Reduced Water Intake Research Articles

Evaluation of Tillage Practices for Maize (Zea mays) Grown on Different Land-Use Systems in Eastern Zambia

<p>Improved fallows of <em>Sesbania sesban</em> (Sesbania) have been known to improve soil physical and chemical properties and increase crop yield compared to traditional fallows. However, the effects of soil tillage practices after improved fallows on soil properties, weeds, labour and subsequent maize crop have not been assessed in Southern Africa. This study aimed to evaluate how tillage practices affect yield of maize and affect soil properties after two years of fallow and subsequent cropping phase. In this study, done at sites in eastern Zambia, maize yield from a two-year planted Sesbania, natural fallow, continuously fertilized and unfertilized maize were compared under conventional, flat till and zero tillage practices. A split plot experiment, with improved fallow systems in the main plot and the tillage practice in the subplot, was established at the sites. The results showed that the increases in grain yield under conventional tillage over zero tillage practice were 17.8% and 28.2% during 2000/2001 and 2001/2002 seasons, respectively, at Msekera. At Chadiza, the increases in grain yield under conventional tillage over zero tillage were 66.3% and 327.4% during 2000/2001 and 2001/2002 seasons, respectively. Greater maize yields were achieved under Sesbania planted fallows compared to the natural fallow and maize monoculture without fertilizer. Overall, zero tillage practice resulted in lower maize grain yield, higher bulk density, reduced water intake, higher weed infestation and high labour demand during weeding compared to conventional tillage.</p>

Catecholaminergic neurons in the comissural region of the nucleus of the solitary tract modulate hyperosmolality-induced responses.

Noradrenergic A2 neurons of the nucleus of the solitary tract (NTS) have been suggested to contribute to body fluid homeostasis and cardiovascular regulation. In the present study, we investigated the effects of lesions of A2 neurons of the commissural NTS (cNTS) on the c-Fos expression in neurons of the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei, arterial pressure, water intake, and urinary excretion in rats with plasma hyperosmolality produced by intragastric 2 M NaCl (2 ml/rat). Male Holtzman rats (280-320 g) received an injection of anti-dopamine-β-hydroxylase-saporin (12.6 ng/60 nl; cNTS/A2-lesion, n = 28) or immunoglobulin G (IgG)-saporin (12.6 ng/60 nl; sham, n = 24) into the cNTS. The cNTS/A2 lesions increased the number of neurons expressing c-Fos in the magnocellular PVN in rats treated with hypertonic NaCl (90 ± 13, vs. sham: 47 ± 20; n = 4), without changing the number of neurons expressing c-Fos in the parvocellular PVN or in the SON. Contrary to sham rats, intragastric 2 M NaCl also increased arterial pressure in cNTS/A2-lesioned rats (16 ± 3, vs. sham: 2 ± 2 mmHg 60 min after the intragastric load; n = 9), an effect blocked by the pretreatment with the vasopressin antagonist Manning compound (0 ± 3 mmHg; n = 10). In addition, cNTS/A2 lesions enhanced hyperosmolality-induced water intake (10.5 ± 1.4, vs. sham: 7.7 ± 0.8 ml/60 min; n = 8-10), without changing renal responses to hyperosmolality. The results suggest that inhibitory mechanisms dependent on cNTS/A2 neurons reduce water intake and vasopressin-dependent pressor response to an acute increase in plasma osmolality.

The antidepressant drugs fluoxetine and duloxetine produce anxiolytic-like effects in a schedule-induced polydipsia paradigm in rats

Similar to the time-course for treating depression, several weeks of administration are required for serotonin (5-HT) reuptake inhibitors to produce anxiolytic effects. Previous studies with the schedule-induced polydipsia paradigm (a putative preclinical anxiety model) have shown that repeated administration of antidepressant drugs is necessary to produce a suppression of polydipsia, which is interpreted as an anxiolytic-like effect. The present study sought to expand past findings by evaluating the selective 5-HT reuptake inhibitor (SSRI) fluoxetine and the 5-HT-norepinephrine reuptake inhibitor duloxetine in the schedule-induced polydipsia paradigm with rats. Dose combinations of the α2 adrenoceptor antagonist yohimbine with fluoxetine were also explored to determine whether α2 adrenoceptor antagonism could enhance the anxiolytic-like effects produced by an SSRI. Fluoxetine and duloxetine significantly reduced water intake over the course of daily administrations. Daily treatment with the combination of fluoxetine and yohimbine produced a significantly greater reduction in water intake than fluoxetine alone. The present results confirmed previous findings that inhibition of 5-HT reuptake reduces water consumption in this paradigm. The results for the α2 antagonist yohimbine (in combination with fluoxetine) also indicate that α2 adrenoceptor antagonism may significantly enhance anxiolytic-like effects of SSRIs.

