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Neuroparalytic keratitis and capsaicin
G G Knyazev1, G B Knyazeva, A F Nikiforov
1Institute of Physiology, Siberian Branch of the Academy of Medical Sciences of the USSR, Novosibirsk.
Acta Physiologica Hungarica
|January 1, 1990
Summary
Capsaicin desensitizes newborn rats to heat pain and inflammation. However, it does not prevent corneal damage after eye surgery, suggesting substance P is not the primary cause of these post-surgical changes.
Area of Science:
- Neuroscience
- Ophthalmology
- Pain Research
Background:
- Capsaicin is known to deplete substance P and other neuropeptides from sensory nerve fibers.
- Substance P plays a role in neurogenic inflammation and pain signaling.
- The role of substance P in corneal changes following surgical deafferentation is not fully understood.
Purpose of the Study:
- To investigate the role of capsaicin-sensitive nerve fibers and substance P in the development of neuroparalytic keratitis after surgical deafferentation of the eye.
- To determine if systemic or local capsaicin pretreatment can prevent corneal damage following deafferentation.
Main Methods:
- Neonatal rats were pretreated with subcutaneous capsaicin to deplete neuropeptides.
- Surgical deafferentation of the eye was performed.
- Corneal changes (keratitis) were assessed.
- Retrobulbar injections of capsaicin were administered to induce keratitis-like changes.
Main Results:
- Subcutaneous capsaicin pretreatment significantly reduced heat pain sensitivity and neurogenic inflammation.
- However, capsaicin pretreatment did not prevent or reduce the severity of neuroparalytic keratitis after eye deafferentation.
- Direct retrobulbar capsaicin injection induced keratitis-like corneal changes, which were not prevented by prior systemic capsaicin treatment.
Conclusions:
- The findings suggest that corneal changes observed after surgical deafferentation are not primarily mediated by the excessive release of substance P from degenerating afferent nerve fibers.
- Capsaicin-sensitive pathways may not be the main contributors to post-deafferentation corneal pathology.
- Further research is needed to elucidate the mechanisms underlying neuroparalytic keratitis.