It had been shown in our previous work that preoptic area might mo- dulate discharges of "pain" units in LH and that the neuronic activities of the preoptic area were also influenced by impulses from acupuncture po- int. So we assumed that the impulses from acupuncture point probably produ- ced the same effect as stimulation of preoptic area on LH. In order to give evidence to this problem

we performed this experiment. Thirty-eight albino rats of both sexes (body weight. 200-320g) were used for this study. The rats were anesthetized with chloralhydrate. The spontaneous firings of LH were recorded by glass microelectrode with co- ordinates: A 4.1 L 0.6 H 4.2. Electrical needling was performed by means of the G6805 type acupunc- ture anesthesia apparatus. The parameters of stimulation were: 100 cycles /sec

intensity 5-7v

4＇-14＇ in duration. The spontaneous firings of 40 units in LH were recorded. "Pain" stimuli (the clamping of tail or electrostimulation of the sciatic nerves)caused art increase in discharge frequency of 29 units (pain-excitation unit

PE)and a decrease in 11 units (pain-inhibition unit

PI) . The 29 PE in LH all were inhibited by electrostimulation of the preoptic area

and 11 PI all were excited by it for comparing the effect of the pr- eoptic area and acupuncture. Then the effect of acupuncture on LH was observed further. Electrical needling "Zusanli" point might inhibit the discharge of PE in LH(24/29

82.8%). This inhitory effect lasted for 1＇--6＇. Otherwise effect of the contralateral point was identical with ipsilateral. On the other hand

electrical needling increased freruency of spontaneous firings of PI in LH(7/11

63.6%)and offset the inhibitcry response to noxious stimuli. From the data presented

it was suggested that the effect of electrical needling "Zusanli" point on two kinds of "pain" unit discharge in LH con- formed with electrostimulation of preoptic area

i.e.

it might modulate discharge of "pain" unit in LH. At last

the relationship between this mo- dulatory effect and acupuncture analgesia was discussed.