Mild, Short-term Stress Alters Dendritic Morphology in Rat Medial Prefrontal Cortex

TLDR: The mild stress of daily injections alone may alter morphology of medial prefrontal cortex, suggesting an exquisite sensitivity to chronic stress.

Abstract: Prefrontal cortex is a target for glucocorticoids, shows neurochemical changes in response to stress and mediates many of the behaviors that are altered by chronic corticosterone administration. Three weeks of either daily corticosterone injections or 3 h daily restraint stress result in dendritic changes in pyramidal neurons in medial prefrontal cortex. Interestingly, vehicle injection results in similar but less pronounced changes. Thus, the mild stress of daily injections alone may alter morphology of medial prefrontal cortex, suggesting an exquisite sensitivity to chronic stress. To further examine this morphological sensitivity, we assessed the effect of 1 week of daily brief restraint stress on dendritic morphology in medial prefrontal cortex. Male rats were restrained 10 min per day for one week, handled daily or left unhandled. Rats were then overdosed and brains were stained using a Golgi--Cox procedure. Layer II--III pyramidal neurons in medial prefrontal cortex were drawn and dendritic morphology was quantified. One week of daily brief restraint resulted in selective remodeling of apical dendrites, with atrophy of up to 22--35% in distal branches and sparing of proximal branches. This pattern of reorganization is similar to that seen after either corticosterone injections or 3 weeks of daily 3 h restraint stress. Thus, the stress-induced dendritic changes in medial prefrontal cortex occur rapidly, and in response to a mild stressor.