Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “THIRST”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMed1997

The neuroendocrinology of thirst and salt appetite: visceral sensory signals and mechanisms of central integration.

This review examines recent advances in the study of the behavioral responses to deficits of body water and body sodium that in humans are accompanied by the sensations of thirst and salt appetite. Thirst and salt appetite are satisfied by ingesting water and salty substances. These behavioral responses to losses of body fluids, together with reflex endocrine and neural responses, are critical for reestablishing homeostasis. Like their endocrine and neural counterparts, these behaviors are under the control of both excitatory and inhibitory influences arising from changes in osmolality, endocrine factors such as angiotensin and aldosterone, and neural signals from low and high pressure baroreceptors. The excitatory and inhibitory influences reaching the brain require the integrative capacity of a neural network which includes the structures of the lamina terminalis, the amygdala, the perifornical area, and the paraventricular nucleus in the forebrain, and the lateral parabrachial nucleus (LPBN), the nucleus tractus solitarius (NTS), and the area postrema in the hindbrain. These regions are discussed in terms of their roles in receiving afferent sensory input and in processing information related to hydromineral balance. Osmoreceptors controlling thirst are located in systemic viscera and in central structures that lack the blood-brain barrier. Angiotensin and aldosterone act on and through structures of the lamina terminalis and the amygdala to stimulate thirst and sodium appetite under conditions of hypovolemia. The NTS and LPBN receive neural signals from baroreceptors and are responsible for inhibiting the ingestion of fluids under conditions of increased volume and pressure and for stimulating thirst under conditions of hypovolemia and hypotension. The interplay of multiple facilitory influences within the brain may take the form of interactions between descending angiotensinergic systems originating in the forebrain and ascending adrenergic systems emanating from the hindbrain. Oxytocin and serotonin are additional candidate neurochemicals with postulated inhibitory central actions and with essential roles in the overall integration of sensory input within the neural network devoted to maintaining hydromineral balance.

Appetite↗
PubMed2000

Effects of low doses of caffeine on cognitive performance, mood and thirst in low and higher caffeine consumers.

RATIONALE: Caffeine is present in many widely consumed drinks and some foods. In the fairly extensive literature on the psychostimulant effects of caffeine, there are few dose-response studies and even fewer studies of the effects of doses of caffeine lower than 50 mg (the range of the amounts of caffeine contained in, for example, a typical serving of tea or cola). OBJECTIVE: This study measured the effects of 0, 12.5, 25, 50 and 100 mg caffeine on cognitive performance, mood and thirst in adults with low and moderate to high habitual caffeine intakes. METHODS: This was a double-blind, within-subjects study. Following overnight caffeine abstinence, participants (n=23) completed a test battery once before and three times after placebo or caffeine administration. The test battery consisted of two performance tests, a long duration simple reaction time task and a rapid visual information processing task, and a mood questionnaire (including also an item on thirst). RESULTS: Effects on performance and mood confirmed a psychostimulant action of caffeine. All doses of caffeine significantly affected cognitive performance, and the dose-response relationships for these effects were rather flat. The effects on performance were more marked in individuals with a higher level of habitual caffeine intake, whereas caffeine increased thirst only in low caffeine consumers. CONCLUSIONS: After overnight caffeine abstinence, caffeine can significantly affect cognitive performance, mood and thirst at doses within and even lower than the range of amounts of caffeine contained in a single serving of popular caffeine-containing drinks. Regular caffeine consumers appear to show substantial tolerance to the thirst-increasing but not to the performance and mood effects of caffeine.

Adolescent↗
PubMed1975

The nature of the thirst stimulus: a factor in conditioned taste-aversion behavior.

Independent groups of rats were compared drinking in response to either water deprivation or osmotic thirst induced by intraperitoneal injections of hypertonic saline. When water or a palatable saccharin solution served as the drinking fluid, deprivation and osmotic thirst produced comparable fluid intakes. In contrast, when a saccharin solution previously associated with the aversive effects of lithium served as the drinking fluid, animals injected with hypertonic saline drank substantially less than water deprived animals. Experiment 2 indicated that this hyperreactivity to a conditioned aversive flavor in animals suffering from osmotic thirst was due to the reduced palatability of the saccharin flavor rather than the previous experience with lithium. Experiment 3 showed that the effect also could not be attributed to differential taste-aversion learning, handling, food deprivation or weight loss before the test sessions. The phenomenon is discussed in terms of various differences between thirst induced by water deprivation and thirst induced by acute cellular dehydration.

