title: One Month of Oral Morphine Decreases Gray Matter Volume in the Right Amygdala of Individuals with Low Back Pain: Confirmation of Previously Reported Magnetic Resonance Imaging Results.
abstract: Prolonged exposure to opioids is known to produce neuroplastic changes in animals; however, few studies have investigated the effects of short-term prescription opioid use in humans. A previous study from our laboratory demonstrated a dosage-correlated volumetric decrease in the right amygdala of participants administered oral morphine daily for 1 month. The purpose of this current study was to replicate and extend the initial findings.
  
  
  
  Twenty-one participants with chronic low back pain were enrolled in this double-blind, placebo-controlled study. Participants were randomized to receive daily morphine (n = 11) or a matched placebo (n = 10) for 1 month. High-resolution anatomical images were acquired immediately before and after the treatment administration period. Morphological gray matter changes were investigated using tensor-based morphometry, and significant regions were subsequently tested for correlation with morphine dosage.
  
  
  
  Decreased gray matter volume was observed in several reward- and pain-related regions in the morphine group, including the bilateral amygdala, left inferior orbitofrontal cortex, and bilateral pre-supplementary motor areas. Morphine administration was also associated with significant gray matter increases in cingulate regions, including the mid cingulate, dorsal anterior cingulate, and ventral posterior cingulate.
  
  
  
  Many of the volumetric increases and decreases overlapped spatially with the previously reported changes. Individuals taking placebo for 1 month showed neither gray matter increases nor decreases. The results corroborate previous reports that rapid alterations occur in reward-related networks following short-term prescription opioid use.
authors.affiliation: *Department of Psychology, University of Alabama at Birmingham, Birmingham, Alabama, USA; jclin@uab.edu.
authors.forename: Joanne C
authors.initials: JC
authors.lastname: Lin
authors.affiliation: Department of Anesthesia, Stanford University School of Medicine, Stanford, California, USA;
authors.forename: Larry F
authors.initials: LF
authors.lastname: Chu
authors.affiliation: Department of Anesthesia, Stanford University School of Medicine, Stanford, California, USA;
authors.forename: Elizabeth Ann
authors.initials: EA
authors.lastname: Stringer
authors.affiliation: School of Psychological Sciences, Monash University, Victoria, Australia.
authors.forename: Katharine S
authors.initials: KS
authors.lastname: Baker
authors.affiliation: Department of Anesthesia, Stanford University School of Medicine, Stanford, California, USA;
authors.forename: Zahra N
authors.initials: ZN
authors.lastname: Sayyid
authors.affiliation: Department of Anesthesia, Stanford University School of Medicine, Stanford, California, USA;
authors.forename: John
authors.initials: J
authors.lastname: Sun
authors.affiliation: *Department of Psychology, University of Alabama at Birmingham, Birmingham, Alabama, USA;
authors.forename: Kelsey A
authors.initials: KA
authors.lastname: Campbell
authors.affiliation: *Department of Psychology, University of Alabama at Birmingham, Birmingham, Alabama, USA;
authors.forename: Jarred W
authors.initials: JW
authors.lastname: Younger
mesh_terms: D000328:Adult; D000679:Amygdala / Q000187:drug effects* / Q000473:pathology; D000701:Analgesics, Opioid / Q000009:adverse effects*; D004311:Double-Blind Method; D005260:Female; D066128:Gray Matter / Q000187:drug effects* / Q000473:pathology; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D017116:Low Back Pain / Q000188:drug therapy*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009020:Morphine / Q000009:adverse effects
chemical_list: D000701:Analgesics, Opioid; D009020:Morphine
keywords: Magnetic Resonance Imaging; Opioids; Tensor-Based Morphometry
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