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At least 19 recordsLinked to original sources
PubMed2006

AT(1) and glutamatergic receptors in paraventricular nucleus support blood pressure during water deprivation.

Water deprivation activates sympathoexcitatory neurons in the paraventricular nucleus (PVN); however, the neurotransmitters that mediate this activation are unknown. To test the hypothesis that ANG II and glutamate are involved, effects on blood pressure (BP) of bilateral PVN microinjections of ANG II type 1 receptor (AT1R) antagonists, candesartan and valsartan, or the ionotropic glutamate receptor antagonist, kynurenate, were determined in urethane-anesthetized water-deprived and water-replete male rats. Because PVN may activate sympathetic neurons via the rostral ventrolateral medulla (RVLM) and because PVN disinhibition increases sympathetic activity in part via increased drive of AT1R in the RVLM, candesartan was also bilaterally microinjected into the RVLM. Total blockade of the PVN with bilateral microinjections of muscimol, a GABA(A) agonist, decreased BP more (P < 0.05) in water-deprived (-29 +/- 8 mmHg) than in water-replete (-7 +/- 2 mmHg) rats, verifying that the PVN is required for BP maintenance during water deprivation. PVN candesartan slowly lowered BP by 7 +/- 1 mmHg (P < 0.05). In water-replete rats, however, candesartan did not alter BP (1 +/- 1 mmHg). Valsartan also produced a slowly developing decrease in arterial pressure (-6 +/- 1 mmHg; P < 0.05) in water-deprived but not in water-replete (-1 +/- 1 mmHg) rats. In water-deprived rats, PVN kynurenate rapidly decreased BP (-19 +/- 3 mmHg), and the response was greater (P < 0.05) than in water-replete rats (-4 +/- 1 mmHg). Finally, as in PVN, candesartan in RVLM slowly decreased BP in water-deprived (-8 +/- 1 mmHg; P < 0.05) but not in water-replete (-3 +/- 1 mmHg) rats. These data suggest that activation of AT(1) and glutamate receptors in PVN, as well as of AT1R in RVLM, contributes to BP maintenance during water deprivation.

Angiotensin II Type 1 Receptor Blockers↗
PubMed1999

Expression of Fos immunoreactivity in rat brain during dehydration: effect of duration and timing of water deprivation.

Water deprivation induces expression of the immediate early gene c-fos in specific brain regions, most likely as a result of the activation of cells that are responsive to changes in osmolality and/or blood volume. We hypothesized that the magnitude of c-fos expression would be a function of both the duration of water deprivation and the time of day at which the deprivation started. This study was designed to examine the pattern of Fos-like immunoreactivity (FLI) following water deprivation in rats under normal light/dark conditions (nLD) and reverse light/dark conditions (rLD). Rats were deprived of water but not food either for 0, 5, 16, 24 or 48 h. As expected, hematocrit ratio (HCT), osmolality (OSM), plasma renin activity (PRA) and weight loss increased as a function of duration of water deprivation. In non-deprived rats (0 h), very little FLI was observed in most brain regions. The number of cells showing FLI increased with duration of water deprivation in the supraoptic nucleus (SON), paraventricular nucleus (PVN), organum vasculosum laminae terminalis (OVLT), median preoptic nucleus (MnPO) and subfornical organ (SFO) in both nLD and rLD conditions. However, the pattern of FLI differed between nLD and rLD conditions. Compared to corresponding nLD groups after 5 or 24-h water deprivation, rLD groups had significantly more FLI in SON and PVN, and higher PRA and HCT. Also, weight loss and FLI in the MnPO were greater after 5 h, and FLI in the SFO was greater after 24 h under rLD compared to nLD conditions. Our findings indicate that the magnitude of c-fos expression, and change in weight and plasma parameters were a function of both the duration of water deprivation and the time of day at which the deprivation started. This may result from ingestion of food early in the deprivation periods during the rLD tests, thus producing greater change in osmolality and blood volume.

Animals↗
PubMed1990

[The characteristics of the reactions of the neurosecretory cells in the supraoptic nucleus of the rat hypothalamus to stimulation of the subiculum under conditions of water deprivation].

