[Age-related peculiarities of the hypothalamo-hypophyseo-adrenal system in chronic heterotypic stress].

Age-related peculiarities of the adaptation of the hypothalamo-hypophyseo-adrenal system (HHAS) to the effect of heterotypic stress was studied experimentally in the context of stress-associated behavioral reactions. Young (3 month old), mature (6 month old) and aging (12 month old) Sprague Dawley rats (total number of animals equal to 36) were exposed to chronic heterotypic stressors for 7 days with the subsequent testing of their behavioral responses. Histological changes were studied in the hypothalamus, pituitary and adrenal glands as compared to age-matched control; immunohistochemical reactions were performed to demonstrate CRF, ACTH, ED1, PCNA and caspase-3 with subsequent image analysis. In the aging organism, as compared to young and mature animals, the degree of HHAS activation indicated the dissociation in its central part and adaptive desensitization prevention, typical to young and mature animals. Specifically, in the aging animals exposed to stress, high hypothalamic CRF expression was noted in association with relatively low hypophyseal ACTH expression and high level of adrenal activity. Reduced HHAS plasticity in the aging animals as compared to that in the other age groups, corresponded to their behavioral changes, demonstrating the reduced capacity of the aging organism to adapt to the exposure of unpredictably changing stressors.

[Immunohistochemical characteristics of the spleen under the effect of various types of stressors].

The effect of different types of stressors (physical and psychoemotional) on the splenic immunoarchitecture in prepubertal Sprague-Dawley rats was evaluated using the quantitative immunohistochemical methods. Rats aged 1 month were exposed to chronic stress for 5 hours daily during 7 consecutive days. After the last stress session, animals were sacrificed, spleen was obtained for weighing and processed for routine histology and immunohistochemistry (CD3, CD8, CD90, CD20, ED1, PCNA, caspase-3) with subsequent computer image analysis. The results obtained demonstrated that the range of stress-induced immunosuppressive changes in the splenic compartments was associated with the type of stressor. Chronic exposure to purely psychological stress resulted in the decreased volume of the splenic white pulp associated mainly with the reduction of T-cell subcompartments with the decrease in their cellularity and the reduction of volume density of CD90+ and CD8+ cells in them compared to those in age-matched control animals, while the physical stressor affected both T- and B-subcompartments of the white pulp causing the reduction of lymphoid nodule volume, marginal zone width and volume density of CD20+ cells. Hypoplasia of the splenic B-zones was mainly associated with increased splenocyte apoptotic rate while that of the T-zones--with decreased proliferation rate and attenuated traffic of the recent thymic immigrants into the spleen.