title: Effects of Kefir on the Cardiac Autonomic Tones and Baroreflex Sensitivity in Spontaneously Hypertensive Rats.
abstract: OBJECTIVE
  It has been previously shown that the probiotic kefir (a symbiotic matrix containing acid bacteria and yeasts) attenuated the hypertension and the endothelial dysfunction in spontaneously hypertensive rats (SHR). In the present study, the effect of chronic administration of kefir on the cardiac autonomic control of heart rate (HR) and baroreflex sensitivity (BRS) in SHR was evaluated.
  
  
  METHODS
  SHR were treated with kefir (0.3 mL/100 g body weight) for 60 days and compared with non-treated SHR and with normotensive Wistar-Kyoto rats. Cardiac autonomic vagal (VT) and sympathetic (ST) tones were estimated through the blockade of the cardiac muscarinic receptors (methylatropine) and the blockade of β1-adrenoceptor (atenolol). The BRS was evaluated by the tachycardia and bradycardia responses to vasoactive drug-induced decreases and increases in arterial blood pressure (BP), respectively. Additionally, spontaneous BRS was estimated by autoregressive spectral analysis.
  
  
  RESULTS
  Kefir-treated SHR exhibited significant attenuation of basal BP, HR, and cardiac hypertrophy compared to non-treated SHR (12, 13, and 21%, respectively). Cardiac VT and ST were significantly altered in the SHR (~40 and ~90 bpm) compared with Wistar rats (~120 and ~30 bpm) and were partially recovered in SHR-kefir (~90 and ~25 bpm). SHR exhibited an impaired bradycardic BRS (~50%) compared with Wistar rats, which was reduced to ~40% in the kefir-treated SHR and abolished by methylatropine in all groups. SHR also exhibited a significant impairment of the tachycardic BRS (~23%) compared with Wistar rats and this difference was reduced to 8% in the SHR-kefir. Under the action of atenolol the residual reflex tachycardia was smaller in SHR than in Wistar rats and kefir attenuated this abnormality. Spectral analysis revealed increased low frequency components of BP (~3.5-fold) and pulse interval (~2-fold) compared with Wistar rats and these differences were reduced by kefir-treatment to ~1.6- and ~1.5-fold, respectively. Spectral analysis also showed an impairment of spontaneous BRS in SHR, but kefir-treatment caused only a tendency to reverse this result.
  
  
  CONCLUSIONS
  The novelty of this study is that daily chronic consumption of a low dose of kefir reduced the impairment of the cardiac autonomic control of HR and of the impaired BRS in SHR.
authors.affiliation: Laboratory of Translational Physiology, Federal University of Espirito Santo Vitoria, Brazil.
authors.forename: Brunella F
authors.initials: BF
authors.lastname: Klippel
authors.affiliation: Pharmaceutical Sciences Graduate Program, Vila Velha University Vila Velha, Brazil.
authors.forename: Licia B
authors.initials: LB
authors.lastname: Duemke
authors.affiliation: Laboratory of Translational Physiology, Federal University of Espirito Santo Vitoria, Brazil.
authors.forename: Marcos A
authors.initials: MA
authors.lastname: Leal
authors.affiliation: Pharmaceutical Sciences Graduate Program, Vila Velha University Vila Velha, Brazil.
authors.forename: Andreia G F
authors.initials: AG
authors.lastname: Friques
authors.affiliation: Department of Physiology, Federal University of Vale Sao Francisco Petrolina, Brazil.
authors.forename: Eduardo M
authors.initials: EM
authors.lastname: Dantas
authors.affiliation: Department of Biochemistry, Institute of Education, Science and Technology Vila Velha, Brazil.
authors.forename: Rodolfo F
authors.initials: RF
authors.lastname: Dalvi
authors.affiliation: Laboratory of Translational Physiology, Federal University of Espirito Santo Vitoria, Brazil.
authors.forename: Agata L
authors.initials: AL
authors.lastname: Gava
authors.affiliation: Pharmaceutical Sciences Graduate Program, Vila Velha UniversityVila Velha, Brazil; Department of Biochemistry, Institute of Education, Science and TechnologyVila Velha, Brazil.
authors.forename: Thiago M C
authors.initials: TM
authors.lastname: Pereira
authors.affiliation: Pharmaceutical Sciences Graduate Program, Vila Velha University Vila Velha, Brazil.
authors.forename: Tadeu U
authors.initials: TU
authors.lastname: Andrade
authors.affiliation: Laboratory of Translational Physiology, Federal University of Espirito Santo Vitoria, Brazil.
authors.forename: Silvana S
authors.initials: SS
authors.lastname: Meyrelles
authors.affiliation: Pharmaceutical Sciences Graduate Program, Vila Velha University Vila Velha, Brazil.
authors.forename: Bianca P
authors.initials: BP
authors.lastname: Campagnaro
authors.affiliation: Laboratory of Translational Physiology, Federal University of Espirito SantoVitoria, Brazil; Pharmaceutical Sciences Graduate Program, Vila Velha UniversityVila Velha, Brazil.
authors.forename: Elisardo C
authors.initials: EC
authors.lastname: Vasquez
keywords: bradycardia; hypertension; probiotic; sympathetic tone; tachycardia; vagal tone