GABAergic effect of valeric acid from Valeriana wallichii in amelioration of ICV STZ induced dementia in rats

Valeriana wallichii DC., Caprifoliaceae, is used to have anti-ulcer, anti-spasmodic, anti-epileptic, memory enhancer, anti-anxiety, anti-rheumatic, sedative, anti-asthmatic and diuretic activities. V. wallichii is reported to contain valpotriates, valeric acid, valerenic acid, valechlorine, valerianine, resins and alkaloids. Valeric acid, found in V. wallichii appears similar in structure to the neurotransmitter GABA. Valeric acid also acts as an NMDA-receptor antagonist. The aim of present study was to investigate the neuroprotective effect of V. wallichii containing valeric acid and its possible mechanism of action in amelioration of intracerebroventricular streptozotocin induced neurodegeneration in Wistar rats. The rhizomes of V. wallichii were powdered coarsely and extracted by percolation method using dichloromethane. Wistar rats (220⿿250g) of either sex were divided into 5 groups, comprising 6 animals each. Valeric acid was isolated from plant extract and characterized using FT-IR. Picrotoxin (2mg/kg) was used as GABA-A antagonist. Intracerebroventricular streptozotocin administration caused significant (p<0.05) increase in escape latency, retention transfer latency on morris water maze on 17th, 18th, 19th and 20th day and elevated plus maze on 19th and 20th day respectively, as compared to normal untreated rats. Treatment with V. wallichii extract 100 and 200mg/kg and valeric acid 20 and 40mg/kg significantly decreased the escape latency and retention transfer latency, as compared to intracerebroventricular-streptozotocin group. Plant extract and valeric acid also decreased the level of lipid peroxidation and restored glutathione level in rat brains. Administration of picrotoxin significantly reversed the effects produced by plant extract and valeric acid in intracerebroventricular-streptozotocin treated rats. The findings may conclude that valeric acid present in V. wallichii has significant GABAergic effect in amelioration of experimental dementia.