title: The role of endogenous opioids in moderate exercise training-induced enhancement of the secondary antibody response in mice.
abstract: OBJECTIVE
  Moderate exercise training (60%-80% of maximal oxygen uptake) enhances the secondary antibody response. The mechanism underlying this enhancement, however, has not been determined. In moderate doses, endogenous opioids such as enkephalins enhance antibody response. Furthermore, serum concentrations of endogenous opioids increase in response to exercise, and training programs augment this effect. Therefore, the enhancement of the secondary antibody response induced by moderate exercise may be brought about, in part, by endogenous opioids. The purpose of this study was to examine the effects of naltrexone (an opioid antagonist) on the enhancement of secondary antibody response induced by moderate exercise in young mice.
  
  
  METHODS
  C57BL/6 mice immunized to human serum albumin (HSA) were randomly assigned to 1 of 3 groups: naltrexone, placebo, or control (received no intervention). Then, the mice in each group were randomly assigned to either an exercise group (treadmill running at 15 m/min, 0ø slope, 5 days per week for 8 weeks) or a non-exercise group. At the end of 8 weeks, booster immunization was given, and the mice in the exercise group continued to exercise. Ten days later, when high levels of antibodies are produced in secondary antibody response, anti-HSA antibodies in serum were measured by enzyme-linked immunosorbent assay (ELISA).
  
  
  RESULTS
  With naltrexone implantation, mice that exercised showed a depression of secondary antibody response as compared with mice that exercised and either received a placebo or did not receive any intervention.
  
  
  CONCLUSIONS
  Endogenous opioids may play a role in the enhancement of the secondary antibody response observed after moderate exercise.
authors.affiliation: Department of Rehabilitation Medicine, Division of Physical Therapy, Emory University School of Medicine, 1441 Clifton Rd NE, Atlanta, GA 30322, USA. zkapasi@emory.edu
authors.forename: Z F
authors.initials: ZF
authors.lastname: Kapasi
authors.forename: P A
authors.initials: PA
authors.lastname: Catlin
authors.forename: J
authors.initials: J
authors.lastname: Beck
authors.forename: T
authors.initials: T
authors.lastname: Roehling
authors.forename: K
authors.initials: K
authors.lastname: Smith
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000917:Antibody Formation / Q000187:drug effects* / Q000502:physiology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D051379:Mice; D008810:Mice, Inbred C57BL; D009271:Naltrexone / Q000494:pharmacology*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D012709:Serum Albumin / Q000008:administration & dosage / Q000276:immunology
chemical_list: D012709:Serum Albumin; D009271:Naltrexone