Essential Pharmacology Flashcards
What are the four types of membrane receptor?
- Ionotropic receptor
- Receptor with intrinsic enzyme activity
- Receptor that directly alters enzyme activity
- 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.
What is the difference between an agonistic drug and an antagonistic drug?
Both agonists and antagonists bind to the receptor.
When an agonist binds, it brings about the ‘normal’ response of the receptor.
When an antagonist binds, it blocks receptor activity.
