Activity-wheel running blunts suppression of splenic natural killer cell cytotoxicity after sympathectomy and footshock

We used chemical sympathectomy by 6-hydroxydopamine (6-OHDA) to examine whe ther adaptation by the sympathetic nervous system (SNS) is a plausible expl anation for our prior finding that activity-wheel running blunts the suppre ssion of splenic natural killer cell cytotoxicity after footshock. Male Fis cher rats were assigned to treatments using a group (activity wheel vs. sed entary) x treatment (6-OHDA vs. saline) x condition (footshock vs. no shock ) design. After 5-6 weeks, rats were injected i.p. with saline or with 40, 80, and 80 mg/kg 6-OHDA on pre experimental days -5, -3, and -1. Half the r ats received 6 min of random footshock during a 40-min period. Cytotoxicity was determined by standard 4-h Cr-51 release assay. Sympathectomy reduced splenic [NE] by 72%. After 6-OHDA injection and footshock, percent lysis wa s 33% lower in sedentary rats compared with activity-wheel runners and home -cage controls, p = 0.048. The results suggest that activity-wheel running leads to adaptations that offset an altered SNS modulation of splenic NK ce ll cytotoxicity in response to footshock. (C) 2000 Elsevier Science Inc. Al l rights reserved.