Water deprivation has been studied for its effect on the character of reactions evoked by subiculum stimulation in the antidromically identified hypothalamic supraoptic neuro-secretory cells of lactating rats. In dehydrated animals as compared with rats under normal conditions the number of neurons which responded to subiculum stimulation by inhibitory reactions, revealed by the blockade of the antidromic action potential, was not modified, but the proportion of different types of inhibitory responses changed: water deprivation caused a significant increase (P less than 0.05) in the number of cells with gradually developed inhibitory reactions and a decrease in the number of cells with transitory inhibition. In addition, the number of inhibitory reactions, revealed in the depression of background activity, has grown. Therefore, one of characteristics of the afferent input from the subiculum to supraoptic neurosecretory cells is its plasticity, in particular, its ability for reorganization under water deprivation.

Animals↗
PubMed1984

Gestation-dependent aspects of the response of the ovine fetus to the osmotic stress induced by maternal water deprivation.

Water deprivation was produced in pregnant sheep by withholding water for 24 h and then giving them 500 ml/d for the subsequent 3 d. All ewes bore chronically cannulated fetuses. Eleven experiments were performed in group I animals (gestation periods of 107-119 d at maximal stress) and eight experiments in group II (126-144 d of gestation). Measurements were made of maternal and fetal plasma osmolalities, fetal urine flow rate and osmolality, amniotic fluid osmolality and fetal plasma antidiuretic hormone (ADH) concentration. The experimental protocol produced a larger increment in maternal and fetal plasma osmolalities in group I than in group II (P less than 0.025). For group I fetuses the relationship between plasma ADH concentration, [ADH] and plasma osmolality was log [ADH] = -4.50 + 0.0174 (osmol) which was significantly different from that for group II fetuses, log [ADH] = -10.46 + 0.0373 (osmol) (P less than 0.02). Thus plasma [ADH] was significantly greater, at a given plasma osmolality, in older (group II) than younger (group I) fetuses. For a given value of fetal plasma [ADH] there was a greater reduction in fetal urine free water clearance in older than younger fetuses. Water deprivation of the ewe did disturb the composition of amniotic fluid and the trend in amniotic fluid osmolality followed the trend in fetal urinary osmolality.

Amniotic Fluid↗
PubMed1981

The effects of water deprivation and water loading during treatment with 1-deamino-8-D-arginine vasopressin in central diabetes insipidus in childhood.

Nine children aged 7 2/12 to 17 9/12 years with central diabetes insipidus were subjected to water deprivation and water loading during treatment with 1-deamino-8-D-arginine vasopressin (DDVAP). Urine output remained unchanged despite the large differences in water intake. Serum osmolarity was not significantly affected by water deprivation. However, there was a marked decrease in serum osmolarity during water loading. This not accompanied by any symptoms of haemodilution. Thus patients apparently tolerate large variations in fluid intake during therapy with DDVAP.

Adolescent↗
PubMed1981

Influence of water deprivation on water consumption, growth, and carcass characteristics of ducks.

Two-week-old White Pekin ducks were granted access to water either 4, 6, 8, 16, or 24 hr per day for a period of 4 weeks. The effects of water deprivation on water consumption, growth parameters, and carcass traits were determined. Compared to all other treatments, ducks allowed access to water for 4 hr per day had significantly lower (P less than .05) water intake, body weight, and feed consumption. Increasing water access time to either 6, 8, or 16 hr per day significantly increased (P less than .05) water consumption. Further significant increases in water consumption were not found when ducks were granted access to water for 24 hr per day. Prediction equations are presented for estimating daily intake of water for each treatment. There were no significant differences in final body weight or total feed consumption among ducks on the 6, 8, and 16 hr treatments. Overall feed conversion did not differ significantly among the treatments. No distinct relationship between length of water deprivation and yield of breast meat were observed. The advantages and disadvantages of limiting commercial ducks access to water for 8 hr per day in order to reduce water consumption are discussed.

Animals↗
PubMed2000

Heroin-induced suppression of saccharin intake in water-deprived and water-replete rats.

