ACTIVITY WHEEL RUNNING REDUCES ESCAPE LATENCY AND ALTERS BRAIN MONOAMINE LEVELS AFTER FOOTSHOCK

We examined the effects of chronic activity wheel running on brain mon oamines and latency to escape foot shock after prior exposure to uncon trollable, inescapable foot shock. Individually housed young (similar to 50 day) female Sprague-Dawley rats were randomly assigned to standa rd cages (sedentary) or cages with activity wheels. After 9-12 weeks, animals were matched in pairs on body mass. Activity wheel animals wer e also matched on running distance. An animal from each matched pair w as randomly assigned to controllable or uncontrollable inescapable foo t shock followed the next day by a foot shock escape test in a shuttle box. Brain concentrations of norepinephrine (NE), dopamine (DA), dihy droxyphenylacetic acid (DOPAC), 5-hydroxytryptamine (5-HT), and 5-hydr oxyindole acetic acid (5-HIAA) were assayed in the locus coeruleus (LC ), dorsal raphe (DR), central amygdala (AC), hippocampus (CA1), arcuat e nucleus, paraventricular nucleus (PVN), and midbrain central gray. A fter prior exposure to uncontrollable foot shock, escape latency was r educed by 34% for wheel runners compared with sedentary controls. The shortened escape latency for wheel runners was associated with 61% hig her NE concentrations in LC and 44% higher NE concentrations in DR com pared with sedentary controls. Sedentary controls, compared with wheel runners, had 31% higher 5-HIAA concentrations in CA1 and 30% higher 5 -HIAA concentrations in AC after uncontrollable foot shock and had 28% higher 5-HT and 33% higher 5-HIAA concentrations in AC averaged acros s both foot shock conditions. There were no group differences in monoa mines in the central gray or in plasma prolactin or ACTH concentration s, despite 52% higher DA concentrations in the arcuate nucleus after u ncontrollable foot shock and 50% higher DOPAC/DA and 17% higher 5-HIAA /5-HT concentrations in the PVN averaged across both foot shock condit ions for sedentary compared with activity wheel animals. The present r esults extend understanding of the escape-deficit by indicating an att enuating role for circadian physical activity. The altered monoamine l evels suggest brain regions for more direct probes of neural activity after wheel running and foot shock. (C) 1997 Elsevier Science Inc.