Animals↗
PubMed1991

The relationship of spontaneous macronutrient and sodium intake with fluid ingestion and thirst in humans.

The amount of solid food eaten by humans in spontaneously ingested bouts is the most important determinant of the amount and timing of fluid ingestion. In order to investigate whether this relationship occurred as a result of the osmotic and volumetric effects of the ingested nutrients, analyses were performed on the data obtained from 219 adult humans. They were paid to maintain diaries for 7 days of everything they ingested, the timing and conditions present at the bout, and pre- and postbout self-ratings of subjective thirst. Carbohydrate and protein intake were found to be the dietary constituents that were most highly related to fluid intake and subjective thirst while sodium and fat were found to be either not at all or only weakly related. Carbohydrate and protein intake were found to be positively related to the amount ingested of total fluid, fluid in excess of digestive requirements, and fluid in the form of "drinks," for the amounts ingested in individual bouts, over the entire day, and over the entire week. In addition, carbohydrate and protein intakes were found to be positively related to the reduction in the subjective state of thirst, while negatively related to the level of thirst self-reported at the end of the bout. The results indicate that fluid intake and subjective thirst are influenced by the repleting characteristics of ingested nutrients and not by their depleting effects, suggesting that fluid intake occurs in response to and as an adjunct of food intake, not fluid homeostasis.

Adolescent↗
PubMed2026

Preoperative Carbohydrate Supplementation Reduces Thirst and Improves Patient Satisfaction Before Elective Cesarean Delivery: A Randomized Controlled Trial.

BACKGROUND & AIMS: Prolonged preoperative fasting is a major source of patient discomfort, particularly thirst, before elective cesarean delivery. This study aimed to evaluate whether preoperative carbohydrate (CHO) supplementation could alleviate these discomforts and improve patient satisfaction without compromising safety. METHODS: In this single-center randomized controlled trial, 262 women scheduled for elective cesarean delivery under neuraxial anesthesia were randomly allocated to either the CHO group (Group CHO, n = 131), which received 355 mL of an oral carbohydrate solution on the night before and the morning of surgery, or the control group (Group C, n = 131), which followed conventional fasting. The primary outcome was the thirst Numeric Rating Scale (NRS, 0-10) score measured immediately before surgery. Secondary outcomes included hunger NRS, satisfaction NRS, and maternal and neonatal safety parameters. RESULTS: Baseline characteristics were comparable between groups. Despite a longer preoperative fasting duration in Group CHO (9.25 &#xb1; 1.05 vs. 8.74 &#xb1; 0.97 h, P < 0.001), this group exhibited significantly lower thirst NRS scores (1.69 &#xb1; 0.90 vs. 4.02 &#xb1; 0.99, P < 0.001) and hunger NRS scores (1.25 &#xb1; 0.94 vs. 2.09 &#xb1; 0.82, P < 0.001), as well as higher satisfaction NRS scores (7.70 &#xb1; 0.69 vs. 5.69 &#xb1; 1.17, P < 0.001). Subgroup analyses confirmed consistent benefits of CHO supplementation across most patient characteristics. Further analyses suggested that the maximum effect on thirst reduction occurred at approximately 9.2 h of solid fasting; however, the interaction between fasting duration and treatment group was not statistically significant (P = 0.187). CONCLUSION: Preoperative carbohydrate supplementation effectively reduces thirst and hunger and improves patient satisfaction before elective cesarean delivery without increasing maternal or neonatal risk. The beneficial effects were consistent across varying fasting durations, with exploratory spline analyses suggested a potential peak effect around 9.2 h, though this was not statistically significant and should be interpreted cautiously. These findings support the incorporation of carbohydrate loading into enhanced recovery protocols. TRIAL REGISTRATION: China Clinical Trial Registry ChiCTR2500097956.

Humans↗
PubMed2001

Altered osmotic thresholds for arginine vasopressin secretion and thirst during superovulation and in the ovarian hyperstimulation syndrome (OHSS): relevance to the pathophysiology of OHSS.

