In:
The Journal of Neuroscience, Society for Neuroscience, Vol. 26, No. 20 ( 2006-05-17), p. 5492-5499
Abstract:
C-nociceptors mediating cutaneous pain in humans can be distinguished in mechano-heat-responsive units (CMH) and mechano-insensitive units (CM i ). However, if sensitized in damaged tissue, CM i play an important role in inflammatory pain. CM i differ from CMH by higher electrical thresholds and by mediating the axon reflex. Using these properties, we established two stimulation paradigms: (1) transcutaneous stimulation (TCS) of low current density below the CM i threshold and (2) intracutaneous stimulation (ICS) of high current density that excites CM i . This was proven by the quantification of the axon-reflex flare. Applying these stimulation paradigms during functional magnetic resonance imaging, we investigated whether nociceptor stimulation that recruits CM i leads to different cerebral activation than stimuli that do not recruit CM i . Brain activation by CM i was inferred by subtraction. Both stimuli recruited multiple afferents other than CM i , and we expected a common network of regions involved in different aspects of pain perception and motor nocifensive reactions in both stimuli. ICS that additionally recruited CM i should activate regions with low acuity that are involved in pain memory and emotional attribution. Besides a common network of pain in both stimuli, TCS activated the supplementary motor area, motor thalamic nuclei, the ipsilateral insula, and the medial cingulate cortex. These regions contribute to a pain processing loop that coordinates the nocifensive motor reaction. CM i nociceptor activation did not cause relevant activation in this loop and does not seem to play a role in withdrawal. The posterior cingulate cortex was selectively activated by ICS and is apparently important for the processing of inflammatory pain.
Type of Medium:
Online Resource
ISSN:
0270-6474
,
1529-2401
DOI:
10.1523/JNEUROSCI.2059-05.2006
Language:
English
Publisher:
Society for Neuroscience
Publication Date:
2006
detail.hit.zdb_id:
1475274-8
SSG:
12
