The concentration of serotonin and its metabolite 5-hydroxyindolacetic acid in brain structures of Wistar and WAG/Rij rats and the influence of imipramine on spike-wave discharges

The concentrations of serotonin and its metabolite 5-hydroxyindoleacetic acid were investigated in various brain structures of WAG/Rij rats, which are a genetic model of human absence epilepsy, and control Wistar rats; as well, the influence of the intraventricular and intraperitoneal injection of imipramine on spike-wave discharges was determined. The animals were first tested for susceptibility to audiogenic seizures. Concentrations of serotonin and its metabolite were investigated in three groups of animals: those that are susceptible to audiogenic seizures, resistant to audiogenic seizures, and a combined group (susceptible and resistant). The influence of imipramine was studied in resistant rats. It was shown that absence epilepsy is associated with a higher activity of the serotoninergic system in the thalamus, where the pacemaker of absence epilepsy discharges is located, and in the medulla oblongata, which is the location of the somas of serotonergic neurons. Selective enhancement of serotonergic system activity by imipramine substantially increased the duration of spike-wave discharges. The mixed form of epilepsy (audiogenic and absence) was accompanied by a reduction of serotonergic system activity in the amygdala. The mixed form of epilepsy was associated with a higher activity of the serotonergic system in the medulla oblongata and cerebellum.