Test 2 Flashcards
How do animals experience pain?
Vertebraes- sense harmful send it to spine, remove hand, get rid of stimulus-
Concious recognition of pain- neurons create sensation in pain- associated with fear, stress
Hurt animasl- tend to wound, make noises, avoid future harm
Osyter, worm and jelly fish- experience nocioception and not concious pain
Those that are smarter- may experience the concious pain
Remember physical sensation- recognixe when pain is cominh
Why Use Animals?
can conduct causation experiments
can stimulate/lesion any tissue
can assay, record from, or extract any tissue
can give unapproved drugs
can alter gene expression (temporarily or permanently)
can control pre-exposures- life history
cheaper, faster, less highly regulated- gestational period= 3 weeks and make 8-12 babies
no malingering- faking it, exaggerating , no demand characteristics- don’t change response based on observation
Can do more with animals than humans
Rat used the most for pain research followed by mice
Boomed bc of transgenic mice
C57-black 6 mouse inbred- making genetic clones brain stem and dicephlon- similar to humans
Mouse brain is flat, has no folds
Why Use Animals?
can conduct causation experiments
can stimulate/lesion any tissue
can assay, record from, or extract any tissue
can give unapproved drugs
can alter gene expression (temporarily or permanently)
can control pre-exposures- life history
cheaper, faster, less highly regulated- gestational period= 3 weeks and make 8-12 babies
no malingering- faking it, exaggerating , no demand characteristics- don’t change response based on observation
Can do more with animals than humans
Rat used the most for pain research followed by mice
Boomed bc of transgenic mice
C57-black 6 mouse inbred- making genetic clones brain stem and dicephlon- similar to humans
Mouse brain is flat, has no folds
onsequentialist Ethics
The normative ethical position holding that the consequences
of one’s conduct are the ultimate basis for any judgment about the rightness of that conduct.- focus on serving greater good, grey zones
Pain and Utilitarianism
Consequentialism= subcategory of this
Maximize pleasure and minimize painPain and Utilitarianism
Pain and Utilitarianism
Consequentialism= subcategory of this
Maximize pleasure and minimize painPain and Utilitarianism
What are we trying to model?
Central sensitization- hyperactive cns- brain or spinal cord causin. Pain
non nocioceptor neuons= cns neurons
Inflamattion- meant to repair damage, causing sensitization
High threshold- need large stimulus to cause nocioception
Neuropathic and csn- pathological
Csn- fobromyalgia and only in cns, not nocioception
NOCERITA
NEUROPATHIC
CORA SENSITATION
system aystuncton
Neurons
Nociceptor and
non-nacicentor
Nociceptor and non-nociceptor
Non-nociceptor
Site
Peripheral and central
Peripheral and central
nervous system
Central nervous
SYSICE
winico
setting
Acute trauma
arthritis
Nerve lesions diabetic neuropathy,
shingles, carpet tunne
Fibromyalgia and a
volesy or outer pon
FunCLOI
healing/repair,
patholocica
ratholodice
Patholodica
rall
sensitivity
hien or low tiresnold Low tresno
Low tiresnore
Chronic pain models in rodents
Inflammatory pain
Can be modeled in rodents by the injection of chemical inflammatory agents and irritants
Common models include foot, ankle or knee joint injections of carrageenan, complete Freund’s adjuvant (CFA), capsaicin, formalin- preserves tissue, zymosan, cinnamaldehyde, mustard oil- foreign and cause immune response
Different agents induce different resolution time courses.
CFA recruits neutrophils and macrophages to the site of injection.
