CHRONIC PSYCHOSOCIAL STRESS INDUCES MORPHOLOGICAL ALTERATIONS IN HIPPOCAMPAL PYRAMIDAL NEURONS OF THE TREE SHREW

The effect of sustained psychosocial stress on the morphology of hippo campal pyramidal neurons was analysed in male tree shrews after 14, 20 , and 28 days of social confrontation. A variety of physioiogical chan ges such as constantly elevated levels of urinary cortisol and norepin ephrine and reduced body weight, which are indicative of chronic stres s were observed in the subordinate, but not in the dominant males. Lig ht microscopic analysis of Nissl-stained hippocampal sections showed t hat the staining intensity of the nucleoplasm in the CA1 and CA3 pyram idal neurons was increased after prolonged psychosocial stress, indica ting a change in the nuclear chromatin structure. These alterations we re observed only in subordinate animals and increased in a time depend ent manner in accordance with the length of the stress period. There w as, however, neither a reduction in density nor a degeneration of pyra midal neurons in chronically stressed animals. Mechanisms which may po ssibly account for the observed alterations are discussed.