Thirst and sodium appetite in rats with experimental nephrotic syndrome

Nephrotic syndrome is a renal disease accompanied by abnormal body fluid balance. The present experiments investigated the role of behavioral mechanisms in contributing to disordered fluid homeostasis in rats with experimentally-induced nephrotic syndrome. The studies examined water and sodium ingestion under ad libitum conditions and in response to dehydration-related challenges in rats made nephrotic by treatment with the antibiotic, adriamycin. Rats with nephrotic syndrome had greater ad libitum water intakes beginning 3weeks after treatment, but daily sodium (0.3M NaCl) intakes were not affected. Nephrotic rats showed attenuated water and sodium intakes after combined treatment with furosemide (10mg/kg) and captopril (2mg/kg), reduced water intakes after 20h of water deprivation, and diminished water intakes, plasma renin activity and aldosterone secretion after subcutaneous isoproterenol (30μg/kg). However, the adriamycin-treated animals had normal water intakes in response to subcutaneous hypertonic saline (4% at 0.75ml/100g) and central injections of angiotensin II (10, 20, and 50ng). The results suggest that water and sodium ingestion in response to hypovolemic/hypotensive stimuli are disturbed in nephrotic rats, and provide evidence that the disordered behaviors reflect disturbances of the peripheral renin–angiotensin–aldosterone system.

Water uptake, chemical characterization, and tensile behavior of modified banana–plantain fiber and their polyester composites

Banana–plantain fibers (BPFs) were treated with acetic anhydride (AA), epichlorohydrin (EP), and an acetic anhydride–epichlorohydrin blend (AA_EP). Natural fiber–polyester composites (PCs) were fabricated using untreated and treated BPF by the hand lay‐up technique. Modified BPF Raman and Infrared spectroscopy (ATR‐FTIR) analysis revealed losses of lignin and hemicelluloses and new chemical bonds that confirmed the replacement of part of the raw fiber hydroxyl groups, which gave rise to a degree of hydrophobicity in the treated fibers. This change altered their water sorption isotherms, swelling behavior in water, impedance spectroscopy, and XRD analysis. Assays of water absorption and tensile resistance for untreated BPF (U) and modified BPF polyester composites demonstrated a remarkable reduction in water intake, whereas tensile strength was maintained (P < 0.05) for the modified BPF polyester composites. POLYM. COMPOS., 37:2960–2973, 2016. © 2015 Society of Plastics Engineers

Diagnostic and prognostic value of hematology and clinical chemistry in bovine peritonitis associated with advanced pregnancy

The present study was conducted on 16 advanced pregnant animals (10 buffaloes and 6 cows) suffering from peritonitis. Seven buffaloes and five cows served as the control. Clinical signs included anorexia, reduced water intake, fever, recurrent and persistent tympany, depression, congested or anaemic mucous membranes and dehydration, loss of defecation or reduced faecal output. Out of 16 cases, septic peritonitis was seen in nine cases and seven had non-septic peritonitis. In general, peritoneal fluid changes were increased volume, altered colour, increased total protein, albumin and lactate concentrations and presence of degenerated neutrophils, fibrin, bacteria and gut contents and based upon the predominance of cells and other constituents, the peritonitis was further classified into fibrinous, fibrinopurulent, frank suppurative and adhesive peritonitis. Fibrinous peritonitis was diagnosed in four, fibrinopurulent in five, frank suppurative peritonitis in two and adhesive peritonitis in five cases. Hematology revealed neutrophilic leukocytosis with reversal of lymphocyte to neutrophil ratio, left shift and toxic changes in neutrophils, in majority of animals. Clinical chemistry revealed increase in globulin, aspartate amino transferase (AST), gamma-glutamyl transferase (GGT), total bilirubin, lactate and creatine phosphokinase (CK) and decrease in albumin, indicating chronic hepatitis. The present investigation was done to determine the value of hematology and clinical chemistry in the diagnosis and prognosis of peritonitis in bovines associated with advanced pregnancy, besides the utility of peritoneal fluid analysis in classifying peritonitis.

