Effect of propofol the expression of inducible nitric oxide synthase in the spinal cord in rats with chronic neuropathic pain

Forty adult Wistar rats of both sexes weighing 200-220 g were used in this study. Chronic neuropathic pain was produced by loose ligatures placed on the left sciatic nerve. Propofol or normal saline (NS) was given intraperitoneally (i.p. ) once a day for 6 days, seven days after sciatic nerve ligation. The animals were randomly divided into 4 groups ( n = 10) : group I received NS 50 ml·kg~(-1) i.p. but no sciatic nerve ligation; groupII received sciatic nerve ligation and NS 50 ml·kg~(-1) i.p.; group M and IV received sciatic nerve ligation and propofol 50 ml·kg~(-1) ( III) or 75 ml·kg~(-1)( IV ) i.p. . Withdrawal threshold of both hind paws to Von Frey filaments was measured on the 6~(th) , 10~(th) and 12~(th) days after sciatic nerve ligation. The animals were then sacrificed and the lumbar segment (L_(4-5) ) of the spinal cord was removed for the detection of iNOS mRNA expression by RT-PCR technique on the 12~(th) day.The withdrawal threshold to Von Frey filament of both hind paws was significantly higher on the 10~(th) and 12~(th) days in the two propofol groups (group III and IV ) than in group II ( P < 0.05). The expression of iNOS mRNA in group IE and IV was significantly lower than that in group II (P < 0.05). The antinociceptive effect of propofol is closely related to its inhibitory action on expression of iNOS mRNA in the spinal cord.