An agonist refers to any molecule that triggers the effects of a receptor. After an agonist binds to a receptor, the receptor should trigger its effects downstream. For example, if a drug binds to a G Protein-Coupled Receptor, then an agonist that binds to this GPCR should cause the GPCR to release its G Protein. A single receptor can have multiple agonists because there are multiple molecules with the same structure that could trigger its effects. In addition, some drugs may be considered to be a partial agonist, which means that it only triggers a portion of the receptor’s total activity. There are also some molecules that could be considered an inverse agonist, which means that they bind to the receptor and trigger the opposite effect when compared to a traditional agonist. Agonists include neurotransmitters that occur naturally in the brain as well as recreational or prescription substances that people administer themselves. Agonists can also be found in substances that occur naturally in nature.