Pre-treatment with new kynurenic acid amide dose-dependently prevents the nitroglycerine-induced neuronal activation and sensitization in cervical part of trigemino-cervical complex

The systemic administration of nitroglycerine induces attacks in migraineurs and is able to activate and sensitize the trigeminal system in animals involving glutamate and α7-nicotinic acetylcholine receptors, among others. Kynurenic acid is one of the endogenous glutamate receptor antagonists, and exerts inhibitory action on the α7-nicotinic acetylcholine receptors. Since kynurenic acid penetrates the blood–brain barrier poorly, therefore a newly synthesized kynurenic acid amide, N -(2- N -pyrrolidinylethyl)-4-oxo-1 H -quinoline-2-carboxamide hydrochloride (KYNA a ) was used with such a side-chain substitution to facilitate brain penetration in our study. We evaluated its modulatory effect on kynurenic acid concentration in the cervical part of trigemino-cervical complex (C1–C2) and in the model of nitroglycerine-induced trigeminal activation using male Sprague–Dawley rats. One hour after 1 mmol/kg bodyweight KYNA a administration, the kynurenic acid level increased significantly in C1–C2, which returned to the basal level at 300 min measured by high-performance liquid chromatography. KYNA a pre-treatment had dose-dependent, mitigating action on nitroglycerine-induced decrease in calcitonin gene-related peptide and increase in c-Fos, neuronal nitric oxide synthase and calmodulin-dependent protein kinase II alpha expression in the C1–C2. KYNA a also mitigated the behavioural changes after nitroglycerine. Thus, in this model KYNA a is able to modulate in a dose-dependent manner the changes in neurochemical markers of activation and sensitization of the trigeminal system directly and indirectly—via forming kynurenic acid, possibly acting on peripheral and central glutamate or α7-nicotinic acetylcholine receptors. These results suggest that application of kynurenic acid derivatives could be a useful therapeutic strategy in migraine headache in the future with a different mechanism of action.