Objective: To verify the effect of Orphanin (O) FQ on cerebral ischemia and observe its influence on electroacupuncture(EA)'s anti cerebral ischemia. Methods: 63 SD rats were randomly divided into sham operation (control) group (n=5)

cerebral ischemia group (n=8)

OFQ 10 μg group (n=7)

OFQ 1 μg group (n=7)

saline group (n=8)

EA+ OFQ 1 μg group (n=8)

EA+saline group (n=7) and EA group (n=6). Cerebral ischemia model was established using the cerebral middle artery occlusion (MCAo) method. "Shuigou"(GV 26) and "Baihui" (GV 20) were stimulated with EA (dense sparse waves

3.85～6.25 Hz

1.4～2 mA) for 60 min. Cerebral somatosensory evoked potential(SEP) was recorded and cerebral infarct volume detected. Thirty minutes after MCAo

OFQ (10 μg/10 μL

1 μg/10 μL

0.1 μg/10 μL) and saline 10 μL were injected into the right lateral cerebroventricle via an implanted catheter. Results: Following cerebral ischemia

the amplitude of SEP decreased

and after intracerebroventricular (icv) administration of OFQ 10 μg and 1 μg respectively

SEP declined further. One hour after cerebral ischemia reperfusion

SEP recovered basically

while that of OFQ 10 μg group remained low level even 3 hr after ischemia reperfusion. A certain dose effect correlation was found between OFQ and SEP suppression reaction. Application of OFQ enlarged the infarct volume

but after icv of OFQ 0.1 μg

changes of the SEP amplitude and infarct volume had no significant difference compared with those of control group (P>0.05). Following icv of OFQ 10 μg and 1 μg

cerebral infarct volume increased considerably in comparison with that of cerebral ischemia group (P<0.05). Following cerebral ischemia

the amplitude of SEP in control group lowered from 71.46±6.42% to 27.64±6.26%

while in EA group

that of SEP decreased from 81.12±4.51% to 55.64±8

81%

existing a significant difference between these two groups (P<0.05); SEP amplitude of EA+OFQ group was significantly lower than that of EA+saline group (P<0.01). The cerebral infarct volumes in ischemia group and EA group were 24.18±1.08 mm 3 and 18.497± 5.112 mm 3 respectively. Following icv OFQ

the cerebral infarction volume EA+OFQ 1 μg group was remarkably larger than that of EA+saline group

suggesting an inhibitory action of OFQ on EA's anti cerebral ischemia. Conclusion: Orphanin FQ 10 μg and 1 μg (icv) deteriorates the degree of ischemic brain damage and reverses the anti cerebral ischemic effect of EA in the adult SD rats.