Reference code: | PT/FB/BL-2004-015.08 |
Location: | Arquivo PCA - Pasta 21/2004
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Title:
| Opioid-mediated control of pain modulation from the medullary dorsal reticular nucleus: a gene therapy and pharmacological study in the monoarthritic rat
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Publication year: | 2006
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URL:
| http://www.abstractsonline.com/viewer/viewAbstractPrintFriendly.asp?CKey={03B744B2-A0B0-4E01-A414-306527CBA56E}&SKey={1134B7F4-DCFE-488D-8972-5C3ED52276BA}&MKey={D1974E76-28AF-4C1C-8AE8-4F73B56247A7}&AKey={3A7DC0B9-D787-44AA-BD08-FA7BB2FE9004}
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Abstract/Results: | ABSTRACT:
Chronic inflammation affects the activity of the supraspinal endogenous pain modulatory system, with an enhancement of facilitatory actions. A pronociceptive action, conveyed by a direct bulbospinal pathway, was ascribed to the dorsal reticular nucleus (DRt) in acute and sustained pain models, but the role of the DRt during chronic inflammation has never evaluated. Based on the expression of opioid receptors in spinally-projecting DRt neurons, we used the monoarthritic rat to evaluate the behavioural effects of local administration of a Herpes Simplex-type 1 vector encoding proenkephalin (HSV-1-PPE) in comparison with the opioid receptor agonists [D-Ala2, Glu4]deltorphin (DELT) and [D-Ala2, NMePhe4Gly-ol5]enkephalin (DAMGO). Male Wistar rats received an intraarticular injection of 50µl of saline (control) or complete Freund's adjuvant (monoarthritic) and 7 days later a guide cannula was implanted in the animals used in the pharmacological study. At the 14th day of monoarthritis, the animals used in the gene therapy study were injected in the DRt with 2µl of HSV-1-PPE or HSV-1 vector with lacZ. Paw withdrawal latencies (PWL) were determined 2, 4, 7, 10 and 14 days after viral injection. In the animals used in the pharmacological study, 0.6 µl of saline, DELT (1.2, 12,120 and 1200 ng) or DAMGO (0.1, 1, 25 and 50 ng) were injected in the DRt and PWL were determined at 15, 30, 45 and 60 minutes post-injections. A one-way ANOVA followed by the SNK post-hoc test was used for each time point studied. After HSV1-PPE injection, nociceptive thresholds were higher in controls at 2 days post-injection and lower in monoarthritic rats at 2 and 4 days. In control animals, PWL decreased after DELT or DAMGO injections, with maximal effects at longer times. In monoarthritic rats, the effects of DELT were similar whereas 50ng of DAMGO increased the PWL. The results suggest that the effects of HSV-1 are due both to actions upon DRt neurons and other brain afferents. The different effects of opioid modulation in control and monoarthritic animals support previous proposals of the adaptative mechanisms during chronic pain.
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Accessibility: | Document exists in file (poster)
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Copyright/Reproduction:
| By permission
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Language:
| eng
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Notes:
| Respective poster in attachment |
Author: | Pinto, M.
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Secondary author(s):
| Tschudy, F., Sousa, M., Wilson, S. P., Lima, D., Tavares, I.
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Document type:
| Online abstract
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Number of reproductions:
| 1
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Reference:
| Pinto, M., Tschudy, F., Sousa, M., Wilson, S. P., Lima, D., & Tavares, I. (2006). Opioid-mediated control of pain modulation from the medullary dorsal reticular nucleus: a gene therapy and pharmacological study in the monoarthritic rat. Program No.249.21/S24. 2006 Neuroscience Meeting Planner. Atlanta, GA: Society for Neuroscience. Online
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Indexed document: | No
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Keywords: | Psychophysiology / Chronic pain
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