Vasopressin and angiotensin receptors of the medial septal area of the brain in the control of thirst and salt appetite induced by vasopressin in water-deprived and sodium-depleted rats

In this study we investigated the influence of d(CH2)(5)-Tyr (Me)-AVP (A(1) AVP) and [Adamanteanacatyl(1),D-ET-D-Tyr(2), Va1(4), aminobutyril(6) ,As-8,As-9]-AVP 9 (A(2)AVP), antagonists of V-1 and V-2 arginine(8)-vasopressin (AVP) receptors, respectively, as well as the effects of losartan and CGP42112A, antagonists of angiotensin II (ANGII) AT(1) and AT(2), receptors, respectively, on water and 0.3 M sodium intake induced by water deprivation or sodium depletion (furosemide treatment) and enhanced by AVP injected into the medial septal area (N4SA). A stainless steel carmulawas implanted into the medial septal area (NISA) of male Holtzman rats AVP injection enhanced water and sodium intake in a dose-dependent manner. Pretreatment with V-1 antagonist injected into the MSA produced a dose-dependent reduction, whereas prior injection of V-2 antagonist increased, in a dose-dependent manner, the water and sodium responses elicited by the administration of AVP. Both AT(1) and AT(2) antagonists administered into the MSA elicited a concentration-dependent decrease in water and sodium intake induced by AVP, while simultaneous injection of the two antagonists was more effective in decreasing AVP responses. These results also indicate that the increase in water and sodium intake induced by AvT was mediated primarily by MSA AT(1) receptors. (c) 2007 Published by Elsevier B.V.

Effect of electrolytic and chemical lesion by ibotenic acid of the septal area on water and salt intake

Water and sodium chloride intake was studied in male Holtzman rats weighing 250-300 g that had been subjected to electrolytic and chemical lesions of the septal area (SA). Water intake increased in animals with electrolytic lesion of the SA bilaterally from 169.37 +/- 8.55 (sham) to 214.87 +/- 23.10 ml/5 days (lesioned). Water intake decreased after ibotenic acid lesion of the SA from 229.33 +/- 27.60 to 127.33 +/- 22.84 ml/5 days. Sodium chloride intake (1.5%) increased in animals with electrolytic lesion of the SA from 10.0 +/- 1.73 to 15.5 +/- 1.95 ml/5 days after lesion. Also sodium chloride (1.5%) intake increased after ibotenic acid injection into the SA to a greater extent (from 7.83 +/- 1.25 to 14.33 +/- 1.87 ml/5 days). The results indicate that the water intake response may be due to lesions that involve cell bodies and fibers of passage and that the sodium intake response can also be induced by lesions which involve only cell bodies. Finally, these results led us to conclude that the SA uses its cell bodies and afferent bodies and fibers for processing inputs mediating water intake and salt appetite and that the cells bodies of the SA are implicated in increased water intake. (C) 1998 Elsevier B.V.

Brain serotonin blockade and paradoxical salt intake in rats

Serotonin antagonism in the lateral parabrachial nucleus (LPBN) enhances sodium appetite induced by hypovolaemia and angiotensin-mineralocorticoid activation, but produces no sodium intake in euhydrated animals. In the present work, male adult rats (n=21) that received bilateral injections of the serotonergic antagonist methysergide (4 mug/ 0.2 mul) into the LPBN combined to intragastric load of 2 M NaCl (2 ml/rat), ingested hypertonic NaCl (ingestion of 4.3+/-1.6 ml/2 h of 0.3 M NaCl versus vehicle into LPBN: 0.2+/-0.2 ml/2 h, P<0.05). Methysergide- and vehicle-treated animals also ingested water (9.5+/-0.7 and 7.2+/-0.5 ml/2 h, respectively, P>0.05) as expected from the state of cell dehydration produced by the load. Ingestion of water (11.0+/-1.2 ml/2 h), and of 0.3 M NaCl (1.1+/-0.7 ml/2 h) were not altered by methysergide in NaCl loaded rats with misplaced LPBN injections (n=15). The ingestion of hypertonic NaCl by rats with serotonergic blockade in the LPBN suggests that the circuits subserving sodium appetite are activated, but at the same time strongly inhibited through the LPBN, during cell dehydration. (C) 2003 IBRO. Published by Elsevier Ltd. All rights reserved.

