Neuroscience 2005 Abstract
| Presentation Number: | 513.11 |
|---|---|
| Abstract Title: | The pathophysiological mechanisms underlying cold allodynia and mechanical hyperalgesia are different: evidence from a mouse model of neuropathic pain. |
| Authors: |
Gilbert, A. K.*1
; Archambault, A. J.1
; Bédard, I.1
; Laird, J. M.1
1BioScience, AstraZeneca R&D Montreal, Montreal, Canada |
| Primary Theme and Topics |
Sensory and Motor Systems - Pain -- Neuropathic pain |
| Session: |
513. Neuropathic Pain: Mechanisms and Mediators I Poster |
| Presentation Time: | Monday, November 14, 2005 3:00 PM-4:00 PM |
| Location: | Washington Convention Center - Hall A-C, Board # Y26 |
| Keywords: | gabapentin, von Frey, oxycodone, amitriptyline |
Cold allodynia and mechanical hyperalgesia are symptoms most often reported by patients suffering from neuropathic pain. While cold allodynia and mechanical hyperalgesia are both commonly detected in patients and in animal models of neuropathic pain, the two symptoms are not necessarily due to the same pathophysiological events. Using acetone as a cooling stimulus and von Frey hairs as mechanical stimuli, we report that, in the spared tibial nerve (STN) injury model in mice the two evoked symptoms are due to different mechanisms. First, cold allodynia and mechanical hyperalgesia have different pharmacological profile. Drugs that reverse cold allodynia in the STN model are the ones most widely prescribed in the clinic. Indeed, gabapentin (200-1250 mmol/kg, ip) and oxycodone (3-30 mmol/kg, sc) were far more efficacious against cold allodynia than against mechanical hyperalgesia. Other drugs such as delta9-THC (3-30 mmol/kg, sc), amitriptyline (10-25 mmol/kg, ip) and tramadol (20-100 mmol/kg, ip) were equally efficacious against mechanical hyperalgesia and cold allodynia. Second, the testing area, that is the area of the hindpaw most sensitive to the two stimuli, differs. The portion of the paw that remains innervated after the surgery (hollow of the footpad) shows hypersensitivity to mechanical stimuli while the denervated area, such as the dorsolateral surface of the paw, is best to trigger cold allodynia. Finally, cold allodynia is longer lasting than mechanical hyperalgesia; cold allodynia is detected up to 60 days after surgery while the latter reverts by day 25. The distinct pharmacology and spatial distribution suggest that different mechanisms underlie the symptoms observed in this model of neuropathic pain. Overactivity in the tibial nerve may account for the mechanical hyperalgesia while increased sensitivity to cold may be due to newly expressed ion channels onto A-delta sensory neurons that are sprouting to previously denervated area of the paw.
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2005 Neuroscience Meeting Planner. Washington, DC: Society for Neuroscience, 2005. Online.
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