The ontogeny of feeding in rats: IV. Taste development as measured by intake and behavioral responses to oral infusions of sucrose and quinine.

Infusions of sucrose or quinine were delivered through cannulas implanted in rat pup's mouths. Intake was measured, and behavioral responses were scored. Responsiveness to sweet and bitter tastes emerged over the first 2 wk of postnatal life. Pups showed discrimination between water and sucrose in their mouthing behavior and general activity from 3 days of age, but in their intake only from 6 days of age. Discrimination between water and quinine was not shown until 9 days of age in either behavior or intake. Even then, the stereotypic aversion reactions (paw treading, chin scraping) that characterize the adult response to quinine were not apparent until 12 days. By 15 days of age, preferences for sucrose and aversions to quinine were robust. They resembled those of adult rats and did not depend on previous experience with either solution.