Effects of chronic neuroticization on the monoaminergic systems of different structures in the brains of rats with different typological characteristics

The levels of monoamines and their metabolites were studied by HPLC with electrochemical detection in homogenates of hypothalamus, hippocampus, prefrontal cortex, and amygdala in intact and neuroticized Wistar rats with different types of behavior in the open field and forced swimming tests. Intact rats with intermediate levels of activity and depressivity had higher serotonin concentrations in the hypothalamus and lower noradrenaline and hydroxyindoleacetic acid levels in the hippocampus than rats characterized by low activity and high depressivity. In neuroticization, the levels of study monoamines and their metabolites decreased in all the brain structures investigated with the exceptions of an increase in the dopamine concentration in the hippocampus and the dihydroxyphenylacetic acid concentration in the prefrontal cortex. The effect of neuroticization on the neurotransmitter systems in all study structures except the hypothalamus depended on the typological characteristics of the rats. This was most marked in rats with the extreme types of behavior — active and passive — in which changes in monoamine and metabolite contents were seen in all brain structures studied. Rats of the intermediate type showed no changes in any of the substances studied in the hippocampus.