Novel heteromeric receptors: ghrelin receptors and dopamine receptors working together

We have made the remarkable discovery that ghrelin receptors are involved in control of digestive function not through an action of ghrelin, but through the action of dopamine.

Ghrelin is a naturally occurring hormone that had been thought to be a transmitter in the central nervous system (CNS), and some years ago we discovered that ghrelin is a powerful CNS-acting stimulant of defecation in animal models and humans. A striking conclusion from our discoveries is that the strong stimulation of defecation by ghrelin agonists is independent of ghrelin, which we discovered to be absent from the CNS.  Our data indicates that the physiological activation of the ghrelin receptor, GHSR, is through dopaminergic transmission acting at a combined GHSR / dopamine 2 receptor (DRD2).