OBJECTIVE: To test the hypothesis that decreases in and maintenance of a new steady state in plasma osmolality and sodium level in ovarian hyperstimulation syndrome (OHSS) are due to altered osmoregulation of arginine vasopressin secretion and thirst. DESIGN: Prospective study. SETTING: IVF-ET program in a university-based assisted reproductive treatment center. PATIENT(S): Eight women undergoing superovulation for IVF-ET and five women with normal menstrual cycles. INTERVENTION(S): Two-hour infusion of 5% saline on day 3 or 4 after hCG administration in patients undergoing IVF or in the early luteal phase in controls. A 5% saline infusion test was done on day 10 after hCG administration in one patient with OHSS and one patient without OHSS, both of whom were undergoing IVF. MAIN OUTCOME MEASURE(S): Comparison of changes in thresholds for thirst and plasma vasopressin to plasma osmolality. Changes in urine osmolality, plasma electrolytes, hemoglobin level, and hematocrit were assessed at baseline and during infusion of 5% saline. RESULT(S): The sensitivity of the changes in arginine vasopressin secretion and thirst after 5% saline infusion was similar in IVF patients on day 3 or 4 after hCG and controls. However, the osmotic threshold was significantly lower by 6 mOsm/kg in IVF patients. By day 10 after hCG, the lower osmotic thresholds for arginine vasopressin secretion and thirst persisted in OHSS, although the sensitivity to arginine vasopressin secretion was markedly reduced. CONCLUSION(S): The osmotic thresholds for arginine vasopressin secretion and thirst are reset to lower plasma osmolality during superovulation for IVF-ET. This new lower body tonicity is maintained until at least day 10 after hCG in OHSS. Decreases in plasma osmolality and plasma sodium levels in OHSS are due to altered osmoregulation rather than electrolyte losses; correction of apparent "electrolyte imbalance" in OHSS is therefore inappropriate.

Adult↗
PubMed1988

Osmoregulation of thirst and vasopressin secretion in insulin-dependent diabetes mellitus.

1. Osmotically stimulated thirst and vasopressin release were studied during infusions of hypertonic sodium chloride and hypertonic D-glucose in euglycaemic clamped diabetic patients and healthy controls. 2. Infusion of hypertonic sodium chloride caused similar elevations of plasma osmolality in diabetic patients (288.0 +/- 1.0 to 304.1 +/- 1.6 mosmol/kg, mean +/- SEM, P less than 0.001) and controls (288.6 +/- 0.9 to 305.7 +/- 0.6 mosmol/kg, P less than 0.001), accompanied by progressive increases in plasma vasopressin (diabetic patients, 0.9 +/- 0.3 to 7.7 +/- 1.5 pmol/l, P less than 0.001; controls 0.5 +/- 0.1 to 6.5 +/- 1.0 pmol/l, P less than 0.001) and thirst ratings (diabetic patients 1.0 +/- 0.2 to 7.1 +/- 0.5 cm, P less than 0.001; controls 1.8 +/- 0.4 to 8.0 +/- 0.5 cm, P less than 0.001) in both groups. 3. Drinking rapidly abolished thirst and vasopressin secretion before major changes in plasma osmolality occurred in both diabetic patients and healthy controls. 4. There were close and significant correlations between plasma vasopressin and plasma osmolality (diabetic patients, r = +0.89, controls r = +0.93) and between thirst and plasma osmolality (diabetic patients r = +0.95, controls r = +0.97) in both diabetic patients and healthy controls during hypertonic saline infusion. 5. Hypertonic D-glucose infusion caused similar elevations in blood glucose in diabetic patients (4.0 +/- 0.2 to 20.1 +/- 1.2 mmol/l, P less than 0.001) and healthy controls (4.3 +/- 0.1 to 19.3 +/- 1.2 mmol/l, P less than 0.001) but did not change plasma vasopressin or thirst ratings.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2005

Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis.