Effects of hydrogen sulfide (H2S) on water intake and vasopressin and oxytocin secretion induced by fluid deprivation

During dehydration, responses of endocrine and autonomic control systems are triggered by central and peripheral osmoreceptors and peripheral baroreceptors to stimulate thirst and sodium appetite. Specifically, it is already clear that endocrine system acts by secreting vasopressin (AVP), oxytocin (OT) and angiotensin II (ANG II), and that gaseous molecules, such as nitric oxide (NO) and carbon monoxide (CO), play an important role in modulating the neurohypophyseal secretion as well as ANG II production and thirst. More recently, another gas—hydrogen sulfide (H2S)—has been studied as a neuronal modulator, which is involved in hypothalamic control of blood pressure, heart frequency and temperature. In this study, we aimed to investigate whether H2S and its interaction with NO system could participate in the modulatory responses of thirst and hormonal secretion induced by fluid deprivation. For this purpose, Wistar male rats were deprived of water for 12 and 24h, and the activity of sulfide-generating enzymes was measured. Surprisingly, 24-h water deprivation increased the activity of sulfide-generating enzymes in the medial basal hypothalamus (MBH). Furthermore, the icv injection of sodium sulfide (Na2S, 260nmol), a H2S donor, reduced water intake, increased AVP, OT and CORT plasma concentrations and decreased MBH nitrate/nitrite (NOX) content of 24-h water-deprived animals compared to controls. We thus suggest that H2S system has an important role in the modulation of hormonal and behavioral responses induced by 24-h fluid deprivation.

Activation of serotonin 5-HT2A receptors inhibits high compulsive drinking on schedule-induced polydipsia.

Schedule-induced polydipsia (SIP) is an established model for studying compulsive behaviour in rats. Serotoninergic drugs effectively reduce compulsive drinking on SIP, and high compulsive drinker rats selected by SIP have shown differences in serotoninergic brain activity. However, the specific serotoninergic receptors that modulate compulsive SIP remain unclear. We investigated the functional role of serotonin 5-hydroxytryptamine 2A or C (5-HT2A/C) receptors in compulsive SIP behaviour. Rats were selected for low (LD) versus high drinking (HD) behaviour on SIP. The effects of the systemic administration of the selective serotonin reuptake inhibitor citalopram, selective norepinephrine reuptake inhibitor atomoxetine, serotonin 5-HT2A/C receptor agonist DOI hydrochloride ((±)-2,5-dimethoxy-4-iodoamphetamine), serotonin 5-HT2C receptor antagonist SB242084, serotonin 5-HT2A receptor antagonist ketanserin and M100907 were assessed on SIP. Subsequently, the effects of DOI were tested after the pre-administration of SB242084, ketanserin and M100907 on SIP. Citalopram and DOI reduced compulsive drinking in HD compared with LD rats on SIP. In contrast, SB242084 increased compulsive drinking in HD compared with LD rats on SIP. Atomoxetine, ketanserin and M100907 had no effect on SIP. The reduction in water intake produced by DOI was blocked by ketanserin and M100907, but not by SB242084 administration, in HD rats. These findings highlight the contribution of serotoninergic 5-HT2A/C receptors compared with noradrenergic mechanisms on SIP and reveal the "therapeutic" activation of serotonin 5-HT2A in the inhibition of the compulsive drinking behaviour in HD rats. Thus, it may represent a potentially new marker of vulnerability and provides additional insight for potential treatments on compulsive behaviours in neuropsychiatric populations.

Different effects of Bifeprunox, Aripiprazole, and Haloperidol on body weight gain, food and water intake, and locomotor activity in rats

Following on the success of Aripiprazole with its high clinical efficacy and minimal side effects, further antipsychotic drugs (such as Bifeprunox) have been developed based on the same dopamine D2 partial agonist pharmacological profile as Aripiprazole. However clinical trials of Bifeprunox have found differing results to that of its predecessor, without the same significant clinical efficacy. This study has therefore investigated the different effects of 10week treatment with Aripiprazole (0.75mg/kg, 3 times per day), Bifeprunox (0.8mg/kg, 3 times per day) and Haloperidol (0.1mg/kg, 3 times per day) on body weight gain, food and water intake, white fat mass, and 8week treatment on locomotor activity. Treatment with Bifeprunox was found to significantly reduce all of the measured parameters except white fat mass compared to the control group. However, Aripiprazole and Haloperidol treatment reduced water intake compared to the control, without any significant effects on the other measured parameters. These findings further demonstrate the potential pharmacological differences between Aripiprazole and Bifeprunox, and identify potential weight loss side effects and increased anxiety behaviour with Bifeprunox treatment.

