Objective To explore the morphological basis of electroacupuncture(EA) in relieving addiction of keta-mine.Methods Forty Sprague-Dawley rats were randomized into normal control

normal saline(10 mL/kg)

model and keta-mine+EA groups.Ketamine-addiction model was established by intraperitoneal administration of ketamine(100 mg/kg)

once a day for 7 days.EA(2 Hz) was applied to "Zusanli"(ST 36) and "Sanyinjiao"(SP 6) for 30 min

once a day for 7 days.The expression of tyrosine hydroxylase(TH) and c-fos in the hippocampal CA 1 region was detected by immunohistochemistry.Results In comparison with the normal control group and normal saline group

the numbers of both TH immuno-reaction(IR)-positive and c-fos IR-positive neurons in the hippocampal region in the model group were increased significantly(P<0.05

P<0.01).Correspondingly

the expression of both TH IR-positive and c-fos IR-positive products in the hippocampal CA1 region in the model group was upregulated evidently(P<0.05

P<0.01).After EA of "Zusanli"(ST 36)-"Sanyinjiao"(SP 6)

compared with the model group

the expression of both TH IR-positive and c-fos IR-positive products was downregulated considerably(P<0.01).Conclusion EA of "Zusanli"(ST 36)-"Sanyinjiao"(SP 6) can downregulate ketamine-addiction induced increase of expression of tyrosine hydroxylase and c-fos in the hippocampal CA1 region in ketamine-addiction rats

which may contribute to its effect in relieving ketamine addiction symptoms in clinic.