Exercise training rescues the electrical activity of liver-projecting DMNV neurones in response to oxytocin in spontaneously hypertensive rats

Electrophysiological Properties and Morphology of Cardiac and Pulmonary Motoneurons within the Dorsal Motor Nucleus of the Vagus of Rats

The dorsal motor nucleus of the vagus (DMV) contains parasympathetic motoneurons that project to the heart and lungs. These motoneurons control ventricular excitability/contractility and airways secretions/blood flow, respectively. However, their electrophysiological properties, morphology and synaptic input activity remain unknown. One important ionic current described in DMV motoneurons controlling their electrophysiological behaviour is the A-type mediated by voltage-dependent K+ (Kv) channels. Thus, we compared the electrophysiological properties, synaptic activity, morphology, A-type current density, and single cell expression of Kv subunits, that contribute to macroscopic A-type currents, between DMV motoneurons projecting to either the heart or lungs of adult male rats. Using retrograde labelling, we visualized distinct DMV motoneurons projecting to the heart or lungs in acutely prepared medullary slices. Subsequently, whole cell recordings, morphological reconstruction and single motoneuron qRT-PCR studies were performed. DMV pulmonary motoneurons were more depolarized, electrically excitable, presented higher membrane resistance, broader action potentials and received greater excitatory synaptic inputs compared to cardiac DMV motoneurons. These differences were in part due to highly branched dendritic complexity and lower magnitude of A-type K+ currents. By evaluating expression of channels that mediate A-type currents from single motoneurons, we demonstrated a lower level of Kv4.2 in pulmonary versus cardiac motoneurons, whereas Kv4.3 and Kv1.4 levels were similar. Thus, with the distinct electrical, morphological, and molecular properties of DMV cardiac and pulmonary motoneurons, we surmise that these cells offer a new vista of opportunities for genetic manipulation providing improvement of parasympathetic function in cardiorespiratory diseases such heart failure and asthma.

Astaxanthin Ameliorates Blood Pressure in Salt-Induced Prehypertensive Rats Through ROS/MAPK/NF-κB Pathways in the Hypothalamic Paraventricular Nucleus

Astaxanthin (AST) has a variety of biochemical effects, including anti-inflammatory, antioxidative, and antihypertensive functions. The aim of the present study was to determine whether AST ameliorates blood pressure in salt-induced prehypertensive rats by ROS/MAPK/NF-κB pathways in hypothalamic paraventricular nucleus.To explore the central effects of AST on the development of blood pressure, prehypertensive rats were induced by a high-salt diet (HS, 8% NaCl) and its control groups were treated with normal-salt diet (NS, 0.3% NaCl). The Dahl salt-sensitive (S) rats with HS diet for 6 weeks received AST or vehicle by gastric perfusion for 6 weeks. Compared to those with NS diet, rats with HS diet exhibited increased mean arterial pressure (MAP) and heart rate (HR). These increases were associated with higher plasma level of norepinephrine (NE), interleukin 1β (IL-1β), and interleukin 6 (IL-6); elevated PVN level of reactive oxygen species (ROS), NOX2, and NOX4, that of IL-1β, IL-6, monocyte chemotactic protein 1 (MCP-1), tyrosine hydroxylase (TH), phosphorylation extracellular-signal-regulated kinase (p-ERK1/2), phosphorylation Jun N-terminal kinases (p-JNK), nuclear factor-kappa B (NF-κB) activity; and lower levels of IL-10, superoxide dismutase (SOD), and catalase (CAT) in the PVN. In addition, our data demonstrated that chronic AST treatment ameliorated these changes in the HS but not NS diet rats. These data suggested that AST could alleviate prehypertensive response in HS-induced prehypertension through ROS/MAPK/NF-κB pathways in the PVN.