Lappaconitine, a C18-diterpenoid alkaloid, exhibits antihypersensitivity in chronic pain through stimulation of spinal dynorphin A expression
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Lappaconitine is a representative C18-diterpenoid alkaloid extracted from Aconitum sinomontanum Nakai and has been prescribed as a pain relief medicine in China for more than 30 years. This study evaluated its antihypersensitivity activity in the rat models of neuropathic and cancer pains and explored its underlying mechanisms. Subcutaneous injection of cumulative doses of lappaconitine produced dose-dependent mechanical antiallodynia and thermal antihyperalgesia in spinal nerve ligation-induced neuropathic rats. The cumulative dose–response analysis exhibited their Emax values of 53.3 and 58.3% MPE, and ED50 values of 1.1 and 1.6 mg/kg. Single intrathecal lappaconitine dose in neuropathy also dose- and time-dependently blocked mechanical allodynia, with an Emax of 66.1% MPE and an ED50 of 0.8 μg. Its multiple twice-daily intrathecal administration over 7 days did not induce mechanical antiallodynic tolerance. Subcutaneous cumulative doses of lappaconitine also produced dose-dependent blockade of mechanical allodynia in the rat bone cancer pain model induced by tibia implantation of cancer cells, with the Emax of 57.9% MPE and ED50 of 2.0 mg/kg. Furthermore, lappaconitine treatment stimulated spinal dynorphin A expression in neuropathic rats, and in primary cultures of microglia but not neurons or astrocytes. Intrathecal pretreatment with the specific microglia depletor liposome-encapsulated clodronate, dynorphin A antibody, and κ-opioid receptor antagonist GNTI totally suppressed intrathecal and subcutaneous lappaconitine-induced mechanical antiallodynia. This study suggests that lappaconitine exhibits antinociception through directly stimulating spinal microglial dynorphin A expression.
KeywordsLappaconitine Neuropathic pain Bone cancer pain Dynorphin a Spinal microglia
Tumor necrosis factor-α
Mitogen-activated protein kinase
Analysis of variance
- % MPE
% maximal possible effect
- ED50 or EC50
Half-effective dose or half-effective concentration
Conceived and designed the experiments: YXW and MLS; performed the experiments: MLS, JPA, YRW, XYL, QH, and TFL; analyzed the data: YXW and MLS; and preparation of the paper: YXW and MLS.
This study was supported in part by a grant from the National Natural Science Foundation of China (no. 81673403).
Compliance with ethical standards
Conflict of interest
The authors declare that there are no competing interests.
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