Experimental Study: Youth Compared to the Experience of Adulthood in Terms of Features of Stress Response

Age differences in the response to acute stress in the organism of young and mature reproductive-age male inbred Wistar rats were studied. It was found that stress determines an increase in the corticosterone level in both age groups, which is accompanied by a decrease in the testosterone level and an increase in the leptin concentration. In response to stress, young rats show a classic decrease in the mass coefficients (MC) of the thymus and liver, as well as an increase in the MC of the adrenal glands and heart. Contrary to the typical reaction, aged rats show a decrease in the MC of the adrenal glands and stability of the MC of other visceral organs under all experimental conditions. When testing after stress in the elevated plus maze (EPM), the behavior of both groups changed in different directions: in young rats, exploratory activity decreased, while in adults it increased. A concept has been put forward that as a result of accumulated life experience, neurons of the dorsal part of the paraventricular nucleus and cerebellum of mature reproductive age rats passed into a state of excitation, which was expressed in the intensification of locomotor activity (LA) and an increase in the effectiveness of the decision-making mechanisms for choosing the direction of movement in the EPM. While the lack of such experience in young animals caused the inhibition of the LA speed and decision-making mechanisms, inducing a feeling of uncertainty when orienting in the space of the EPM. The data obtained can have a wide range of applications in preclinical studies related to health, aging, stress and modeling of various diseases.