Delayed hyperphagia and increased body length after hypothalamic knife cuts in weanling rats.

Four-week-old female rats received parasagittal hypothalamic knife cuts. Polydipsia began right surgery, but hyperphagia, obesity, and excessive nose-anal length did not begin until after the rats were 7-8 wk. old. The delayed onset appears to await some maturational event that is required for the expression of hypothalamic obesity. It appears likely that puberty is the critical maturational event.