Ferulic acid (FA), a phenolic phytochemical, has been reported to exert antioxidative and neuroprotective effects. In this study, we investigated the protective effects of FA against the dysfunction of the swallowing reflex induced by ligation of bilateral common carotid arteries (2VO) in rats. In 2VO rats, topical administration of water or citric acid to the pharyngolaryngeal region evoked a diminished number of swallowing events with prolonged latency compared to sham-operated control rats. 2VO rats had an increased level of superoxide anion radical, and decreased dopamine and tyrosine hydroxylase enzyme levels in the striatum, suggesting that 2VO augmented cerebral oxidative stress and impaired the striatal dopaminergic system. Furthermore, substance P (SP) expression in the laryngopharyngeal mucosa, which is believed to be positively regulated by dopaminergic signaling in the basal ganglia, was decreased in 2VO rats. Oral treatment with FA (30 mg/kg) for 3 weeks (from one week before 2VO to two weeks after) improved the swallowing reflex and maintained levels of striatal dopamine and laryngopharyngeal SP expression in 2VO rats. These results suggest that FA maintains the swallowing reflex by protecting the dopamine-SP system against ischemia-induced oxidative damage in 2VO rats.
Keywords: cerebral hypoperfusion; dopaminergic neuron; ferulic acid; oxidative stress; substance P; swallowing dysfunction.