title: Induction of chronic non-inflammatory widespread pain increases cardiac sympathetic modulation in rats.
abstract: Fibromyalgia (FM) is characterized by chronic non-inflammatory widespread pain (CWP) and changes in sympathetic function. In attempt to elucidate the pathophysiological mechanisms of FM we used a well-established CWP animal model. We aimed to evaluate changes in cardiac autonomic balance and baroreflex function in response to CWP induction in rats. CWP was induced by two injections of acidic saline (pH 4.0, n=8) five days apart into the left gastrocnemius muscle. Control animals were injected twice with normal saline (pH 7.2, n=6). One day after the second injection of acidic saline or normal saline, the animals had pulse interval (PI) and systolic arterial pressure (SAP) variability, and spontaneous baroreflex sensitivity (BRS) evaluated. After induction of CWP, there was an increase of power in the low frequency (LF) band of PI spectrum (12.75 ± 1.04 nu), a decrease in the high frequency (HF) band (87.25 ± 1.04 nu) and an increase of LF/HF ratio (0.16 ± 0.01), when compared to control animals (7.83 ± 1.13 nu LF; 92.16 ± 1.13 nu HF; 0.08 ± 0.01 LF/HF). In addition, there was an increase of power in the LF band of SAP spectrum (7.93 ± 1.39 mmHg(2)) when compared to control animals (2.97 ± 0.61 mmHg(2)). BRS was lower in acidic saline injected rats (0.59 ± 0.06 ms/mmHg) when compared to control animals (0.71 ± 0.03 ms/mmHg). Our results showed that induction of CWP in rats shifts cardiac sympathovagal balance towards sympathetic predominance and decreases BRS. These data corroborate findings in humans with FM.
authors.affiliation: Department of Physiology, Federal University of Sergipe, São Cristovão, Brazil.
authors.forename: Larissa Resende
authors.initials: LR
authors.lastname: Oliveira
authors.forename: Vitor Ulisses
authors.initials: VU
authors.lastname: de Melo
authors.forename: Fabricio Nunes
authors.initials: FN
authors.lastname: Macedo
authors.forename: Andre Sales
authors.initials: AS
authors.lastname: Barreto
authors.forename: Daniel
authors.initials: D
authors.lastname: Badaue-Passos
authors.forename: Marcio Roberto
authors.initials: MR
authors.lastname: Viana dos Santos
authors.forename: Daniel Penteado Martins
authors.initials: DP
authors.lastname: Dias
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Sluka
authors.forename: Josimari M
authors.initials: JM
authors.lastname: DeSantana
authors.forename: Valter J
authors.initials: VJ
authors.lastname: Santana-Filho
mesh_terms: D000818:Animals; D017704:Baroreflex / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D059350:Chronic Pain / Q000503:physiopathology*; D003627:Data Interpretation, Statistical; D005356:Fibromyalgia / Q000150:complications / Q000503:physiopathology; D006321:Heart / Q000294:innervation* / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology; D008297:Male; D059352:Musculoskeletal Pain / Q000503:physiopathology; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000502:physiology; D010812:Physical Stimulation; D051381:Rats; D017208:Rats, Wistar; D013564:Sympathetic Nervous System / Q000503:physiopathology*