Figure 8.

Overview of 7TM receptors involved in the control of ghrelin secretion directly at the ghrelin cell level. (A) Overview of expression of 7TM receptors involved in control of hormone secretion in FACS-separated ghrelin-hrGFP positive cells (Y-axis) versus expression in ghelin-hrGFP negative cells (X-axis) isolated from gastric mucosa (see Figure 1 and text for details). Receptors stimulating ghrelin secretion are marked in green, receptors inhibiting ghrelin release are marked in red, receptors functionally tested without effect on ghrelin secretion are marked in black and receptors not tested functionally are marked in gray. (B) Schematic overview of the 7TM receptors judged to be either stimulating (in green to the right) or inhibiting (red or orange to the left and top) ghrelin secretion directly on the ghrelin cell. The main signaling pathway (Gα_s or Gα_i) employed by each of the receptors in the ghrelin cell is indicated inside the receptor in black. No Gα_q-coupled receptor effectively stimulating ghrelin secretion was identified but some receptors are known to be able to signal through Gα_q and stimulate secretion in other cell systems (indicated in orange). Main endogenous ligands are indicated for each receptor.