BACKGROUND: Most patients on haemodialysis (HD) have to maintain a fluid-restricted diet to prevent a high interdialytic weight gain (IWG). The prevalence of xerostomia (the feeling of a dry mouth) is higher in HD patients than in controls. Recently, we demonstrated that xerostomia and thirst were positively correlated with IWG in HD patients. Thus, this may play a role as a stimulus for fluid intake between dialysis sessions. The aim of the present study was to investigate the effect of chewing gum or a saliva substitute on xerostomia, thirst and IWG. METHODS: This study was a randomized two-treatment crossover design with repeated measures. After the use of chewing gum or saliva substitute for 2 weeks, a wash-out period of 2 weeks was introduced and hereafter the other regimen was carried out. Xerostomia and thirst were assessed by validated questionnaires as xerostomia inventory (XI) and dialysis thirst inventory (DTI), at baseline and after each treatment period, as were IWG and salivary flow rates. RESULTS: Sixty-five HD patients (42 men, 54.6+/-14.1 years; 23 women, 54.7+/-16.3 years) participated in this study. Chewing gum decreased XI from 29.9+/-9.5 to 28.1+/-9.1 (P<0.05). Chewing gum as well as a saliva substitute reduced DTI significantly (P<0.05), but no differences occurred for the average IWG or salivary flow rates. CONCLUSIONS: The use of chewing gum and, to a lesser extent, a saliva substitute may alleviate thirst and xerostomia in some HD patients.

Adult↗
PubMed1997

Effects of oral and intravenous rehydration on ratings of perceived exertion and thirst.

The purpose of this investigation was to compare the effects of oral and intravenous saline rehydration on differentiated ratings of perceived exertion (RPE) and thirst. Eight men underwent three randomly assigned rehydration treatments following a 2- to 4-h exercise-induced dehydration bout to reduce body weight by 4%. Treatments included 0.45% saline infusion (i.v.), 0.45% saline oral ingestion (ORAL), and no fluid (NF). Following rehydration and rest (2 h total), subjects walked at 50% VO2max for 90 min at 36 degrees C (EX). Central RPE during ORAL was lower (P < 0.05) than i.v. and NF throughout EX. Local RPE during NF was higher (P < 0.05) than i.v. and ORAL at minutes 20 and 40 of EX and overall RPE during NF was higher (P < 0.05) than ORAL at minutes 20 and 40 of EX. Significant correlations were found between overall RPE and mean skin temperature for i.v. (r = 0.72) and NF (r = 0.75), and between overall RPE and thirst ratings for i.v. (r = 0.70). Thirst ratings were not different among trials at postdehydration. Following rehydration, thirst was higher (P < 0.05) during NF than i.v. and ORAL and lower (P < 0.05) during ORAL than i.v. at all subsequent time points. Results suggest that oral rehydration is likely to elicit lower RPE and thirst ratings compared with intravenous rehydration.

Adult↗
PubMed1986

Recurrent pregnancy-induced polyuria and thirst due to hypothalamic diabetes insipidus: an investigation into possible mechanisms responsible for polyuria.

A young patient developed hypothalamic diabetes insipidus due to histiocytosis in infancy and was satisfactorily treated with Pitressin. As a teenager she no longer had thirst or polyuria after treatment was stopped. These symptoms only returned during her two pregnancies. When non-pregnant her urine output was 1.7-2.0 1/24 h, basal plasma osmolality 288-290 mOsm/kg, and during pregnancy 24 h urine volume was 4.5-5.21, plasma osmolality 278-280 mOsm/kg. Studies on osmoregulation of thirst and AVP release, and on renal sensitivity to the V2 agonist desmopressin and endogenous vasopressin were performed in pregnant and non-pregnant states. She had no circulating antibodies to AVP, and the effect of pregnancy-associated vasopressinase was eliminated. Results showed lowered basal plasma osmolality and osmolar thirst threshold in pregnancy but no failure of the renal concentrating mechanism. Plasma AVP concentrations after osmotic stimulation were lower in pregnancy. We propose that she developed thirst and polyuria during pregnancy because of lowering of her osmolar thirst threshold to plasma osmolalities which caused her to drink sufficient quantities of fluid to further reduce AVP secretion. We cannot exclude, however, the possibility that there was increased clearance of circulating AVP.

Adult↗
PubMed1991

The effect of drinking on atrial natriuretic peptide, vasopressin and thirst appreciation in hyperosmolar man.

