Latency to withdrawal
Withdrawal experiments are behavioral methods that assess the reaction of an animal to a nociceptive stimulus in order to measure pain-like behaviors. This is the most common method to quantify nociception in animal models.
These experiments can be performed using different types of stimuli such as heat, cold, and mechanical or electrical stimuli. The stimulus is normally applied to the paw of the animal and the time taken to withdraw the paw is recorded as the latency to withdrawal.
When the animals withdraw the paw, it means that an action potential has been triggered in their nociceptors, transmitting the pain sensation that makes them move their paw. Thus, the longer the latency to withdrawal, the less sensitive the animal is to that nociceptive stimulus.
These experiments are useful to test the ability of new drugs to reduce pain against existing stimuli that could potentially be used in humans in the future.