1. Leukemia inhibitory factor (LIF) potentiates antinociception activity and inhibits tolerance induction of opioids 
H.J. Tu, K.H. Kang, S.Y. Ho, H.C. Liou, H.H. Liou, C.P. Lin, W.M. Fu 
British Journal of Anaesthesia 
Volume 117, Issue 4, Pages (October 2016)
DOI: /bja/aew247
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2. Fig 1
Chronic morphine administration increases the expression of endogenous LIF in rats. Morphine (2 mg kg−1 or 10 mg kg−1) was administered subcutaneously once per day. Lumbar dorsal horn samples were collected 30 min after morphine treatment on Days two, four and eight. (a) mRNA expression determined by real-time PCR revealed that different morphine doses could increase LIF mRNA expression (F value for 2 mg morphine F(3,16)=10.38, P<0.001; F value for 10 mg morphine F(3,16)=10.61, P<0.001). (b) Protein concentrations quantified using specific ELISA kits showed a time-dependent increase of endogenous LIF after morphine treatment (F value for 2 mg morphine F(3,16)=2.58, P=0.09; F value for 10 mg morphine F(3,16)=33.04, P<0.001). Data are presented as mean [sem (n=5)]. *, P<0.05 compared with the control group. (c) Double immunofluororescent staining showed that chronic morphine (10 mg−1 kg−1 day−1) treatment for five days increased the expression of LIF in the spinal cord. Note that LIF (green) expression is mainly colocalized with microglia marker CD11b (red). Scale bars: 10 µm.
British Journal of Anaesthesia  , DOI: ( /bja/aew247)
Copyright © 2016 The Author(s) Terms and Conditions

3. Fig 2
Exogenous LIF enhances morphine analgesic efficacy in rats. Exogenous LIF was intrathecally administered 30 min before morphine treatment (2 mg kg−1, s.c.). The antinociceptive effect of morphine was measured at different time intervals after morphine treatment. (a) Exogenous LIF enhanced the analgesic action and reached 100% MPE at 15 min (F-value for morphine vs. morphine+LIF (1,11)=138.2, P<0.001). (b) Administration of anti-LIF antibody did not affect the morphine analgesic effect (F-value=0.73, P=0.63). (c) Intrathecal administration of exogenous LIF alone did not affect the basal tail-flick latency. Data are presented as mean [sem (n=5∼8)]. *, P<0.05 compared with control at corresponding time points.
British Journal of Anaesthesia  , DOI: ( /bja/aew247)
Copyright © 2016 The Author(s) Terms and Conditions

4. Fig 3
Exogenous LIF potentiates the effect of DAMGO on outward potassium current in the dorsal horn neurones. (a) µ-opioid receptor selective agonist DAMGO at 1 µM enhanced outward potassium current compared with the control. LIF alone did not affect the potassium current. Co-perfusion of LIF (10 ng ml−1) with DAMGO (1 µM) further enhanced the effect of DAMGO on the outward potassium current. (b) Voltage–current curves. Quantitative results are shown in (c). Normalized peak outward potassium currents were recorded at +50 mV (F (3,27)=17.06, P<0.001). Data are presented as mean [sem (n=7∼8)]. *, P<0.05 compared with the control group. #, P<0.05 compared with DAMGO alone.
British Journal of Anaesthesia  , DOI: ( /bja/aew247)
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5. Fig 4
Exogenous LIF inhibits the development of morphine tolerance in rats. (a) Different LIF doses (5, 10 and 50 ng day−1) were intrathecally administered, and morphine (10 mg kg−1 day−1) was subcutaneously injected 30 min later. Note that exogenous LIF suppressed morphine tolerance in a dose-dependent manner (F value for the different treatment groups until day nine, F (3,15)=235.2, P<0.001). (b) Long-term intrathecal administration of LIF alone did not affect the basal tail-flick latency. (c) Anti-LIF antibody (5 µg) or control IgG (5 µg) was intrathecally administered 30 min before the daily morphine treatment. Administration of the anti-LIF antibody, but not control IgG, accelerated the induction of morphine tolerance (F value for the different treatment groups, F (2,11)=67.0, P<0.001). (d) Neither LIF neutralizing antibody nor control IgG alone affected the pain threshold. Data are presented as mean (sem) (n=3∼5). *, P<0.05 compared with the control group at each time point.
British Journal of Anaesthesia  , DOI: ( /bja/aew247)
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6. Fig 5
Exogenous LIF inhibits spinal microglial activation induced by chronic morphine treatment. Chronic morphine treatment increased the expression of microglial activation marker Iba-1 compared with saline-infused control rats. Note that LIF administration suppressed morphine-induced microglial activation. Scale bars: 250 and 25 µm, respectively.
British Journal of Anaesthesia  , DOI: ( /bja/aew247)
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7. Fig 6
Endogenous LIF is upregulated in the cerebrospinal fluid (CSF) of opioid-tolerant patients. (a) Twenty patients under regular high-dose opioid analgesics for cancer pain management, and 10 opioid-naive control participants were recruited. Quantitative data are represented in bar charts. *, P=0.01 compared with opioid-naive control participants. (b) LIF concentrations were positively correlated with the daily opioid-equivalent dose. r2=0.39, P=0.003.
British Journal of Anaesthesia  , DOI: ( /bja/aew247)
Copyright © 2016 The Author(s) Terms and Conditions

8. British Journal of Anaesthesia 2016 117, 512-520DOI: (10
British Journal of Anaesthesia  , DOI: ( /bja/aew247)
Copyright © 2016 The Author(s) Terms and Conditions