title: Enhancement of natural immunity seen after voluntary exercise in rats. Role of central opioid receptors.
abstract: Chronic voluntary exercise in wheels for 5 weeks in spontaneously hypertensive rats (SHR) augments in vivo natural killer (NK) cell cytotoxicity. Endogenous beta-endorphin is increased in cerebrospinal fluid after voluntary exercise in rats and we have recently shown that beta-endorphin administered i.c.v. augments NK cell mediated cytotoxicity in vivo in a similar way as chronic voluntary exercise. We have now further investigated the involvement of central opioid systems in the exercise-induced augmentation in natural immunity. Exercise consisted of voluntary running in wheels for 5 weeks. In vivo cytotoxicity was measured as clearance of injected 51Cr-labeled YAC-1 lymphoma cells from the lungs. The clearance of YAC-1 cells in vivo was significantly increased in runners as compared to sedentary controls. Selective delta, kappa, or mu-opioid receptor antagonists were administered i.c.v. with osmotic minipumps during the last 6 days of the 5 weeks of running. The delta-receptor antagonist naltrindole (40-50 microg/day) significantly but not completely inhibited the enhanced NK-cell cytotoxicity seen after 5 weeks of exercise. Neither the kappa-receptor antagonist nor-BNI or the mu-receptor antagonist beta-FNA influenced the augmentation in NK cell cytotoxicity. Nor-BNI per se significantly augments in vivo cytotoxicity, indicating some inhibiting effect on natural immunity that could be mediated through the kappa-opioid receptor. Our data suggest the involvement of central delta-opioid receptors in the enhancement of natural cytotoxicity seen after chronic voluntary exercise.
authors.affiliation: Institute of Physiology and Pharmacology, Department of Physiology, Göteborg University, Sweden. inga.jons@fysiologi.gu.se
authors.forename: I H
authors.initials: IH
authors.lastname: Jonsdottir
authors.forename: K
authors.initials: K
authors.lastname: Hellstrand
authors.forename: P
authors.initials: P
authors.lastname: Thorén
authors.forename: P
authors.initials: P
authors.lastname: Hoffmann
mesh_terms: D000818:Animals; D007113:Immunity, Innate; D007276:Injections, Intraventricular; D009271:Naltrexone / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D011957:Receptors, Opioid / Q000502:physiology*
chemical_list: D009292:Narcotic Antagonists; D011957:Receptors, Opioid; C051844:norbinaltorphimine; D009271:Naltrexone; C024524:beta-funaltrexamine; C055382:naltrindole