LONG-TERM STRESS DEGENERATES, BUT IMIPRAMINE REGENERATES, NORADRENERGIC AXONS IN THE RAT CEREBRAL-CORTEX

Exposed to a forced walking stress for 2 weeks, some rats became persi stently inactive (depression-model rats), whereas others gradually rec overed from exhaustion (spontaneous recovery rats), We also studied mt s exposed to short-term stress, rats without stress, and the model mts treated with imipramine or saline, We examined the density of noradre nergic axons in the frontal cortex using retrograde labeling of the lo cus coeruleus with horseradish peroxidase injected into the cortex and immunohistochemical staining of cortical axons with dopamine beta-hyd roxylase antiserum, The density was significantly lower in the depress ion-model mts, but tended to be higher in the recovery mts and short-t erm stressed mts, Chronic treatment with imipramine significantly incr eased the density in the model mts, There was also a correlation betwe en the density of noradrenergic axons and the recovery rate of activit y. Our results suggest that cortical noradrenergic degeneration is inv olved in the pathogenesis of depression. (C) 1997 Society of Biologica l Psychiatry.