation. We will evaluate the effects of acute acoustic stimulation and of audiogenic kindling.Tested substances will be 0.9% saline (control animals), toluene (C7H8) (Ebert & Löscher, 1997) and TMT (2,4,5 - trimethyl tiazoline; Zibroswski and Vanderwolf, 1997), a component found in the feces of predators like the fox. The animals will undergo stereotactic surgery for unilateral implantation of recording electrodes in the inferior colliculus, hippocampus and piriform cortex. EEG signals and behavioral data will be recorded from rats exposed to acute acoustic stimuli and during the 1st, 20th and 21st acoustic stimuli of the kindling protocol. The tonic-clonic and limbic seizures will be classified according to the categorized mesencephalic severity index (Rossetti et al, 2006) and Racine scores (Racine, 1972). Behavioral analyses will be executed using the ETHOMATIC statistical program (Garcia-Cairasco et al., 1992) and the data displayed as flowcharts. The EEG recordings will be evaluated to identify its waveform and the presence or lack of epileptiform discharges in the implanted regions. Brain tissues will be processed for subsequent immunohistochemical analyses to assess cellular neurodegeneration (Fluoro-Jade C) or neural activation (c-Fos), mainly in the piriform cortex, hippocampus and olfactory bulb.
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