Hostname: page-component-848d4c4894-4hhp2 Total loading time: 0 Render date: 2024-06-07T14:08:29.038Z Has data issue: false hasContentIssue false

Distinct central representations of inescapable and escapable pain: observations and speculation

Published online by Cambridge University Press:  08 March 2002

Kevin A. Keay
Affiliation:
Department of Anatomy and Histology and Pain Management and Research Centre, Royal North Shore Hospital, The University of Sydney, New South Wales 2006, Australia
Richard Bandler
Affiliation:
Department of Anatomy and Histology and Pain Management and Research Centre, Royal North Shore Hospital, The University of Sydney, New South Wales 2006, Australia
Get access

Abstract

It is well established clinically that the affective response to pain of deep origin (muscles, joints and viscera) is distinct from that evoked by cutaneous pain. Cutaneous pain triggers a fight-flight reaction (active emotional coping), whereas deep pain evokes a reaction of quiescence, decreased vigilance and vasodepression (passive emotional coping). These observations led to suggestions of distinct central representations for deep versus cutaneous pain. Indeed, studies using immediate early gene (c-fos) expression revealed selective activation of ventrolateral versus lateral columns of the midbrain periaqueductal grey region (PAG) by persistent pain of deep origin versus intermittent cutaneous pain. Ventrolateral versus lateral PAG activation had been found earlier to evoke passive versus active emotional coping. However, not all cutaneous pain triggers active coping. Persistent cutaneous pain (e.g. burns) instead, usually evokes passive coping. This raised the question of whether the behavioural significance of pain (i.e. its escapability versus inescapability), rather than its tissue origin, is represented in supraspinal regions such as the PAG. Subsequent study revealed that a persistent (inescapable) noxious cutaneous manipulation (clip of the neck) evoked both selective ventrolateral PAG Fos expression and passive emotional coping. Such data suggest that pain representation in the PAG reflects a quality akin to behavioural significance, rather than tissue origin. In contrast, in the spinal cord predominantly superficial dorsal horn Fos expression was seen after either persistent or intermittent noxious cutaneous stimuli, leaving the question of the pathway(s) via which persistent (inescapable) cutaneous pain activates the vlPAG unanswered. One experimental approach to this question is suggested. Experimental Physiology (2002) 87.2, 275-279.

Type
Physiological Society Symposium - Nociceptors as Homeostatic Afferents: Central Processing
Copyright
© The Physiological Society 2002

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)