Antagonists block receptors. Source: <a href="https://en.wikipedia.org/wiki/User:JWSchmidt" class="extiw" title="en:User:JWSchmidt">JWSchmidt</a> made this diagam with ClarisDraw.
<a href="//commons.wikimedia.org/wiki/User:%D0%94.%D0%98%D0%BB%D1%8C%D0%B8%D0%BD" title="User:Д.Ильин">Д.Ильин</a>: vectorization, translation
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span> based on <a href="//commons.wikimedia.org/wiki/File:Antagonist_2.png" title="File:Antagonist 2.png">File:Antagonist 2.png</a> by <a href="https://en.wikipedia.org/wiki/User:JWSchmidt" class="extiw" title="en:User:JWSchmidt">JWSchmidt</a>