Clinical Significane Of Receptor Regulation Flashcards
What can result from excessive agonist exposure?
Tachyphylaxis
If there is agonist deprivation or high concentration, the cell becomes…
Suprasensitive
What 4 factors can cause changes in tachyphylaxis/supra sensitivity?
Change in receptor number, change in receptor to second messenger signalling, change in second messenger availability, change in cell responsiveness.
What are u-opioid receptors associated with?
Pain relief, analgesia, sedation and euphoria.
What happens during repeated opioid use?
There is down regulation and so tachyphylaxis occurs. More opioid is required for the same response.
In patients taking opioids, what happens when concentration starts to fall?
As the opioid leaves the receptor, this gives a feeling of pain. This is withdrawal.
Why is it important that we monitor drug use closely?
Every patient is different and will have a different threshold at which ADRs occur.
Does phaeochromocytoma cause tachyphylaxis or supra sensitivity?
This causes neither. The catecholamine secretion is intermittent and so there is not constant filling of the receptors.
What happens if a patient with Angina stops taking their B blockers?
Due to up regulation, if a patient has been taking B blockers then they will have an increased number of B receptors. This means if they suddenly stop taking them then there will be a massive sympathetic innervation of the heart leading to increased heart workload and ischaemia.
What is important about age-dependant catecholamine sensitivity?
As age increases, there is decreased endogenous catecholamines. This means that the HR is less responsive to exogenous catecholamines and so it is possible to give too much drug because they will have excess pharmacological efficacy.
