Capsaicin was applied to the sciatic and saphenous nerves of rats under anaesthesia. The time-course of the response to intraplantar formalin and formalin-induced c-FOS expression and alterations in substance P (SP) immunoreactivity (IR) were assessed in capsaicin-treated rats. The foot withdrawal latency to 48°C water was also recorded from 1--75 days after surgery. Formalin-induced pain was reduced by both capsaicin and its vehicle at the earliest test, 3 days after surgery. Formalin pain in the vehicle-treated group recovered by 14 days, and scores in the capsaicin-treated group remained depressed until 28 days. By 75 days, capsaicin-treated rats were hyperalgesic in the first phase. Thermal hyposensitivity was apparent from the first day after surgery until day 75. Capsaicin reduced c-FOS IR and both treatments reduced SP IR at day 14. Thermal hypoalgesia occurs prior to changes at the terminals of unmyelinated afferents and may involve depletion of peptides in the periphery due to disrupted axonal transport. The effects on formalin-induced pain may be due to axonal transport disruption, and by desensitization of the afferents.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.30805 |
| Date | January 2001 |
| Creators | Albanese, Marie-Claire. |
| Contributors | Abbott, Frances V. (advisor), Franklin, Keith B. J. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Psychiatry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001803196, proquestno: MQ70365, Theses scanned by UMI/ProQuest. |
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