The aim of the. work was to study the effects of capsaicin (Cap) blocking afferent C fibers of n.peroneus communis innervating "Zusanli" and the influence of Cap on analgesia produced by elec-troacupuncture (EA) at "Zusanli".The highest antidromic C waves of n. peroneus communis in rats were recorded. 1 %

1. 5% capsaicin soi 25μl were topically applied on the nerve between the electrodes of stimulation and record

and the changes of C wave amplitude were analysed.After 1 % Cap was applied to the nerve

the C waves were immediately reduced to 68. 3 % of con-trol before Cap treatment and kept at 55. 4 % for 45 minutes (P

<

0. 001

n =9)

having not been re-covered but they were not yet completely blocked. The vehicle (10% Tween80 liquid paraffin) applied on the nerve have not the effects on C waves (n = 7).Then the dose of capsaicin was increased to 1. 5 % Cap sol 25μl

after it was applied on the nerve trunk

the C waves were decreased immediately to 77. 7% of control

then the C wave amplitudes were decreased to 46. 2 % (P

<

0.01 ) in 5 minutes

then maintained at 54. 5 % 1. 5% capsaicin soi 25μl were topically applied on the nerve between the electrodes of stimulation and record

and the changes of C wave amplitude were analysed.After 1 % Cap was applied to the nerve

the C waves were immediately reduced to 68. 3 % of con-trol before Cap treatment and kept at 55. 4 % for 45 minutes (P

<

0. 001

n =9)

having not been re-covered but they were not yet completely blocked. The vehicle (10% Tween80 liquid paraffin) applied on the nerve have not the effects on C waves (n = 7).Then the dose of capsaicin was increased to 1. 5 % Cap sol 25μl

after it was applied on the nerve trunk

the C waves were decreased immediately to 77. 7% of control

then the C wave amplitudes were decreased to 46. 2 % (P

<

0.01 ) in 5 minutes

then maintained at 54. 5 %

53. 3 % for 15 53. 3 % for 15

30 minutes (P

<

0. 05) (n = 4). But the C waves were not yet completely blocked.When the action time of 1. 5 % capsaicin sol was prolonged for 24 hours

the C waves were de-creased in 4/6 experimental examples

and they were completely blocked only another 2 examples.The analgesia of electroacupuncture (EA) at "Zusanli" before and after 1. 5 % Cap applying on the nervi peroneus communis for 30 minutes was observed. Before Cap treatment

EA at "Zusanli" could obviously inhibit the nociceptive responses of NRM neuron induced by stimulation of rats tail tip in 0 10. 15 .20 and 30 minutes (P

<

0. 05

n = 7). But after Cap

the inhibition of EA at "Zusanli" .on the nociceptive responses was clearly weakened(P

>

0. 05

n = 7 ). In a case (NO. 88107 )

that C wave was nearly completely b1ocked

analgesia of EA at the lateral "Zusanli" disappeared

but EA at con-tralateral "Zusanli" could still produce analgesia.It is shggested .that role of afferent C fibers in EA analgesia is very important and itidispensable