Lecture 20 - Opioids Flashcards
What is the difference between NTs and neuropeptides (peptide NTs)?
-different from NT –> they are peptides
-peptides are short chains of amino acids [proteins] (9-20 amino acids long)
How does the release of neuropeptides work? What does it bind to?
-neuropeptides can often be co-released with classical NTs
-can also be released by their own neurons (e.g., oxytocin)
-typically bind to GPCRs
-peptides can also act as hormones when released into the circulatory system
What is the synthesis of neuropeptides like?
-peptides are NOT synthesized in the terminal; synthesized in the soma
-created from amino acids
-often originate from cleaved proteins
-transported to the terminal once synthesized
How does the release of neuropeptides happen?
-stored in large dense vesicles
-these vesicles are not readily released
-only released during times of increased neuronal firing
-synaptic vesicles empty their contents under normal firing, but LDCV release only during higher firing rates
What is signal termination like in neuropeptides?
-since they are peptides, they are slowly degraded by proteases
-long-lasting signal
How many neuropeptides are there? What are 3 examples?
-there are over 100 neuropeptides identified so far
1. opioids (involved in pain regulation)
2. CRH (involved in stress)
3. oxytocin (involved in pair-bonding)
What is the difference between opioids and endogenous opioids?
-labelled because of the effects of opiates (e.g., opium, heroin, morphine)
-endogenous opioids are produced by the body; they act on opioid receptors which are all GPCRs
What are the 3 primary opioid receptors?
-Mu (MOR) –> responds to most of opiates and synthetic opioids
-Delta (DOR)
-Kappa (KOR)
What are the 2 other opioid receptors (not important)?
-Nociceptin (NOP)
-Zeta (OGFr)
What are some endogenous opioids?
-enkephalin (Met and Leu)
-POMC
-prodynorphin
-endomorphin
-nociceptin
What are the characteristics of enkephalin?
-have their own neurons CNS and PNS
What are the characteristics of POMC?
-it is the precursor to B-endorphin
-own neurons in the pituitary and hypothalamus
-most potent endogenous opioid
What are the characteristics of prodynorphin?
-precursor to dynorphin A and dynorphin B
-own neurons bind more specifically to KOR receptor
What are the characteristics of endomorphin?
-CNS and PNS
-MOR receptor
What are the characteristics of nociceptin?
-it is its own receptor
-not that important for pain relief
