(178) Diffuse noxious inhibitory controls observed across the lifespan

Abstract

Diffuse noxious inhibitory controls (DNIC) is an endogenous pain inhibition system. DNIC is believed to evoke descending supraspinal mechanisms in such a way that pain in a local area (experimental stimulus) is inhibited by a second pain that can be experienced at another location in the body (conditioning stimulus). The purpose of this study was to examine age-related differences using a DNIC protocol. Four older female adults and three older male adults were matched according to sex and individualized temperature settings to younger adult controls. During a training session, the temperature for the remaining sessions were determined based on the heat stimulus that produced a 40-50 rating and the cold water stimulus that produced a rating of 20-30 (0-100 VAS). Participants experienced the conditioning stimuli, cold water immersion (8-16oC) of the right foot, and the experimental stimuli, thermal stimuli (44-49oC) applied to the left palm, concurrently in order to induce DNIC. Participants underwent a control session using a 23oC water bath. Each session consisted of five 60-second trials. Peak pain ratings and area under the curve (AUC) scores were summed across each of the five trials. The dependent variables were aggregated experimental condition ratings minus control session ratings. The ANOVA analysis for peak pain ratings was significant (F=6.347, p=.027) with the older subjects reporting increased pain (mean= -1.6 (SD=4.0)) compared to younger subjects, who reported pain inhibition (5.2 (SD=5.9). For AUC, group differences approached significance (F=3.010, p=.115). Older adults process pain differently than younger adults. DNIC is an indicator of healthy pain inhibition. These findings suggest that older adults have reduced ability to inhibit pain, possibly because of dysfunction of their endogenous pain inhibition systems. This research was supported by a UFCD Student Summer Research Fellowship and NIH- NIDCR grant T32 DE007200. Diffuse noxious inhibitory controls (DNIC) is an endogenous pain inhibition system. DNIC is believed to evoke descending supraspinal mechanisms in such a way that pain in a local area (experimental stimulus) is inhibited by a second pain that can be experienced at another location in the body (conditioning stimulus). The purpose of this study was to examine age-related differences using a DNIC protocol. Four older female adults and three older male adults were matched according to sex and individualized temperature settings to younger adult controls. During a training session, the temperature for the remaining sessions were determined based on the heat stimulus that produced a 40-50 rating and the cold water stimulus that produced a rating of 20-30 (0-100 VAS). Participants experienced the conditioning stimuli, cold water immersion (8-16oC) of the right foot, and the experimental stimuli, thermal stimuli (44-49oC) applied to the left palm, concurrently in order to induce DNIC. Participants underwent a control session using a 23oC water bath. Each session consisted of five 60-second trials. Peak pain ratings and area under the curve (AUC) scores were summed across each of the five trials. The dependent variables were aggregated experimental condition ratings minus control session ratings. The ANOVA analysis for peak pain ratings was significant (F=6.347, p=.027) with the older subjects reporting increased pain (mean= -1.6 (SD=4.0)) compared to younger subjects, who reported pain inhibition (5.2 (SD=5.9). For AUC, group differences approached significance (F=3.010, p=.115). Older adults process pain differently than younger adults. DNIC is an indicator of healthy pain inhibition. These findings suggest that older adults have reduced ability to inhibit pain, possibly because of dysfunction of their endogenous pain inhibition systems. This research was supported by a UFCD Student Summer Research Fellowship and NIH- NIDCR grant T32 DE007200.