Cells that cause infklammation- give rise to nocioception
Cytokines and and white blood cells- cause inflammatory response
Injecting different dosed of carrageenan- seaweed extract- changes sensitixation easily
Pay attention to change in time- can tell you what test used
Inflammatory pain- last up to 8 weejs for mice
Differences in pain sensitivity based on what used and dose
Formalin phases mimic neuronal activity
Inflammatory teste
Measures- nicioceptive defensive behaiour, prevent or respond to to pain
Example= lick paw/wounds, cold water
Injected into hind paw- starts to lick paw
Purple= quiescent- calms Dowm
Then picks up again in late phase(central spinal cord activity)
Interested most in late phase
First 10 minutes= activation nocioceptor
C fiber- detetcts nocioception
Hyperalgesic priming
Hyperalgesic priming
Carrageenan or CFA is injected into the paw of a group of animals. This will resolve over a couple of hours or days.
After the resolution of inflammatory sensitivity, a second inflammatory substance is
injected into the same region (i.e., PGE2- cause inflammation)
Sensitivity is significantly longer in duration than what is observed in a group of animals that did not receive the first injection (naïve). Tests neuronal pain memory and plasticity
Hyperalgesic priming- if hyperalgesia affects subsequent experience
Inject pge2, have transient pain response but if before, inject inflammation- will experience more pain for longer- bc of inflammation sensitizing neurons, have memory of pain, want to protect self, change threshold
Musculoskeletal pain
Musculoskeletal pain
Pain originating from muscle, bone or joints (i.e., OA and RA)
Most common symptom reported in pain patients
OA is modeled with injection of monosodium-iodoacetate into the joint or
surgical transection of ligaments
RA modeled with injection of collagen and CFA into the knee joint. Can cause
release of proinflammatory cytokines (IL-1, IL-6, TNFa) Inflammation causes release of inflammatory cytokines
DBAv strain- susceptible to collagen artritis- when inject it makes it more inflammatory
Neuropathic pain
Neuropathic pain
Pain caused by damage or disease of the somatosensory nervous system-MS
Surgically induced in periphery of rodents by stretching, compression, or transection of peripheral nerves (i.e., sciatic nerve)
Non-surgical models include chemotherapy-induced lesions, multiple sclerosis, diabetes and viral infection
Surgical Non-surgical
Chemotherapy Paclitaxal, oxiplatin, cause pain, chemotherapeutic induced
Diabetes streptozotocin (STZ)- targets b cells, disrupting insulin production, causing hypogylcemia Postherpetic neuralgia herpes varicella- zoster virus- shingles pain, this is when left with shingles pain
After a stroke- especially in thalamus
Target leg or foot- most accessible and easy to test
Spare nerve injury- cut two nerves, leaving sural nerve and it becomes hyperexcitable, causing more pain
Cci- tie off sciatica- causing slow strangulation, prevents oxygen floe, kills of nerves- chronic constriction injury
Cci and sni- used widely
Surgical- models trauma, cut nerve, car crash
Meausre sensitivity in feet
Neuropathic pain occurs first in legs bc these are longest nerves- more susceptible
Occurs after 2-3 weeks
Visceral pain models
Visceral pain models
Pain in the abdomen, chest and pelvic organs
Commonly induced using chemicals or trauma
Bowel injection of capsaicin, mustard oil or zymosan- cell wall of yeast, activates immune system- getting rid of agent causes pain or bowel distension
Researchers don’t have immediate access to the organs. Instead, will measure changes in behaviour including spontaneous pain, grooming of the region, torso constrictions. Capsaicin- chemical found in spicy things
Mustard oil- burning sensation
Rything response- mouse elongates abdomen and constricts torso – to induce, inject acetic acid
magnesium sulfate
hyper-/hypotonic saline
Bradykinin- released during inflammation, causes sensitization
Pain testing in rodents
How do we assess rodent pain
Evoked behaviour and spontaneous behaviour
Mechanical and thermal stimuli allodynia and hyperalgesia
Spontaneous behaviour facial expressions and quality of life
Mechanical evoked behaviour tests
Series of monofilaments applied to hindpaw (von Frey test)
Positive response withdrawal response following application of filament
VF calculates force required to evoke withdrawal in 50% of animals
R-S calculates mechanical pressure threshold of deep tissue.
Other tests include pinprick test and brush test.