Abstract 356: Serum Amyloid A Augments Aortic Aneurysm Formation Induced by Mineralocorticoid Receptor Agonists in the Presence of High Salt

Objectives: The annual mortality in the United States from ruptured aortic aneurysms is ~15000. Therapeutic interventions that prevent AAA progression and rupture remain to be identified. In humans, plasma concentrations of the acute phase reactant serum amyloid A (SAA) correlates with aortic dimensions before aneurysm formation. We have shown that endogenous SAA augments AAA in the well-established angiotensin II (AngII) infusion mouse model (unpublished data). Here we investigated whether endogenous SAA impacts aneurysm formation induced by deoxycorticosterone acetate (DOCA), a mineralocorticoid receptor agonist, in the presence of high salt. Approach and results: DOCA pellets (50mg, 21 day release) were implanted subcutaneously in the lateral dorsal region of 8-month old male C57BL/6 (SAAWT) mice and C57BL/6 mice lacking both acute phase SAA isoforms, SAA1.1 and SAA2.1 (SAAKO). The mice were also provided drinking water containing 0.9% NaCl and 0.2% KCl for 21 days (n = 7-8). As expected, DOCA + salt resulted in significantly increased systolic blood pressure, which was not affected by the absence of SAA. Unexpectedly SAAKO mice displayed a reduced urine output, accompanied by a reduced water intake. Plasma sodium and potassium concentrations in SAAWT and SAAKO mice were similar after treatment. The maximal luminal diameter of the abdominal aorta, as determined by ultrasound, was significantly lower in SAAKO mice compared to SAAWT mice after a 3-week DOCA + salt regime. Aneurysm incidence, determined by ultrasound and ex vivo analyses, was 67% for SAAWT mice and 25 % for SAAKO mice. Notably, plasma SAA was markedly increased in the SAAWT mice that formed aneurysms compared to those that did not. In SAAWT mice, immunohistochemical staining and in situ zymography identified SAA in aneurysmal aortic tissue, but not control aortas, that co-localized to regions of enhanced matrix metalloproteinase (MMP) activity, suggesting a role for SAA in MMP activation. Conclusions: We conclude that endogenous SAA augments aortic aneurysm formation induced by mineralocorticoid receptor agonists in the presence of high salt. Thus, SAA contributes to pathological processes leading to aortic aneurysm in two robust and mechanistically distinct animal models.

Utilization of Wood Modification for the Purpose of Moisture Volume Changes Reduction

Application of timber structures in civil engineering is completely traditional technology. On the other hand, the materials with better durability characteristics are preferred in present construction. Increased or fluctuating moisture of wood is a significant limiting factor of its life. Wood modification, which results in water intake reduction and also serves to maintain the low equilibrium moisture, may significantly improve the properties of wood, reduces the caused volumetric changes and extends its durability. Utilization of partial or total wood mineralization is just one of the material modification possibilities. This method seems to be promising due to so far gathered results, namely the anti swelling efficiency was greater than 65% for tested wooden species.

Anorexigenic effect of serotonin in an alternative vertebrate model (728.18)

Serotonin (5HT) is a central anorexia factor that inhibits food intake in mammals. Here, we used an avian model to study the effect of 5HT on appetite regulation, which may provide insight on the evolutionary aspects of food intake. Chicks treated with 24 nmol 5HT had reduced food intake up to 30 min following injection. Those that received 48 nmol 5HT had reduced food intake following injection throughout the 60 min observation time. The dose of 12 nmol was not effective. No chick treated with 5HT reduced water intake. We designed experiment 2 to determine if the anorexigenic effect of 5HT was primary by conducting a comprehensive behavior analysis. Those chicks treated with 5HT had increased deep rest, decreased feeding pecks, locomotion, steps, defecations, and chirps, but time spent sitting, standing, and preening were not affected. Exploratory pecks, jump, and drinks were also not affected. In sum, 5HT is associated with sedation, however, the effects on food intake are likely not due to malice because 5HT chicks did not reduce water intake and the number of drinks. These data support that 5HT function as a direct satiety factor in chicks.

