Dynamic changes in excitatory and inhibitoty amino acid neurotransmitter release in the spinal cord in a rat model of incisional pain / 中华麻醉学杂志

ABSTRACT

Objective To examine the dyllamic changes in excitatory and inhibitory amino acid neurotransmitter release in the spinal cord in a rat model of incisional pain.Methods Twelve healthy adult male SD rats weighing 250-300g were anesthetized with intraperitoneal chloral hydrate 300 mg/kg.A loop microdialysis catheter was implanted into the subarachnoid space via the atlanto-occipital membrane and advanced for 8.5 cm candad until lumbar region.The animals were randomly divided into 2 groups(n=6 each) control group(C) and incisional pain group(I).Incisional pain was produced by the plantar incision in the tight hindpaw under 1.2% isoflurane in group I while group C received only anesthesia with 1.2% isoflurane.The microdialysis samples were collected before incision(To,baseline)at 3 h,1 d,2 d and 3 d after incision(T1-4) for determination of amino acid using HPLC.The pain behavior was assessed and scored (O=no pain,2=severe pain) at the above time paints.Results In group I the aspartate and glutamate concentrations in the microdialysis samples were significantly increased at 3 h after incision(T1) as compared with the baseline value at To and returned to the baseline level at l d(T2);the glyeine and r-amino butyric acid concentrations were signifieantly increased at ld (T2)and returned to the baseline level at 2 d(T3).The cumulated pain scores were significantly increased at 3 h,1 d and 2 d after incision and returned to baseline level at 3 d (T4) in group I.Conclusion The increased release of excitatory amino acid neurotransmitter in the early phase after incision may be involved in hyperalgesia while the increased release of inhibitory amino acid neurotransmitter in the later phase may be involved in the pain relief.