TABLE 3

Effects of μ-opioid agonist analgesics (e.g., morphine) in assays of pain-related CPA

SubjectPain Stimulus (Time before Conditioning)Conditioning SessionsMorphineResultReference
#DurationDose (Route)Time
minmg/kgmin
RatsSpinal nerve ligation (−3 wk) +  von Frey (1/min × 15 min)1020 (2/day)0.3, 3 (s.c.)−45 Blocked CPA without CPPaHummel et al., 2008
RatsIntraplantar carrageenan (−4 h) +  von Frey (1/min × 15 min)220 (2/day)0.3, 3 (s.c.)−45Blocked CPA without CPPaHummel et al., 2008
Male SD ratsIntraplantar carrageenan (−4 h)240 0.005–10 (i.p.)−15Blocked CPA; less potent  to produce CPPavan der Kam et al., 2008
Male SD ratsIntraplantar CFA (−2 h)230 (2/day)0.5–1.0 (i.p.)−30Blocked CPA without CPPaZhang et al., 2012
Male ICR miceIntraperitoneal acid (0 min)240 (2/day)0.1–3.2 (s.c.)−15Blocked CPA; less potent  to produce CPPaBagdas et al., 2016
Male/female SD ratsIntraplantar formalin (0 min)245 0.5–4.0 (s.c.)−15Blocked CPA without CPPaHarton et al., 2017
Male/female Fischer 344 ratsBone cancer (−11 days) +  leg movement (0 min)230 (2/day)75-mg pellet (s.c.)−1 dayDid not block CPAHavelin et al., 2017
Male SD ratsIntraplantar formalin (0 min)260 (2/day)1, 10 nmol (vBNST)−10 minBlocked CPA without CPPaMaruyama et al., 2018
  • ICR, Institute of Cancer Research; SD, Sprague-Dawley; vBNST, ventral bed nucleus of the stria terminalis.

  • a These results indicate an antinociceptive drug profile.