Migraine is characterized by severe pain and somatic symptoms like allodynia and photophobia, driven by neuroinflammation that sensitizes the trigeminal vascular system (TVS). This study investigated how neuroinflammation induced by systemic lipopolysaccharide (LPS) affects migraine-related nociceptive signaling. Using a chronic migraine model in rats with nitroglycerin (NTG), we compared prenatal and acute postnatal LPS administration. Rats with prenatal LPS exhibited lower mechanical thresholds and enhanced allodynia and photophobia after NTG. Acute LPS also increased allodynia, but not photophobia. Both LPS groups showed increased mast cell degranulation in the dura mater. Plasma CGRP after NTG administration was elevated in the acute LPS group. Electrophysiology revealed enhanced trigeminal afferent responses to serotonin in both acutely and prenatally LPS-treated rats. Calcium imaging demonstrated increased neuronal responses to serotonin and capsaicin, suggesting an upregulation of serotonin and TRPV1 receptors. Our findings show that LPS-induced neuroinflammation, whether prenatal or acute, promotes sensitization of peripheral and central nociceptive pathways, involving serotoninergic mechanisms.

Migraines are a common neurological disorder that significantly reduces quality of life. The sensitization of trigeminal afferents is a key factor in the development of the pain syndrome associated with migraine. Carbon monoxide (CO) is produced endogenously by heme oxygenase (HO), widely expressed in structures involved in pain processing. In our study, the role of CO in an acute and chronic nitroglycerin (NTG)-induced rat migraine model was investigated using behavioral, electrophysiological, biochemical and histological methods. The repeated administration of a CO donor (CORM-2) or an HO-1 inducer (CoPP) decreased mechanical hypersensitivity and photophobia of rats in the NTG-induced migraine model. Additionally, CORM-2 and CoPP prevented an increase in trigeminal afferent excitability, which was evaluated by the frequency of action potentials in response to KCl application. Preliminary CORM-2 or CoPP injections promoted mast cell stability in the meninges and prevented NTG-induced CGRP elevation in blood plasma. Our results suggest that exogenously or endogenously produced CO has a protective potential in preventing inflammation and the sensitization of peripheral trigeminal afferents, the activity of which underlies the occurrence of pain in migraine. This could contribute to the development of new approaches for migraine prevention.