OBJECTIVETo compare effects of catgut embedding at "Zusanli" (ST 36) and "Shenshu" (BL 23) on Morphine analgesic tolerance and locomotor sensitization induced by chronic Morphine administration and the mechanism.

METHODSThe rats were randomly divided into a model group, a non-acupoint group, a Shenshu group and a Zusanli group. The rats, except those in the model group, were pretreated with acupoint catgut-embedding 10 days before the first Morphine injection. The Morphine-tolerance model was established and the pain threshold was detected by hot-plate test every day. Locomotor activities were recorded after the first Morphine injection and Morphine-challenging 1 week after withdrawal of Morphine. The positive neurons of nitric oxide synthetase (NOS) were showed by NADPH-d histochemical method.

RESULTSCompared with the non-acupoint group, catgut embedding at "Zusanli" (ST 36) could attenuate the Morphine analgesic tolerance and the increase of locomotor activities in rats. Meanwhile, the expression of NOS positive neurons in nucleus accumbens septi and dorsal striatum decreased in the Zusanli group. There were no significant differences between the Shenshu group and the non-acupoint group in the analgesic threshold and locomotor sensitization, but the expression of NOS positive neurons in the striatum region significantly decreased.

CONCLUSIONCatgut embedding at "Zusanli" (ST 36) can attenuate Morphine analgesic tolerance and reverse formation of locomotion sensitization induced by chronic Morphine administration, which are possibly related with inhibition of the expression of NOS positive neurons in nucleus accumbens septi and dorsal striatum.