Suckling: developmental indicator of genetic obesity in mice

The Bar Harbor obese-hyperglycemic mouse (ob/ob) characteristically develops its obese phenotype during the postweaning period, when access to food is unrestricted and its behavioral phenotype of hyperphagia appears. In the present study suckling behavior (viz., nipple attachment latencies and total suckling time) of lean and preobese mouse pups, derived from matings of heterozygous lean patients, was measured in either fed or fasted conditions from 6 to 21 days postpartum on anesthetized dams. Twenty-hour milk deprivation selectively channeled pup activity into suckling for both preobese and lean mice, although, in general, preobese mice nipple-attached sooner and suckled longer than leans. In particular, fed preobese pups suckled longer than fed lean pups from 18 days on, providing a preweaning behavioral indicant of a genetic tendency to obesity when environmental constraints on overeating are minimized.