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Chronic inorganic arsenic (iAs) exposure induces deleterious effects on CNS including oxidative stress, cognitive deficits and altered brain neurochemistry. Little is known about the association between iAs and estrogen receptor expression in brain regions. Owing to the neuroprotective and estrogenic activities of resveratrol (RES), we examined the combined effects of arsenic trioxide (As2O3) and RES on neurobehavioural functions, estrogen signalling and associated neurochemical changes in mouse hippocampus. As2O3 alone (2 and 4 mg/kg bw) or along with RES (40 mg/kg bw) was administered orally for 45 days to adult female mice. From days 33 to 45, open field, elevated plus maze and Morris water maze tests were conducted to evaluate locomotion, anxiety and learning and memory. On day 46, animals were euthanized and brain tissue and hippocampi obtained therefrom were processed for atomic absorption spectrophotometry and western blotting respectively. As2O3 alone exposure resulted in enhanced anxiety levels, reduced locomotion and impaired learning and memory. As2O3-induced behavioural deficits were accompanied by downregulation of estrogen receptor (ERα) expression with a concomitant reduction of BDNF and NMDAR 2B levels in the hippocampus. However, the behavioural alterations and expression of these markers were restored in RES-supplemented mice. Moreover, a dose-dependent iAs accumulation was observed in serum and brain tissues of mice receiving As2O3 alone whereas simultaneous administration of As2O3 with RES facilitated iAs efflux. These results suggest that reduced ERα expression with associated downregulation of BDNF and NMDAR 2B levels could be a mechanism by which iAs induces cognitive impairment; hence, the modulation of estrogen-NMDAR-BDNF pathway by RES represents a potential avenue to recover behavioural deficits induced by this neurotoxin.

Global cerebral ischemia/reperfusion (I-R) injury often results in an irreparable brain damage like behavioral impairment and neuronal death. This neurological complication involves diverse intricate pathological mechanisms like oxidative stress, inflammation, and apoptosis. Recently, the therapeutic value of plant-based polyphenols has gained researcher's attention. The present study focused on the putative neuroprotective role of negundoside on behavioral and oxidative stress status in an experimental model of global cerebral ischemia and reperfusion-induced brain injury. Negundoside was isolated from the leaves of Vitex negundo Linn. by chromatography for investigating its possible neurobehavioral and neuropharmacological implications. Healthy Balb/C mice of either sex were subjected to 10 min of global cerebral ischemia (GCI) followed by 24-h reperfusion. Mice were pre-treated intraperitoneally with negundoside at varying doses (1, 3, 5, 10, and 15 mg/kg) 60 min before the induction of GCI. Mice were later subjected to a battery of behavioral tests for evaluating memory-related and motor abilities. Elevated plus maze (EPM) was used to determine the anxiety levels and short-term memory whereas motor abilities were evaluated by inclined beam-walking test, rotarod, and lateral push test. TBARS and reduced glutathione (GSH) content in brains were analyzed spectrophotometrically as oxidative stress markers. Behavioral study revealed enhanced anxiety-related responses and motor deficits in I-R injured mice. Additionally, GSH and TBARS levels were found to be altered following I-R-induced neuronal injury. Contrastingly, negundoside administration was able to alleviate the behavioral and biochemical alterations to the normal levels. Together, our findings provide preliminary evidence of neuroprotective role of negundoside against global cerebral ischemia and reperfusion-induced behavioral dysfunction and oxidative damage in mice brain.