[Role of the brain neurochemical systems in altering the reactivity of the hypophyseal-adrenal system in the gray rat selected for behavior].

Studies have been made of the interrelationship between brain monoaminergic system and pituitary-adrenal function in two groups of the grey rat Rattus norvegicus Berk. One group consisted of non-aggressive rats selected for lack of agonism towards experimentator, the other one included aggressive animals. Domesticated animals exhibited the decreased reaction of the pituitary-adrenocortical complex to emotional stress as well as the decreased response of the endocrine system during stimulation of noradrenaline or serotonin mechanisms of the brain. In addition, noradrenaline and serotonin content of the brain decreased in domesticated rats during emotional stress to a lower extent, as compared to that in aggressive ones. Therefore, one of the sources of correlational changes in the activity of the pituitary-adrenocortical complex during selection for domesticated behaviour is the effect of selection on neurochemical, in particular monoaminergic systems of the brain.