Opioids Flashcards
What are the key pharmacological effects of mu receptors?
Analgesia
Respiratory depression
Reward
***Constipation also mu mediated
What are key pharmacological effects of delta receptors?
Analgesia
Affective disorder (Anxiety)
**Also Seizures
What are key pharmacological effects of kappa receptors?
Analgesia
Dysphoria
Psychomimetic effect
***Also Diuresis
What are the endogenous opioid peptides that act at mu receptors?
B-endorphin
Endomorphin 1 and 2
What are the endogenous opioid peptides that act at delta receptors?
Met-Enkephalin
Leu-Enkephalin
What are the endogenous opioid peptides that act at kappa receptors?
Dynorphin peptides
Mu receptors are how many amino acids?
398
Delta receptors are how many amino acids?
372
Kappa receptors are how many amino acids?
380
Where do antagonists bind?
Extracellular tail
Where do agonists bind?
Extracellular domain
All opioid receptors are coupled to what proteins?
Gi and Go
What is the result of opioid receptor binding?
INHIBITION. ALWAYS.
Activation of opioid receptors induces G-proteins to:
Inhibit adenylyl cyclase activity (Gi) - decreases cAMP
Activate receptor-operated K+ channels (Gi) - Increases K+ leaving the cell, hyperpolarizes it, less action potentials
Suppress voltage-gated Ca2+ currents (Go) - influx of Calcium also hyperpolarizes
Analgesia is the result of what receptor(s) in what area(s)?
Mu, Kappa, Delta
Spinal cord, PAG, Thalamus, Cortex, Limbic system
Respiratory depression is the result of what receptor(s) in what area(s)?
Mu
Medulla
Reward is the result of what receptor(s) in what area(s)?
Mu and delta in the striatum increase reward
Kappa in striatum decrease reward
Pupil constriction is the result of what receptor(s) in what area(s)?
Mu and Kappa receptors
Edinger-Westphal nucleus
Cough relief is the result of what receptor(s)?
Dextramorphan receptors! Not opioid receptors, but opioids can bind to it
Nauseant and emetic effects are due to what receptor(s) in what area(s)?
Mu
Chemoreceptor Trigger Zone
Sedation is due to what receptor(s) in what area(s)?
Mu and Kappa
Inhibition of the locus ceruleus
Describe the pain pathway
Dorsal root ganglia (Delta and Kappa, few Mu)
Substantia gelatinosa - incoming pain signals (hyperpolarize these cells to decrease pain signals)
Spinal cord ventral horn (Dynorphin interneurons synapse on spinothalamic axons)
Thalamus (Spinothalamic neurons connect cortex to limbic system, also have input to PAG and RAS)
Descending pathways from PAG, Locus ceruleus (NE) and Raphe nuclei (5HT) - serve to inhibit incoming pain activity in primary afferent arteriole
How can Kappa agonists be used against addiction? Why aren’t they used?
There are kappa receptors on the PRESYNAPTIC TERMINAL (test Q!) of dopamine receptors to inhibit release. So you have inhibition of dopamine release and you lose inhibition of inhibiting dopamine release.
This leads to dysphoria, which can lead to depression. Patients would rather be in pain.
What effects do opioids have on the CV system?
Nothing directly
Histamine indirectly causes vasodilation and CO2 blunting reflex of vasoconstriction
What effects do opioids have on bronchial smooth muscle?
Constriction bc histamine
Contraindication in asthmatics