The mechanism of protective effect of syringic acidin the experimental model of parkinson's disease

Objective: 6-hydroxydopamine (6-OHDA) is a widely used chemical to create an animal model of Parkinson's disease. Although there are several studies demonstrating the therapeutic effects of many phenolic compounds against 6-OHDA toxicity, there aren't any published studies over the syringic acid (SA) mechanism of action. The present study aimed to evaluate the effect of SA on 6-OHDA-induced parkinson rat model by biochemical analyses, immunofluorescence methods, and motor activity tests. Method: Rattus norvegicus Wistar albino adult male rats (250-300 g) were randomly divided into 5 groups, 15 in each group (n=75). Groups were determined as Group I (Sham), Group II (Syringic acid), Group III (Syringic acid + Parkinson), Group IV (Parkinson + Syringic acid), Group V (Parkinson). Syringic acid (20 mg / kg) was administered daily by oral gavage. The animal model of Parkinson's disease was created by injection of 6-OHDA into the medial forebrain band with stereotaxic surgery. All groups were tested for locomotor activity, rotarod performance test and catatonia test. At the end of the experiment, rats were anesthetized and sacrificed for biochemical and immunofluorescence analysis by transcardial perfusion method. Results: Syringic acid significantly increased levels of dopamine and tyrosine hydroxylase in the substantia nigra (SN) of rats, which were induced with 6-OHDA to create Parkinson's rat model (p<0.001). Syringic acid had a protective effect on motor activity, it significantly increased total antioxidant capacity of SN (p<0.05) and reduced total oxidant capacity (p<0.001). Syringic acid decreased the expression of inducible nitric oxide synthase (iNOS), and reduced nitrite and nitrate levels (p<0.05). Conclusion: These data conclude that SA has neuroprotective outcome due to its antioxidant and anti-inflammatory effects in 6-OHDA-induced Parkinson's rat model. Key words: Parkinson's model, syringic acid, 6-OHDA, iNOS