Cardiovascular responses to hydrogen peroxide into the nucleus tractus solitarius

Leonardo Máximo Cardoso, Débora Simões De Almeida Colombari, José V. Menani, Glenn M. Toney, Deoclécio Alves Chianca, Eduardo Colombari

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

The nucleus tractus solitarius (NTS), a major hindbrain area involved in cardiovascular regulation, receives primary afferent fibers from peripheral baroreceptors and chemoreceptors. Hydrogen peroxide (H2O2) is a relatively stable and diffusible reactive oxygen species (ROS), which acting centrally, may affect neural mechanisms. In the present study, we investigated effects of H2O2 alone or combined with the glutamatergic antagonist kynurenate into the NTS on mean arterial pressure (MAP) and heart rate (HR). Conscious or anesthetized (urethane and α-chloralose) male Holtzman rats (280-320 g) were used. Injections of H2O2 (125 to 1500 pmol/40 nl) into the intermediate NTS of anesthetized rats evoked dose-dependent and transient hypotension (-18 ± 3 to -55 ± 11 mmHg) and bradycardia (-16 ± 5 to -116 ± 40 bpm). Injection of the catalase inhibitor 3-amino-1,2,4-triazole (100 nmol/40 nl) into the NTS also produced hypotension and bradycardia. Previous injection of the ionotropic L-glutamate receptor antagonist kynurenate (7 nmol/40 nl) attenuated by 48% the bradycardic response, without changing the hypotension evoked by H2O2 (500 pmol/40 nl) in anesthetized rats. The antioxidant L-ascorbate (600 pmol/80 nl) injected into the NTS attenuated the bradycardic (42%) and hypotensive (67%) responses to H2O2 (500 pmol/40 nl) into the NTS. In conscious rats, injection of H 2O2 (50 nmol/100 nl) into the NTS also evoked intense bradycardia (-207 ± 8 bpm) and hypotension (-54 ± 6 mmHg) that were abolished by prior injection of kynurenate (7 nmol/100 nl). The results show that H2O2 into the NTS induces hypotension and bradycardia probably due to activation of glutamatergic mechanisms.

Original languageEnglish (US)
Pages (from-to)R462-R469
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume297
Issue number2
DOIs
StatePublished - Aug 2009

Keywords

  • Blood pressure
  • Catalase inhibition
  • Heart rate
  • Kynurenic acid
  • Reactive oxygen species

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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