To study the expression of preproenkephalin (PPE) mRNA following electroacupuncture (EA) combined with droperidol (Dro), an antagonist of dopamine receptors.The brains of Sprague-Dawley rats were sectioned after combination of EA with Dro and nonradioactive in situ hybridization histochemistry (ISHH) technic was used.Ten hours after EA, the expression of PPE mRNA was enhanced; when EA was combined with Dro, the expression of PPE mRNA was further enhanced in many pain-modulation-related nuclei, such as caudate-putamen, accumbens, septal nucleus, diagonal band nucleus, amygdala, hypothalamus, periaqueductal gray (PAG), interpeduncular nucleus, substantia nigra, and the dorsal horn of spinal cord (layer I-II and III-IV).Dro promoted EA's action on the PPE mRNA expression, which underlie the mechanisms of Dro potentiation on acupuncture analgesia.