The association between paināinduced autonomic reactivity and descending pain control is mediated by the periaqueductal grey
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Abstract: There is a strict interaction between the autonomic nervous system (ANS) and pain, which might involve descending pain modulatory mechanisms. The periaqueductal grey (PAG) is involved both in descending pain modulation and ANS, but its role in mediating this relationship has not yet been explored. Here, we sought to determine brain regions mediating ANS and descending pain control associations. Thirty participants underwent conditioned pain modulation (CPM) assessments, in which they rated painful pressure stimuli applied to their thumbnail, either alone or with a painful cold contralateral stimulation. Differences in pain ratings between āpressureāonlyā and āpressure + coldā stimuli provided a measure of descending pain control. In 18 of the 30 participants, structural scans and two functional MRI assessments, one paināfree and one during coldāpain were acquired. Heart rate variability (HRV) was simultaneously recorded. Normalised lowāfrequency HRV (LFāHRVnu) and the CPM score were negatively correlated; individuals with higher LFāHRVnu during pain reported reductions in pain during CPM. PAGāventroāmedial prefrontal cortex (vmPFC) and PAGārostral ventromedial medulla (RVM) functional connectivity correlated negatively with the CPM. Importantly, PAGāvmPFC functional connectivity mediated the strength of the LFāHRVnuāCPM association. CPM response magnitude was also negatively correlated with vmPFC GM volume. Our multiāmodal approach, using behavioural, physiological and MRI measures, provides important new evidence of interactions between ANS and descending pain mechanisms. ANS dysregulation and dysfunctional descending pain modulation are characteristics of chronic pain. We suggest that further investigation of bodyābrain interactions in chronic pain patients may catalyse the development of new treatments. image Key points: Heart rate variability (HRV) is associated with descending pain modulation as measured by the conditioned pain modulation protocol (CPM). There is an association between CPM scores and the functional connectivity between the periaqueductal grey (PAG) and ventroāmedial prefrontal cortex (vmPFC). CPM scores are also associated with vmPFC grey matter volume. The strength of functional connectivity between the PAG and vmPFC mediates the association between HRV and CPM. Our data provide new evidence of interactions between the autonomic nervous system and descending pain mechanisms.
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1469-7793