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Title: Studies of chronic inflammatory pain in lambs after rubber ring castration and tail-docking : self-administration of analgesic and neurohistochemistry to validate behavioural assessment
Author: Rennie, Anita Ellen
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2005
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Following castration and tail-docking by rubber ring, lambs suffer from severe acute pain lasting up to 3 hours. The subsequent formation of inflammatory lesions, at the site of the ring, may be associated with chronic pain. Behaviour that has been used to assess acute pain in castrated lambs, has been associated with these lesions and validation of the use of these behaviours for assessment of chronic pain is necessary. Two approaches were used for validation. Firstly a model in which lambs could learn to self-administer analgesic was developed and used to indicate the presence of chronic pain. As lesions began to form after castration and tail-docking, lambs were given the opportunity to learn about the consequences of consuming a feed containing the non-steroidal anti-inflammatory, flunixin meglumine and an identical feed containing no drug. The lambs were then given the opportunity to choose between these feeds until the lesions healed. In the second part of this project, neurohistochemical evidence of chronic inflammatory pain was sought. In situ hybridisation histochemistry was used to seek evidence of a change in the expression of AVP and CRF mRNA in the paraventricular nucleus of the hypothalamus of lambs castrated and tail docked by rubber ring. The lesions produced in these studies were as severe as those found in lambs of the same ages in previous studies. Some evidence of ‘pain’ behaviours was found in castrated and tail-docked lambs. Despite this, no evidence that castrated and tail-docked lambs learned to self-administer analgesic was obtained despite trends observed in initial studies. In addition no neurohistochemical evidence of chronic inflammatory pain was found. This evidence suggests that any chronic pain associated with castration and tail-docking lesions is not sufficiently severe to provoke learning about the pain relieving properties of a drugged feed or to induce evidence of a chronic stress response in the HPA axis. However, it is argued that the damage to the tissue at the site of the rubber rings may have induced a local anti-inflammatory and analgesic response, which was sufficient to prevent any pain from the lesions.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available