The ontogeny of the onset of drinking and plasma osmotic pressure regulation

Body fluid deviations were examined in albino rats of both genders between 30 and 100 days of age during food deprivation. Plasma volume declined with age in free-feeding control groups. Hypovolemia induced by starvation (4 days) was more intense in 30- to 60-day-old animals than in 80- and 100-day groups. Plasma ismolality concentration of control groups indicated increases with age leveling off after 60 days. The initiation of drinking during fasting was accompanied by physiologically significant elevations in plasma osmolality over ad libitum concentrations at each age tested. In a second experiment, repeated exposure to short periods of food deprivation (2 days) during development resulted in the maintenance of intravascular fluid at control volumes. Longer periods (4 days) of deprivation did not result in savings of intravascular volume loss evidenced during starvation. These results suggest that rats compensate for hypovolemia induced by short-term starvation when provided experience with food restriction during development.

Section: Discussionsupporting

confidence: 95%

Section: Subjects and Proceduresmentioning

confidence: 72%

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confidence: 98%

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The ontogeny of plasma osmolality and intravascular volume maintenance during short‐term starvation in rats

Wright

Kenny

Reynolds

1977

“…Rat pups as young as 2 days old respond to cellular dehydration with a vigorous increase in mouthing and swallowing when water is infused directly into their mouths (Almi, 1973;Bruno, 1981;Wirth & Epstein, 1976). This demonstrates the precocial development of a physiological sensitivity to dehydration, and the capability of young pups to increase oromotor responding when water contacts the mouth.…”

Section: Introductionmentioning

confidence: 93%

Effects of prior experience with dehydration and water on the time course of dehydration‐induced drinking in weanling rats

Myers

Hall

2001

Although cellular dehydration increases oral responding and swallowing of orally infused water in rats as young as 2 days old, it is not until well after the time of weaning that dehydration stimulates immediate water-seeking and initiation of drinking in situations where the water source must be approached voluntarily. Recent work has shown that the goal-directed appetitive sequence for drinking-orienting, approaching, and initiating contact with water-matures much later than the more precocial oral licking and swallowing behaviors, and normally comes to be elicited by dehydration only after post-weaning experience with dry food. In the current experiments we evaluate some critical features of post-weaning experience with dehydration and drinking, and find that prior experience with initiating drinking while dehydrated, but not experience with dehydration nor water per se, alters the time course of water intake during a subsequent hydrational challenge. The effects of experience are manifested as an increased proportion of water consumed in the early portion of the test, rather than a general increase in total consumption. These findings are consistent with the interpretation that prior experience is necessary for the coordination of water-oriented appetitive behaviors that lead to the initiation and maintenance of drinking bouts, and provide further evidence for an associative learning account of the acquisition of dehydration-induced drinking.

“…These results suggest that, although intake is enhanced by both cellular and extracellular dehydration in very young pups, the behavioral changes responsible for the enhancement of intake after cellular dehydration are different from the behavioral changes resulting from extracellular dehydration. This dissociation of behavioral effects of dehydration in young pups demonstrates that intake measures alone may obscure subtle differences in behavior and argues for the utility of dissection of behavioral components in understand- Numerous studies have demonstrated a profound impact of hydrational state on ingestion in rat pups from very early ages (e.g., Adolph, 1957;Almli, 1973; …”

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confidence: 98%

Effects of physiological state on oral habituation in developing rats: Cellular and extracellular dehydration

Swithers

1995

Hydrational state has been demonstrated to influence intake of various solutions in young rat pups. For instance, both cellular and extracellular dehydration produce an enhancement of intake in pups tested at 6 days of age. However, the behavioral mechanisms that result in increased intake following manipulations of hydrational state have been less extensively studied. The impact of hydrational state on behavioral responsiveness in young rat pups was examined by assessing the pattern of responding to a series of repeated oral infusions of diet. Pups were tested at 6, 12, or 18 days of age following either acute cellular dehydration produced by injection of 1 M NaCl or acute extracellular dehydration produced by injection of 10% polyethylene glycol (PEG). Oral responsiveness to a series of 30 brief infusions of one of four taste solutions (water, 10% sucrose, 0.135 M NaCl, or 1 M NaCl) was measured. Each infusion lasted 3 s and there was 1 min between infusions. The pattern of oral responding to solutions was affected by the developmental age of the pup, the hydrational state of the pup, and the solution offered, with the largest effects of dehydration observed in the youngest animals. In all conditions except one, pups habituated to repeated infusions. The exception was the failure of extracellularly dehydrated 6-day-old pups to display habituation to oral infusions of sucrose. These results suggest that, although intake is enhanced by both cellular and extracellular dehydration in very young pups, the behavioral changes responsible for the enhancement of intake after cellular dehydration are different from the behavioral changes resulting from extracellular dehydration. This dissociation of behavioral effects of dehydration in young pups demonstrates that intake measures alone may obscure subtle differences in behavior and argues for the utility of dissection of behavioral components in understanding the neural and physiological control of behavior.