Pain Update: Dr. Carl Saab

Neuroscientists are reluctant to commit because they know next month’s journal may have something important. We thank this world famous scientist for bringing us up to speed. Many are afraid to commit because they know they may not want to be held to anything more than about six months old.

10/28/03
Opinion

This article aims at guiding the general reader through the tangled web of information regarding research on pain (inflammatory, neuropathic, central, etc.) and animal models of pain. The reader will find keywords of major topics of focus in pain research illustrated and in bold characters.


Contents

I- DEFINING PAIN
II- ANIMAL MODELS OF HUMAN PAIN
1. Models of peripheral pain
2. Models of central pain
3. Models of visceral pain
III- PATHWAYS OF PAIN
1. Somatic touch and pain
2. Visceral pain
3. What is a pathway or a tract?
(Illustration)

Carl Y. Saab, Ph. D.
PVA-EPVA Center for Neuroscience and Regeneration Research
Yale University School of Medicine

I- DEFINING PAIN

I begin by defining pain as an unpleasant aversive emotion in response to a noxious stimulus. Exceptions to this definition include pain evoked in the absence of an overt noxious stimulus (central and neuropathic pain), and rare incidence of paradoxical pleasure derived from pain (masochism). However, this qualitative definition eludes any reasonable quantitative assessment of pain; a standardized universal pain scale does not exist, and this constitutes the first level of difficulty in understanding pain mechanisms. Pain investigators found their way around this obstacle by using behavior as a reliable measure of pain. A corollary to this postulate is the use of animal behavior as predictor to animal pain (assuming animals may