The effects of electroacupuncture on dorsal hippocampal pyramidal ce- lls spontaneous firing under the condition of electrical stimulation or le- sion of locus coeruleus (LC) were investigated in urethane anesthetized ra- ts. The spontaneous firing of dorsal hippocampal cells was mainly inhibi- ted when electroacupuncting ‘Jiaji’points. Similar inhibitory effects of electrical stimulatinn on LC were observed. The effects of electroacupun- cture were not appeared after lesions of bilateral LC

or partially blocke- d after iv phentolamine (an a-receptor antagonist)

and completely blocke- d after yohimbine (an a_2-antagonist). Clonidine (an a_2-receptor agonist) was ineffective in this regard. These results suggest that LC may be an important links in effect of electroacupuncture on pyramidal cells firing of hippocampus. It also showed that the effect of electroacupuncture seemed to be mediated by a-receptor

especially that by a_2 receptor.