title: Expectancy Effects on Conditioned Pain Modulation Are Not Influenced by Naloxone or Morphine.
abstract: Recent studies suggest that participant expectations influence pain ratings during conditioned pain modulation testing. The present study extends this work by examining expectancy effects among individuals with and without chronic back pain after administration of placebo, naloxone, or morphine.
  
  
  
  This study aims to identify the influence of individual differences in expectancy on changes in heat pain ratings obtained before, during, and after a forearm ischemic pain stimulus.
  
  
  
  Participants with chronic low back pain (n = 88) and healthy controls (n = 100) rated heat pain experience (i.e., "test stimulus") before, during, and after exposure to ischemic pain (i.e., "conditioning stimulus"). Prior to testing, participants indicated whether they anticipated that their heat pain would increase, decrease, or remain unchanged during ischemic pain.
  
  
  
  Analysis of the effects of expectancy (pain increase, decrease, or no change), drug (placebo, naloxone, or morphine), and group (back pain, healthy) on changes in heat pain revealed a significant main effect of expectancy (p = 0.001), but no other significant main effects or interactions. Follow-up analyses revealed that individuals who expected lower pain during ischemia reported significantly larger decreases in heat pain as compared with those who expected either no change (p = 0.004) or increased pain (p = 0.001).
  
  
  
  The present findings confirm that expectancy is an important contributor to conditioned pain modulation effects, and therefore significant caution is needed when interpreting findings that do not account for this individual difference. Opioid mechanisms do not appear to be involved in these expectancy effects.
authors.affiliation: Department of Psychology, Ohio University, 251 Porter Hall, Athens, OH, 45701, USA. France@ohio.edu.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: France
authors.affiliation: Department of Behavioral Science, Rush University, Chicago, IL, USA.
authors.forename: John W
authors.initials: JW
authors.lastname: Burns
authors.affiliation: Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN, USA.
authors.forename: Rajnish K
authors.initials: RK
authors.lastname: Gupta
authors.affiliation: Department of Anesthesiology, Rush University, Chicago, IL, USA.
authors.forename: Asokumar
authors.initials: A
authors.lastname: Buvanendran
authors.affiliation: Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN, USA.
authors.forename: Melissa
authors.initials: M
authors.lastname: Chont
authors.affiliation: Department of Behavioral Science, Rush University, Chicago, IL, USA.
authors.forename: Erik
authors.initials: E
authors.lastname: Schuster
authors.affiliation: Department of Behavioral Science, Rush University, Chicago, IL, USA.
authors.forename: Daria
authors.initials: D
authors.lastname: Orlowska
authors.affiliation: Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN, USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Bruehl
mesh_terms: D000328:Adult; D000701:Analgesics, Opioid / Q000037:antagonists & inhibitors / Q000494:pharmacology; D059031:Anticipation, Psychological; D059350:Chronic Pain / Q000523:psychology*; D003213:Conditioning, Psychological / Q000187:drug effects*; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000523:psychology*; D008297:Male; D009020:Morphine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology; D010147:Pain Measurement / Q000187:drug effects / Q000523:psychology*; D055815:Young Adult
chemical_list: D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D009270:Naloxone; D009020:Morphine
keywords: Conditioned pain modulation; Heat pain; Ischemic pain; Opioid
references.citation: Brain Res. 1981 Jul 20;216(2):313-21
references.pmid: 6454457
references.citation: Clin J Pain. 2007 Jul-Aug;23(6):506-10
references.pmid: 17575490
references.citation: Pain. 2008 Aug 15;138(1):87-97
references.pmid: 18164819
references.citation: J Behav Med. 2013 Jun;36(3):315-27
references.pmid: 22534819
references.citation: Curr Opin Anaesthesiol. 2010 Oct;23(5):611-5
references.pmid: 20543676
references.citation: Eur J Pharmacol. 1990 Jul 3;182(2):347-55
references.pmid: 2168836
references.citation: Pain. 1992 Aug;50(2):177-87
references.pmid: 1408314
references.citation: J Pharmacol Exp Ther. 1975 Dec;195(3):499-504
references.pmid: 1195133
references.citation: Percept Mot Skills. 2004 Oct;99(2):679-87
references.pmid: 15560360
references.citation: Pain. 2010 Apr;149(1):57-63
references.pmid: 20122805
references.citation: Brain Res. 1982 Mar 25;236(2):329-37
references.pmid: 6978166
references.citation: Pain. 2011 Feb;152(2):428-39
references.pmid: 21196078
references.citation: J Pers Assess. 1996 Dec;67(3):588-97
references.pmid: 8991972
references.citation: Pain. 2007 Jul;130(1-2):137-43
references.pmid: 17215080
references.citation: J Neurosci. 2005 Nov 9;25(45):10390-402
references.pmid: 16280578
references.citation: Eur J Pain. 2010 Apr;14(4):339
references.pmid: 20227310
references.citation: Eur J Pain. 2015 Jul;19(6):805-6
references.pmid: 25330039
references.citation: J Pain. 2013 Feb;14(2):114-25
references.pmid: 23260452
references.citation: Ann Intern Med. 1976 Dec;85(6):765-8
references.pmid: 187095
references.citation: Pain. 2013 Sep;154(9):1856-64
references.pmid: 23748117
references.citation: Methods Find Exp Clin Pharmacol. 1991 Nov;13(9):643-7
references.pmid: 1817489
references.citation: Neuron. 2009 Aug 27;63(4):533-43
references.pmid: 19709634
references.citation: Psychosom Med. 2011 Sep;73(7):612-9
references.pmid: 21862829
references.citation: Neuroscience. 2007 Jun 29;147(2):260-71
references.pmid: 17379417
references.citation: Pain. 2006 Oct;124(3):287-94
references.pmid: 16725261
references.citation: Brain Res. 1982 Nov 11;251(1):83-92
references.pmid: 6293648
references.citation: Pain Headache. 1987;9:129-59
references.pmid: 2825156
references.citation: J Pain. 2005 Feb;6(2):116-24
references.pmid: 15694878
references.citation: Pain. 2002 Sep;99(1-2):223-33
references.pmid: 12237200