L-theanine prevent quinolinic acid induced motor deficit and striatal neurotoxicity: Reduction in oxido-nitrosative stress and restoration of striatal neurotransmitters level.

L-theanine has been documented to possess anti-oxidant, anti-inflammatory and neuroprotective potential in various animal models of neurological disorders. The present study was anticipated to investigate the effect of L-theanine against quinolinic acid induced motor deficits, oxido-nitrosative stress, neuro-inflammation and neurotransmitters alteration in rats. Rats were stereotaxically injected QA (200nmol/2µl saline; intrastriatal); bilaterally on 0 day and L-theanine (25 & 50mg/kg; p.o.) was administered for 21 days starting from day 1 of QA injection. Either, L-NAME (10mg/kg; i.p.), a nitric oxide synthase inhibitor and L-arginine (50mg/kg; i.p.), a nitric oxide synthase precursor were administered with L-theanine in respective groups. Behavioral observations were evaluated on weekly basis using rota-rod, grip strength, narrow beam walking and open field test. QA treatment induces significant alteration in body weight, motor coordination, oxidative defense, pro-inflammatory cytokines and striatal neurotransmitters level. L-theanine treatment alone, at both the tested doses, significantly attenuated QA induced alterations. In addition, treatment of L-theanine with L-NAME significantly enhances the protective effect of L-theanine whereas treatment of L-theanine with L-arginine significantly ameliorated the protective effect of L-theanine. The protective effect of L-theanine is attributed to its anti-oxidant, anti-inflammatory and modulatory effect on nitric oxide pathway and neurotransmitters level in striatum. This suggests use of L-theanine in the clinical settings of HD.