Anxiogenic-like profile of Wistar adult rats based on the pilocarpine model: an animal model for trait anxiety?

There is extensive evidence indicating the influence of seizures on emotional responses observed in human and animals, but so far few studies are focusing on the behavioral profile of animals that do not have seizures despite being treated with convulsant agents. We aimed to establish the behavioral profile, biochemical, and electrographic features of rats submitted to the pilocarpine model of temporal lobe epilepsy Rats treated with pilocarpine (20 to 350 mg/kg, i.p.) that did not develop status epilepticus or spontaneous recurrent seizures were evaluated 1 month later in the elevated plus maze (EPM), T-maze (ETM), open-field (OF), and step-down avoidance tests. Electroencephalographic (EEG), glutamate uptake, and hippocampal neuronal death assays were also performed Pilocarpine (150 or 350 mg/kg) promoted anxiogenic-like effects in rats evaluated in the EPM, ETM, and OF tests, whereas only the highest dose evoked spike-wave discharges during EEG recordings. Hippocampal theta rhythm was increased by pilocarpine 150 or 350 mg/kg and only the highest dose reduced the l-[H-3]-glutamate uptake and cell viability on hippocampal slices. Subconvulsant doses of pilocarpine promote long-lasting alterations on neural circuitry, reflected by an increased theta activity in the hippocampus and an anxiety-like profile of rats evaluated 1 month after the treatment which is independent of seizure occurrence and is not related to changes in glutamate uptake or hippocampal damage. These results prompt us to suggest that a systemic administration of subconvulsant doses of pilocarpine could be useful as a new tool to model trait anxiety in rats.