ABSTRACT
Objective To evaluate the effects of intrathecal 2-PMPA on chronic inflammatory pain in rats . Methods Twenty four male Sprague-Dawley rats ,aged 4-6 months ,weighing 200-250 g ,were randomly divided into 3 groups (n=8 each) using a random number table :normal saline (NS) group ,complete Freund′s adjuvant (CFA ) group and N-acetylaspartylglutamate peptidase inhibitor 2-PMPA group (group 2-PMPA ) . Chronic inflammatory pain was induced by injecting 100μl of CFA into the plantar surface of the left hindpaw .Immediately after injection of CFA ,2-PMPA 100 μg was injected intrathecally once a day for 3 consecutive days in group 2-PMPA ,while the equal volume of NS was given instead of 2-PMPA in NS and CFA groups .The paw withdrawal latency to thermal nociceptive stimulus (TWL ) and paw withdrawal threshold (PWT ) to von Frey filament stimulation were measured before injection of CFA (baseline ,T1 ) and after the last injection of CFA (T2 ) .Then the rats were sacrificed and the L4 ,5 segments of the spinal cord were removed for determination of NR2B expression by Western blot .Results Compared with group NS ,TWL and PWT were significantly decreased at T2 and the expression of NR2B was up-regulated in CFA and 2-PMPA groups ( P<0.05 ) .Compared with group CFA ,TWL and PWT were significantly increased at T2 and the expression of NR2B was down-regulated in group 2-PMPA ( P<0.05) .Conclusion Intrathecal 2-PMPA can alleviate CFA-induced chronic inflammatory pain in rats ,and inhibition of NR2B expression in the spinal cord is involved in the mechanism .