To observe the effects of electroacupuncture(EA)stimulation of"Zusanli"(ST 36)and"Sanyinjiao"(SP 6)at different time-points of a day on the expression of c-fos and neuronal nitric oxide synthase(nNOS)in the medial prefrontal cortex(mPFC)in rats with ketamine addiction.Methods A total of 56SD rats were randomized into control group

saline group

model group and EA group.The EA group was further divided into Zi-shi(23:00)

Mao-shi(05:00)

Wu-shi(11:00)and You-shi(17:00)subgroups(n=8in each group or subgroup).Ketamine addiction model was established by intraperitoneal administration of ketamine(100mg/kg)

once a day for 7days.EA(2Hz

3V)was applied to unilateral"Zusanli"(ST 36)and"Sanyinjiao"(SP 6)acupoints for 30min

once daily for 7days.The expression of c-fos and nNOS in the mPFC was detected by immunohistochemistry.Results Following EA intervention for 7days

the animals' daily life activities including body stretching

standing

jumping

circling

falling on the back and fur-licking in the EA group(Wu-shi and You-shi subgroups)were close to those of the normal control and saline groups

being much better than the model group.Compared with the normal control group and saline group

the expression levels of c-fos and nNOS in the mPFC in the model group were significantly upregulated(P<0.05).Compared with the model group

the expression levels of both c-fos and nNOS were considerably down-regulated in the Wu-shi(11:00)and You-shi(17:00)subgroups(P<0.05)

rather than in the Zi-shi(23:00)and Mao-shi(05:00)subgroups(P>0.05).Conclusion EA of ST 36and SP 6at 11:00and 17:00can decrease the expression of c-fos and nNOS in the mPFC in ketamine addiction rats

which may contribute to its effects in improving the rats' behavior activity.