Agonists and Antagonists Flashcards
What effect(s) would you expect a muscarinic antagonist such as atropine to have?
Dilate the bronchi and reduce salivation
Salmeterol acta at a lower dose than salbutamol, therefore it is said to be more … what?
Potent
Prolonged treatment with an agonist can lead to … what?
Desensitisation
What type of molecules are receptors?
Proteins
Name the two types of receptors for the neurotransmitter acetylcholine
Muscarinic and nicotinic
What term would you use to describe a drug that activates a receptor protein to cause intracellular signalling?
Agonist
Name the four broad structural types of receptors.
Ligand-gated ion channel, G protein coupled, tyrosine kinase and cytoplasmic/nuclear.
Which type of receptor is best suited to very fast responses?
Ligand-gated ion channel receptor
Drugs working at which type of receptor are likely to take a day or more to generate a response?
cytoplasmic/nuclear
True or False: in a drug-receptor complex, the receptor alters the substrate site of the drug
False
Naloxone can be described as what in regards to morphine?
Competitive antagonist
An increase in the concentration of mepyramine during an allergic response would decrease the action of what agonist at which receptors?
Histamine at the H1 receptors
What response would be displayed if Naloxone was given in the absence of opiate use?
Nothing
Name the two receptor subtypes
Voluntary and smooth muscle
What action does atracurium have on nicotinic receptors, and what effect does this have on the body?
Competitive antagonist, paralysis
Atropine is a selective antagonist for what receptor subtype?
Muscarinic
What effect does acetylcholine (a neurotransmitter) have on muscarinic receptors in smooth muscle?
Salivation and constriction of bronchi
What effect does acetylcholine (a neurotransmitter) have on nicotinic receptors in voluntary muscle?
Contraction and movement
True or False: salbutamol and adrenaline are chemically similar
True
Salbutamol’s desired effect is on what receptors in smooth muscle?
Beta-2 adrenergic receptors
What unintended effect can Salbutamol have due to binding to another receptor site?
Tachycardia and arrhythmias due to binding in the atrial beta-2 adrenergic receptors
What is cyclic adenosine monophosphate (cAMP)?
Intracellular messenger
How would you describe an antagonist that binds at a different site to an agonist?
Non-competitive antagonist
What are the three subunits of G proteins?
Alpha, beta and gamma
Drug agonists are made to imitate the action of ligands, name some ligands of G-protein coupled receptors.
Ions, amino acids, neurotransmitters, peptides, proteins and hormones.
Ligand gated ion channels are important in what types of cells, and why?
Nerve and muscle cells, because they rely on changes in electrical energy caused by the movement of ions
Examples of ligand gated channel receptors include
Acetylcholine, GABA, glycine, 5HT3
Insulin interacts with what type of receptor?
Enzyme linked receptor
Cytoplasmic/nuclear receptor ligands must be able to cross the cell membrane because the receptors lie inside the cell, these ligands are mainly from what family of proteins?
Hormones
40% of medicines interact with what type of receptor?
G-protein coupled
Gap junctions between cells provide quick communication and transfer of small molecules between adjacent cells, this is important where?
In electrical activity such as between cardiac myocytes
Both antagonists and agonists have affinity for a receptor but only agonists have efficacy. What is affinity and efficacy?
Affinity- how tightly the drug binds to the receptor
Efficacy- activates and stimulates a response
What is potency?
The concentration required to give half the maximum response
What is an allosteric antagonist?
Binds to the allosteric site (different to main receptor site)
What is IC50 in relation to antagonists?
Inhibitory concentration for 50% inhibition/potency