Orexin-1 and orexin-2 receptor antagonists reduce ethanol self-administration in high-drinking rodent models

To examine the role of orexin-1 and orexin-2 receptor activity on ethanol self-administration, compounds that differentially target orexin (OX) receptor subtypes were assessed in various self-administration paradigms using high-drinking rodent models. Effects of the OX1 antagonist SB334867, the OX2 antagonist LSN2424100, and the mixed OX1/2 antagonist almorexant (ACT-078573) on home cage ethanol consumption were tested in ethanol-preferring (P) rats using a 2-bottle choice procedure. In separate experiments, effects of SB334867, LSN2424100, and almorexant on operant ethanol self-administration were assessed in P rats maintained on a progressive ratio operant schedule of reinforcement. In a third series of experiments, SB334867, LSN2424100, and almorexant were administered to ethanol-preferring C57BL/6J mice to examine effects of OX receptor blockade on ethanol intake in a binge-like drinking (drinking-in-the-dark) model. In P rats with chronic home cage free-choice ethanol access, SB334867 and almorexant significantly reduced ethanol intake, but almorexant also reduced water intake, suggesting non-specific effects on consummatory behavior. In the progressive ratio operant experiments, LSN2424100 and almorexant reduced breakpoints and ethanol consumption in P rats, whereas the almorexant inactive enantiomer and SB334867 did not significantly affect the motivation to consume ethanol. As expected, vehicle-injected mice exhibited binge-like drinking patterns in the drinking-in-the-dark model. All three OX antagonists reduced both ethanol intake and resulting blood ethanol concentrations relative to vehicle-injected controls, but SB334867 and LSN2424100 also reduced sucrose consumption in a different cohort of mice, suggesting non-specific effects. Collectively, these results contribute to a growing body of evidence indicating that OX1 and OX2 receptor activity influences ethanol self-administration, although the effects may not be selective for ethanol consumption.

Clinico Hemato Biochemical Findings, Clinical Management, and Production Performance of Bovines with Late Pregnancy Indigestion (Type IV Vagal Indigestion).

This prospective study was conducted on 15 animals (eight buffaloes and seven cows), diagnosed with late pregnancy indigestion. Ten buffaloes and 10 cows served as the control group. The animals were in advanced pregnancy and had partial or complete anorexia, reduced water intake, loss of defecation or scanty faecal output, and mild to moderate dehydration. Heart and respiration rates were increased and rumen motility was reduced. Five animals had persistent tympany and moderate distension of left abdomen, and two animals each had bilateral abdominal distension and papple shaped abdomen. Neutrophil and lymphocyte counts were significantly higher and lower than the control values. Total bilirubin, AST, total protein, globulin, BUN, glucose, and lactate were significantly higher, and chloride and calcium were significantly lower than the control values. Levels of ALP, GGT, albumin, creatinine, cholesterol, triglyceride, fibrinogen, fibrinogen ratio, sodium, potassium, phosphorus, and magnesium did not differ significantly from the control values. Rumen chloride concentration was higher than the reference range. Majority of animals were managed symptomatically until parturition. There was no effect on fetal survival or milk yield in current and subsequent lactation. So, late pregnancy indigestion causes clinical and hemato biochemical alterations which require special consideration when treating diseased animals.

Effects of Cagemate Gender and the Cagemate's access to ethanol on ethanol and water intake of the proximal male or the proximal female CD-1 mouse

