Delayed or precocious hyperphagia after symmetrical or asymmetrical hypothalamic knife cuts in male and female weanling rats

Abstract Hypothalamic knife cuts were made in weanling rats. Following bilateral parasagittal knife cuts in either sex there was an initial 1– weeks of marginally excessive weight gain followed by 1–2 weeks of no gain or even weight loss followed finally by a sustained excessive weight gain. Following asymmetrical knife cuts (unilateral parasagittal cut + contralateral coronal cut) in either sex the obesity was also delayed. With these asymmetrical cuts, however, there was no initial excessive gain and subsequent loss. With both types of knife cuts the onset of the delayed excessive weight gain did not coincide with puberty. For a few rats with either type of cut there was no delay at all, the knife cut weanlings gaining excessively and continuously beginning from the day of surgery.