FELASA Module 8: Pain, Anaesthesia and Euthanasia
Pain is an unpleasant sensory and emotional experience associated with, or resembling
that associated with, actual or potential tissue damage, or described in terms of such
damage
Pain is always a subjective experience
2020 update says that:
Pain is a personal experience
Pain and nociception are not the same
Pain is dependent on experience and learning
If a person claims to be in pain, we should believe them
Pain can cause adverse effects and suffering, even if it is through a necessary
mechanism
Subjects don’t necessarily have to use language to express pain
When studying pain we are really assessing nociception as pain is an experience
Nociception comes from the latin nocere which means to hurt
Nociception makes the distinction between detection of a noxious event or potentially
harmful event (nociception) and psychological and other responses to it (pain)
Nociception originates in the peripheral tissue
Here a noxious stimuli (e.g. injury) triggers nociceptors (receptors of noxious stimuli)
This triggers nerve conduction in afferent nerve fibres (first order neurons) which
transmit signal to the spinal cord
Signal switches into a second order neuron in the spinal cord and activates
subcortical regions of the brain
Third order neurons run from the thalamus to the cerebral cortex
If an organism is unconscious they cannot sense pain, but nociception is still active
This can cause adverse consequences like stress and chronic pain
We must inhibit nociception in animals even if the animal is unconscious
We can’t definitely say animals experience pain, however we cant rule it out if:
The animals nociceptive system and physiological mechanisms are similar to those
involved in pain perception in humans
The animals display behavioural responses to noxious stimuli known to cause pain in
humans
The response is inhibited by analgesic drugs that are known to inhibit pain in humans
Criteria for nociception and pain related behaviours
All mammals share the same criteria
Most birds, fish and cephalopods share the same criteria
Cephalopods includes squid and octopi (invertebrates)
Cephalopods didn’t used to be covered by EU conventions but recent studies show
they can experience pain at the same level as vertebrates
They are now protected
Reptiles and amphibians still need to be investigated
Insects share criteria on nociception but their cognitive abilities are not considered
sufficient for experiencing pain
As pain may be a source of suffering we have a moral obligation to avoid it
In science pain may alter the stress response, impair recovery after surgery and
increase risk of development of chronic pain
I.e. it can increase animal suffering and risk biasing experimental data
Stress is the body’s response to stressors, stressors are factors that trigger stress
Stress occurs when an animal encounters a stimuli that disturbs its normal
physiological and mental equilibrium
This increases variation between subjects and impacts experimental data
The animal modifies its behaviour and physiological conditions to cope with stress
If stress exceeds the natural regulatory capacity of an organism it can increase
unpredictability and uncontrollability
Acute stress (positive stress)
Pain is an unpleasant sensory and emotional experience associated with, or resembling
that associated with, actual or potential tissue damage, or described in terms of such
damage
Pain is always a subjective experience
2020 update says that:
Pain is a personal experience
Pain and nociception are not the same
Pain is dependent on experience and learning
If a person claims to be in pain, we should believe them
Pain can cause adverse effects and suffering, even if it is through a necessary
mechanism
Subjects don’t necessarily have to use language to express pain
When studying pain we are really assessing nociception as pain is an experience
Nociception comes from the latin nocere which means to hurt
Nociception makes the distinction between detection of a noxious event or potentially
harmful event (nociception) and psychological and other responses to it (pain)
Nociception originates in the peripheral tissue
Here a noxious stimuli (e.g. injury) triggers nociceptors (receptors of noxious stimuli)
This triggers nerve conduction in afferent nerve fibres (first order neurons) which
transmit signal to the spinal cord
Signal switches into a second order neuron in the spinal cord and activates
subcortical regions of the brain
Third order neurons run from the thalamus to the cerebral cortex
If an organism is unconscious they cannot sense pain, but nociception is still active
This can cause adverse consequences like stress and chronic pain
We must inhibit nociception in animals even if the animal is unconscious
We can’t definitely say animals experience pain, however we cant rule it out if:
The animals nociceptive system and physiological mechanisms are similar to those
involved in pain perception in humans
The animals display behavioural responses to noxious stimuli known to cause pain in
humans
The response is inhibited by analgesic drugs that are known to inhibit pain in humans
Criteria for nociception and pain related behaviours
All mammals share the same criteria
Most birds, fish and cephalopods share the same criteria
Cephalopods includes squid and octopi (invertebrates)
Cephalopods didn’t used to be covered by EU conventions but recent studies show
they can experience pain at the same level as vertebrates
They are now protected
Reptiles and amphibians still need to be investigated
Insects share criteria on nociception but their cognitive abilities are not considered
sufficient for experiencing pain
As pain may be a source of suffering we have a moral obligation to avoid it
In science pain may alter the stress response, impair recovery after surgery and
increase risk of development of chronic pain
I.e. it can increase animal suffering and risk biasing experimental data
Stress is the body’s response to stressors, stressors are factors that trigger stress
Stress occurs when an animal encounters a stimuli that disturbs its normal
physiological and mental equilibrium
This increases variation between subjects and impacts experimental data
The animal modifies its behaviour and physiological conditions to cope with stress
If stress exceeds the natural regulatory capacity of an organism it can increase
unpredictability and uncontrollability
Acute stress (positive stress)
