Pain and Aging: Brain Structure and the Effects of Oxytocin (Doctoral dissertation)

Abstract

Chronic pain disproportionately affects older adults. Age-related alterations in brain morphology, including white matter integrity, may contribute to increased incidence of chronic pain susceptibility in older adults. Oxytocin (OT) is associated with brain morphology and OT receptors (OXTR) are expressed in pain processing regions, namely the basal ganglia, thalamus, and brainstem. Single-dose intranasal OT attenuates acute experimental pain and may be low side-effect treatment for chronic pain management in older adults. This two-study project investigated the associations between pain and brain morphology in the context of aging to determine the intranasal OT’s potential for chronic pain management in older adults. Study 1 (n=52) and Study 2 (n=36) participants completed self-report chronic pain measures, pain threshold tests, and structural MRI scans. For Study 2, procedures were completed at baseline and repeated following a four-week intranasal OT or placebo intervention. Structural images were segmented using Freesurfer 6.0.0. White matter pathways were reconstructed with Tracula. In Study 1, regression analyses were used to determine the association between patient reported chronic pain intensity and pain thresholds with brain morphology. For Study 2, baseline to post-intervention change was compared between OT and placebo groups for chronic pain intensity, pain thresholds, and brain morphology. Lower fractional anisotropy (FA) of the right cingulum angular bundle and left corticospinal tract were associated with greater chronic pain intensity. Higher brainstem volumes, lower age, and sex predicted greater pain thresholds at the quadriceps. OT and placebo showed between-group differences in change for chronic pain intensity, temporal summation of pain at the patella, and brainstem volume, with increased chronic pain intensity and decreased temporal summation of pain ratings for placebo. These early findings suggest that long-term intranasal OT may help slow or prevent increase in chronic pain, potentially via neuroprotective properties, and may reduce neuroinflammation in the brainstem. More human research, particularly older adults, is needed to confirm these effects. Results from this line of work increase scientific understanding of the role of long-term intranasal OT administration on brain mechanisms underlying pain experience in aging and have potential for clinical application.

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Publication
University of Florida
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Désirée Lussier
Postdoctoral research fellow

I am currently a postdoctoral research fellow with the SIMEXP laboratory at the Centre de recherche de l'Institut universitaire de gériatrie de Montréal (CRIUGM), Université de Montréal.

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