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. Author manuscript; available in PMC: 2018 Sep 15.
Published in final edited form as: Neuropharmacology. 2017 May 17;124:3–12. doi: 10.1016/j.neuropharm.2017.05.018

Fig. 2. Schematic depiction of allosteric modulation of a GPCR.

Fig. 2

Classically, an orthosteric agonist (O) binds to the GPCR and facilitates signaling through several G protein (only one shown for clarity) and non-G protein pathways (G and B, respectively). The relative strength of signaling often varies among signaling pathways (functional selectivity).An allosteric modulator (A) will bind to the receptor at a site independent from the orthosteric site. The allosteric modulator may positively (PAM) or negatively (NAM) influence orthosteric ligand binding (α) and/or signaling pathways (β), as depicted by thick and thin arrows and discussed in the text.