Rats suppress intake of a saccharin conditioned stimulus (CS) when paired with an aversive unconditioned stimulus such as lithium chloride. This phenomenon is referred to as a conditioned taste aversion (CTA). Rats also suppress intake of a saccharin CS when paired with a rewarding sucrose solution and when paired with a drug of abuse. Although the suppressive effects of drugs of abuse have long been interpreted as CTAs, evidence suggests that rats may suppress intake of the saccharin CS following taste-drug pairings because they are anticipating the rewarding rather than the aversive properties of the drug. Oddly, however, while all other drugs of abuse tested suppress intake of a gustatory CS, the highly reinforcing drug, heroin, is reportedly ineffective. The present study reexamined this issue in both water-deprived and water-replete rats using procedures that sustain both morphine- and cocaine-induced suppression of CS intake. The results showed that heroin greatly reduced CS intake following saccharin-heroin pairings and that this effect was less variable when assessed in water-replete subjects. When taken with other reports, these data suggest that rats suppress intake of a saccharin CS in anticipation of the availability of all drugs of abuse tested.

Analysis of Variance↗
PubMed1983

Renal papillary necrosis in horses after phenylbutazone and water deprivation.

Acute renal papillary necrosis occurred in five horses given normal therapeutic doses of phenylbutazone and deprived of water for 36 to 48 hours prior to euthanasia. Five horses given phenylbutazone alone and four horses subjected to water deprivation alone did not develop papillary necrosis. Urinalyses were normal prior to water deprivation, and also after water deprivation in the horses that did not receive phenylbutazone, but the water-deprived, phenylbutazone-treated horses had many red blood cells, transitional epithelial cells, and large numbers of oxalate crystals in their urine. Ulceration of the alimentary tract was seen in more than 50% of these horses. Tongue ulceration was present in one of five horses given phenylbutazone and one of five horses which had phenylbutazone and water deprivation. Ulceration of the gastric mucosa was seen in two of the five phenylbutazone-treated horses, four of five horses with phenylbutazone treatment and water deprivation, and one of four horses with water deprivation alone. Severe colonic ulceration with perforation and peritonitis was present in one horse given phenylbutazone for three months. No other significant changes in the small or large intestine were seen in the other 13 horses.

Animals↗
PubMed2004

Excitatory amino acids in rostral ventrolateral medulla support blood pressure during water deprivation in rats.

Water deprivation is associated with regional increases in sympathetic tone, but whether this is mediated by changes in brain stem regulation of sympathetic activity is unknown. Therefore, this study tested the hypothesis that water deprivation increases excitatory amino acid (EAA) drive of the rostral ventrolateral medulla (RVLM), by determining whether bilateral microinjection of kynurenate (Kyn; 2.7 nmol) into the RVLM decreases arterial pressure more in water-deprived than water-replete rats. Plasma osmolality was increased in 48-h water-deprived rats (313 +/- 1 mosmol/kgH2O; P < 0.05) compared with 24-h water-deprived rats (306 +/- 2 mosmol/kgH2O) and water-replete animals (300 +/- 2 mosmol/kgH2O). Kyn decreased arterial pressure by 28.1 +/- 5.2 mmHg (P < 0.01) in 48-h water-deprived rats but had no effect in water-replete rats (-5.9 +/- 1.3 mmHg). Variable depressor effects were observed in 24-h water-deprived animals (-12.5 +/- 2.4 mmHg, not significant); however, in all rats the Kyn depressor response was strongly correlated to the osmolality level (P < 0.01; r2 = 0.47). The pressor responses to unilateral microinjection of increasing doses (0.1, 0.5, 1.0, and 5.0 nmol) of glutamate were enhanced (P < 0.05) during water deprivation, but the pressor responses to intravenous phenylephrine injection were smaller (P < 0.05). These data suggest that water deprivation increases EAA drive to the RVLM, in part by increasing responsiveness of the RVLM to EAA such as glutamate.

Animals↗
PubMedDate not supplied

Regulation of fluid intake in dogs following water deprivation.

