Additivity of stimuli for drinking in rats

Chemical Senses

In nature, water is present as a low-salt solution, thus we hypothesized that thirst would increase taste responses to low-salt solutions. We investigated the effect of thirst on the 2 different salt detection mechanisms present in the rat chorda tympani (CT) nerve. The first mechanism is dependent upon the epithelial sodium channel (ENaC), is blocked by benzamil, and is specific to the cation sodium. The second mechanism, while undefined, is independent of ENaC, and detects multiple cations. We expected thirst to increase benzamil-sensitive sodium responses due to mechanistically increasing the benzamil-sensitive ENaC. We recorded CT whole-nerve electrophysiological responses to lingual application of NaCl, KCl (30, 75, 150, 300, 500, and 600 mM), and imitation rainwater in both control and 24-h water-restricted male rats. NaCl solutions were presented in artificial saliva before and after lingual application of 5µM benzamil. Water restriction significantly increased the integrated CT responses to NaCl but not to KCl or imitation rainwater. Consistent with our hypothesis, only the benzamil-sensitive, and not the benzamil-insensitive, CT sodium response significantly increased. Additionally, CT responses to salt were recorded following induction of either osmotic or volemic thirst. Both thirsts significantly enhanced the integrated CT responses to NaCl and KCl, but not imitation rainwater. Interestingly, osmotic and volemic thirsts increased CT responses by increasing both the benzamil-sensitive and benzamil-insensitive CT sodium responses. We propose that thirst increases the sensitivity of the CT nerve to sodium.

American journal of physiology. Regulatory, integrative and comparative physiology, 2007

Marked increases in the consumption of concentrated NaCl solution were elicited in rats by daily injection of the synthetic mineralocorticoid, deoxycorticosterone acetate (DOCA). DOCA-treated rats drank different volumes of NaCl solution depending on its concentration (between 0.15 M and 0.50 M), with less consumed (in milliliters) the more concentrated the fluid was. In consequence, total Na(+) intake (in milliequivalents) was roughly similar in all groups. Gastric emptying of Na(+) also diminished as the concentration of the ingested NaCl solution increased, and the delivery of Na(+) to the small intestine was remarkably similar in all groups. Cumulative volume of ingested fluid in the stomach and small intestine was very closely related to intake (in milliliters) of the concentrated NaCl solutions. Systemic plasma Na(+) levels did not increase until after rats stopped consuming concentrated NaCl solution, although they were elevated at the onset of water ingestion. The situation ...

Quarterly journal of experimental physiology and cognate medical sciences, 1976

Forty-eight hours of sodium depletion by acute cannulation of a parotid duct, via the buccal papilla, in the sheep, resulted in a progressive decrease in salivary secretion rate, salivary, urinary and plasma [Na] and no change in plasma [K]. In the first 24 h of Na depletion water intake was significantly increased. As normal sheep parotid saliva [Na] is higher than plasma [Na] and salivary loss over the first 24 h represented Na loss in excess of water relative to extracellular proportions, increased water intake was not osmotically induced. However, the animals did not replace their water deficit on either of the 2 days of Na depletion. This would appear to be valuable experimental model of increased water intake probably induced by hypovaolaemia, but uncomplicated concurrent osmotic stimuli, or any other factors which might result with the other commonly used experimental stimuli of thirst such as haemorrhage.

World journal of experimental medicine, 2012

To contrast the effects of various modifications of body fluid volumes on thirst as reported by healthy volunteers. Ten male volunteers aged between 19 and 37 years (mean 22 years) underwent four experiments each, which comprised infusion of 400-800 mL of acetated Ringer's solution and intake of 600 mL of tap water. Half of the experiments were preceded by volume depletion (median 1.7 L) with furosemide. A visual analogue scale (0-100 mm) was used to assess perceived thirst during each experiment. Volume depletion (P < 0.001) and tap water (P < 0.03) both affected thirst by 13 mm per L of fluid, whereas spontaneous diuresis and infusion of Ringer's acetate did not significantly change the thirst rating (multiple regressions). More detailed analyses showed that the volume depletion increased the median (25th-75th percentiles) thirst rating from 28 mm (21-43) to 59 mm (46-72, P < 0.001) while no change occurred in those who were only slightly thirsty (< 30 mm) befo...

