Effects of repeated conditioning pain modulation in healthy volunteers

Abstract

Conditioning pain modulation can be assessed in 5-min intervals by cuff algometry with a fixed conditioning stimulus. Without applying conditioning stimuli the pain sensitivity of test-stimuli habituated. As a consequence, it can be speculated that the conditioning stimulus may negate the temporal habituation effects during repeated sessions, whereas this may not be the case for unconditioned stimuli. Applying both conditioned and unconditioned repeated test-stimuli may be a way to assess different parts of the pain modulatory system, and a model for measuring a netCPM-effect, which could indicate a balance between habituation and sensitization, is proposed.

Delayed effects of attention on pain sensitivity and conditioned pain modulation

“…In line with a large body of evidence, this study showed pain reduction during conditioning pain modulation at grouplevel based on a cuff algometry CPM paradigm at baseline Hoegh et al, 2018;Kennedy et al, 2016;Petersen et al, 2017). The phasic cuff teststimuli paradigm (5 s pressure stimulations) showed excellent reliability.…”

“…Particularly, the net CPM effect (i.e. the difference between the effect of repeated conditioned and repeated unconditioned test‐stimuli) is interesting since it may provide novel insights to the balance between facilitative and inhibitory descending control systems (Arendt‐Nielsen et al., ; Groves & Thompson, ; Hoegh et al., ). Accordingly, an exploratory analysis of the changes between the sessions ( Δ VAS) was conducted for the 1st and the 2–4th test‐stimuli, respectively.…”

“…The upper and lower borders of the cuff were visually marked on the participant's skin to ensure the cuffs remained in place throughout the experiment. This method has previously been shown to produce reliable measurements of CPM based on PDT and PTT (Graven‐Nielsen et al., ), with CPM based on PDT providing the most stable and robust CPM effects (Hoegh et al., ). Healthy men appear to have more efficient CPM compared to healthy women (Skovbjerg et al., ) and thus the current study was performed only in men.…”

“…Pain inhibition during distraction and CPM are not the same (Lautenbacher, Prager, & Rollman, 2007;Moont, Crispel, Lev, Pud, & Yarnitsky, 2012;Moont et al, 2010). In support of this, CPM effects do not diminish when repeated over 20 minutes (Hoegh, Petersen, & Graven-Nielsen, 2018) while attention-induced analgesia does (Silvestrini & Rainville, 2013). However, some authors suggest that CPM and attention could depend on the capacity of the same descending control systems (MacLeod, 1992;Silvestrini & Rainville, 2013;Stroop, 1935).…”

“…VAS scores during the 1st test stimulus were lower in Pain-II compared to Pain-I. It is unlikely that the difference between Pain-I and Pain-II VAS-scores are related to carry-over effects because they were separated by a 5-min break, which has previously been found to be sufficient to reduce the risk of carry-over effects Hoegh et al, 2018;Imai, Petersen, Mørch, & Arendt-Nielsen, 2016;McPhee & Graven-Nielsen, 2018), was included between the two sessions. Two recent studies have used phasic test-stimuli (Lie et al, 2017;McPhee & Graven-Nielsen, 2018) of which one does not find CPM effects (McPhee & Graven-Nielsen, 2018) while the other study does show a CPM effect (Lie et al, 2017).…”