Geeta Chaudhary

Protective effect of resveratrol against oxidative stress in middle cerebral artery occlusion model of stroke in rats.

Free radicals have been implicated in neuronal injury during ischemia reperfusion in stroke. Trans resveratrol, a potent antioxidant, polyphenolic compound found in grapes and wines has recently been shown to have neuroprotective activity against oxidative stress in in vitro studies. In the present study the effect of chronic treatment of trans resveratrol was evaluated in focal ischemia induced by middle cerebral artery [MCA] occlusion in rats. Male Wistar rats were pretreated with trans resveratrol 20 mg/kg i.p. for 21 days and were subjected to focal ischemia by occlusion of MCA using intraluminal thread. After two hours of MCA occlusion reperfusion was allowed by retracting the thread. Animals were assessed for motor performance after 24 hours and subsequently rats were sacrificed for estimation of markers of oxidative stress [malondialdehyde [MDA] and reduced glutathione] and for evaluation of volume of infarction. Control group received vehicle and similar protocol was followed. Significant motor impairment, with elevated levels of MDA and reduced glutathione was observed in the vehicle treated MCA occluded rats. Treatment with trans resveratrol prevented motor impairment, rise in levels of MDA and reduced glutathione and also significantly decreased the volume of infarct as compared to control. The study provides first evidence of effectiveness of trans resveratrol in focal ischemia most probably by virtue of its antioxidant property.

Protective effect of trans-resveratrol against kainic acid-induced seizures and oxidative stress in rats

Overexcitation of excitatory amino acid is an important mechanism in seizure genesis wherein free radicals have recently been suggested to play a critical role. Thus, intervention by antioxidants can be a potential beneficial approach in the treatment of epilepsy. The present study was undertaken to see the effect of trans-resveratrol, a potent antioxidant, against kainic acid-induced seizures, and effect on markers of oxidative stress in brain. Kainic acid, 10 mg/kg ip, induced long-lasting seizures and associated symptoms. The brain level of malondialdehyde (MDA) was found to be significantly raised after kainic acid administration (295 +/- 18 nmol/g wet tissue) as compared to control (195 +/- 26 nmol/g wet tissue). Pretreatment (5 min) of single dose of trans-resveratrol (40 mg/kg i.p.) could not inhibit the convulsions though the latency was significantly increased. When multiple doses of trans-resveratrol were injected in two-dose schedules in different animals (20 and 40 mg/kg ip, 5 min prior and repeated 30 and 90 min after kainic acid), there was significant reduction in incidence of convulsions in both treatment schedules. The brain MDA levels were found to be significantly attenuated in the trans-resveratrol-treated groups (multiple doses of 20 and 40 mg/kg) as compared to the kainic acid alone. However, the glutathione level in control, kainic acid- and trans-resveratrol-treated animals were not significantly different. The protective effect of trans-resveratrol against kainic acid-induced convulsions and the attenuation of raised MDA level suggest the potential use of antioxidants at least as adjunct therapy in epilepsy.

Evaluation of Withania somnifera in a middle cerebral artery occlusion model of stroke in rats

1. Stroke causes brain injury in millions of people worldwide each year. Despite the enormity of the problem, there is currently no approved therapy that can reduce infarct size or neurological disability. One of the approaches that can be used in limiting the neurological damage after stroke is the use of prophylactic treatment in patients with a high‐risk of stroke. The present study was undertaken to investigate the effect of the Indian herbal plant Withania somnifera as a prophylactic treatment in the middle cerebral artery (MCA) occlusion model of stroke in rats.

Protective effect of resveratrol against pentylenetetrazole-induced seizures and its modulation by an adenosinergic system.

The effect of trans-resveratrol (resveratrol), a polyphenolic compound with potent antioxidant activity, was investigated against pentylenetetrazole (PTZ) induced seizures in rats. Resveratrol (20, 40, and 80 mg/kg i.p.) administered 20 min prior to convulsive challenge with PTZ (60 mg/kg i.p.) dose dependently reduced the percent incidence of generalized tonic-clonic convulsions. Resveratrol (40 mg/kg) also potentiated the effect of sodium valproate (150 mg/kg) and diazepam (2 mg/kg) against PTZ-induced seizures. Since adenosine, an endogenous anticonvulsant, has been demonstrated to modulate the action of various antiepileptics, experiments were also carried out to determine whether an adenosinergic mechanism is involved in the anticonvulsant action of resveratrol. When a subanticonvulsant dose of adenosine (500 mg/kg) was administered together with resveratrol, a significant reduction in the percent incidence of generalized tonic-clonic convulsions was observed. Moreover, the nonspecific adenosine receptor antagonist theophylline (50 mg/kg i.p.) significantly reversed the resveratrol-induced protection, whereas the specific adenosine A2 receptor antagonist 3,7-dimethyl-1-propargylxanthine (1 mg/kg i.p.) could not reverse the resveratrol-induced protection. The findings of the present study suggest an antiepileptic potential of resveratrol and that an adenosinergic mechanism may play a role in its anticonvulsant activity.

