Abstract
The gastric emptying of liquids was investigated in male Wistar rats (8 to 10 weeks old, 210-300 g) dehydrated by water deprivation. In this model of dehydration, weight loss, hematocrit and plasma density were significantly higher in the dehydrated animals than in the control groups after 48 and 72 h of water deprivation (P < 0.05). Three test meals (saline (N = 10), water (N = 10) and a WHO rehydrating solution containing in one liter 90 mEq sodium, 20 mEq potassium, 80 mEq chloride and 30 mEq citrate (N = 10)) were used to study gastric emptying following water deprivation for 24, 48 and 72 h. After 72 h, gastric emptying of the water (39.4% retention) and rehydrating solution (49.2% retention) test meals was significantly retarded compared to the corresponding control groups (P < 0.05, Mann-Whitney test). The 72-h period of deprivation was used to study the recovery from dehydration, and water was supplied for 60 or 120 min after 67 h of deprivation. Body weight loss, hematocrit and plasma density tended to return to normal when water was offered for 120 min. In the animals supplied with water for 60 min, there was a recovery in the gastric emptying of water while the gastric emptying of the rehydrating solution was still retarded (53.1% retention; P < 0.02, Kruskal-Wallis test). In the group supplied with water for 120 min, the gastric emptying of the rehydrating (51.7% retention) and gluco-saline (46.0% retention) solutions tended to be retarded (P = 0.04, Kruskal-Wallis test). In this model of dehydration caused by water deprivation, with little alteration in the body electrolyte content, gastric emptying of the rehydrating solution was retarded after rehydration with water. We conclude that the mechanisms whereby receptors in the duodenal mucosa can modify gastric motility are altered during dehydration caused by water deprivation.
Highlights
The sense of thirst is a basic instinct in animals and constitutes an emergency mechanism for correcting liquid deficit [1]
The similar gastric retentions for the saline meal observed in the control and treated groups indicate the lack of involvement of mechanisms that regulate the gastric emptying of inert meals and the lack of influence of local control mechanisms in the gastrointestinal tract [11,21,22,23]
The lower gastric retentions observed for the saline and water test meals compared to the rehydrating solution reflected the influences of osmotic concentration and of the calorie content of the meals upon gastric emptying, as reported in other studies (2428)
Summary
The sense of thirst is a basic instinct in animals and constitutes an emergency mechanism for correcting liquid deficit [1]. The various systems involved in controlling thirst include the volume receptors located on the walls of the right and left atria, the renalangiotensin-aldosterone complex, antidiuretic hormone and the supra-optic nucleus of the anterior hypothalamus that contains neural cells specialized as osmosis receptors [2,3]. Studies investigating the oral replacement of liquids generally employ an intestinal water loss model because of the action of enteropathogens [8,9,10]. In such experiments, the replacement liquids usually have a water and ion composition similar to that of the model being used
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