FIGURE 4.

(A) Structure of galanin in three species. Galanin is composed of 29 amino acids in most species, except humans (30 amino acids). Note conservation of N-terminal portion. (B) Signaling pathways of galanin receptor subtypes. Galanin, via GalR1 and GalR3, opens potassium channels leading to membrane hyperpolarization. Galanin can via GalR2 activate PLC resulting in generation of IP3, release of Ca²⁺ from the smooth endoplasmic reticulum, opening of Ca²⁺ channels and eventually transmitter release. AC, adenylate cyclase; cAMP, 3′, 5′-cyclic adenosine monophosphate; DAG, diacylglycerol; K⁺, G-protein-regulated inwardly rectifying potassium channel; sER, smooth endoplasmic reticulum; IP₃, inositol triphosphate; PIP₂, phosphatidylinositol bisphosphate; PKC, protein kinase C; PLC, phospholipase C. Modified from Iismaa and Shine (1999) and Lang et al. (2015). Drawing by Mattias Karlén.