Protective effect of exogenous administration of α‐tocopherol in middle cerebral artery occlusion model of cerebral ischemia in rats

Oxidative stress due to increased free radical generation and depletion of endogenous antioxidants have been implicated in ischemia–reperfusion‐induced neuronal injury. The present study was carried out to study the effect of acute administration of α‐tocopherol in the middle cerebral artery (MCA) occlusion model of stroke in rats. Rats were anesthetized using chloral hydrate (400 mg/kg i.p.) and subjected to 2 h of transient MCA occlusion. α‐Tocopherol was administered at the dose of 125 and 250 mg/kg orally 1 h prior to the occlusion of MCA. Motor performance test (grip test, foot fault test, rotarod performance test, spontaneous locomotor activity), markers of oxidative stress and 2,3,5‐triphenyl tetrazolium chloride staining were carried out 24 h after MCA occlusion. A vehicle‐treated group was run parallel. It was observed that α‐tocopherol at the dose of 125 mg/kg neither improved neurologic deficit, nor decreased the raised level of oxidative stress markers in comparison with the MCA‐occluded rats. However, higher dose of α‐tocopherol (250 mg/kg p.o.) afforded significant protection as evident by increase in motor performance tests and a decrease in the volume of infarction. The raised levels of malondialdehyde after MCA occlusion were also significantly attenuated. The results demonstrate that exogenous administration of α‐tocopherol is able to reduce the neuronal damage caused during ischemia–reperfusion, which can be attributed to its antioxidant activity.

Transient focal ischemia induces motor deficit but does not impair the cognitive function in middle cerebral artery occlusion model of stroke in rats

The effect on cognition was evaluated in the transient ischemia model of stroke in rats. Male Wistar rats were subjected to 2 h of transient ischemia by occluding the middle cerebral artery using the 4-0 intraluminal nylon thread. Neurological tests performed after 24 h, 7 and 15 days of middle cerebral artery (MCA) occlusion showed motor impairment as evidenced by decrease in the rota rod performance test. This was also confirmed histologically. However, when the learning and memory tests were performed, no change was observed in the learning and behavior as evidenced by insignificant difference in the retention latency in the passive avoidance test (334+/-31 s) and the transfer latency in the elevated plus maze (11+/-4.5 s) as compared to the sham-operated rats 369+/-34 and 8+/-1.7 s, respectively. The results of the present study demonstrates that transient occlusion of middle cerebral artery does not impair the learning and memory behavior of the rats.

Protective effect of adenosine against neuronal injury induced by middle cerebral artery occlusion in rats as evidenced by diffusion-weighted imaging

In the present study, adenosine, an inhibitory neuromodulator, was studied in male Wistar rats subjected to 2 h of transient middle cerebral artery (MCA) occlusion. Adenosine (500 mg/kg ip) was administered twice-once at the time of MCA occlusion and again at the time of reperfusion-and evaluated for its protective effect by using diffusion-weighted imaging (DWI) (30 min after reperfusion). After the DWI experiments, one group of animals was euthanized 2 h after reperfusion for the estimation of oxidative stress markers, while in another group, neurological deficit was assessed 24 h after MCA occlusion. In the adenosine-treated group, percent hemispheric lesion area (%HLA) in DWI was significantly attenuated (11.7+/-5.2) as compared to vehicle-treated group (21.4+/-4.7). The level of malondialdehyde (MDA) (301.8+/-22 nmol/g wet tissue) in the adenosine-treated group was significantly decreased as compared to that in the vehicle-treated MCA-occluded rats (420+/-20 nmol/g wet tissue). An insignificant change was observed in the levels of glutathione in both the vehicle-treated MCA-occluded and the adenosine-treated groups. The neurological deficit was significantly improved in the adenosine-treated group (1.8+/-0.06) as compared to the vehicle-treated (2.9+/-0.38) group. This is the first study to demonstrate the effectiveness of adenosine using DWI in the MCA-occluded rats.

Lithium does not synergize the peripheral action of cholinomimetics as seen in the central nervous system

Lithium is known to synergize the action of cholinomimetics in the CNS such that pilocarpine induces seizures in low concentration (1/13th of per se dose) in rats. The present study was undertaken to see if lithium priming also enhances the peripheral effects of acetylcholine and pilocarpine i.e. change in blood pressure in rats and contractions of the isolated guinea pig ileum. In anaesthetized rats the blood pressure was recorded from cannulated carotid artery connected through the pressure transducer to Coulbourn polygraph. The blood pressure response of pilocarpine was not different either in magnitude or in duration when administered 1, 2 and 4 h after lithium chloride (3 meq/kg) pretreatment as compared to the control. Similarly acetylcholine effect remained unchanged after lithium chloride priming. In the isolated guinea pig ileum experiments, ileum was incubated for 1 h in different concentrations of lithium chloride and effect on acetylcholine induced contractions were observed. Lithium in concentration of 2.8 x 10(-3) M had no effect on acetylcholine induced contractions while incubation with higher concentrations of 1.4 x 10(-2) M and 2.8 x 10(-2) M significant inhibition of acetylcholine contractions were observed. At this concentration, histamine induced contractions were also inhibited. The results indicate that lithium does not synergize the action of cholinomimetics in the periphery as that seen in the CNS. The inhibition of acetylcholine and histamine induced contractions in guinea pig ileum at high concentration of lithium seems to be non-specific effect.