MECHANISM OF ANALGESIC EFFECTS OF PROPOFOL ON INCISIONAL PAIN:A RAT MODEL STUDY

Objective To clarify the role of propofol in controlling incisional pain and its potential effects on the spinal opioid receptor expression. Methods A postoperative model of nociception was established in male Sprague-Dawley rats weighing 200-250 g. A total of 96 rats were randomly divided into 8 groups. All drugs were administered intravenously either 5 min pre-operation or 5 min post-operation. The analgesic effects of systemic propofol were demonstrated by the measurement of a cumulative pain score (CPS). After that, the lumbar enlargement of the spinal cord was removed to evaluate the mRNA level of the μ-opioid receptor (MOR) and δ-opioid receptor (DOR) by RT-PCR. Results CPS and DOR mRNA expressions significantly increased after the operation. Both propofol post-treatment and propofol pre-treatment groups showed significant suppression of the increased CPS and the expression of DOR mRNA evoked by pain stimulation. Interestingly, propofol pre-treatment had a more pronounced effect in decreasing CPS and the expression of DOR mRNA. Furthermore, these observations were dose-dependent. MOR mRNA expression significantly increased after operation in all animals and propofol treatment had no impact on it. Conclusion Based on these findings, we suggest that propofol can serve as a valuable adjunct in acute postoperative pain management. Systemic propofol induces an analgesic effect on acute incisional pain in a dose-dependant manner, and this effect is mediated in the spinal cord and may be associated with the spinal DOR.

Objective To clarify the role of propofol in controlling incisional pain and its potential effects on the spinal opioid receptor expression. Methods A postoperative model of nociception was established in male Sprague-Dawley rats weighing 200 -250 g. A total of 96 rats were randomly divided into 8 groups. All drugs were administered intravenously either 5 rain pre-operation or 5 rain post-operation. The analgesic effects of systemic propofol were demonstrated by the measurement of a cumulative pain score （ CPS ）. After that, the lumbar enlargement of the spinal cord was removed to evaluate the mRNA level of the μ-opioid receptor （ MOR ） and δ-opioid receptor （ DOR） by RT-PCR. Results CPS and DOR mRNA expressions significantly increased after the operation. Both propofol post-treatment and propofol pre-treatment groups showed significant suppression of the increased CPS and the expression of DOR mRNA evoked by pain stimulation. Interestingly, propofol pre-treatment had a more pronounced effect in decreasing CPS and the expression of DOR mRNA. Furthermore, these observations were dose-dependent. MOR mRNA expression significantly increased after operation in all animals and propofol treatment had no impact on it. Conclusion Based on these findings, we suggest that propofol can serve as a valuable adjunct in acute postoperative pain management. Systemic propofol induces an analgesic effect on acute incisional pain in a dose-dependant manner, and this effect is mediated in the spinal cord and may be associated with the spinal DOR.