Drug Receptors Flashcards
Bind substances called ligands (drugs or endogenous substances)
Receptors
Anticancer drugs; blocks normal metabolic pathways in the body
Antimetabolites
Pharmacological doses of vitamins; supplementing normal metabolized substances
Metabolites
Chemical reactions; a basic substance that reduces acidity
Antacids
Binds to heavy metals to prevent them from interacting with the body
Chelating Agents
Component that binds the drug and determines the action of the drug or endogenous compound
receptor
The _______ component of the cell surface receptor binds drug or endogenous compound
Extracellular
These type of receptors usually bind ligands that are water soluble
Cell surface receptors
These type of receptors bind ligands that are able to pass through the lipid-bilyare cell membrane
Intracellular receptors
The _____ component of the cell surface receptor mediates the action
Intracellular
Name 3 different linked cell membrane receptors
- Ion channels
- Enzymes
- Regulatory G-proteins
________-linked receptors are ion channels; ligand binding can open (or close) the ion channel and depolarize or polarize the cell membrane
Ion channel
Receptor at the neuromuscular junction
Nicotinic
_______-linked receptors where the binding of ligand to extracellular domain activates the enzyme component of the receptor
Enzyme
_______- linked receptors affect cells through intermediate regulatory proteins; these regulatory proteins are activated by binding to guanine nucleotides
G-protein
What are 4 common causes in alterations in the G-protein in its synthesis and function?
- Alcoholism
- Diabetes mellitus
- Heart failure
- Certain tumors
What are the ligands for intracellular receptors and their characteristics?
steroids and steroid-like substances; small, hydrophobic and lipophilic
Measure of attraction between drug and receptor
Affinity
Low concentration of drug needed to bind to unoccupied receptors
High affinity
High drug concentration needed to bind to low unoccupied receptors
Low affinity
A drug affects only one type of cell or tissue and produces a specific physiological response
Selective
How specific a drug is for one type of receptor
Drug selectivity
____________ curve related to the number of receptors which have bound the drug; percent is related to percent occupancy of receptors but is not an absolute correlation
Dose-response
The ability of a drug to have an effect on a cell
Efficacy
Remember: efficacy does NOT necessarily relate to the affinity of a drug
Binds to a receptor and has an effect; has affinity; has efficacy
Agonist
Binds to a receptor and does not have an effect; blocks effects of normal chemicals; has affinity; does not have efficacy
Antagonist
Bind to the same site on the receptor as the agonist, but have no efficacy
Competitive Antagonist
Bind to the receptor at a site other than where the agonist binds; binds to a receptor and stays bound, which essentially inactivates the receptor; long-lasting effects
Noncompetitive Antagonist
Act as agonists, but do not produce a maximal response, even if all receptors are binding the drug; appear to bind but not to fully activate the receptor
Partial agonists
Increased receptor stimulation by agonists can result in (increased/decreased) sensitivity or a (increase/decrease) in receptor numbers
Decreased; decrease
Decreased receptor stimulation [lack of agonist or treatment with antagonist] can result in (increased/decreased) sensitivity or a (increase/decrease) in receptor numbers
Increased; increase
The response to overstimulation of receptors; due to prolonged stimulation of receptors by agonist or chemical modification of receptor proteins; return to normal state may occur within minutes after agonist is removed
Desnesitization
Slower, more prolonged response compared to desensitization; number of receptors is decreased due to increased receptor removal or decreased receptor synthesis; can last several days
Receptor down-regulation
Desensitization and down-regulation are examples of ______ feedback system
Negative
________ may be the mechanism for the action of several drug categories such as antidepressants
Down-regulation
Two responses to decreased activation of receptors
- Supersensitivity
2. Receptor up-regulation
Increase in sensitivity of receptors; fairly rapid and transient response
Supersensitivity
Slower and longer lasting increase in number of receptors; making new receptors
Receptor up-regulation
In peripheral nervous system when a nerve is severed; a reversible condition where axons can grow back and NMJ is formed
Denervation
When individual muscle fibers spontaneously depolarize and contract in a non-coordinated function due to loss of innervation to those muscle cells; happens in polio as well
Fibrillations
When a nerve is severed, the total number of ACh receptors on the muscle fiber _______; this happens _____ in denervation
increases; first
In a denerved muscle fiber, ACh receptors are found __________; this happens ______ in denervation
Over the whole surface; second
True or false:
Similar changes that occur in the end plate of the NMJ that has been denerved also happens with long-term antagonist treatment
True; such as with beta-blockers