American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2015

iSodium intake occurs either as a spontaneous or induced behavior, which is enhanced, i.e., sensitized, by repeated episodes of water deprivation followed by subsequent partial rehydration (WD-PR). In the present work, we examined whether repeated WD-PR alters hypothalamic transcripts related to the brain renin-angiotensin system (RAS) and apelin system in male normotensive Holtzman rats (HTZ). We also examined whether the sodium intake of a strain with genetically inherited high expression of the brain RAS, the spontaneously hypertensive rat (SHR), responds differently than HTZ to repeated WD-PR. We found that repeated WD-PR, besides enhancing spontaneous and induced 0.3 M NaCl intake, increased the hypothalamic expression of angiotensinogen, aminopeptidase N, and apelin receptor transcripts (43%, 60%, and 159%, respectively) in HTZ at the end of the third WD-PR. Repeated WD-PR did not change the daily spontaneous 0.3 M NaCl intake and barely changed the need-induced 0.3 M NaCl int...

Bulletin of the psychonomic society, 1983

Organizing action of prenatally administered testosterone propionate on the tissues mediating mating behavior in the female guinea pig.

Brain Research, 1994

Thirst, the longing or compelling desire to drink, arises physiologically by two main mechanisms-extracellular and cellular dehydration. The hormone angiotensin II has been implicated m the former but not in the latter brain mechanism. To test this apparent difference, experiments m 5 mammalian species examined the effect of mtracerebroventricular infusion of Iosartan, an angiotensin II type I receptor antagonist, on the thirst induced by intracerebroventricular infusion of an artificial cerebrospinal fluid made hypertonic by the inclusion of 500 mM NaC1. The losartan infusion reduced the water intake due to increased brain sodium concentration in all 5 species, cattle, sheep, rabbits, rats and mice. Thus, the thirst evoked by cellular dehydration, as well as the thirst evoked by extracellular dehydration, may be mediated by angiotensin II.

Physiology & Behavior, 2002

Male adult rats that received an intragastric load of 2 ml of 12% NaCl (n = 13) ingested both water (4.0 ± 0.2 ml/2 h) and 0.9% NaCl (3.7 ± 1.0 ml/2 h) when compared with rats that received intragastric load of 2 ml of water (water: 0.1 ± 0.1; 0.9% NaCl: 0.5 ± 0.3 ml/2 h, n = 12) in a two-bottle test. Intragastric sodium load increased plasma sodium concentration and osmolality by 5% and reduced plasma renin activity by half compared to rats that received intragastric load of water. Intravenous infusion of 1.5 ml/10 min of 10% NaCl (n = 16) also induced ingestion of water (6.2 ± 0.8 ml/2 h) and 0.9% NaCl (2.9 ± 0.8 ml/2 h) compared with intravenous infusion of 1.5 ml/10 min of 0.9% NaCl (water: 0.9 ± 0.4; 0.9% NaCl: 0.5 ± 0.2 ml/2 h, n = 14). Therefore, a sodium load that raises natremia and plasma osmolality, and therefore induces cell dehydration, results in both 0.9% NaCl and water ingestion when the rats have a two-bottle choice. D

1998

1995

Sprague-Dawley male rats surgically equipped with a chronic gastric catheter were tested for drinking after 2 ml intragastric infusions of 290, 600, 900, 1200: or 1800 mOsm/kg NaCI. Rats with bilateral transection of renal nerves (RD) drank less than neurologically intact rats (S) after 600 and 900 mOsm/kg NaC1 infusions. The RD rats were capable of a rapid and robust drinking response to relatively mild experimental challenges, because they drank appropriately in response to SC angiotensin H and to a dose of histamine that is a threshold dose for increasing water intake. The RD rats ate less than S rats, but RD rats drank appropriate amounts of water when eating and drinking after 24-h food deprivation. When nondeprived and ingesting one, two, or four small (0.57 g) salted crackers, the RD rats drank significantly less water than S rats. At the time drinking was initiated after ingestion of one salted cracker, plasma osmolality, sodium, protein, and packed cell volume were not changed from baseline conditions (i.e., no eating) in neurologically intact rats; plasma reniJa activity was significantly elevated at the time drinking was initiated following the ingestion of one or two small crackers. These findings (a) demonstrate a role for renal nerves in drinking behavior in rats, and (b) suggest the working hypothesis that the ingestion of a small meal, and the subsequent delivery of a relatively small osmotic load to the gastrointestinal tract and/or hepatic-portal vein, activates mechanisms for drinking that include a change in activity of renal nerves to increase plasma renin activity without cellular dehydration or hypovolemia. Such mechanisms may be activated to mobilize drinking behavior in advance of postprandial fluid deficit. Renal nerves Drinking Angiotensin II Histamine Food-related drinking Ingestive behavior Water intake Renal denervation Plasma renin activity

