Human and Nonhuman Primate Reactions to Painful Electrocutaneous Stimuli and to Morphine

Abstract

Indices of Pain Sensations and Reactions • Escape Latency as a Measure of Pain and Morphine Hypalgesia • Control for Response Suppression by Mor-phine • Importance of the Source of Experimental Pain • Summary The difficulties inherent in the process of discriminating the pres-ence of pain and its intensity in another individual are similar when evaluating nonhumans or humans. Humans have the advantage of utilizing unique verbal descriptors of pain intensity and quality, but reliance solely on verbal descriptors can be misleading. For example, an individual can verbally deny pain and yet display somatic and autonomic motor signs of nociception. We give special credence to verbal reports of pain sensations because the precision and efficiency of language is appropriate and necessary for qualitative distinctions. Verbal reports are advantageous for defining the spatial location and extent of a sensation and are necessary for distinguishing between varieties of pain such as sharp, dull, burning, pricking, or itching. However, the magnitudes of somatic and autonomic motor activities can reflect pain intensity, and quantification of these responses can be accomplished in a variety of animals. The challenge of comparative algesimetry is to establish measures of pain reactivity that are valid and reliable indicators of pain intensity. Indices of Pain Sensations and Reactions Humans can identify four component sensations that are elicited by 117 R. L. Kitchell et al. (eds.), Animal Pain