The effects of social stimulation on ethanol drinking in humans may depend on the gender of the drinker, the gender of the social stimulus, and the availability of ethanol provided to the social stimulus. The present study employed the Proximal Cagemate Drinking (PCD) Procedures to evaluate the effects of the gender of the social stimulus Cagemate mouse and the effects of providing ethanol to the Cagemate mouse on the drinking of ethanol and water by the male or female CD-1 Drinker mouse. Twelve groups of subjects were arranged in a 3 × 2 × 2 factorial design with 3 levels of Cagemate Gender (Male vs. Female vs. None), 2 levels of Drinker Gender (Male vs. Female), and 2 levels of Cagemate Ethanol (Ethanol vs. No Ethanol). In the 8 groups assigned to social housing conditions, each Drinker mouse was housed with a Cagemate mouse on opposite sides of a clear plastic shoebox cage equipped with a clear plastic barrier that divided the cage lengthwise into 2 equal compartments. Six groups of Drinkers and 4 groups of Cagemates were provided with continuous access to 2 bottles (ethanol vs. water), while the 4 groups of Cagemates in the No Ethanol condition were provided with 2 bottles containing water. Results revealed that providing the Cagemate with ethanol elevated ethanol intake and ethanol preference but reduced water intake in Drinkers in Other-Gender Pairings (Male Drinker-Female Cagemate or Female Drinker-Male Cagemate) relative to Drinkers in Same-Gender Pairings (Male Drinker-Male Cagemate or Female Drinker-Female Cagemate). In contrast, when the Cagemate was not provided with access to ethanol, the opposite effects were observed. These novel PCD procedures reveal that the gender of the Cagemate and the Cagemate's access to ethanol influenced ethanol drinking in proximal-housed CD-1 Drinker mice.

The role of estradiol in adrenal insufficiency and its interaction with corticosterone on hydromineral balance

Estradiol (E2) plays an important role in controlling the homeostasis of body fluids. Several studies have reported the involvement of the hypothalamic pituitary adrenal axis (HPA) in the homeostatic control of hydromineral balance and the influence of estrogens on the modulation of this system. Nevertheless, until now, the physiological relevance of HPA axis activity on the hydromineral balance in females has not yet been fully elucidated. Therefore, the objective of the present study was to evaluate the effects of E2 (20μg/animal) pretreatment on neuroendocrine and hydroelectrolyte changes induced by adrenalectomy (ADX) with or without glucocorticoid hormone replacement (corticosterone, CORT; 10mg/kg) in ovariectomized rats (OVX). The results show that sodium appetite, natriuresis and the elevated plasma angiotensin II (ANG II) concentration induced by ADX were attenuated by E2 pretreatment. Additionally, a reduction of AT1 mRNA expression in the subfornical organ (SFO) and an increase in plasma atrial natriuretic peptide (ANP) concentrations by E2 pretreatment were observed. E2 pretreatment reversed the reduction in water intake induced by ADX in ADX CORT-replaced rats. Moreover, E2 pretreatment attenuated corticotropin releasing factor (CRF) mRNA expression in the paraventricular nucleus (PVN) induced by ADX. In contrast, E2 pretreatment increased CRF mRNA expression in the PVN in ADX CORT-replaced rats. Taken together, these results suggest that E2 has an important role in the modulation of behavioral and neuroendocrine responses involved in the maintenance of body fluid homeostasis in ADX rats with or without glucocorticoid replacement therapy.

The anteroventral third ventricle region is critical for the behavioral desensitization caused by repeated injections of angiotensin II

A single central injection of angiotensin II (AngII) potently increases water intake; however, a growing body of research suggests that repeated, acute intracerebroventricular injections of AngII cause a reduction in the dipsogenic response to subsequent AngII. This AngII-induced behavioral desensitization is specific to the effects of angiotensin and mediated by the angiotensin type-1 (AT1) receptor. The neuroanatomical substrate for this phenomenon, however, remains unknown. The anteroventral third ventricle (AV3V) region is an important site for the behavioral and physiological actions of AngII. Therefore, we hypothesized that this region also mediates the effects of repeated central AngII administration. In support of this hypothesis, we found that repeated injections of AngII into the AV3V reduced water intake stimulated by a test injection of AngII given into this region. Moreover, repeated AngII injections in the AV3V reduced water intake after AngII was injected into the lateral ventricle. These studies also demonstrate that activation of the AT1 receptor within the AV3V is required for AngII-induced behavioral desensitization because direct injection of the AT1 receptor antagonist, losartan, into the AV3V blocked the desensitizing effect of repeated AngII injections into the lateral ventricle. These findings provide additional support for a role of the AV3V in the dipsogenic actions of AngII, and suggest that this region is critical for the desensitization that occurs after acute repeated central injections of AngII.

