Flashcards in Essential Pharmacology Deck (12):
What are the four types of membrane receptor?
1. Ionotropic receptor
2. Receptor with intrinsic enzyme activity
3. Receptor that directly alters enzyme activity
4. G-Protein coupled receptor
What Is meant by an ionotropic receptor?
A receptor which functions as an ion channel. They have fast IPSPs and EPSPs.
What is the difference between a receptor with intrinsic enzyme activity and a receptor that alters enzyme activity?
In the case of a receptor with intrinsic enzyme activity, it is the receptor itself that functions as the enzyme.
This is not the case with receptors that alter enzyme activity.
How do G-Protein coupled receptors operate?
-Neurotransmitter stimulates receptor coupled to G protein.
-Alpha subunit of G protein is stimulated to go off and regulate the activity of the first enzyme (e.g. adenylyl cyclase)
-First enzyme releases second messenger (cAMP)
-Second messenger (cAMP) goes on to regulate activity of second enzyme (PKA)
In G Protein coupled receptors, Calcium ions can be used as the second receptor. From what sources can these calcium ions be obtained?
-From internal sources (ER.) Their release is stimulated by presence of calcium ions or IP3- ions.
-From external stores, which have entered the cell via voltage or ligand gated ion channels.
NB: Calcium presence in the cell can be maintained by inhibiting calcium movement out of cell.
What is meant by the affinity of a drug?
The affinity of a drug is the attraction between that drug and the receptor.
What is meant by the EC50 of a drug?
The log[drug] which will produce half the maximum response.
What does a low EC50 indicate?
High affinity between drug and receptor
What does a high EC50 indicate?
Low affinity between drug and receptor
On a graph of log[drug] against degree of response, there are two sigmoidal curves, one showing the response of drug A and the other showing the response of drug B. The curve for drug A sits to the right of that for drug B. How do their affinities compare?
Drug B has a higher affinity than drug A.
What is meant by the efficacy of a drug?
The degree to which a drug activates receptors to produce the desired response.