What is Agonist?
[[File:Agonist full and partial.svg|thumb|320px|Agonists activating hypothetical receptors]] [[Image:Efficacy spectrum.png|right|thumb|320px|Efficacy spectrum of receptor ligands]] An '''agonist''' is a type of chemical known as a [[ligand]]. It binds to a [[Receptor (cell biology)|receptor]]. It activates (switches on) the receptor to produce a response. An agonist causes an action. There are also [[Receptor antagonist|antagonist]]s which block the action of the agonists, and there are [[inverse agonist]]s which cause an action opposite to that of the agonist. This is typical of the systems which [[wikt:regulate|regulate]] the body. Being able to [[control]] activity is the basis of [[homeostasis]]. == Types of agonists == [[Receptor (cell biology)|Receptors]] can be activated by either [[wikt:endogenous|endogenous]] or [[wikt:exogenous|exogenous]] agonists. Both types result in a biological response. Endogenous agonists include [[hormone]]s and [[neurotransmitter]]s. Exogenous agonists include [[medication|drugs]]. A substance which causes the same bodily responses, but does ''not'' bind to the same receptor is called a [[physiological]] agonist. == Examples == *The endogenous agonist for [[serotonin]] receptors is serotonin, and the endogenous agonist for [[dopamine]] receptors is dopamine.<ref>Goodman and Gilman's Manual of Pharmacology and Therapeutics. (11th edition, 2008). p14. {{ISBN|0-07-144343-6}}</ref> *[[Morphine]] is an exogenous agonist. It mimics the actions of [[endorphins]] at certain receptors in the [[central nervous system]].<ref>they are called μ-opioid receptors</ref> == References == {{reflist}} [[Category:Biochemistry]] [[Category:Physiology]]