Species distribution modelling using bioclimatic variables to determine the impacts of a changing climate on the western ringtail possum (Pseudocheirus occidentals; Pseudocheiridae)

SUMMARYThe ngwayir (western ringtail possumPseudocheirus occidentalis) is an arboreal species endemic to south-western Australia. The range and population of this species have been significantly reduced through multiple anthropogenic impacts. Classified as vulnerable, the ngwayir is highly susceptible to extremes of temperature and reduced water intake. Ngwayir distribution was determined using three different species distribution models using ngwayir presence records related to a set of 19 bioclimatic variables derived from historical climate data, overlaid with 2050 climate change scenarios. MaxEnt was used to identify core habitat and demonstrate how this habitat may be impacted. A supplementary modelling exercise was also conducted to ascertain potential impacts on the tree species that are core habitat for ngwayir. All models predicted a reduction of up to 60% in the range of the ngwayir and its habitat, as a result of global warming towards the south-west of the project area, with a mean potential distribution of 10.3% of the total modelled area of 561 059 km2. All three tree species modelled (jarrah, marri and peppermint) were predicted to experience similar contractions in range throughout most of the predicted ngwayir range, although their distributions differed. Populations of ngwayir persisting outside core habitat may indicate potential conservation opportunities.

Facilitation of sodium intake by combining noradrenaline into the lateral parabrachial nucleus with prazosin peripherally

Injections of noradrenaline into the lateral parabrachial nucleus (LPBN) increase arterial pressure and 1.8% NaCl intake and decrease water intake in rats treated with the diuretic furosemide (FURO) combined with a low dose of the angiotensin converting enzyme inhibitor captopril (CAP). In the present study, we investigated the influence of the pressor response elicited by noradrenaline injected into the LPBN on FURO+CAP-induced water and 1.8% NaCl intake. Male Holtzman rats with bilateral stainless steel guide-cannulas implanted into LPBN were used. Bilateral injections of noradrenaline (40nmol/0.2μl) into the LPBN increased FURO+CAP-induced 1.8% NaCl intake (12.2±3.5, vs., saline: 4.2±0.8ml/180min), reduced water intake and strongly increased arterial pressure (50±7, vs. saline: 1±1mmHg). The blockade of the α1 adrenoceptors with the prazosin injected intraperitoneally abolished the pressor response and increased 1.8% NaCl and water intake in rats treated with FURO+CAP combined with noradrenaline injected into the LPBN. The deactivation of baro and perhaps volume receptors due to the cardiovascular effects of prazosin is a mechanism that may facilitate water and NaCl intake in rats treated with FURO+CAP combined with noradrenaline injected into the LPBN. Therefore, the activation of α2 adrenoceptors with noradrenaline injected into the LPBN, at least in dose tested, may not completely remove the inhibitory signals produced by the activation of the cardiovascular receptors, particularly the signals that result from the extra activation of these receptors with the increase of arterial pressure.

Nesfatin-1 induces Fos expression and elicits dipsogenic responses in subfornical organ

Nesfatin-1 (Nes-1), an 82-amino acid protein cleaved from nucleobindin-2, has been suggested to play a role in ingestive behaviors. Intracerebroventricular (icv) injections of Nes-1 reduce water intake, although the sites of action for this effect are not known. Two series of experiments were done to identify potential sites of action of Nes-1 in drinking behavior. In the first series, icv injections of Nes-1 were made in urethane-anesthetized rats to investigate the distribution of neurons containing Fos-like immunoreactivity (Fos-ir) within the forebrain. Circumventricular organs, including subfornical organ (SFO), were found to contain neurons expressing Fos-ir. Additionally, several hypothalamic, thalamic and limbic nuclei also contained Fos-labeled neurons. As SFO is a pivotal central site in the regulation of water intake, a second series of experiments was done to investigate the role of direct injections of Nes-1 into SFO on water intake in conscious, freely moving rats. Nes-1 (2pmol) injections into SFO induced an increase in water intake compared to vehicle injections. However, when food was made available for ingestion after the Nes-1 injection, the dipsogenic effects of Nes-1 were attenuated. Additionally, the drinking response to Nes-1 was found to be more potent than that observed after injections of ANG II into SFO. Neither simultaneous injections ANG II nor the ANG II type-1 receptor blocker losartan affected the Nes-1 dipsogenic response. Taken together, these results suggest that Nes-1 is a potent dipsogenic agent in SFO, and that Nes-1 may act independently of the SFO angiotensinergic system to elicit the dipsogenic effect.