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

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.