Effects of intrathecal gabapentin and/or morphine on amino acid neurotransmitters in spinal cord of rat incision pain models

Objective To study the effects of intrathecally administering gabapentin and/or morphine on the amino acid neurotransmitters in spinal cord of rat incision pain models.Methods Forty male SD rats were randomly divided into five groups (n=8) and were intrathecally inserted catheter.Paw incision models were made 5d later.Gabapentin (50 μg,group Ⅲ) or morphine(2.5 μg,group Ⅳ) or both (group Ⅴ) were intrathecally injected 30 min before incision.Another two groups were regarded as shame (group Ⅰ) or control (group Ⅱ).Pain behavior was determined 2 h later using mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL).The content of four amino acids including glutamate,aspartate,glycine and γ-aminobutyric acid in rat spinal cord were detected.Results MWT and TWL decreased and the content of glutamate and aspartate in spinal cord increased significantly 2 h after incision(P＜0.05)in groups Ⅱ,Ⅲ and Ⅳ (without statistically differences among three groups),but not in group Ⅴ,compared to them in group Ⅰ.There were no differences in the content of glycine and γ-aminobutyric acid in rat spinal cord 2 h after incision among four groups.Conclusion Intrathecal gabapentin significantly enhances the antinociceptive effect of intrathecal morphine in rat incision pain model,which may owe to the decreased level of excitatory amino acids in spinal cord. Key words: Gabapentin; Morphine; Amino acid; Spinal cord