Table 1.

Classification of the various allosteric modulators and description of their effect.

Allosteric Modulator	Description of the Effect
PAM (positive allosteric modulator)	Increases orthosteric ligand affinity and/or efficacy
NAM (negative allosteric modulator)	Decreases orthosteric ligand affinity and/or efficacy
SAM (silent allosteric modulator)	Does not affect orthosteric ligand activity, but prevents other modulators from binding to the allosteric site, thus inhibiting their modulation
PAM agonist	Works like PAM, but also functions as an agonist with and without the orthosteric ligand it modulates
PAM antagonist	Works like PAM, but also functions as an antagonist and lowers the efficacy of the orthosteric ligand
NAM agonist	Works like NAM, but also as an agonist with and without the orthosteric ligand it modulates
NAM inverse agonist	Works like NAM, but also functions as an inverse agonist without the orthosteric ligand it modulates