American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2006

Hyperosmotic intravenous infusions of NaCl are more potent for inducing drinking and vasopressin (AVP) secretion than equally osmotic solutions of glucose or urea. The fact that all three solutes increased cerebrospinal fluid osmolality and sodium concentration led the investigators to conclude that critical sodium receptors or osmoreceptors for stimulating drinking and AVP secretion were outside the blood-brain barrier (BBB) in the circumventricular organs (CVOs). We tested an obvious prediction of this hypothesis: that all three solutes should increase c-Fos-like immunoreactivity (Fos-ir) inside the BBB, but that only NaCl should increase Fos-ir in the CVOs. We gave intravenous infusions of 3.0 Osm/l NaCl, glucose, or urea to rats for 11 or 22 min at 0.14 ml/min and perfused the rats for assay of Fos-ir at 90 min. Controls received isotonic NaCl at the same volume. Drinking latency was measured, but water was then removed. Drinking consistently occurred with short latency during h...

Journal of Neuroscience Methods, 2010

Standard methods for behavioral and neurophysiological experiments in the non-human primate rely on controlled water access as a means for motivating subject performance. It is, however, still not clear whether animals are able to regulate their fluid balance appropriately under these experimental settings. Further, the physical state associated with a subject monkey's thirst has not yet been objectively assessed under these conditions. Both of these deficiencies arise from the lack of a method for independently evaluating the hydration state of these subjects during experimental testing. To address these limitations, we measured the blood osmolality, the most widely used hematological index of hydration status, of three rhesus monkeys under conditions of controlled water access while they participated in a standard reinforced behavioral task for fluid rewards. We found that day-to-day hydration levels, as measured by serum osmolality, appears to be well regulated in a narrow range of values (300-320mOsmo/kgH(2)O) by experimental subjects under these conditions: animals work harder and longer to earn more water rewards on a day when they are in a lower hydration state (higher osmolality) than when they are in a higher hydration state (lower osmolality). We also found that osmolality level decreases almost immediately after water intake, within 30min, in a surprisingly linear manner. Osmolality thus seems to provide a fairly precise reflection of the monkeys' hydration state on a timescale of minutes. This evidence suggests that osmolality can be used as a tool for monitoring the hydration level of experimental subjects.

Nigerian Journal of Physiological Sciences, 2014

This study examined the effect of drinking and gargling on thirst perception (TP) in 33 young dehydrated female subjects (18-25 yrs), using the visual analogue scale (VAS). Group A subjects drank, while group B gargled the fluid provided - 0.0%, 0.9% and 1.8% NaCl (7.0 ml/kg body weight of fluid). The procedure was alternated two weeks later. All subjects dehydrated for 18 hours prior to the study, and the last 12-hour urine was collected and volume recorded. Subject who provided a 12 hr urine volume greater than 400 ml was excluded from the study. After recording the baseline TP, and voiding the bladder, drinking/gargling was done within 5 minutes, and the subsequent TPs were recorded at 5 minutes interval for 25 minutes. Blood samples were collected before and at the end of the 30 minutes, when urine volumes were recorded. Drinking (0.0% and 1.8% NaCl) resulted in an initial decrease in thirst perception, which was statistically significant (p<0.05) only up to 10 minutes. Water...

The Journal of Physiology, 1957

This paper describes the changes in salt consumption, taste thresholds and salivary secretion, which took place in two normal subjects during an 11-day period of drinking about 8-101. of water a day.

Physiology & Behavior, 1992

Central injection of the tachykinins (TKs) neurokinin A (NKA), eledoisin (ELE), and kassinin (KASS) produced long-lasting inhibition (up to 6 h) of drinking induced by subcutaneous hypertonic NaCI, while substance P (SP) and physalaemin (PHYS) evoked short-lasting effects. The hypothesis that water retention or increased Na + excretion by the kidney (induced by TKs) may reduce the need for water ingestion was tested. The results obtained both in urine collection experiments and in nephrectomized rats showed that the duration of the effect of NKA, ELE, and KASS is not due to water retention or increased Na + excretion by the kidney. The effect of NKA, but not that of ELE and KASS, was shortened by nephrectomy, even though NKA did not modify urine volume or Na + excretion, lndomethacin pretreatment, like nephrectomy, reduced the duration of the NKA effect, suggesting that renal prostaglandins are involved in it. On the other hand, the long-lasting effect of the three TKs cannot be easily explained in terms of slow metabolic degradation, particularly for NKA. Alternatively, it might be hypothesized that these TKs produce a modification of osmoreceptor function lasting well beyond the life of the peptide, and/or that they produce Na + loss through emunctories different from the kidney.