Delayed inflammation in rat meninges: implications for migraine pathophysiology

Area of Science:

• Neuroscience
• Immunology
• Pharmacology

Background:

• Nitric oxide (NO) is implicated in migraine pathogenesis, evidenced by headaches after nitroglycerin (GTN) infusion.
• Inhibiting NO synthesis with NOS inhibitors reduces migraine headaches in a significant portion of patients.
• NO's link to inflammation and cytokine expression suggests a role in delayed migraine responses.

Purpose of the Study:

• To investigate the delayed inflammatory consequences of GTN infusion on meningeal inflammation in a rat model.
• To explore the role of inducible nitric oxide synthase (iNOS) and cytokine induction in this response.
• To determine if the inflammatory response is mediated by direct action on the dura mater.

Main Methods:

• Administered GTN to rats and assessed dose-dependent changes in dura mater.
• Measured iNOS mRNA and protein expression, and levels of interleukin-1beta and interleukin-6.
• Evaluated plasma protein leakage, myeloperoxidase-positive cells, and mast cell degranulation; used L-NIL to inhibit iNOS.

Main Results:

• GTN infusion caused dose-dependent iNOS mRNA and protein upregulation in dura mater macrophages.
• Interleukin-1beta and interleukin-6 were induced in the dura mater and cerebrospinal fluid.
• GTN led to plasma protein leakage and mast cell degranulation, suppressed by L-NIL.

Conclusions:

• Brief GTN infusion induces a delayed inflammatory response in the rat meninges, mediated by iNOS.
• The inflammatory cascade involves cytokine induction, iNOS expression in macrophages, and plasma leakage.
• Findings suggest direct action on the dura mater, supporting a similar mechanism in human migraine.