Role of spinal κ-opioid receptors in remifentanil-induced postoperative central sensitization in a rat model of incisional pain: by in vivo electrophysiology / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the role of spinal κ-opioid receptors in remifentanil-induced postoperative central sensitization in a rat model of incisional pain by in vivo electrophysiology.Methods Sixty adult male Sprague-Dawley rats in which intrathecal catheters were successfully implanted,weighing 230-270 g,were divided into 5 groups (n=12 each) using a random number table:control group (group C),incisional pain group (group I),remifentanil group (group R),remifentanil plus incisional pain group (group R+I),and κ-opioid receptor agonist U50488H group (group U).A 1 cm longitudinal incision was made through skin,fascia and muscle of the plantar aspect of the right hind paw in isofiurane-anesthetized rats to establish the model of incisional pain.Remifentanil was intravenously infused for 1 h at a rate of 10 μg · kg 1 · min-1 in group R.In group R+I,remifentanil was intravenously infused for 1 h at a rate of 10 μg · kg-1 · min 1,and the model of incisional pain was established at the same time.In group U,U50488H 10 μg/10μl was injected intrathecally,30 min later remifentanil was intravenously infused for 1 h at a rate of 10 μg · kg-1 · min-1,and the model of incisional pain was established.Six rats in each group were randomly selected,the mechanical pain threshold (MPT) was measured in bilateral hind paws before implanting intrathecal catheter (T0),before operation (T1),and at 1 h,4 h and 1,2 and 3 clays after operation (T2-6).Six rats in each group were randomly selected to record the C fiber-evoked filed potentials in the spinal dorsal horn from 60 min before administration or operation to 180 min after administration or operation,the long-term potentiation (LTP) induced was also recorded,and the area under the curve (AUC) of C-fiber-evoked field potentials was calculated.Results No LTP was recorded in C,I and U groups,and the LTP was recorded in R and R+I groups.Compared with group C,the MPT in bilateral hind paws at T5,6 was significantly decreased in group R,the MPT in ipsilateral hind paws at T2 6 was decreased in group I,the MPT in ipsilateral hind paws at T2-6 and in contralateral hind paws at T5,6 was decreased in group R+I,the MPT in ipsilateral hind paws at T2-4 was decreased in group U,and the AUC of C-fiber-evoked field potentials was increased in R and R+I groups (P＜0.05).Compared with group Ⅰ,the MPT in ipsilateral hind paws at T4-6 and in contralateral hind paws at T5,6 was significantly decreased,and the AUC of C-fiber-evoked field potentials was increased in group R+I (P＜0.05).Compared with group R+ I,the MPT in ipsilateral hind paws at T2-6 and in contralateral hind paws at T5,6 was significantly increased,and the AUC of C-fiber-evoked field potentials was decreased in group U (P＜0.05).Conclusion The results of in vivo electrophysiology confirm that inhibition of spinal κ-opioid receptor function mav be involved in the mechanism by which remifentanil induces postoperative central sensitization in a rat model of incisional pain.