Objective: To investigate the analgesic activity of four cardiac glycosides-cinobufagin

telocinobufagin

arenobufagin and periplocin and the analgesic mechanism of cinobufagin. Method: According to the requirements

the KM mice were divided into the blank group

the asprin positive group (200 mg·kg-1)

and groups of high

medium and low dose of test compounds. The analgesic effects of the four cardiac glycosides in mice were observed by the hot-plate test and acetic acid writhing methods. Moreover

the potential analgesic mechanism of cinobufagin was preliminarily investigated by injecting naloxone hydrochloride (2 mg·kg-1) and peripheral opioid receptor antagonist naloxone methiodide (NAL-M

20 mg·kg-1). Result: Compared with the blank group

all of the four cardiac glycosides can increase the pain threshold of paw-licking induced by hot plate (P<0.05

P<0.01) and decrease the number of writhing induced by acetic acid in mice (P<0.05

P<0.01). The intraperitoneal injection with naloxone hydrochloride and NAL-M can antagonize the increase in the pain threshold of paw-licking induced by hot plate (P<0.05

P<0.01). Conclusion: Cinobufagin

telocinobufagin

arenobufagin and periplocin have the analgesic effect

and the analgesic effect of cinobufagin may be correlated with the peripheral opioid receptor.