Pain Flashcards
(29 cards)
Define pain
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.
What makes pain chronic?
Pain that outlives acute pains warning role - 3-4 months
Epidemiology of chronic pain
1 in 5 people. On average sufferers live with chronic pain for 7 years.
Epiphatic tranmission
Between peripheral fibres and cell bodies in the DRG, increasing excitability.
Woolf (1980s)
Decerbrate rat model to measure nociception through spinal reflexes. Greater response to the same stimuli could be elicited after an injury to the contralateral paw, cannot be accounted for with peripheral sensitisation.
Torebjork (1992)
Electrical interneural stimulation of single Ab mechanoreceptive dibres could elicit non-painful sensation before capsaicin injection, could later produce pain if fibres lay in zone of secondary mechanical hyperalgesia produced by capsaicin injection in humans
Samad (2001)
Pain hypersensitivity in response to injury in rats was inhibited when IL1b receptor antagonists injected into CSF
What is the role of glial cells in chronic pain?
Substance P released from neurons acts on glial cells to upregulate COX2, producing PGE2 and Il2, increasing the excitability of neurons. Increase cell connectivity and axonal sprouting.
Main descending modulation sites
Peri-aqueductal Gray and rostro-ventromedial medulla (RVM). RVM off cells, decrease firing preceeding nociceptive input and are thought to be inhibitory.
Pacher (2007)
CB1-/- mice show that endocannabinoids meditae an inhibitory tone on nociceptive activity. Reterograde synaptic inhibition, decreasing presynaptic calcium concentrations and activating K+ channels.
Cui (1999)
Early stimulation studies of PAG found it released serotonin into SC.
Beecher (1946)
Noted remarkable attenuation of pain experienced by soldiers in combat situations. Early evidence for pain modulatory mechanism.
Berna (2010)
fMRI studies show disruption of emotional regulatory circuits leads to a significantly increase in pain unpleasantness ratings and directly influences brain processing.
Ploghaus (2001)
Visual signal associated with pain or neutral, another associated with neutral. Anxiety rating higher on exposure to signal 1, just showing signal 1 without pain produces more pain than signal 2 and neutral pain.
Singer (2004)
fMRI of women experiencing physical pain activate similat brain regions to those involved when feeling empathy for their partner’s suffering.
Baliki (2012)
fMRI studies showing increased functional connectivity between nucleus accumbens and VM prefrontal cortex and amygdala in CP patients. Reward based learning and addiction?
Bayesian theorem
Theorem provides a way to update the plausibility of hypotheses based on new information. Eippert - SC is never rest, shows spontaenous yet well organised fluctuations of activity.
Bingel (2011)
Role of placebo. Repeated constant thermal pain. Pain ratings decrease slightly when opiod given, decreases much more when told given, increases again when opiod still given but expect withdrawral.
Decerbrate rat model to measure nociception through spinal reflexes. Greater response to the same stimuli could be elicited after an injury to the contralateral paw, cannot be accounted for with peripheral sensitisation.
Woolf 1980s
Electrical interneural stimulation of single Ab mechanoreceptive dibres could elicit non-painful sensation before capsaicin injection, could later produce pain if fibres lay in zone of secondary mechanical hyperalgesia produced by capsaicin injection in humans
Torebjork (1992)
Pain hypersensitivity in response to injury in rats was inhibited when IL1b receptor antagonists injected into CSF
Samad (2001)
CB1-/- mice show that endocannabinoids meditae an inhibitory tone on nociceptive activity. Reterograde synaptic inhibition, decreasing presynaptic calcium concentrations and activating K+ channels.
Pacher (2007)
Early stimulation studies of PAG found it released serotonin into SC.
Cui (1999)
Noted remarkable attenuation of pain experienced by soldiers in combat situations. Early evidence for pain modulatory mechanism.
Beecher (1946)
