Nitric oxide modulates blood pressure through NMDA receptors in the rostral ventrolateral medulla of conscious rats

• Published in: Brain research 2016-07, Vol.1643, p.159-167
• Main Authors: Machado, Natalia L.S, Silva, Fernanda C.S, Chianca-Jr, Deoclecio A, de Menezes, Rodrigo C
• Format: Article
• Language: English
• Subjects: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid - administration & dosage; Animals; Arterial Pressure - drug effects; Blood pressure; Conscious rats; Enzyme Inhibitors - administration & dosage; Excitatory Amino Acid Agonists - administration & dosage; Glutamic Acid - administration & dosage; Heart Rate - drug effects; Male; Medulla Oblongata - drug effects; Medulla Oblongata - physiology; N-Methylaspartate - administration & dosage; Neurology; NG-Nitroarginine Methyl Ester - administration & dosage; Nitric oxide; Nitric Oxide - antagonists & inhibitors; Nitric Oxide - physiology; NMDA receptors; Rats; Rats, Inbred F344; Receptors, AMPA - agonists; Receptors, AMPA - physiology; Receptors, N-Methyl-D-Aspartate - agonists; Receptors, N-Methyl-D-Aspartate - physiology; Rostral ventrolateral medulla
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2016.05.001

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 the central nervous system including the RVLM, however the pathways driving NO affects and the correlation between NO and glutamate-induced mechanisms are still not well established. Here, we investigate the influence of NO on 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 the 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.