Ontogeny of oral behavior induced by tail pinch and electrical stimulation of the tail in rats

In sated adult rats, a mild tail pinch induces stimulation-bound eating. Experiment 1 showed that during preweaning development the response to tail pinch changes in (a) type, from mouth opening to licking, gnawing, and eating; (b) duration, from intermittent to stimulation-bound; (c) direction, from indiscriminate licking to focused on food pellets; and (3) intensity of stimulation required to elicit it, from high to low. These changes were also observed with electrical stimulation of the tail (Experiment 2). In Experiment 3, tail stimulation did not induced suckling, which suggests that it does not activate all the behavioral patterns available to the pup or potentiate its responsiveness to all environmental stimuli. Furthermore, in contrast to food deprivation, it did not induce licking of milk in 5-day-old pups. It seems, therefore, that tail stimulation reveals a mode of control over ingestive response patterns that is different from the one exerted by food deprivation.