Pain Flashcards
difference between hyperalgesia and allodynia?
Hyperalgeisia – a painful stimulus becomes even more painful
Allodynia – a normally not-painful stimulus becomes painful
2 reasons for pain hypersensitivity
Inflammatory Pain – caused by inflammatory mediators (ATP, H+, Capsaicin, Prostaglandins) at site of injury
Neuropathic pain – caused by lesion or disease affecting the somatosensory system
causes of neuropathic pain?
diabetes, post herpetic neuralgia (VZV), cancer
causes of inflammatory pain?
trauma, Sx, arthritis
what is peripheral sensitization?
- sensitizes c-fibers and A-delta fibres, lower threshold for activation
what is central sensitization?
plasticity of DRG neuron which amplify pain signals from c-fibres and a-delta fibres
NSAIDs (aspirin, ibuprofen
COX-inhibitor
Morphine
Mu-opioid receptor agonist
Gabapentin
Calcium channel blocker
Carbamazepine
Sodium channel blocker
Ketamine
NMDAR blocker
tricyclic antidepressants
NOR/5HT uptake inhibitor – via descending control of pain (locus corelus/raphe nuclei)
triptans
5-HT1b/d receptor agonist
migraine
triptans
inflammatory pain
NSAIDs (aspirin, ibuprofen
Morphine
neuropathic pain
Gabapentin
Carbamazepine
Ketamine***
Tricyclic antidepressants
what receptor do all opioid drugs act on?
Mu opioid receptor
Codeine
Mu opioid partial agonist
Fentanyl
ynthetic opioid agonist
what is the antidote for opioid overdose?
naloxone
what fibres have opioid receptors?
c-fibres and A-delta
what sensations are not affected by opioids?
a-beta fibres:
fine and discriminative touch
what is the effect of opioids on presynaptic receptors?
on presynaptic opioid receptors (75%) to inhibit release of glutamate and other peptide inflammatory mediators
(via opening K+ channel to reduce Ca2+ influx to reduce NT release),
what is the effect of opioid receptors on postsynaptic receptors?
post-synaptic receptors (25%) to inhibit neuronal activity
via opening K+ channel to cause hyperpolarisation
