title: Nitric oxide modulates blood pressure through NMDA receptors in the rostral ventrolateral medulla of conscious rats.
abstract: The rostral ventrolateral medulla (RVLM) is an important site of cardiovascular control related to the tonic excitation and regulating the sympathetic vasomotor tone through local presympathetic neurons. Nitric oxide (NO) has been implicated in the modulation of neurotransmission by several areas of the central nervous system including the RVLM. However the pathways driving NO affects and the correlation between NO and glutamate-induced mechanisms are not well established. Here, we investigate the influence of NO on the cardiovascular response evoked by the activation of NMDA and non-NMDA glutamatergic receptors in the RVLM in conscious rats. For that, we examined the influence of acute inhibition of the NO production within the RVLM, by injecting the nonselective constitutive NOS inhibitor, l-NAME, on responses evoked by the microinjection of excitatory amino acids l-glutamate, NMDA or AMPA agonists into RVLM. Our results show that the injection of l-glutamate, NMDA or AMPA agonists into RVLM, unilaterally, induced a marked increase in the mean arterial pressure (MAP). Pretreatment with l-NAME reduced the hypertensive response evoked by the glutamate injection, and also abolished the pressor response induced by the injection of NMDA into the RVLM. However, blocking the NO synthesis did not alter the response produced by the injection of AMPA agonist. These data provide evidence that the glutamatergic neurotransmission within the RVLM depends on excitatory effects exerted by NO on NMDA receptors, and that this mechanism might be essential to regulate systemic blood pressure.
authors.affiliation: Laboratory of Cardiovascular Physiology, Department of Biological Sciences (DECBI), Institute of Exact and Biological Sciences, Federal University of Ouro Preto, Ouro Preto, MG, Brazil; Laboratory of Hypertension, Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil. Electronic address: nmachado@bidmc.harvard.edu.
authors.forename: Natalia L S
authors.initials: NL
authors.lastname: Machado
authors.affiliation: Laboratory of Cardiovascular Physiology, Department of Biological Sciences (DECBI), Institute of Exact and Biological Sciences, Federal University of Ouro Preto, Ouro Preto, MG, Brazil. Electronic address: fernandasilva_nut@yahoo.com.br.
authors.forename: Fernanda C S
authors.initials: FC
authors.lastname: Silva
authors.affiliation: Laboratory of Cardiovascular Physiology, Department of Biological Sciences (DECBI), Institute of Exact and Biological Sciences, Federal University of Ouro Preto, Ouro Preto, MG, Brazil. Electronic address: deochianca@gmail.com.
authors.forename: Deoclecio A
authors.initials: DA
authors.lastname: Chianca
authors.affiliation: Laboratory of Cardiovascular Physiology, Department of Biological Sciences (DECBI), Institute of Exact and Biological Sciences, Federal University of Ouro Preto, Ouro Preto, MG, Brazil. Electronic address: rodrigo.menezes@iceb.ufop.br.
authors.forename: Rodrigo C
authors.initials: RC
authors.lastname: de Menezes
mesh_terms: D000818:Animals; D062186:Arterial Pressure / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000008:administration & dosage; D018690:Excitatory Amino Acid Agonists / Q000008:administration & dosage; D018698:Glutamic Acid / Q000008:administration & dosage; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000502:physiology*; D016202:N-Methylaspartate / Q000008:administration & dosage; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000502:physiology*; D051381:Rats; D011916:Rats, Inbred F344; D018091:Receptors, AMPA / Q000819:agonists / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists / Q000502:physiology*; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000008:administration & dosage
chemical_list: D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D009569:Nitric Oxide; D018698:Glutamic Acid; D016202:N-Methylaspartate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D019331:NG-Nitroarginine Methyl Ester
keywords: Blood pressure; Conscious rats; NMDA receptors; Nitric oxide; Rostral ventrolateral medulla