PHAR 340 Lecture Notes - Lecture 3: Adrenergic Receptor, Macromolecule, Beta Blocker
18 Sep 2017
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Physiological antagonism, chemical antagonism, spare receptors (or receptor reserve), Physiological antagonism drugs have opposite effects via different receptor systems. So say we have histamine and epinephrine. Histamine binding to the histamine receptor results in a decrease in blood pressure. Epinephrine binding to the epinephrine receptor results in a increase in blood pressure. Chemical antagonism so chemical antagonism is not receptor mediated. This one drug binding to the second drug inactivates it! It is possible to have maximal response without full receptor occupancy. Essentially, there are spare receptors because not all receptors have to be. We can have spare receptors if there is a factor that limits the coupling of receptor occupancy to response . The spareness of receptors can be temporal : the receptor does not need to be occupied for the response to occur! Binds to promoter region of target gene. You can have the expression of the gene long after the drug.
