[Concentrations of monoamines in the brain structures and features of behavior in the two-month old WAG/Rij rats].

The first spike-wave discharges (SWDs) in WAG/Rij rats begin to appear at age of 2-3 months and are fully manifested by 5-6 months. Occurrence of SWDs in the EEG is the main indicator of absence epilepsy. Extensive absence epilepsy in 5-6 months-old WAG/Rij rats is accompanied by decreases in dopamine and its metabolites concentrations in the meso-cortico-limbic and nigro-striatal dopaminergic brain systems, resulting in the expression of depression-like behavioral symptoms. In 36 day-old WAG/Rij rats, SWDs are not manifested, deficiency of dopamine is not revealed, and symptoms of depression-like behavior are not expressed. In this study, behavior and monoamines and their metabolites concentrations were investigated in 5 brain structures (prefrontal cortex, nucleus accumbens, hypothalamus, striatum, hippocampus) in 2 month-old WAG/Rij rats in comparison with Wistar rats of the same age. Reduction of the dopamine and its metabolites concentration in 2 month-old WAG/Rij rats was found only in the prefrontal cortex, indicating rapid response of the prefrontal cortex or its high sensitivity. Rapid response of the prefrontal cortex is supposed to be a.fundamental property of this brain structure. Decreases in the dopamine and its metabolites concentration in the prefrontal cortex in 2 month-old WAG/Rij rats were associated with features of behavior which can be regarded as a state of so called pre-pathology (increased anxiety and stress reactivity) preceding the development of depression-like behavior typical for 5-6-months old rats of this strain.