1 Current work has shown the importance of spinal cyclooxygenase (COX) products in facilitatory processes leading to tissue injury induced hyperalgesia. This cascade must originate with free arachidonic acid (AA) released by the activity of spinal phospholipase A 2 's (PLA 2 ). In the present work, we studied the role of PLA 2 's in spinal sensitization. 2 We first demonstrate the presence of constitutive mRNA in the spinal cord for PLA 2 Groups IB, IIA, IIC, IVA, V and VI by reverse transcription-polymerase chain reaction (RT-PCR) and sequencing. Using quantitative-PCR, we found that Group IVA cPLA 2 and Group VI iPLA 2 are the predominant PLA 2 messages in the spinal cord. Western blotting and activity assays specific for Group IVA cPLA 2 and Group VI iPLA 2 verified the presence of these enzymes. PLA 2 activity in spinal cord homogenates was suppressed by methyl arachidonyl fluorophosphonate (MAFP) and arachidonyl trifluoromethylketone (AACOCF 3 ), mixed inhibitors of Group IVA cPLA 2 and Group VI iPLA 2 as well as by bromoenol lactone (BEL), a Group VI iPLA 2 inhibitor. The spinal expression of PLA 2 mRNA or protein was not altered in the face of peripheral inflammation. Secondly, we showed that intrathecal (i.t.) administration of MAFP and AACOCF 3 , but not BEL, dosedependently prevented thermal hyperalgesia induced by intraplantar carrageenan as well as formalininduced flinching. Finally, i.t. injection of AACOCF 3 , at antihyperalgesic doses, decreased the release of prostaglandin E 2 (PGE 2 ) into spinal dialysate evoked by i.t. NMDA, while i.t. injection of BEL had no effect. 3 Taken together, this work points to a role for constitutive Group IVA cPLA 2 in spinal nociceptive processing.

Phospholipase A 2 (PLA 2 ) appears to play a fundamental role in cell injury in the central nervous system. We have investigated PLA 2 expression in the astrocytoma cell line 1231N1, and found that GIVA, GIVB, GIVC and GVI PLA 2 messages are expressed. PLA 2 activity is increased by in£am-matory/injury stimuli such as interleukin-1L L and lipopolysaccharide in these cells but with very di¡erent time courses. The arachidonic acid liberated is converted to prostaglandin E 2 , possibly by cyclooxygenase-2, which is induced by in£ammatory stimuli. This cell system emerges as a model to study injury/ in£ammation-related activation of the new PLA 2 forms GIVB and GIVC.

Current work emphasizes that peripheral tissue injury and inflammation results in a heightened sensitivity to subsequent noxious input (hyperalgesia) that is mediated in large part by the spinal synthesis and release of eicosanoids, in particular prostaglandins. Secreted phospholipase A(2)s (sPLA(2)s) form a class of structurally related enzymes that release arachidonic acid from cell membranes that is further processed to produce eicosanoids. We hypothesized that spinal sPLA(2)s may contribute to inflammation-induced hyperalgesia. Spinal cord tissue and cerebrospinal fluid were collected from rats for assessment of sPLA(2) protein expression and sPLA(2) activity. A basal sPLA(2) protein expression and activity was detected in spinal cord homogenate (87+/-17 pmol/min/mg), though no activity could be detected in cisternal cerebrospinal fluid, of naive rats. The sPLA(2) activity did not change in spinal cord tissue or cerebrospinal fluid assessed over 8 h after injection of carrageenan into the hind paw. However, the sPLA(2) activity observed in spinal cord homogenates was suppressed by addition of LY311727, a selective sPLA(2) inhibitor. To determine the role of this spinal sPLA(2) in hyperalgesia, we assessed the effects of lumbar intrathecal (IT) administration of LY311727 in rats with chronic IT catheters in three experimental models of hyperalgesia. IT LY311727 (3-30 microg) dose-dependently prevented intraplantar carrageenan-induced thermal hyperalgesia and formalin-induced flinching, at doses that had no effect on motor function. IT LY311727 also suppressed thermal hyperalgesia induced by IT injection of substance P (30 nmol). Using in vivo spinal microdialysis, we found that IT injection of LY311727 attenuated prostaglandin E(2) release into spinal dialysate otherwise evoked by the IT injection of substance P. Taken together, this work points to a role for constitutive sPLA(2)s in spinal nociceptive processing.

OBJECTIVE To perform 3-D inverse dynamics analysis of the entire forelimb of healthy dogs during a walk and trot. ANIMALS 5 healthy adult Beagles. PROCEDURES The left forelimb of each dog was instrumented with 19 anatomic markers. X-ray fluoroscopy was used to optimize marker positions and perform scientific rotoscoping for 1 dog. Inverse dynamics were computed for each dog during a walk and trot on the basis of data obtained from an infrared motion-capture system and instrumented quad-band treadmill. Morphometric data were obtained from a virtual reconstruction of the left forelimb generated from a CT scan of the same dog that underwent scientific rotoscoping. RESULTS Segmental angles, torque, and power patterns were described for the scapula, humerus, ulna, and carpus segments in body frame. For the scapula and humerus, the kinematics and dynamics determined from fluoroscopy-based data varied substantially from those determined from the marker-based data. The dominant action of scapular rotation for forelimb kinematics was confirmed. Directional changes in the torque and power patterns for each segment were fairly consistent between the 2 gaits, but the amplitude of those changes was often greater at a trot than at a walk. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that control of the forelimb joints of dogs is similar for both a walk and trot. Rotation of the forelimb around its longitudinal axis and motion of the scapula should be reconsidered in the evaluation of musculoskeletal diseases, especially before and after treatment or rehabilitation.

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