AgRP neuron

AgRP neurons are the accelerator pedal of hunger. When the body senses it is running low on fuel, these neurons fire intensely and generate a powerful, almost irresistible urge to find and eat food. In animal experiments, switching them on instantly drives ravenous eating even in a full, satisfied animal.

These arcuate-nucleus neurons are the counterpart to POMC neurons. They release agouti-related peptide (AgRP), which blocks the melanocortin-4 receptor and so cancels out the “stop eating” signal from POMC neurons. They also release neuropeptide Y and the inhibitory transmitter GABA, all of which push hunger upward. AgRP neurons are activated by ghrelin and by falling levels of leptin and insulin, making them especially active during fasting.

Because AgRP neurons defend so vigorously against energy deficit, they are a major reason why lost weight tends to come back. Their activity rises during dieting and signals genuine, gnawing hunger — a biological drive, not merely a lack of discipline.