Study Overview

Description: The study developed and characterized a novel, injury-free rat model of functional pain.

Source: PubMed

Summary

• The study developed and characterized a novel, injury-free rat model of functional pain.
• Rats were exposed to red light-emitting diodes (RLED) to induce nociceptive sensitization.
• RLED exposure resulted in time- and dose-dependent thermal hyperalgesia and mechanical allodynia in both male and female rats.
• Females showed an earlier onset of mechanical allodynia than males.
• The pronociceptive effects of RLED were mediated through the visual system.
• Medications commonly used for widespread pain reversed RLED-induced hyperalgesia and allodynia.
• Increased descending facilitation in the pain pathway was implicated.

Participants

• Sprague-Dawley rats (both male and female)

Intervention

• Exposure to red light-emitting diodes (RLED) (660 nm) at an intensity of 50 Lux for 8 hours daily for 5 days.

Methods

• Rats were exposed to RLED.
• Thermal hyperalgesia and mechanical allodynia were assessed.
• Effects of various medications (gabapentin, tricyclic antidepressants, serotonin/norepinephrine reuptake inhibitors, nonsteroidal anti-inflammatory drugs, acetaminophen) were tested.
• Bicuculline (GABA-A receptor antagonist) was administered into the rostral ventromedial medulla.
• Replication study conducted with randomization, investigator blinding, inclusion of all data, and high levels of statistical rigor.

Conclusion

• RLED-induced thermal hyperalgesia and mechanical allodynia without injury offers a novel injury-free rodent model useful for the study of functional pain syndromes with widespread pain.
• RLED exposure emphasizes the different biological effects of different colors of light exposure.
• Understanding the underlying biology of red light-induced widespread pain may offer insights into functional pain states.