Dendritic reorganization in pyramidal neurons in medial prefrontal cortex after chronic corticosterone administration

Chronic stress produces deficits in cognition accompanied by alterations in neural chemistry and morphology. For example, both stress and chronic admi nistration of corticosterone produce dendritic atrophy in hippocampal neuro ns (Woolley C, Gould E, McEwen BS. 1990. Exposure to excess glucocorticoids alters dendritic morphology of adult hippocampal pyramidal neurons. Brain Res 531:225-231; Watanabe Y, Gould E, McEwen BS, 1992b. Stress induces atro phy of apical dendrites of hippocampal CA3 pyramidal neurons. Brain Res 588 :341-345). Prefrontal cortex is also a target for glucocorticoids involved in the stress response (Meaney MJ, Aitken DH. 1985. [H-3]Dexamethasone bind ing in rat frontal cortex. Brain Res 328:176-180); it shows neurochemical c hanges in response to stress (e.g., Luine VN, Spencer RL, McEwen BS. 1993. Effect of chronic corticosterone ingestion on spatial memory performance an d hippocampal serotonergic function. Brain Res 616:55-70; Crayton JW, Joshi I, Gulati A, Arora RC, Wolf WA. 1996. Effect of corticosterone on serotoni n and catecholamine receptors and uptake sites in rat frontal cortex. Brain Res 728:260-262; Takao K, Nagatani T, Kitamura Y, Yamawaki S. 1997. Effect s of corticosterone on 5-HT1A and 5-HT2 receptor binding and on the recepto r-mediated behavioral responses of rats. Eur J Pharmacol 333:123-128; Sandi C, Loscertales M. 1999. Opposite effects on NCAM expression in the rat fro ntal cortex induced by acute vs. chronic corticosterone treatments. Brain R es 828:127-134), and mediates many of the behaviors that are altered by chr onic corticosterone administration (e.g., Lyons DM, Lopez JM, Yang C, Schat zberg AF. 2000. Stress-level cortisol treatment impairs inhibitory control of behavior in monkeys. J Neurosci 20:7816-7821). To determine if glucocort icoid-induced morphological changes also occur in medial prefrontal cortex, the effects of chronic corticosterone administration on dendritic morpholo gy in this corticolimbic structure were assessed. Adult male rats received s.c. injections of either corticosterone (10 mg in 250 muL sesame oil, n = 8) or vehicle (250 muL; n = 8) daily for 3 weeks. A third group of rats ser ved as intact controls (n = 4). Brains were stained using a Golgi-Cox proce dure and pyramidal neurons in layer II-III of medial prefrontal cortex were drawn; dendritic morphology was quantified in three dimensions. Sholl anal yses demonstrated a significant redistribution of apical dendrites in corti costerone-treated animals: the amount of dendritic material proximal to the soma was increased relative to intact rats, while distal dendritic materia l was decreased relative to intact animals. Thus, chronic glucocorticoid ad ministration dramatically reorganized apical arbors in medial prefrontal co rtex. This reorganization likely reflects functional changes and may contri bute to stress-induced changes in cognition. (C) 2001 John Wiley & Sons, In c.