Peripheral amylin activates circumventricular organs expressing calcitonin receptor a/b subtypes and receptor-activity modifying proteins in the rat.

The pancreatic hormone amylin (AMY) and the AMY-receptor-agonist salmon-calcitonin (sCT) reduce short-term food-intake after binding to the area postrema (AP), a circumventricular organ (CVO) lacking blood-brain-barrier characteristics. AMY has also been proposed to induce drinking via another CVO, the subfornical organ (SFO). In cellular systems, AMY-binding is generated by interaction of calcitonin-receptor a/b (CT((a))/CT((b))) with receptor-activity modifying proteins (RAMPs). By using in situ hybridization, the codistribution of CT((a))/CT((b)) with RAMP1-3 and c-fos was mapped in CVOs of rats. AMY and sCT induced c-fos within the SFO which contained CT((a)) and/or CT((b)) and RAMP1/2 mRNA. AMY and sCT also activated AP neurons, which express the CT((a)), but not the CT((b)), receptor and RAMP2/3 mRNA. These data emphasize the important role of these structures as primary targets for circulating AMY.