title: Catalase inhibition into the fourth cerebral ventricle affects bradycardic parasympathetic response to increase in arterial pressure without changing the baroreflex.
abstract: Exogenous catalase influences neural control of cardiovascular system; however, we do not know yet if its inhibition into the fourth cerebral ventricle (4(th) V) influences baroreflex regulation. We evaluated the effects of central catalase inhibition on baroreflex in conscious Wistar rats. We used males Wistar rats (320-370 g), which were implanted with a stainless steel guide cannula into 4(th) V. The femoral artery and vein were cannulated for mean arterial pressure (MAP) and heart rate (HR) measurement and drug infusion, respectively. After basal MAP and HR recordings, the baroreflex was tested with a pressor dose of phenylephrine (PHE, 8 μg/kg, bolus) and a depressor dose of sodium nitroprusside (SNP, 50 μg/kg, bolus). Baroreflex was evaluated before 5, 15, 30 and 60 minutes after 3-amino-1, 2, 4-triazole (ATZ, 0.001 g/100 μL) injection into the 4(th) V. Vehicle treatment did not change baroreflex responses. ATZ attenuated bradycardic peak and reduced HR range at 30 minutes. ATZ into the 4(th) V reduced bradycardic and tachycardic reflex responses to increase and decrease MAP, respectively (p<0.05) 30 minutes after its microinjection without significantly changing the basal MAP and HR. In conclusion, central catalase inhibition influenced the highest parasympathetic response to MAP increase in conscious Wistar rats without change baroreflex gain.
authors.affiliation: Departamento de Medicina, Disciplina de Cardiologia, Universidade Federal de São Paulo (UNIFESP), Rua Napoleão de Barros, 715 - Térreo 04039-032 São Paulo, SP, Brasil. vitor.valenti@gmail.com
authors.forename: Vitor E
authors.initials: VE
authors.lastname: Valenti
authors.forename: Luiz Carlos
authors.initials: LC
authors.lastname: De Abreu
authors.forename: Monica A
authors.initials: MA
authors.lastname: Sato
authors.forename: Fernando L A
authors.initials: FL
authors.lastname: Fonseca
authors.forename: Andrés R Pérez
authors.initials: AR
authors.lastname: Riera
authors.forename: Celso
authors.initials: C
authors.lastname: Ferreira
mesh_terms: D000640:Amitrole / Q000008:administration & dosage; D000818:Animals; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D001919:Bradycardia / Q000201:enzymology*; D002374:Catalase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000008:administration & dosage; D020546:Fourth Ventricle / Q000187:drug effects / Q000201:enzymology*; D057967:Infusions, Intraventricular; D008297:Male; D010275:Parasympathetic Nervous System / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D004791:Enzyme Inhibitors; D002374:Catalase; D000640:Amitrole