Agrp, a novel gene implicated in the control of feeding.

Rapid progress has recently been made to characterise a new pathway involved in the control of feeding behaviour, referred to as the melanocortinergic pathway. Studies of the obese phenotype of the yellow mouse mutant (Ay) suggested the existence of this feeding circuit for some time, but the precise molecular and biochemical regulation was unclear. Through pharmacological and genetic approaches, specific melanocortin receptors expressed within the brain are now known to play a pivotal role. Since receptor agonists decrease food intake, and blocking receptor activity (through antagonists or mutations) increases food intake, this pathway is thought to provide a tonic inhibitory effect on food consumption. A unique feature of this pathway seems to be the regulation of receptor activity by an endogenous protein antagonist, agouti-related protein (AGRP). The molecular characterisation and biochemical activity of this gene suggest that it plays a role in the regulation of feeding behaviour.