The effects of crowding stress on histological structure of mouse spleen

Regarding to remarkable growth of population and consequent crowding of it in big cities and immune system sensitivity against environmental agents، the present study aimed to investigate the effects of social stress on spleen of mouse. Methods and Materials: Thirty adult male mice of the NMRI strain were selected at the age of 5-6 weeks and were randomly divided into 2 groups. In control group، 5 animals per cage (3 cages) and in stress group، 15 animals per cage were housed for a period of two months. All animals were anesthetized with an intrapritoneally injection of ketamine and xylazine after two months. The sample of blood from left ventricle of heart was provided by heparinized syringe. Serum samples were used for hormonal study by radioimmunoassay. Spleen was weighted after removing and the samples of spleen were fixed for light microscopic study. The mean numbers of macrophage and megakaryocyte cells were determined. The data has been compared using statistical methods (t-test and Mann-Whitney test). The mean weight of spleen and corticosterone level of serum was insignificantly reduced in stress group compared to control group. The mean numbers of macrophage cells in stress group were insignificantly increased compared to control group. The results showed that the mean numbers of megakaryocyte cells were significantly reduced between stress and control group (P=0. 007). The results showed that the crowding stress can be resulted in decreased number of megakaryocyte cells whereas no significant effect on macrophage cells، serum cortisol hormone level and weight of spleen were found. However، further studies in this area are needed to confirm it.