Pain: no completely satisfactory definition exists;
that proposed by the International Association for the Study of Pain (for
people) is the most widely accepted: "Pain is an unpleasant sensory
and emotional experience associated with actual or potential tissue damage,
or described in terms of such damage." ie, pain consists of both
a sensory component and an affective component. Some people also include
a cognitive component, but I consider this a response to pain. (Other
people deny that animals are capable of thinking.)
Analgesia = a lack of pain.
Nociception = the sensory component of pain. Since it
is not possible to definitively prove that animals can feel pain, this
term is sometimes misused (particularly by American physiologists) to
mean pain in animals. A nociceptor is a nerve fibre used for pain signals.
Hyperalgesia and allodynia These are conditions which
occur after pain perception has been altered by central or peripheral
sensitisation. Hyperalgesia occurs when a stimulus which would have been
painful before is now more painful; allodynia is when a previously innocuous
stimulus (such as light touch) becomes painful. Sometimes these conditions
persist after the injury has healed (hyperpathia).
Algogenic = something which produces pain.
Placebo = Latin “I will please” = inactive
drug given to people who believe that it will do some good.
Nocebo = Latin “I will hurt” = inactive drug
given to people who believe that it will cause problems. Most animals probably regard most veterinary drugs as nocebos.
Assessment of pain
Pain pathways
Gate theory
Response to injury
Analgesia
University of Edinburgh's Animal Pain web site
