Regional and temporal changes in prostaglandin E 2 and thromboxane B 2 concentrations after spinal cord injury

Background context: Inflammatory metabolites of arachidonic acid likely play a significant role in secondary injury after spinal cord trauma. Purpose: We sought to characterize the regional and temporal alterations in prostaglandin concentrations after injury in a rat model. Study design/setting: Prostaglandin E 2 (PGE 2 ) and thromboxane B 2 (TxB 2 ) concentrations were measured in cerebrospinal fluid (CSF) and in different parts of the injured spinal cord at various time points after spinal cord injury. Outcome measures: PGE 2 and TxB 2 levels were measured by means of an enzyme immune assay. Methods: Forty-six adult Long Evans rats were subject to spinal cord injury using the NYU impactor. Animals were divided into three groups. Fourteen animals were used in a pilot study to determine the timing and location of PGE 2 production after spinal cord injury. These animals were sacrificed, and samples of injured cord, rostral cord and CSF were assayed for PGE 2 concentration. The remaining 32 animals were used to establish the time course of prostaglandin production. Twenty-eight animals were subjected to a spinal cord injury, and four animals served as sham-operated controls. These animals were sacrificed at predetermined time points 2 to 72 hours after injury, and the injured segments of spinal cord were harvested. Results: Both PGE 2 and TxB 2 concentrations increased immediately after injury in the injured segment. PGE 2 concentrations increased faster and more dramatically in the injured segment of spinal cord than in CSF or noninjured segments. Elevations in PGE 2 and TXB 2 concentrations were persistent for 72 hours after injury. Conclusion: Elevated concentrations of arachidonic acid metabolites can be detected in the injured segment of the spinal cord for at least 72 hours after injury. Concentration changes are detected earlier and are more dramatic in the injured cord segment than in rostral segments or the CSF.