Attenuation of oxidative stress and neurotoxicity involved in the antidepressant-like effect of the MK-801(dizocilpine) in Bacillus Calmette-Guerin-induced depression in mice.

Background The emerging line of research suggests that neuro-inflammation and oxidative stress are linked to the development of depression-like behavior. The tryptophan metabolizing enzyme, indolamine 2,3-dioxygenase (IDO), serves as an important interface between chronic inflammation and depression. IDO is induced by pro-inflammatory cytokines and diverts tryptophan towards the kynurenine pathway, decreasing serotonin synthesis. Further, the metabolites of kynurenine pathway increase brain oxidative stress and also cause N-methyl-D-aspartate (NMDA) receptor-mediated exitotoxicity. The resulting oxidative damage and dysfunction in glutamatergic neurotransmission alters the network connectivity of the brain, which may be the further mechanism for emergence of depression-like symptoms. Methods A depression-like illness was induced in mice by injecting Bacillus Calmette-Guerin (BCG) suspended in isotonic saline at a dose of 107 CFU I.P. The mice were then divided into different groups and were administered MK-801 or normal saline for the next 21 days, after which a battery of behavior and biochemical tests were conducted to assess them. Results The BCG group had significantly reduced sucrose preference index and an increase in immobility time in forced swim test (FST) and Tail Suspension Test (TST) as compared to the saline group. There was also a significant increase in the brain MDA levels and a decline in the brain GSH levels. The hippocampal tissue from the BCG group had significantly more comet cells than the saline group. The NMDA receptor antagonist, MK-801, was able to reverse the BCG-induced depression-like behaviour. MK-801 also showed significant decrease in brain oxidative stress but failed to show significant protection against BCG-induced neurotoxicity observed in comet assay. Conclusions The NMDA receptor antagonist, MK-801, mitigated BCG-induced, depressive-like behavior in mice by improving the sucrose preference and decreasing the duration of immobility time in TST and FST. The overall improvement in depression-like behavior was accompanied by a reduction in brain oxidative stress and comet cells, thus suggesting the antioxidant and neuroprotective action of MK-801.

An Experimental Study to Evaluate the Effect of Memantine in Animal Models of Anxiety in Swiss Albino Mice.

BACKGROUND: Due to the adverse effects produced by the present conventional medicines for anxiety disorders, research for newer drugs is still desirable. From the literature it is evident that NMDA receptors play a key role in animal models of anxiety. AIM: The present study is done to evaluate the antianxiety effect of memantine in swiss albino mice. MATERIALS AND METHODS: The experimental study was conducted from November 2014 to January 2015. Animals were divided into four groups. Twelve mice were randomly allotted in each group. Animals in the first group received normal saline as a control 10ml/kg, lorazepam 0.5mg/kg was administered to second group, memantine 3mg/kg as a test drug was given to the third group and memantine 3mg/kg + lorazepam 0.5mg/kg was administered to the fourth group. All the drugs were given for 7 consecutive days by intraperitoneal route. RESULTS: Results were analyzed by one-way ANOVA followed by Post-hoc Tukey's test. On the 1(st) day, memantine treated group did not show statistical significant anxiolytic effect in both the behavioural paradigms when compared to control group. On the 8(th) day, the animals showed significant decrease p<0.001 in step down latency period in shock free zone (185.4±3.87 Vs 278.3±5.49), significant increase p<0.001 in step down errors (6.8±0.78 Vs 1.4±0.19) and significant increase p<0.001 in total time spent in shock zone (32.1±2.22 Vs 5.6±0.6). In open field test, on 8(th) day the animals treated with memantine when compared to control group, showed significant increase p<0.001 in number of squares crossed (112.7± 2.69 Vs 83.2±2.96), time spent in central square (11.5±1.26 Vs 3.4±0.65), no. of rearings (32.4±2.61 Vs 17±1.81) and significant decrease p<0.001 in freezing time (15.2±1.12 Vs 20.2±2.29). Memantine showed synergistic antianxiety effect when combined with lorazepam. CONCLUSION: Memantine showed significant anxiolytic effect in open field and passive avoidance response tests which are commonly used experimental models to assess anxiety states in animals.