What are spare receptors?
A certain number of receptors are “spare.” Spare receptors are receptors that exist in excess of those required to produce a full effect. Dose-response relationships are a common way to portray data in both basic and clinical science. The dose a which 50% of the maximal effect is observed is referred to as the ED50.
What is a spare receptor agonist?
SPARE RECEPTORS •RECEPTORS MAY BE CONSIDERED SPARE WHEN THE MAXIMAL RESPONSE IS ELICITED BY AN AGONIST AT A CONCENTRATION THAT DOES NOT PRODUCE FULL OCCUPANCY OF THE AVAILABLE RECEPTORS.
Do partial agonists have spare receptors?
A partial agonist must have a different nonlinear relation- ship between contraction and receptor occupation than does a full agonist. A partial agonist appears to have more spare receptors than a full agonist.
Where are spare receptors sequestered?
cytosol
Spare receptors are sequestered in the cytosol.
What are the 4 types of receptors?
Broadly, sensory receptors respond to one of four primary stimuli:
- Chemicals (chemoreceptors)
- Temperature (thermoreceptors)
- Pressure (mechanoreceptors)
- Light (photoreceptors)
What are irreversible drugs?
An irreversible antagonist is a type of antagonist that binds permanently to a receptor, either by forming a covalent bond to the active site, or alternatively just by binding so tightly that the rate of dissociation is effectively zero at relevant time scales.
What is a full agonist drug?
An agonist is a drug that activates certain receptors in the brain. Full agonist opioids activate the opioid receptors in the brain fully resulting in the full opioid effect. Examples of full agonists are heroin, oxycodone, methadone, hydrocodone, morphine, opium and others.
What is drug affinity?
Affinity can be defined as the extent or fraction to which a drug binds to receptors at any given drug concentration or the firmness with which the drug binds to the receptor. Potency is a measure of necessary amount of the drug to produce an effect of a given magnitude.
Which drug is a partial agonist?
Partial agonist opioids activate the opioid receptors in the brain, but to a much lesser degree than a full agonist. Buprenorphine is an example of a partial agonist. An antagonist is a drug that blocks opioids by attaching to the opioid receptors without activating them.
Can a partial agonist be more potent than a full agonist?
A partial agonist has lower efficacy than a full agonist. It produces sub-maximal activation even when occupying the total receptor population, therefore cannot produce the maximal response, irrespective of the concentration applied.
What is a partial agonist drug?
Partial agonists are ligands that bind to the agonist recognition site but trigger a response that is lower than that of a full agonist at the receptor.
What are receptors give example?
A receptor is a cell present in the sense organs that is sensitive to specific stimuli. Example: The eyes have light receptors which can detect light and the ears have sound receptors which can detect sound.
What is the difference between EC50 and spare receptors?
EC50 is the concentration at which an agonist produces half its maximal effect. I.e. the potency of the drug. The smaller the EC50, the greater the drug potency The concentration of an agonist producing a maximum response may not result in occupancy of all the receptors. These receptors are said to be “spare”.
How are spare receptors related to the potency of an agonist?
• BECAUSE THE PRESENCE OF SPARE RECEPTORS INCREASES THE POTENCY OF AN AGONIST. • TISSUES WITH A HIGH PROPORTION OF SPARE RECEPTORS WILL RESPOND TO AGONISTS AT LOWER CONCENTRATIONS, EVEN IF THEY CONTAIN EXACTLY THE SAME RECEPTOR SUBTYPES. 22. •THIS MEANS THAT IF AN AGONIST HAS A DIFFERENT EC50 IN TWO DIFFERENT TISSUES.
What happens when there are no spare receptors?
It still produces a maximal effect as spare receptors are still available. Curve C shows the largest concentration of antagonist where the available receptors are no longer spare, instead, they are just sufficient to mediate an undiminished maximal response, but with higher doses of agonist. Emergency Physician.
How are spare receptors related to dose response curve?
I.e. may be longer than the time spent bound to the receptor. This results in “spare receptors” Draw a dose response curve for an irreversible antagonist as the spare receptors become occupied. The curves shift to the right as the spare receptors become occupied at increasing doses of antagonist. Curve A represents pure agonist.
