Role of spinal cord opioid receptors in antinoclceptive effect of propofol in rats / 中华麻醉学杂志

ABSTRACT

Objective To investigate the role of spinal cord opioid receptors in the antinocieeptive effect of propefol in rats. Methods Male SD rats weighing 220-280 g were anesthetized with intraperitoneal chloral hydrate 300 mg/kg. Intratbecal (IT) catheter was placed at L5～6 interspace. Correct placement was confirmed by lower extremity motor block after injection of 2% lidocaine 15 μl via the iv catheter. Animals which were lame or paralyzed were excluded. Ninety SD rats in which IT catheters were successfully placed were randomly divided into 9 groups (n = 10 each) group Ⅰ propofol 10μg IT (P);group Ⅱ dimethyl suipbexide (DMSO-solvent for propofol) 5 μl IT (D);group Ⅲ artificial cerebral spinal fluid (ACSF) 5 μl IT;group Ⅳ propoful 10 μl + naloxone 15 μg IT (PN);group Ⅴ DMSO 5 μl IT + naloxone 15 μg IT (DN);group Ⅳ propofol 10μg IT + CTOP Ⅰμg IT (PC);group Ⅶ DMSO 5 μl IT + CTOP 1μg IT (DC);group Ⅷ propofol 10 μg IT + ICI 174, 864 1 μg IT (PI) and group ⅨDMSO 5 μl 1T + ICI 174, 864 1 μg IT (DI). In group Ⅳ-Ⅸ naloxone or CTOP (μ-receptor antagonist) or ICI 174, 864 (δ-receptor antagonist) was injected 5 min after propofol/DMSO. Pain threshold was measured before the first drug administration (T0) and at 10 min (T1), 20 min (T2) and 40 min (T3) after the first drug administration using hot water tail-withdrawal test. The latency for withdrawal of the tail from hot water was recorded. Results The pain threshold was significantly higher in group P, PN, PC and PI than in group D, DN, DC and DI respectively. The pain threshold was significantly increased at T1.2 compared with the baseline value at T0 in group P, PN, PC and PI. The pain threshold was significantly lower at T3 than at T1 and T2 in group P, PN, PC and PI. The pain threshold was significantly lower after drug administration in group PN and PI than in group P and PC. Conclusion Spinal cord δ-oploid receptors are involved in the anfinocicepfive effect of propofol.