Expression of N-methyl-D-aspartate receptor subunit 2B containing N-methyl-D-aspartate receptors in the spinal dorsal horn of rats with hydrogen sulfide-induced pain

Abstract

Objective To investigate the role of N-methyl-D-aspartate receptor subunit 2B (NR2B) containing N-methyl-D-aspartate (NMDA) receptors in the spinal dorsal horn of rats with hydrogen sulfide-induced pain.Methods Thirty male SD rats aged 7 weeks were randomly divided into 3 groups (n =10 each):control group (group C),H2S group (group S),and ketamine group (group K).Intraplantar administration of NaHS (H2S donor) 1 nmol (100 μl) for 5 days in group S and group K,and the equal volum (100 μl) of nodal saline (NS) in group C (once each day) was done.Then rats in group K were injected with ketamine 10 mg/kg (0.2 ml) intramuscularly for 7 days,and the equal volum of NS was injected in group C and group S (once each day).The paw withdrawal threshold (PWT) to mechanical stimulation was measured at first day before the first administration of NaHS/NS (Tc),20 min after the first administration of NaHS/NS (T1),20 min after the fifth administration of NaHS/NS (T2),and 20 min after the seventh administration of ketamine/NS (T3).The rats were sacrificed after the last PWT measurement.The lumber segment of the spinal cord was removed for determination of the expressions of NR2B subunit by using RT-PCR and Western blotting.Results The PWT at T1,T2 and T3 was (2.72 ± 1.17),(1.48 ± 0.57) and (2.40 ± 0.89) g respectively in group S,which was significantly lower than in group C,and the expressions of NR2B mRNA and protein in spinal dorsal horn was (0.75 ±0.07) and (1.36 ± 0.08) respectively,which was significantly higher than in group C.The PWT at T3 was (8.89 ±1.09)g in group K,which was higher than in group S,and the expression of NR2B mRNA and protein in spinal dorsal horn was (0.55 ± 0.05) and (1.02 ± 0.06) respectively,which was lower than in group S.Conclusion The upregnlation of NR2B subunit in spinal dorsal horn was one of meachanisms in hydrogen sulfide-induced pain and inhibition of NR2B expression may contribute to the antinociceptive effects of ketamine. Key words: Hydrogen sulfide; Ketamine; N-methyl-D-aspartate receptor subunit 2B; Spinal dorsal horn; Pain