title: Can repeated exposure to morphine change the spinal analgesic effects of lidocaine in rats?
abstract: BACKGROUND
  Chronic opium exposure leads to altered response to opioid compounds. The aim of this study was to assess the behavioral effects of opium tolerance on the analgesic effects of intrathecal lidocaine in rats.
  
  
  METHODS
  Twenty-four adult male Sprague Dawley rats with intrathecal (IT) catheters were divided into 3 groups of 8. The first group was morphine tolerant and received IT lidocaine (ML). Rats in the second group were not morphine tolerant and received IT lidocaine (L), while the third group consisted of not morphine tolerant rats that received IT placebo. Tail flick test was done and maximal possible antinociceptive effects (MPAE) were compared using analysis of variance (ANOVA).
  
  
  RESULTS
  While percent of MPAE significantly increased in the L group, it had a significant reduction in the ML group (P < 0.001).
  
  
  CONCLUSIONS
  After intrathecal lidocaine administration, a hyperalgesic response was seen in morphine tolerant rats and an analgesic response was seen in the lidocaine group.
authors.affiliation: Associate Professor, Fellowship in Cardiac Anesthesiology, Anesthesiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Ali
authors.initials: A
authors.lastname: Dabbagh
authors.forename: Shervin Farkhondehkish
authors.initials: SF
authors.lastname: Moghadam
authors.forename: Samira
authors.initials: S
authors.lastname: Rajaei
authors.forename: Zahra
authors.initials: Z
authors.lastname: Mansouri
authors.forename: Homa Shardi
authors.initials: HS
authors.lastname: Manaheji