title: Age-related differences in conditioned pain modulation of sensitizing and desensitizing trends during response dependent stimulation.
abstract: The current study evaluated age differences in conditioned pain modulation using a test stimulus that provided the opportunity to evaluate changes in heat pain sensitivity, sensitization, and desensitization within the same paradigm. During this psychophysical test, pain intensity clamping uses REsponse Dependent STIMulation (REDSTIM) methodology to automatically adjust stimulus intensity to maintain a desired pain rating set-point. Specifically, stimulus intensity increases until a pre-defined pain rating (the setpoint) is exceeded, and then decreases until pain ratings fall below the setpoint, with continued increases and decreases dictated by ratings. The subjects are blinded in terms of the setpoint and stimulus intensities. Younger and older subjects completed two test sessions of two REDSTIM trials, with presentation of conditioning cold stimulation between the trials of one session but not the other. The results indicated that conditioning cold stimulation similarly decreased the overall sensitivity of younger and older subjects, as measured by the average temperature that maintained a setpoint rating of 20 (on a scale of 0-100). The conditioning stimulus also significantly enhanced sensitization following ascending stimulus progressions and desensitization following descending stimulus progressions in older subjects relative to younger subjects. Thus, older subjects experienced greater swings in sensitivity in response to varying levels of painful stimulation. These results are discussed in terms of control over pain intensity by descending central modulatory systems. These findings potentially shed new light on the central control over descending inhibition and facilitation of pain.
authors.affiliation: Pain Research and Intervention Center of Excellence, College of Dentistry, University of Florida, P.O. Box 103628, Gainesville, FL 32611, USA. Electronic address: kmnaugle@iupui.edu.
authors.forename: Kelly M
authors.initials: KM
authors.lastname: Naugle
authors.affiliation: Pain Research and Intervention Center of Excellence, College of Medicine, University of Florida, 2004 Mowry Road, Gainesville, FL 32611, USA.
authors.forename: Yenisel
authors.initials: Y
authors.lastname: Cruz-Almeida
authors.affiliation: Department of Neuroscience, McKnight Brain Institute, University of Florida, P.O. Box 103628, Gainesville, FL 32611, USA.
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Vierck
authors.affiliation: Neuroanalytics Corporation, 3700 NW 91st St. C200, Gainesville, FL 32606, USA.
authors.forename: Andre P
authors.initials: AP
authors.lastname: Mauderli
authors.affiliation: Pain Research and Intervention Center of Excellence, College of Dentistry, University of Florida, P.O. Box 103628, Gainesville, FL 32611, USA.
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Riley
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D003080:Cold Temperature; D003213:Conditioning, Psychological; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008297:Male; D008875:Middle Aged; D059225:Nociception; D010146:Pain / Q000523:psychology*; D010147:Pain Measurement; D017288:Pain Threshold; D010812:Physical Stimulation; D011601:Psychophysics; D055815:Young Adult
keywords: Aging; Older adults; Pain inhibition; Pain modulation; Pain sensitivity; Response dependent stimulation (REDSTIM)