Typically use von frey test- von frey filaments applied to bottom of foot and see its response, can determine threshold and pain response- keep inc strength until it responds- then go down
Apply different force of filament until it responds then go down one level – hone in on threshold
Apply pain threshold dec
Randall-Selitto test- apply pressure- done for rats, put paw in clamp and once animal makes response- threshold
Vs and rs are mechanical tests
Changes pain responses
Thermal evoked behaviour tests
Thermal evoked behaviour tests
Hot or cold temperature
More noxious the stimulus, the faster the animal’s tail will flick, paw removed,
paw licking or animal escapes
Common tests include tail flick, hot plate, cold plate, acetone evaporation test Why do we need all these- get at different pain pathways and responses
Flick tail when neuronl activation of spinal nerve
Even when disturb brain function- still occurs- spinal function
Latncy to firt response- how long for one of these responses to occur
C- expose heat once at a time, if have injured side can use non injured as control
Acetone test- dries the skin, its cold, if have injurt esp neuropathic, this turns into cold pain- flicking of paw
Apply dry ice under glass floor- cold floor
Spontaneous behaviour tests
Spontaneous behaviour tests
Can involve measuring licking in response to formalin, capsaicin, mustard oil, acetic acid – nocifensive behaviour, causes rything
Animal’s gait, weight bearing behaviour, conditioned place preference, facial
grimacing in response to an injury C- total weight sitribution- cat walk test
nocifensive be- nocioception and defensive behavoiour- escaping, licking- meant to protect anaimal
A Measure of Spontaneous Pain in Mice: The Mouse
Grimace Scale
Bulges nose, puffs cheeks, tighten ears, get pulled back
The Mouse Grimace Scale
Works For Pain of Moderate Duration
Only changes in response to specific stimuli
30 min- a day- chsnge in pain face
Secobsa- minutes probaby unable to capture the face chabge
Conditioning Methods to Study Pain
Operant Conditioning
learned escape from pain- learn to go to nonpainful area
from electric shock
from noxious heat/cold
learned analgesic self-administration
motivational conflict
between pain vs. food/water- has inury, has to obercome pain to get food or water
Classical (Pavlovian) Conditioning
conditioned place avoidance
to formalin-paired chamber
to chamber where allodynia is experienced
conditioned place preference
to analgesic-paired chamber
Relief from pain= reward, activate system when redfuce pain
Motivational Conflict Between Pain and Drinking
Injected into mouth
Have to put head in slot to acheieve reward
At slot have thermode- hot
Did in rats when have injection vs not at normal temp and high temp
Normal rats- didn’t affect them, pained rats- when inc temp, do it much less
Grey bar- apply analgesiac
Conditioned Place Preference to Analgesia
Prefer rewarding environment- drugs
Want to provide analegisiac without activating rewards system
Gabapentin- calms down neuronal firing
Sham= surgey but don’t touch nerve
Post sni- prefer pain relief chamber
Mice in Chronic Pain Have Anxiety/depressive-like behaviour?
Acetic acid-induced muscle pain
Pain thresholds and negative emotions measured
Negative emotions (anxiety/depression) reversed by pregabalin (gabapentin) Anxiety- elevated plus maze- spend more time in open space- less anxious
Induce pain- more anxioud
Forced swim- learn no way out and stop trying, pain= more immobilized
Burrowing as a Quality-of-Life Measure?
Either measures amount displaxed or time till remove it all
Naïve vs cfa- causes inflammation, models chronic inflammation- deal bacteria tht causes immune response
Voluntary Wheel Running (1 h/day) in Mice with Inflammatory Pain
only inflammatory pain
-only bilateral CFA- have to be in both feet Restricted running wheel time to one day, give cfa- will run less than control
Animal pain Researchers are Studying the “Wrong” Symptom!
Most crhonic pain- have spontaneous pain
In rodents- study thermal hyperalgesia tge most
Spontaneous pain- hard to measure
Individual differences in pain sensitivity
Those with lower rating had less brain activity in pain area
With higer- acc and somatic sensory cortex
Causalgia- neuropathic
