Our previous work demonstrated that microinjection of OFQ into PAG antagonized e lectroacupuncture (EA) analgesia; increased the release of Glu in spinal dorsal horn and decreased the release of GABA

5 HT and NE; and significantly facilita t ed c fibre response and post discharge of WDR neurons of spinal dorsal horn in t he rats. The aim of current study is to observe the effect of microinjection of OFQ into PAG and simultaneous EA on the release of monoamines and Amino acids in spinal dorsal horn in the rats

by the methods of nucleus injection

micro dia lysis and HPLC EC. The results were as follows: After microinjection of OFQ into PAG and simultaneous EA

extracellular concentr ation of Glu was significantly decreased

whereas extracellular concentratio ns of GABA

5 HT and 5 HIAA

NE and MHPG were significantly increas ed (P<0.05～0.01)

indicating significant differences in comparison wi t h OFQ control group (microinjection of OFQ into PAG alone) in the corresponding phases (P<0.5～0.001). The results suggest there are opposite effects on the descending pain modulating system between OFQ in the brain and EA

so this may be one of the mechanisms of OFQ in the brain antagonizing EA analgesia.