OBJECTIVES: To assess whether drinking and oropharyngeal stimuli mediate the release of plasma atrial natriuretic peptide (ANP) in man. DESIGN: Hypertonic saline was infused into male volunteers to stimulate thirst. In order to avoid any effect of volume change on ANP release, the studies were performed with the subject in the seated position. SUBJECTS: Seated normal male volunteers (n = 6) were infused with hypertonic saline at a rate of 0.06 ml/kg/min for 90 min on two separate occasions. After a 15-min equilibrium period, subjects were allowed to drink for the following 45-min period on one occasion, but no drinking was permitted on the other occasion. MEASUREMENTS: Aliquots of blood were withdrawn at 30-min intervals for 90 min during hypertonic saline infusion, and +3, 6, 9, 12, 15, 30 and 45 min during the drinking/control period for the measurement of plasma ANP, plasma vasopressin, plasma osmolality, serum sodium and haematocrit; thirst was assessed at the same time points using a visual analogue scale. Blood pressure was measured at 15-min intervals. RESULTS: Hypertonic saline infusion induces increases in plasma vasopressin, plasma osmolality, serum sodium and thirst appreciation (P less than 0.005), and blood volume (P less than 0.05) on both study days; there was no increase in plasma ANP during hypertonic saline infusion. During the drinking period there was the expected decrease in plasma vasopressin (P less than 0.01), plasma osmolality (P less than 0.05), serum sodium (P less than 0.05) and thirst appreciation (P less than 0.01); no significant changes occurred in plasma atrial natriuretic peptide, mean arterial blood pressure or haematocrit during either the drinking or the control period. CONCLUSIONS: The drinking-mediated inhibition of thirst appreciation and plasma vasopressin is not associated with any change in plasma ANP concentrations; it does not appear that oropharyngeal stimuli contribute to the release of ANP in man.

Adult↗
PubMed2004

Abnormal regulation of thirst and vasopressin secretion following surgery for craniopharyngioma.

OBJECTIVE: In this study we aimed to establish the frequency of postoperative diabetes insipidus and the incidence and characteristics of abnormalities of thirst in a cohort of patients with craniopharyngioma, in whom neurosurgery had been performed. DESIGN: Diabetes insipidus was determined by either standard criteria for diagnosis in the immediate postoperative period, or by water deprivation test, in all craniopharyngioma and pituitary tumour patients who underwent surgery in Beaumont Hospital between the years 1986 and 1998. Osmoregulated thirst and vasopressin release were studied during a 2-h infusion of hypertonic (5%) saline followed by a 30-min period of free access to water. PATIENTS: Data on the incidence of postoperative diabetes insipidus was collected in 26 patients with craniopharyngioma and 154 patients with pituitary adenomata. We recruited 16 healthy control patients, 16 patients with cranial diabetes insipidus following pituitary tumour surgery and 16 patients with cranial diabetes insipidus following craniopharyngioma resection for the hypertonic saline infusion study. RESULTS: Twenty-five patients out of 26 (96%) patients developed diabetes insipidus after surgery for craniopharyngioma, a much higher incidence than after surgery for suprasellar (26/88, 30%, P < 0.001) or intrasellar pituitary tumours (9/66, 14%, P < 0.001). Hypertonic saline infusion identified abnormal thirst responses in five of the 16 craniopharygioma patients studied; all of the pituitary tumour patients had a normal thirst response. Three of the craniopharyngioma patients had adipsic diabetes insipidus whilst two had polydipsic diabetes insipidus. CONCLUSION: This study demonstrates following surgery for craniopharyngioma there is a high incidence of cranial diabetes insipidus and a significant incidence of abnormal thirst responses to osmotic stimuli.

Adult↗
PubMed1987

Hypernatraemia due to a reset osmostat for vasopressin release and thirst, complicated by nephrogenic diabetes insipidus.

We describe a patient with chronic hypernatraemia (plasma sodium 148-155 mmol/l) and partial nephrogenic diabetes insipidus who had received prolonged lithium treatment. Despite stopping the drug for one year the abnormalities remained. Infusion of hypertonic saline (NaCl 855 mmol/l) allowed the characterization of osmoregulation of thirst and vasopressin secretion. Linear regression analysis of plasma vasopressin and osmolality defined the function, pAVP = 0.27 (pOsm - 301), and analysis of thirst measured by a visual analogue scale and plasma osmolality, the function, thirst = 0.16 (pOsm - 302) where pAVP and pOsm represent plasma arginine vasopressin and osmolality respectively. The slopes of the regression lines which describe the sensitivity of the osmoreceptors were within the normal range, but both abscissal intercepts, which define the thresholds for vasopressin release and thirst, were markedly elevated in comparison to normal (upper limit less than 290 mOsm/kg). Other investigations of electrolytes, anterior pituitary function and high definition computed tomographic scanning of hypothalamo-pituitary region were all normal. We conclude that this patient's chronic hypernatraemia was due to resetting of the osmostats for both vasopressin release and thirst, a rarely described mechanism to account for hypernatraemia. Although it is probable that the partial nephrogenic diabetes insipidus was related to prolonged lithium therapy, the cause of the reset osmostats remains unclear.