Lateral hypothalamus lesions influences water and salt intake, and sodium and urine excretion, and arterial blood pressure induced by L-NAME and FK 409 injections into median preoptic nucleus in conscious rats

Male Holtzman rats weighting 200-250 g were anesthetized with zoletil 50 mg/Kg (tiletamine chloridrate 125,0 mg and zolazepan chloridrate 125,0 mg) into quadriceps muscle and submitted an electrolytic lesion of the lateral hypothalamus (LH) and a stainless steel cannula was implanted into their median preoptic nucleus (MnPO). We investigated the effects of the injection into the (MnPO) of FK 409 (20 mug/0.5 mul), a nitric oxide (NO) donor, and N-W-nitro-L-arginine methyl ester (L-NAME) 40 mug/0.5 mul, a nitric oxide synthase inhibitor (NOSI), on the water and sodium appetite and the natriuretic, diuretic and cardiovascular effects induced by injection of L-NAME and FK 409 injected into MnPO in rats with LH lesions. Controls were injected with a similar volume of 0.15 M NaCl. L-NAME injected into MnPO produced an increase in water and sodium intake and in sodium and urine excretion and increase de mean arterial pressure (MAP). FK 409 injected into MnPO did not produce any change in the hydro electrolytic and cardiovascular parameters in LH-sham and lesioned rats. FK 409 injected before L-NAME attenuated its effects. These data show that electrolytic lesion of the LH reduces fluid and sodium intake as well as sodium and urine excretion, and the pressor effect induced by L-NAME. LH involvement with NO of the MnPO excitatory and inhibitory mechanisms related to water and sodium intake, sodium excretion and cardiovascular control is suggested. (C) 2004 Elsevier B.V. All rights reserved.

Role of the alpha(1)- and alpha(2)-adrenoceptors of the paraventricular nucleus on the water and salt intake, renal excretion, and arterial pressure induced by angiotensin II injection into the medial septal area

In this study we investigated the influence of cu-adrenergic antagonists injections into the paraventricular nucleus (PVN) of the hypothalamus on the thirst and salt appetite, diuresis, natriuresis, and presser effects of angiotensin II (ANG II) stimulation of medial septal area (MSA). ANG II injection into the MSA induced water and sodium intake, diuresis, natriuresis, and presser responses. The previous injection of prazosin (an alpha (1)-adrenergic antagonist) into the PVN abolished, whereas previous administration of yohimbine (an alpha (2)-adrenergic antagonist) into the PVN increased the water and sodium intake, urinary, natriuretic, and presser responses induced by ANG ii injected into the MSA. Previous injection of a nonselective alpha -adrenergic antagonist, regitin, into the PVN blocked the urinary excretion, and reduced the water and sodium intake, sodium intake, and presser responses induced by ANG II injected into the MSA. The present results suggest that alpha -adrenergic pathways involving the PVN are important for the water and sodium excretion, urine and sodium excretion, and presser responses, induced by angiotensinergic activation of the MSA. (C) 2001 Elsevier B.V.

Water deprivation and the double- depletion hypothesis: common neural mechanisms underlie thirst and salt appetite

Water deprivation-induced thirst is explained by the double-depletion hypothesis, which predicts that dehydration of the two major body fluid compartments, the extracellular and intracellular compartments, activates signals that combine centrally to induce water intake. However, sodium appetite is also elicited by water deprivation. In this brief review, we stress the importance of the water-depletion and partial extracellular fluid-repletion protocol which permits the distinction between sodium appetite and thirst. Consistent enhancement or a de novo production of sodium intake induced by deactivation of inhibitory nuclei (e.g., lateral parabrachial nucleus) or hormones (oxytocin, atrial natriuretic peptide), in water-deprived, extracellular-dehydrated or, contrary to tradition, intracellular-dehydrated rats, suggests that sodium appetite and thirst share more mechanisms than previously thought. Water deprivation has physiological and health effects in humans that might be related to the salt craving shown by our species.

Higher salt preference in heart failure patients

Heart failure (HF) is a complex syndrome that involves changes in behavioral, neural and endocrine regulatory systems. Dietary salt restriction along with pharmacotherapy is considered an essential component in the effective management of symptomatic HF patients. However, it is well recognized that HF patients typically have great difficulty in restricting sodium intake. We hypothesized that under HF altered activity in systems that normally function to regulate body fluid and cardiovascular homeostasis could produce an increased preference for the taste of salt. Therefore, this study was conducted to evaluate the perceived palatability (defined as salt preference) of food with different concentrations of added salt in compensated chronically medicated HF patients and comparable control subjects. Healthy volunteers (n = 25) and medicated, clinically stable HF patients (n = 38, NYHA functional class II or III) were interviewed and given an evaluation to assess their preferences for different amounts of saltiness. Three salt concentrations (0.58, 0.82, and 1.16 g/100 g) of bean soup were presented to the subjects. Salt preference for each concentration was quantified using an adjective scale (unpleasant, fair or delicious). Healthy volunteers preferred the soup with medium salt concentration (p = 0.042), HF patients disliked the low concentration (p < 0.001) and preferred the high concentration of salted bean soup (p < 0.001). When compared to healthy volunteers, HF patients demonstrated a significantly greater preference for the soup with a high salt concentration (p = 0.038). It is concluded that medicated, compensated patients under chronic treatment for HF have an increased preference for salt. (C) 2011 Elsevier Ltd. All rights reserved,

Right atrial stretch alters fore- and hind-brain expression of c-fos and inhibits the rapid onset of salt appetite

