Opioid Receptors Flashcards
What is codeine?
It is a morphine pro-drug
Are opioid receptors agonists or antagonist?
Agonists
What is given to reverse opioid overdose?
What class of drug is therefore is this?
Which opioid receptor does naloxone have highest affinity to? What about least?
Naloxone
Opioid receptor antagonist
Highest = M Medium = D Lowest = K
What are the 3 main types of opioid receptor?
On which receptor do most drugs act?
M (Mor) (most act here)
D (Dor) (few act here)
K (Kor) (some act here)
What type of receptor are opioid receptors?
GPCR
What are the main neurotransmitters involved in the nociceptive pathway of pain?
What receptor does each one bind to post-synaptically?
Glutamate = NMDA and AMPA
Substance P = NK-1
Where are opioid receptors found with respect to the synapse?
Both pre- and post-synaptically
What do opioid receptors do when activated pre-synaptically?
Closing of voltage gated calcium channels
Reduced calcium influx
Prevents neurotransmitter release (glutamate, substance P)
What do opioid receptors do when activated post-synaptically?
Which opioid receptor does not do this?
Hyperpolarises post-synaptic nerve by opening voltage gated K channels
D opioid receipts DO NOT do this
What is a side effect of opioids and why?
Constipation
Due to opioid receptors being found in the parasympathetic nerve supply of the GI tract, which usually stimulates the tract (therefore when blocked constipation can occur)
Which GPCR subunit do opioid receptors work on and what do they cause in terms of second messengers signalling?
Gi
Inhibit adenylyl cyclase = decreases cAMP levels
What happens when people stop opioids?
What does this mean in terms of how they tend to feel?
The body will have produces increased levels of adenylyl cyclase when on the opioid
The withdrawal symptoms felt therefore are the opposite of the opioid effects
