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Pharmacology Unit 1 Chapter 1

Terms in this set (43)

There are four receptor families: (1) kinase-linked receptors, (2) ligand-gated ion channels, (3) G protein-coupled receptor systems, and (4) nuclear receptors. The term ligand-binding domain is the site on the receptor at which drugs bind.

• Kinase-linked receptors. The ligand-binding domain for drug binding is on the cell surface. The drug activates the enzyme (inside the cell), and a response is initiated.

• Ligand-gated ion channels. The channel spans the cell membrane and, with this type of receptor, the channel opens, allowing for the flow of ions into and out of the cells. The ions are primarily sodium and calcium.

• G protein-coupled receptor systems. There are three components to this receptor response: (1) the receptor, (2) the G protein that binds with guanosine triphosphate (GTP), and (3) the effector that is either an enzyme or an ion channel. The system works as follows:

drug→activatesreceptors→activatesG protein→activateseffect.

• Nuclear receptors. Found in the cell nucleus (not on the surface) of the cell membrane. Activation of receptors through the transcription factors is prolonged. With the first three receptor groups, activation of the receptors is rapid.

Drugs act through receptors by binding to the receptor to produce (initiate) a response or to block (prevent) a response. The activity of many drugs is determined by the ability of the drug to bind to a specific receptor. The better the drug fits at the receptor site, the more biologically active the drug is. It is similar to the fit of the right key in a lock. Figure 1-5 illustrates a drug binding to a receptor.