The inflation of an intravascular balloon positioned at the superior vena cava and right atrial junction (SVC-RAJ) reduces sodium or water intake induced by various experimental procedures (e.g. sodium depletion; hypovolaemia). In the present study we investigated if the stretch induced by a balloon at this site inhibits a rapid onset salt appetite, and if this procedure modifies the pattern of immunohistochemical labelling for Fos protein (Fos-ir) in the brain. Male Sprague-Dawley rats with SVC-RAJ balloons received a combined treatment of furosemide (Furo; 10 mg (kg bw)(-1)) plus a low dose of the angiotensin-converting enzyme inhibitor captopril (Cap; 5 mg (kg bw)(-1)). Balloon inflation greatly decreased the intake of 0.3 M NaCl for as long as the balloon was inflated. Balloon inflation over a 3 h period following Furo-Cap treatment decreased Fos-ir in the organum vasculosum of the lamina terminalis and the subfornical organ and increased Fos-ir in the lateral parabrachial nucleus and caudal ventrolateral medulla. The effect of balloon inflation was specific for sodium intake because it did not affect the drinking of diluted sweetened condensed milk. Balloon inflation and deflation also did not acutely change mean arterial pressure. These results suggest that activity in forebrain circumventricular organs and in hindbrain putative body fluid/cardiovascular regulatory regions is affected by loading low pressure mechanoreceptors at the SVC-RAJ, a manipulation that also attenuates salt appetite.

Macrophage Migration Inhibitory Factor in the Paraventricular Nucleus Plays a Major Role in the Sympathoexcitatory Response to Salt

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

An Arabidopsis Mitochondrial Uncoupling Protein Confers Tolerance to Drought and Salt Stress in Transgenic Tobacco Plants

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of lithium additive on the microstructure and electrical responses of 0.9PMN-0.1PT ceramics

Structural effects of lithium additive on 0.9PMN-0.1PT powders prepared by Ti-modified columbite route were studied. The substitution of Li+ ions for Mg2+ ions in the B-site sub-lattice of 0.9PMN-0.1PT perovskite structure was explained in terms of lead and oxygen vacancies generation originated as consequence of the ionic compensation of negatively charged Li'(Mg) sites. The rise in mass transport as consequence of the increasing of Pb2+ and O2- vacancies produces more agglomerated particles during the powder synthesis and changes the mechanical characteristics between grain and grain boundary of sintered ceramic. The relation between K-m and T-m values, the difference between ionic radii of B cation and the molar volume were used to explain the changes in the relaxor behavior and diffusiveness of phase transition as function of lithium doping, which are corroborated by the results obtained through the ferroelectric characterization.

Influence of light intensity and salt-treatment on mode of photosynthesis and enzymes of the antioxidative response system of Mesembryanthemum crystallinum

The metabolic switch From C-3-photosynthesis to crassulacean acid metabolism (CAM),and the antioxidative response of Mesembryanthemum crystallinum L. plants cultured under severe salt stress and high light intensities, and a combination of booth stress conditions, were studied. High light conditions led to a more rapid CAM induction than salinity. The induction time was still shortened when both stress factors were combined. A main pattern observed in CAM plants was a decrease in mitochondrial Mn-superoxide dismutase (SOD) activity during the day. The activities of the chloroplastic Fe-SOD and cytosolic CuZn-SOD were increased due to salt treatment after a lag phase, while catalase activity was decreased. Combination of salt and light stress did not lead to a higher SOD activity as found after application of one stress factor alone, indicating that there is a threshold level of the oxidative stress response. The fact that salt-stressed plants grown under high light conditions showed permanent photoinhibition and lost the ability for nocturnal malate storage after 9 d of treatment indicate serious malfunction of metabolism, leading to accelerated senescence. Comparison of CuZn-SOD activity with CuZn-SOD protein amount, which was determined immunologically, indicates that the activity of the enzyme is at least partially post-translationally regulated.

Osmotic dehydration of apples in sugar/salt solutions: Concentration profiles and effective diffusion coefficients

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Plasmid DNA partitioning and separation using poly(ethylene glycol)/poly(acrylate)/salt aqueous two-phase systems

Phase diagrams of poly(ethylene glycol)/polyacrylate/Na2SO4 systems have been investigated with respect to polymer size and pH. Plasmid DNA from Escherichia coil can depending on pH and polymer molecular weight be directed to a poly(ethylene glycol) or to a polyacrylate-rich phase in an aqueous two-phase system formed by these polymers. Bovine serum albumin (BSA) and E. coil homogenate proteins can be directed opposite to the plasmid partitioning in these systems. Two bioseparation processes have been developed where in the final step the pDNA is partitioned to a salt-rich phase giving a total process yield of 60-70%. In one of them the pDNA is partitioned between the polyacrylate and PEG-phases in order to remove proteins. In a more simplified process the plasmid is partitioned to a PEG-phase and back-extracted into a Na2SO4-rich phase. The novel polyacrylate/PEG system allows a strong change of the partitioning between the phases with relatively small changes in composition or pH. (C) 2012 Elsevier B.V. All rights reserved.