PO-87 | Dual inhibition of FAAH and TRPV1 receptors counteracts nitroglycerin-induced migraine-like symptoms only in male rats

Background: Substantial evidence supports the involvement of anandamide (AEA), an endogenous ligand of cannabinoid receptors, in the modulation of migraine pain. AEA also exerts effects via other targets, including transient receptor potential vanilloid type 1 (TRPV1). Inhibiting AEA degradation by fatty acid amide hydrolase (FAAH) and TRPV1 antagonism have both shown anti-nociceptive effects. Emerging studies suggest that inhibiting both FAAH and TRPV1 simultaneously may offer enhanced analgesic efficacy. The aim of this study was to investigate the interaction between the endocannabinoid system (ECS) and TRPV1 in migraine-related pain and anxiety-like behavior in a nitroglycerin (NTG)-based animal model using a dual FAAH inhibitor and TRPV1 antagonist (arachidonoyl serotonin, AA-5-HT) as a pharmacological probe. Methods: Adult male and female Sprague-Dawley rats received NTG (10 mg/kg, i.p.) or vehicle 4 hours before behavioral testing. Fifteen minutes before testing, animals were treated with AA-5-HT (5 mg/kg, i.p.), a dual FAAH/TRPV1 blocker, or vehicle. Behavioral tests included the elevated plus maze (EPM) test, immediately followed by the orofacial formalin test. Subsequently, rats were euthanized for the assessment of serum CGRP levels in both sexes. Results: In the EPM test, NTG induced anxiety-like behavior, detected as a reduction in the time spent and the distance traveled in the maze open arms, only in male rats. This behavior was not influenced by AA-5-HT administration. NTG administration induced an increase in nocifensive behavior during the second phase of the orofacial formalin test and in CGRP serum levels in both sexes. However, only in males, the administration of AA-5-HT counteracted NTG-induced increase in nocifensive behavior and serum CGRP levels. Conclusion: The dual inhibition of AEA degradation and TRPV1 activity induces sex-specific effects in the NTG-induced migraine model, with anti-hyperalgesic effects observed exclusively in males. These results suggest a sex-specific role of the endocannabinoid system in migraine.