Fifty-seven rats were used and divided into three groups:the blank control group

the arthritis group and electro-acupuncture(EA)group. The experimental arthritis produced by Freund's complete adjuvant injection. All arthritis rats in the EA group were given electro-acupuncture at “Huantiao”points bilaterally for 20 minutes every day.After stimes successive EA treatment

the rats of EA group were decapitated.Their Leu-enkephalia contents of pituitary gland and spinal cord were analysed by radioimmttnoassay.The procedure with the rats of the other two groups was the same as the EA group but without needling. It was found that the mean value of LEK content in pituitary gland arthritic rats(23.89

5

.41 pg/mg)is much lower than that of normal rats(36.62±13.36 pg/mg)

there is a significant difference between these two groups(p

<

0.05).But the LEK level of EA group(33.85±11.07 pg/mg)resumed at the control level.The LEK contents of spinal cord in arthritis group(25.93±3.02pg/mg)is much higher than that in blank control group(19.53±1.67 pg/mg)and EA group(19.99±2.03 pg/mg).A comparison was made between arthritis group and EA group(p

<

0.05). The results showed that the pathological variation of LEK revels both in pituitary gland and spinal cord in experimental arthritic rats could turn to normal by EA treatment.It clearly proved that there is a close relationship between the content of LEK in central nervous system and the analgesic effect of EA.