Whereas water loss in land living animals occurs continuously, water intake takes place discontinuously. At the normal operating set point of plasma osmolality, urine is more concentrated than plasma due to secretion of vasopressin. Thus animals operate around a state of mild dehydration. As water loss occurs, the severity of dehydration and thirst increase in intensity and at some point water intake occurs. Sufficient water is consumed to return plasma osmolality to the normal operating set point. Food intake and water balance are interdependent as food provides the osmoles which determine obligatory renal solute excretion. When dry food with the same osmotic content was substituted for canned food (water content 74%), dogs increased water intake from 24.2 +/- 4.3 to 62.2 +/- 8.8 ml/kg. Urine output and urine osmolality were unchanged, as under conditions of normal hydration, near maximal urine concentration is achieved. Changing water intake is the only available variable to maintain water balance. During water deprivation, the major renal mechanism appears to be natriuresis. In rehydration, satiety mechanisms ensure appropriate water intake and renal sodium conservation restores sodium balance.

Animals↗
PubMed1991

Comparative quantitative ultrastructural studies of the choroidal epithelium of hydrocephalic (hpy/hpy) and normal mice, and the effect of stress induced by water deprivation.

Animals homozygous for the recessive, pleiotropic, mutation hpy(hydrocephalic-polydactyl) develop hydrocephalus early in the postnatal period. The condition develops in the apparent absence of any overt indications of obstruction in the cerebrospinal fluid (CSF) drainage system suggesting a continued, inappropriate, secretion of CSF. Electron microscope investigations were undertaken to both characterize and quantify the cell types present in the choroidal epithelium of mutants and their wild-type littermates and to gauge their response to a prolonged (24 h) deprivation of water, which has severe adverse effects on the general body fluid balance. Collectively, the findings indicate that the cellular makeup of the choroidal epithelium of normal animals and the manner of its response to changing fluid conditions is more complex than formerly anticipated. Also that inferences derived from a simple extrapolation of findings from other fluid-transporting epithelia to choroidal cells are misleading and erroneous. In wild-type animals allowed free access to water light cells with clavate microvilli (secretory cells) predominated whereas, following water deprivation there was a preponderance of dark cells with filiform microvilli, abundant mitochondria, multivesicular bodies and osmiophilic droplets (resorptive cells). In hydrocephalic mutants, the makeup of the choroidal epithelium of non-water-deprived animals resembled that of water-deprived wild-type mice and showed little change following water deprivation. These findings suggest that while the choroidal cells of mutants are capable of mounting a response to conditions having adverse effects on water balance (i.e., hydrocephalus) their response falls short of the level needed to fully redress the imbalance and is not materially increased by imposition of further, stringent, conditions (e.g., water deprivation). Thus, the findings lend support to the view that the mutational event affects the regulation of solute transport rather than effecting abrogation of the membrane pump itself.

Animals↗
PubMedDate not supplied

Renal pathology in chicks following water deprivation.

Total water deprivation of 2-day-old broiler chicks for 24, 48, 72, 96, and 120 hours did not result in visceral urate deposits. Renal tubular changes consisted of increased spaces between membrane infoldings of the distal convoluted tubular epithelium, increased number of cytoplasmic vacuoles in proximal convoluted tubules, and increased mucin production and dilation of collecting ducts.

Animals↗
PubMed1987

[Effect of prolonged water deprivation on weight gain and water metabolism in a gerbillid rodent (Meriones shawi shawi)].

The effect of prolonged water deprivation, applied progressively since weaning, was studied on body weight in growing sub-desert rodents (Meriones shawi). Then, water metabolism, food consumption and kidney weight were measured in these adults animals. During partial water deprivation the weight curve was similar to that of controls, whereas with total water deprivation three different stages were noticed: a decrease, a stabilization and an increase in body weight as a function of age. At the end of the experiment, the body water volume was similar in dehydrated and in control animals. However, in water deprived animals, there was a lower rate of water influx and efflux compared to controls. Their food consumption was two-fold that of controls. Dehydrated meriones showed a significant increase in kidney weight as compared to controls.

Animals↗