Latent sensitization: a model for stress-sensitive chronic pain.

Area of Science:

• Neuroscience
• Pain Research
• Animal Models

Background:

• Latent sensitization is a rodent model for studying chronic pain.
• It mimics pain's episodic nature and stress sensitivity.
• The model exhibits distinct hyperalgesic and remission phases.

Purpose of the Study:

• To detail the procedures for inducing and monitoring latent sensitization in rats and mice.
• To elucidate the mechanisms underlying the remission phase of latent sensitization.
• To investigate the role of opioid receptors and stress in pain chronification.

Main Methods:

• Induction of latent sensitization through various injuries (inflammatory agents, nerve damage).
• Administration of μ-opioid receptor inverse agonists (naloxone, naltrexone) during remission.
• Application of stress to trigger pain reinstatement.
• Monitoring of hyperalgesia and remission phases in rodent models.

Main Results:

• Latent sensitization follows a predictable time course with hyperalgesic and remission phases.
• Remission is not a return to baseline but a state where pain is masked by opioid receptor activity.
• Opioid receptor inverse agonists and stress can reinstate hyperalgesia during remission.

Conclusions:

• Latent sensitization provides a valuable model for chronic pain research.
• Opioid receptor activity plays a crucial role in masking pain during remission.
• Stress is a significant factor in reactivating pain in latent sensitization models.