Our current textbooks teach us that the hypothalamus is an important integration site for adiposity and satiety signals, along with nutrients and information related to the rewarding properties of food (pleasant taste, good memories, good company). This of course was not always textbook information. Some of the earlier clues for this came from experiments by G.R. Hervey in the late 1950s. He was the first to use parabiosis to predict that a circulating factor existed that relays information on our body’s fat mass to the hypothalamus.
Parabiosis is an experimental paradigm where two animals are surgically joined in a way that they will develop a shared circulation. Factors circulating in either of the ‘parabionts’ could thus cross over into the circulatory system of the other.