title: Chronic mercury exposure impairs the sympathovagal control of the rat heart.
abstract: Mercury is known to cause harmful neural effects affecting the cardiovascular system. Here, we evaluated the chronic effects of low-dose mercury exposure on the autonomic control of the cardiovascular system. Wistar rats were treated for 30 days with HgCl2(1st dose 4.6 μg/kg followed by 0.07 μg/kg per day, intramuscular) or saline. The femoral artery and vein were then cannulated for evaluation of autonomic control of the hemodynamic function, which was evaluated in awake rats. The following tests were performed: baroreflex sensitivity, Von Bezold-Jarisch reflex, heart rate variability (HRV) and pharmacological blockade with methylatropine and atenolol to test the autonomic tone of the heart. Exposure to HgCl2for 30 days slightly increased the mean arterial pressure and heart rate (HR). There was a significant reduction in the baroreflex gain of animals exposed to HgCl2. Moreover, haemodynamic responses to the activation of the Von Bezold-Jarisch reflex were also reduced. The changes in the spectral analysis of HRV suggested a shift in the sympathovagal balance toward a sympathetic predominance after mercury exposure, which was confirmed by autonomic pharmacological blockade in the HgCl2group. This group also exhibited reduced intrinsic HR after the double block suggesting that the pacemaker activity of the sinus node was also affected. These findings suggested that the autonomic modulation of the heart was significantly altered by chronic mercury exposure, thus reinforcing that even at low concentrations such exposure might be associated with increased cardiovascular risk.
authors.affiliation: Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil. yllars@hotmail.com.
authors.forename: M R
authors.initials: MR
authors.lastname: Simões
authors.affiliation: Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil.
authors.forename: B F
authors.initials: BF
authors.lastname: Azevedo
authors.affiliation: Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil.
authors.forename: J
authors.initials: J
authors.lastname: Fiorim
authors.affiliation: Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil.
authors.forename: D D
authors.initials: DD
authors.lastname: Jr Freire
authors.affiliation: Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil.
authors.forename: E P
authors.initials: EP
authors.lastname: Covre
authors.affiliation: Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil.|Health Science Centre of Vitória, EMESCAM, Vitória, ES, Brazil.
authors.forename: D V
authors.initials: DV
authors.lastname: Vassallo
authors.affiliation: Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil.
authors.forename: L
authors.initials: L
authors.lastname: Dos Santos
mesh_terms: D000818:Animals; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology; D002318:Cardiovascular Diseases / Q000139:chemically induced / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects* / Q000502:physiology; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology; D008297:Male; D008628:Mercury / Q000008:administration & dosage / Q000633:toxicity*; D051381:Rats; D017208:Rats, Wistar; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology; D014630:Vagus Nerve / Q000187:drug effects* / Q000502:physiology
chemical_list: D008628:Mercury
keywords: baroreflex; chemoreflex; chronic exposure; heart rate variability; mercury; sympathetic tone