Activation of cyclo-oxygenase-2 contributes to motor and cognitive dysfunction following diffuse traumatic brain injury in rats.
1. Post-traumatic inflammation may play a significant role in the development of delayed secondary brain damage following traumatic brain injury. 2. During post-traumatic inflammation, metabolic products of arachidonic acid, known as prostanoids (prostaglandins and thromboxanes) are released and aggravate the injury process. Prostanoid synthesis is regulated by the enzyme cyclo-oxygenase (COX), which is present in at least two isoforms, COX-1 (the constitutive form) and COX-2 (the inducible form). 3. In the present study, we examine the temporal and spatial profiles of COX-2 expression and the effects of the COX-2 inhibitor nimesulide on motor and cognitive outcome following diffuse traumatic brain injury in rats. 4. Adult male Sprague-Dawley rats were injured using the 2 m impact acceleration model of diffuse traumatic brain injury. At preselected time points after injury, animals were killed and the expression of COX-2 was measured in the cortex and hippocampus by western blotting techniques. 5. Increased expression of COX-2 was found in the cortex at 3 days and in the hippocampus as early as 3 h postinjury and this persisted for at least 12 days. 6. Administration of nimesulide (6 mg/kg, i.p.) at 30 min after injury and daily over a 10 day post-traumatic neurological assessment period resulted in a significant improvement compared with vehicle (2% dimethylsulphoxide diluted in isotonic saline)-treated controls in cognitive deficits, as assessed by the Barnes circular maze. There was also a significant improvement in motor dysfunction as assessed by the rotarod test on days 1 and 2 post-trauma compared with vehicle-treated controls. 7. These results implicate the involvement of COX-2 in cognitive and motor dysfunction following diffuse traumatic brain injury.
Cernak
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Department of Physiology and Pharmacology, James Cook University, Townsville, Queensland, Australia. ifc@georgetown.edu
O'Connor
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Vink
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D000818:Animals; D001930:Brain Injuries / Q000150:complications / Q000201:enzymology* / Q000503:physiopathology; D003072:Cognition Disorders / Q000201:enzymology* / Q000209:etiology / Q000378:metabolism; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004195:Disease Models, Animal; D004789:Enzyme Activation; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013449:Sulfonamides / Q000494:pharmacology
D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D007527:Isoenzymes; D013449:Sulfonamides; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C012655:nimesulide