Aged↗
PubMed2006

Sodium depletion activates the aldosterone-sensitive neurons in the NTS independently of thirst.

Thirst and sodium appetite are both critical for restoring blood volume. Because these two behavioral drives can arise under similar physiological conditions, some of the brain sensory sites that stimulate thirst may also drive sodium appetite. However, the physiological and temporal dynamics of these two appetites exhibit clear differences, suggesting that they involve separate brain circuits. Unlike thirst-associated sensory neurons in the hypothalamus, the 11-beta-hydroxysteroid dehydrogenase type 2 (HSD2) neurons in the rat nucleus tractus solitarius (NTS) are activated in close association with sodium appetite (16). Here, we tested whether the HSD2 neurons are also activated in response to either of the two physiological stimuli for thirst: hyperosmolarity and hypovolemia. Hyperosmolarity, produced by intraperitoneal injection of hypertonic saline, stimulated a large increase in water intake and a substantial increase in immunoreactivity for the neuronal activity marker c-Fos within the medial NTS, but not in the HSD2 neurons. Hypovolemia, produced by subcutaneous injection of hyperoncotic polyethylene glycol (PEG), stimulated an increase in water intake within 1-4 h without elevating c-Fos expression in the HSD2 neurons. The HSD2 neurons were, however, activated by prolonged hypovolemia, which also stimulated sodium appetite. Twelve hours after PEG was injected in rats that had been sodium deprived for 4 days, the HSD2 neurons showed a consistent increase in c-Fos immunoreactivity. In summary, the HSD2 neurons are activated specifically in association with sodium appetite and appear not to function in thirst.

11-beta-Hydroxysteroid Dehydrogenase Type 2↗
PubMed1981

Plasma angiotensin II concentrations and experimentally induced thirst.

The systemic administration of angiotensin II or its precursors will result in increased water intake. Several manipulations that result in hypovolemia and/or hypotension (extracellular thirst challenges) are known to activate the peripheral renin-angiotensin system and also produce drinking. Although there are without question multiple mediators of thirst associated with extracellular thirst challenges, one of the major factors responsible for water intake has been hypothesized to be the action of angiotensin II. In the experimental analysis of thirst, several types of hypovolemic-hypotensive manipulations have been employed. However, there is a paucity of data available that characterize the systematic changes of angiotensin II levels following such challenges. The present studies determined plasma angiotensin II levels and drinking responses after isoproterenol administration, caval ligation, and subcutaneous polyethylene glycol treatment. The experimental protocols for treatment of the animals closely approximated conditions commonly employed in the experimental analysis of thirst. The results indicated that endogenous levels of angiotensin II increase after these treatments to levels that in all likelihood are sufficient to make a substantial contribution to the drinking response.

Angiotensin II↗
PubMed1983

Thirst and solute excretion: their effectiveness in osmostatic control of body fluid.

The effect of intravenous infusion of hypertonic NaCl at three different rates (series I, 4.0 mmol/min; series II, 8.0 mmol/min; series III, 16.0 mmol/min) on osmotic thirst threshold and postloading restitution of plasma osmolality (Posm) has been determined in dogs. Osmotic thirst threshold increased proportionally to the rate of delivery of the osmotic load. Relative suppression of osmotic thirst at the higher rates of infusion was temporary and largely disappeared within 10 min after the end of hypertonic infusion. During the postloading period excretion of osmotic load and water intake was proportional to the magnitude of the load administered. However, the animals with high osmotic thirst threshold stopped drinking at a higher Posm than those with a low osmotic thirst threshold. In series I and II, Posm decreased during 1 h to a level not significantly different from the preloading value. In each series renal excretion of osmotic load was more important than water intake for restitution of Posm during 1 h. Amount of water ingested during this period was significantly smaller than that theoretically required to restore resting Posm when excretion of osmotic load was not taken into account. However, total amount of water intake and osmotic load excreted during 1 h were together well adjusted to restore preloading Posm.

Animals↗
PubMed1997

Mechanism of attenuated thirst in aging: role of central volume receptors.

