title: The respiratory cycle modulates brain potentials, sympathetic activity, and subjective pain sensation induced by noxious stimulation.
abstract: To test the hypothesis that a respiratory cycle influences pain processing, we conducted an experimental pain study in 10 healthy volunteers. Intraepidermal electrical stimulation (IES) with a concentric bipolar needle electrode was applied to the hand dorsum at pain perceptual threshold or four times the perceptual threshold to produce first pain during expiration or inspiration either of which was determined by the abrupt change in an exhaled CO2 level. IES-evoked potentials (IESEPs), sympathetic skin response (SSR), digital plethysmogram (DPG), and subjective pain intensity rating scale were simultaneously recorded. With either stimulus intensity, IES during expiration produced weaker pain feeling compared to IES during inspiration. The mean amplitude of N200/P400 in IESEPs and that of SSR were smaller when IES was applied during expiration. The magnitude of DPG wave gradually decreased after IES, but a decrease in the magnitude of DPG wave was less evident when IES was delivered during expiration. Regardless of stimulus timing or stimulus intensity, pain perception was always concomitant with appearance of IESEPs and SSR, and changes in DPG. Our findings suggest that pain processing fluctuates during normal breathing and that pain is gated within the central nervous system during expiration.
authors.affiliation: Department of Physical Therapy, Faculty of Health Sciences, Aomori University of Health and Welfare, 58-1 Mase, Hamadate, Aomori 030-8505, Japan. Electronic address: iwabe@me.com.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Iwabe
authors.affiliation: Department of Physical Therapy, Faculty of Health Sciences, Aomori University of Health and Welfare, 58-1 Mase, Hamadate, Aomori 030-8505, Japan. Electronic address: isamu@auhw.ac.jp.
authors.forename: Isamu
authors.initials: I
authors.lastname: Ozaki
authors.affiliation: Department of Neurosurgery, Faculty of Medicine, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan. Electronic address: hashizume@jinyoukai.or.jp.
authors.forename: Akira
authors.initials: A
authors.lastname: Hashizume
mesh_terms: D000204:Activity Cycles / Q000502:physiology*; D000704:Analysis of Variance; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D002245:Carbon Dioxide / Q000494:pharmacology; D004558:Electric Stimulation / Q000009:adverse effects; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects / Q000502:physiology*; D005712:Galvanic Skin Response / Q000502:physiology*; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D010146:Pain / Q000209:etiology / Q000503:physiopathology*; D017288:Pain Threshold / Q000187:drug effects; D010991:Plethysmography; D012119:Respiration / Q000187:drug effects; D011795:Surveys and Questionnaires; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide
keywords: A concentric bipolar needle electrode; Autonomic function; Digital plethysmogram; Intraepidermal stimulation; Pain intensity rating scale; Sympathetic skin response