Edward Deaux

Emergence of systemic cues evoking food-associated drinking☆

Abstract Rats maintained on a feeding schedule of eight 1.5-g portions of Purina Lab Chow per day consistently initiate drinking following food ingestion. In order to establish whether systemic cues accompany the onset of drinking, the rats were sacrificed and serum osmolality was determined. The control group was sacrificed at the time of day they normally received the first portion of food. The experimental group was sacrificed at the moment of initiation of drinking following consumption of the first portion of food. The difference in serum osmolality between the groups indicates that a systemic cue had emerged at the time of initiation of drinking.

Thirst Satiation and the Temperature of Ingested Water

Ingestion in rats given limited daily access to water of 12�, 24�, and 37�C is a positive function of water temperature, even though ingestion of warm water decreases blood osmotic concentration faster than cold water. The paradox suggests that temperature-dependent gastric factors and water-transport factors determine stomach distention cues of thirst satiation.

Emotionally Induced Increases in Effective Osmotic Pressure and Subsequent Thirst

Following a brief period of handling or enclosed rotation, rats increased the frequency of drinking relative to eating. Handling also delayed or eliminated eating behavior in hypoosmotic rats. Osmometric analysis revealed a rapid increase in serum osmolality during stress which may account for the emergence of thirst and disruption of eating.

A psychophysiological influence on the choice of illicit drugs

The variable of “augmenting” and “reducing,” as measured by kinesthetic figural aftereffects, was found to relate to the choice of amphetamines or barbiturates as a predominant drug, and differences were also found between males and females within each drug category. At the conceptual level, the need for stimulation (“nStim”) is presented as a hypothetical construct which relates the KFA measure to the choice of drug. The strength of the relationship and the significance of the results suggest the possible use of the KFA test in determining the appropriateness of prevention and treatment methods, which are typically applied without the specific consideration of the need for stimulation.

The temperature of ingested water: Its effect on body temperature

The ingestion of water of different temperatures was found to have a pronounced effect on body temperature in rats. Drinking 12° and 24° C water led to sharp decreases in body temperature of as large as 1.2°C, and, when free access to the water was given, recovery failed to occur within the 20-min test period. The results are related to mechanisms of preabsorptive satiety.

Stomach distention as a regulation of fluid intake

Rats kept on a 23.5-h/day water-deprivation schedule were given 30 min access to four solutions, each on a separate test day, which were comprised of the factorial combination of two temperatures (12° and 37°C) and two NaCl concentrations (150 and 450 mOsm/kg). Food, which was available ad lib, and solution consumption measures were taken. More 37°C 150-mOsm/kg solution, which has the fastest stomach clearance rate of the four, was consumed than of the other three; short-term and long-term food consumption measures were differentially affected by the solution’s temperature and concentration. The hypothesis that cues of preabsorptive satiety originate from stomach distention was supported.

The temperature of ingested water: Preference for cold water as an associative response

Rats were found to prefer 12° over 36° C water when their choice was restricted to those temperatures, but no clear preference was shown between water of 12° and 24°C or 24° and 36°C. The hypothesis that preference for cooler water is based on the animals’ history of drinking cooler water is supported by a successful shift to preferring 36°C water after restricted exposure to that temperature for 15 days.

Aphagia in the presence of drinking an isosmotic NaCl solution

Abstract Rats with familial diabetes insipidus (D.I.) were exposed to liquids in which the solute was either excreted (NaCl), metabolized (glucose), or partially excreted-metabolized (milk). In the presence of an isosmotic solution where all the solvent was utilized for clearance of the solute (NaCl), rats continued to drink but displayed aphagia; decrease in the osmolality of NaCl solutions resulted in a proportional recovery of solid food ingestion. Exposure to milk resulted in hypophagia. Glucose solution did not interfere with the maintenance of eating, however, rats with D.I. did not increase their intake of glucose solution during solid food deprivation. Experimental evidence supports the view that the state of hydration as indicated by the body-fluid osmolality is essential for the maintenance of solid food ingestion. The evidence for a primary caloric regulation was doubtful.

Influence of sham stomach loading on serum osmolality.

Abstract Stomach sham-loading in rats was accompanied by a significant increase in serum osmolality which was highly correlated with the time involved in the sham-loading procedure. A decrease in serum osmolality followed a stomach loading of 8 ml of distilled water, but the change was smaller than that observed to follow oral ingestion of the same volume of water.

Stress induced osmotic changes as a function of deprivation state

A series of experiments determined the relationship between the internal osmotic balance of rats and the direction and magnitude of stress-induced, body-fluid osmolality (BFO) changes. The state of BFO was varied by food or water deprivation. Two forms of stress were applied: rotation or sham stomach loading. The results indicate that animals deprived of food or water failed to respond to rotation, but deprivation conditions had no influence on the BFO change induced by sham stomach loading. Although the change of BFO in response to nonspecific, stressful stimuli appeared to be in the hyperosmotic direction, the magnitude of BFO increase was a function of the severity of stress and the state of BFO.