High blood pressure (BP) is associated with reduced pain sensitivity, known as BP-related hypoalgesia. The underlying neural mechanisms remain uncertain, yet arterial baroreceptor signaling, occurring at cardiac systole, is implicated. We examined normotensives using functional neuroimaging and pain stimulation during distinct phases of the cardiac cycle to test the hypothesized neural mediation of baroreceptor-induced attenuation of pain.
Eighteen participants (10 women; 32.7 (6.5) years) underwent BP monitoring for 1 week at home, and individual pain thresholds were determined in the laboratory. Subsequently, participants were administered unpredictable painful and nonpainful electrocutaneous shocks (stimulus type), timed to occur either at systole or at diastole (cardiac phase) in an event-related design. After each trial, participants evaluated their subjective experience.
Subjective pain was lower for painful stimuli administered at systole compared with diastole, F(1, 2283) = 4.82, p = 0.03. Individuals with higher baseline BP demonstrated overall lower pain perception, F(1, 2164) = 10.47, p < .0001. Within the brain, painful stimulation activated somatosensory areas, prefrontal cortex, cingulate cortex, posterior insula, amygdala, and the thalamus. Stimuli delivered during systole (concurrent with baroreceptor discharge) activated areas associated with heightened parasympathetic drive. No stimulus type by cardiac phase interaction emerged except for a small cluster located in the right parietal cortex.
We confirm the negative associations between BP and pain, highlighting the antinociceptive impact of baroreceptor discharge. Neural substrates associated with baroreceptor/BP-related hypoalgesia include superior parietal lobule, precentral, and lingual gyrus, regions typically involved in the cognitive aspects of pain experience.
From the Neuroimaging Laboratory (Ottaviani, Fagioli, Macaluso, Bozzali), IRCCS Santa Lucia Foundation; Department of Psychology (Ottaviani), Sapienza University of Rome; Department of Cardiovascular, Dysmetabolic and Aging-associated Diseases (Mattei, Censi, Calcagnini), Italian Institute of Health, Rome, Italy; Institute of Metabolism and Systems Research (Edwards), College of Medical and Dental Sciences, Birmingham University, UK; ImpAct Team (Macaluso), Lyon Neuroscience Research Center, France; and Psychiatry, BSMS Department of Neuroscience (Critchley), Brighton and Sussex Medical School, University of Sussex, Brighton, UK.
Address correspondence to Cristina Ottaviani, PhD, Department of Psychology, via dei Marsi 78, 00185 Rome, Italy. E-mail: firstname.lastname@example.org
Received for publication June 1, 2017; revision received January 8, 2018.