Central nitrergic system regulation of neuroendocrine secretion, fluid intake and blood pressure induced by angiotensin-II

Abstract

BackgroundNitric oxide (NO) synthesis has been described in several circumventricular and hypothalamic structures in the central nervous system that are implicated in mediating central angiotensin-II (ANG-II) actions during water deprivation and hypovolemia. Neuroendocrine and cardiovascular responses, drinking behavior, and urinary excretions were examined following central angiotensinergic stimulation in awake freely-moving rats pretreated with intracerebroventricular injections of Nω-nitro-L-arginine methyl ester (L-NAME, 40 μg), an inhibitor of NO synthase, and L-arginine (20 ug), a precursor of NO.ResultsInjections of L-NAME or ANG-II produced an increase in plasma vasopressin (VP), oxytocin (OT) and atrial natriuretic peptide (ANP) levels, an increase in water and sodium intake, mean arterial blood pressure and sodium excretion, and a reduction of urinary volume. L-NAME pretreatment enhanced the ANG-II response, while L-arginine attenuated VP and OT release, thirst, appetite for sodium, antidiuresis, and natriuresis, as well as pressor responses induced by ANG-II.Discussion and conclusionThus, the central nitrergic system participates in the angiotensinergic responses evoked by water deprivation and hypovolemia to refrain neurohypophysial secretion, hydromineral balance, and blood pressure homeostasis.

Evaluation of Intrarenal Oxygenation in Iodinated Contrast-Induced Acute Kidney Injury–Susceptible Rats by Blood Oxygen Level–Dependent Magnetic Resonance Imaging

“…In 2 additional animals where we acquired additional R 2 maps (data not shown), the data did suggest an increase in R 2 in IM after iodixanol; however, the magnitude of change was relatively small (approximately 10 s –1 ) compared with the observed R 2* change (approximately 100 s –1 ). Because it was also previously shown that L-NAME could reduce urine output, 41 it may explain why the R 2* was lower in the CIAKI-susceptible group after iodixanol. Although ioxalgate did show statistically significant increase in R 2* in IM, the values were comparable with the defined threshold (estimated slope of 0.32 versus 0.3).…”

Enhanced Expression of Heme Oxygenase‐1 and Carbon Monoxide Excitatory Effects in Oxytocin and Vasopressin Neurones During Water Deprivation

“…In this sense, numerous studies demonstrated high expression levels of the neuronal isoform of nitric oxide synthase (nNOS) in both OT and VP neurons (31, 42) which similar to our findings with HO-1, is upregulated in an activity-dependent manner during osmotic challenges (43, 44). Differently from the HO/CO system however, the general consensus is that NO is constitutively produced within the SON and PVN, acting as a strong inhibitor of neuronal activity (31, 45, 46), and hormone release from the posterior pituitary (24, 25, 47, 48). Taken together, these studies support the notion that NO and CO are two functionally relevant gas molecules with opposing actions in the magnocellular system (i.e., NO inhibitory and CO excitatory).…”

“…Gas neurotransmitters, particularly nitric oxide (NO), have been shown to play important roles in neuroendocrine regulation (24)(25)(26). In the present study, we aimed to determine whether CO, another functionally relevant gas molecule in the brain (1,2), plays a role in the modulation of magnocellular neurosecretory activity.…”

Angiotensin II protects cortical neurons against oxygen-glucose deprivation-induced injury in vitro

“…Ang II is best known for its role in the regulation of blood pressure, fluid balance and neuroendocrine function (11)(12)(13). It was recently demonstrated that Ang II primarily activated circumventricular neurons, leading to the activation of neurons in other forebrain regions (14), indicating that Ang II may exert multiple effects on neuronal activity.…”