Objective: To study the analgesic mechanisms of two extraction part of Ceratostigma willmottianum(CW)in rat pain model induced by formaldehyde. Method: Fifty-six SD rats were randomly divided into 6 groups with 8 in each group

including normal group

model group

CW alcohol extract's ethyl acetate part group(30

15 mg·kg-1)

n-butanol part group(15

8 mg·kg-1). Each group was given corresponding drugs by intragastric injection

respectively

once a day for 7 days. At the 7th day

the animals were fasted for 12 hours

and ig 40 min later

except normal group

the other groups were given subcutaneous injection of 10% formaldehyde solution 50 μL for establishing the pain models. The impact of CW active site was observed and serum glutamate and Ca2+ were detected with biochemical kit

and the expression of c-fos and substance P(SP) was assayed with immunohistochemeistry(IHC). Result: Compared with normal group

model group showed a typical pain behavior

amounts of c-fos and SP were detected in the brain and spinal cord

and raised serum glutamic acid concentration

Ca2+ content with significant difference (P<0.05)

meaning that the pain model of rats induced by formaldehyde was successful.Compared with model group

the low dose of ethyl acetate part of CW alcohol extract(15 mg·kg-1) and n-butanol part(8 mg·kg-1)can obvious inhibition to the first phase damage response(P<0.05)

make serum glutamic content

brain c-fos protein expression decreased significantly(P<0.05)

serum Ca2+increased significantly(P<0.05);the high dose of two parts decreased the expression of c-fos in spinal dorsal cord significantly(P<0.05);both of high and low dose of CW alcohol extract's ethyl acetate and n-butanol part decreased the expression of SP significantly(P<0.05)in central nervous system(CNS). Conclusion: Two extraction parts of CW alcohol extract have exact analgesic action in rat pain model induced by formaldehyde

and its analgesic mechanisms may be related to inhibiting the intracellular Ca2+ concentration and glutamate content in the body

reducing the expression of c-fos and SP in CNS.