To test the hypothesis that the inhibitory action of central blood volume expansion on thirst and renal fluid regulation is attenuated with aging, we monitored the drinking and renal responses of dehydrated older (70 +/- 2 yr, n = 6) and younger (24 +/- 1 yr, n = 6) subjects during 195 min of head-out water immersion (HOI), which shifts blood centrally and increases plasma volume (PV). Subjects dehydrated by exercising for 2 h at 36 degrees C in the evening and refraining from fluids overnight before HOI in 34 degrees C water or a seated control in water perfusion suit [time control (TC)] the next morning. Ad libitum water intake was allowed after 15 min of HOI. Dehydration decreased PV by 10.6 +/- 1 and 7.3 +/- 1.8% (P < 0.05) and increased plasma osmolality by 6 +/- 2 and 7 +/- 1 mosmol/kg H2O (P < 0.05) in older and younger subjects, respectively. Thirst ratings increased in both groups, but pre-HOI thirst perception on a line rating scale was lower in older (69 +/- 8 mm) than younger (94 +/- 6 mm, P < 0.05) subjects. Fifteen minutes of HOI restored PV by 7.8 +/- 1.0 and 5.7 +/- 1.0% in older and younger subjects, respectively, but suppressed thirst rating in younger subjects only (P < 0.05). Fluid intake was reduced in HOI compared with TC in younger (6.3 +/- 0.5 vs. 14.3 +/- 2.2 ml/kg, P < 0.05) but not in older (6.7 +/- 2.1 vs. 8.4 +/- 3.3 ml/kg) subjects. During HOI, older subjects had smaller suppression of plasma renin activity and aldosterone concentration but a greater increase in the plasma atrial natriuretic peptide concentration (P[ANP], P < 0.05). HOI increased fractional sodium excretion in both groups, but mean arterial pressure increased only in the older subjects (P < 0.05). We conclude that the inhibitory influence of central volume expansion on thirst and drinking behavior is diminished with aging. Furthermore, in contrast to younger people, HOI natriuresis is associated with exaggerated increases in P[ANP] and arterial blood pressure in older people, suggesting arterial baroreceptors may be involved in the fluid regulatory response to central blood volume expansion in older people.

Adult↗
PubMed2004

Effect of hydration status on thirst, drinking, and related hormonal responses during low-intensity exercise in the heat.

During exercise-heat stress, ad libitum drinking frequently fails to match sweat output, resulting in deleterious changes in hormonal, circulatory, thermoregulatory, and psychological status. This condition, known as voluntary dehydration, is largely based on perceived thirst. To examine the role of preexercise dehydration on thirst and drinking during exercise-heat stress, 10 healthy men (21 +/- 1 yr, 57 +/- 1 ml x kg(-1) x min(-1) maximal aerobic power) performed four randomized walking trials (90 min, 5.6 km/h, 5% grade) in the heat (33 degrees C, 56% relative humidity). Trials differed in preexercise hydration status [euhydrated (Eu) or hypohydrated to -3.8 +/- 0.2% baseline body weight (Hy)] and water intake during exercise [no water (NW) or water ad libitum (W)]. Blood samples taken preexercise and immediately postexercise were analyzed for hematocrit, hemoglobin, serum aldosterone, plasma osmolality (P(osm)), plasma vasopressin (P(AVP)), and plasma renin activity (PRA). Thirst was evaluated at similar times using a subjective nine-point scale. Subjects were thirstier before (6.65 +/- 0.65) and drank more during Hy+W (1.65 +/- 0.18 liters) than Eu+W (1.59 +/- 0.41 and 0.31 +/- 0.11 liters, respectively). Postexercise measures of P(osm) and P(AVP) were significantly greater during Hy+NW and plasma volume lower [Hy+NW = -5.5 +/- 1.4% vs. Hy+W = +1.0 +/- 2.5% (P = 0.059), Eu+NW = -0.7 +/- 0.6% (P < 0.05), Eu+W = +0.5 +/- 1.6% (P < 0.05)] than all other trials. Except for thirst and drinking, however, no Hy+W values differed from Eu+NW or Eu+W values. In conclusion, dehydration preceding low-intensity exercise in the heat magnifies thirst-driven drinking during exercise-heat stress. Such changes result in similar fluid regulatory hormonal responses and comparable modifications in plasma volume regardless of preexercise hydration state.

Adult↗