Current studies have indicated that donepezil as a cholinesterase inhibitor can attenuate morphine-induced tolerance. The present study aimed to evaluate the possible role of N-methyl-d-aspartate receptors (NMDARs), protein kinase C (PKC) and CaM-dependent kinase II (CaMKII) pathways in this effect. Female Wistar rats received daily morphine (10 mg/kg, i.p.) alone or in combination with donepezil (1.5 or 2 mg/kg, gavaged) for 14 days. The analgesic effect was assessed by Von-frey, hotplate and tail flick test. On the 15th day, the periaqueductal gray (PAG) and lumbar spinal cord of rats were dissected. Then, protein levels of NMDAR-NR1, NR2B, PKCγ and CaMKIIα were tested using Western blot method. The results showed that morphine tolerance was seen after 8–10 days of injection compared with control group, while daily co-administration of donepezil with morphine prolonged the occurrence of analgesic tolerance. Western blot showed that morphine significantly increased NR1, PKCγ and CaMKIIα expressions in PAG, and significantly increased PKCγ and CaMKIIα in spinal cord. In contrast, donepezil downregulated NR1 and PKCγ in PAG, and downregulated PKCγ and CaMKIIα in spinal cord. Moreover, donepezil alone activates NR1 and NR2B in spinal cord, which needs to be further studied. Thus, the present results suggest that the attenuation effects of donepezil on morphine tolerance are possibly mediated by preventing morphine-induced upregulations in NR1, PKCγ and CaMKIIα expressions.

目前的研究表明，多奈哌齐作为胆碱酯酶抑制剂可以减弱吗啡诱导的耐受性。本研究旨在评估N-甲基-d的可能作用-天冬氨酸受体 (NMDARs)、蛋白激酶 C (PKC) 和 CaM 依赖性激酶 II (CaMKII) 通路在此作用中。雌性 Wistar 大鼠每天单独接受吗啡（10 毫克/千克，腹腔注射）或与多奈哌齐（1.5 或 2 毫克/千克，强饲）联合给药 14 天。通过 Von-frey、热板和甩尾试验评估镇痛效果。第15天，解剖大鼠导水管周围灰质（PAG）和腰脊髓。然后，使用蛋白质印迹方法测试 NMDAR-NR1、NR2B、PKCγ 和 CaMKIIα 的蛋白质水平。结果显示，与对照组相比，注射8-10天后出现吗啡耐受，而多奈哌齐与吗啡每日联合给药可延长镇痛耐受的发生。蛋白质印迹显示吗啡显着增加 PAG 中 NR1、PKCγ 和 CaMKIIα 的表达，并显着增加脊髓中的 PKCγ 和 CaMKIIα。相比之下，多奈哌齐下调 PAG 中的 NR1 和 PKCγ，下调脊髓中的 PKCγ 和 CaMKIIα。此外，多奈哌齐单独激活脊髓中的NR1和NR2B，这需要进一步研究。因此，目前的结果表明，多奈哌齐对吗啡耐受的减弱作用可能是通过阻止吗啡诱导的 NR1、PKCγ 和 CaMKIIα 表达上调来介导的。