Known to be produced in the gut and to trigger the brain to promote eating, a hormone known as ghrelin partly initiates the need to eat.

However, nobody exactly knows how ghrelin affects different parts of the brain.

BUT in a study that appeared online October 19 and in advance of publication in the December print issue of the Journal of Clinical Investigation, Yale University researchers demonstrated that in mice and rats, ghrelin triggers the same neurons as delicious food, sexual experience, and many recreational drugs (read: neurons that provide the sensation of pleasure and the expectation of reward).

These neurons produce dopamine and are located in a region of the brain known as the ventral tegmental area (VTA).

Tamas Horvath and colleagues showed that ghrelin bound its receptor on neurons of the VTA and triggered their production of dopamine.

Importantly, infusion of ghrelin into the VTA of rats increased their food intake. Conversely, infusion of inhibitors of the ghrelin receptor into the VTA of rats
decreased the amount they consumed after a 24-hour fast.

The said study identified the VTA as a site of action for ghrelin to induce food intake.

Because VTA is also triggered by many recreational drugs and is known to be where the expectation of reward is produced, the study authors suggest that ghrelin stimulation of the VTA might be involved in diseases of food abuse.

Source: Yale University Press Release and Science Daily