C.S. Paulose

Bacopa monnieri and Bacoside-A for ameliorating epilepsy associated behavioral deficits.

Bacopa monnieri is an outstanding nervine tonic used for raising the mental performance. It helps in concentration, comprehension, recall and alertness, Brahmi is particularly beneficial as it aids in categorizing information in brain and its subsequent expression. Bacopa is also called as a natural antioxidant which may give details its neuroprotective role seen in the memory centers of the brain. Epilepsy is neuronal disorder characterized by learning, cognitive and memory impairments. The present review summarizes information concerning botany, chemistry and beneficial effect of Bacopa monnieri on epilepsy associated behavioral deficits.

Neuroprotective role of curcumin in the cerebellum of streptozotocin-induced diabetic rats

AIMS Chronic hyperglycaemia in diabetes involves a direct neuronal damage caused by intracellular glucose which leads to altered neurotransmitter functions and reduced motor activity. The present study investigated the effect of curcumin in the functional regulation of muscarinic and alpha7 nicotinic acetylcholine receptors, insulin receptors, acetylcholine esterase and Glut3 in the cerebellum of streptozotocin (STZ)-induced diabetic rats. MAIN METHODS All studies were done in the cerebellum of male Wistar rats. Radioreceptor binding assays were done for total muscarinic, M(1) and M(3) receptors using specific ligands, and the gene expression was also studied using specific probes. KEY FINDINGS Our results showed an increased gene expression of acetylcholine esterase, Glut3, muscarinic M1, M3, alpha7 nicotinic acetylcholine and insulin receptors in the cerebellum of diabetic rats in comparison to control. Scatchard analysis of total muscarinic, M1 and M3 receptors showed an increased binding parameter, B(max) in diabetic rats compared to control. Curcumin and insulin inhibited diabetes-induced elevation in the gene expression of acetylcholine esterase, Glut3, insulin and cholinergic receptors in the cerebellum of diabetic rats. SIGNIFICANCE Our studies suggest that curcumin plays a vital role in regulating the activity of cholinergic and insulin receptors and mechanism of glucose transportation through Glut3, which results in normalizing the diabetes-mediated cerebellar disorders. Thus, curcumin has a significant role in a therapeutic application for the prevention or progression of diabetic complications in the cerebellum.

Cholinergic, dopaminergic and insulin receptors gene expression in the cerebellum of streptozotocin-induced diabetic rats: Functional regulation with Vitamin D3 supplementation

The study was to find out the effect of Vitamin D3 supplementation on preventing the altered gene expression of cholinergic, dopaminergic, insulin receptors and GLUT3 gene expression in cerebellum of diabetic rats. Radioreceptor binding assays and gene expression were done in the cerebellum of male Wistar rats. Rota rod has been used to evaluate motor coordination. Our results showed a significantly increased gene expression of dopamine D2, muscarinic M1, M3, alpha7 nicotinic acetylcholine, insulin receptors, acetylcholine esterase, GLUT3 and Vitamin D receptor in the cerebellum of diabetic rats. There was a down-regulation of dopamine D1 receptor. Total dopamine receptor showed a decreased and total muscarinic, muscarinic M1 and M3 receptors showed an increased binding parameter, B(max). Rota rod experiment showed a significant decrease in the retention time on the rotating rod in diabetic while treatment improved retention time near to control. Vitamin D3 and insulin treatment markedly recovered the altered gene expression and binding parameters to near control. Our study showed Vitamin D3 functional regulation through dopaminergic, cholinergic and insulin receptors and glucose transport mechanism through GLUT3 in the cerebellum of diabetic rats which play a major role in neuroprotection in diabetes which has clinical application.

Enhanced NMDAR1, NMDA2B and mGlu5 receptors gene expression in the cerebellum of insulin induced hypoglycaemic and streptozotocin induced diabetic rats.

Glucose homeostasis in humans is an important factor for the functioning of the nervous system. A decrease in glucose content below a minimal level or hypoglycemia is dangerous for cells of the central and peripheral nerve system. In the present study we showed the effects of insulin induced hypoglycaemia and streptozotocin induced diabetes on the cerebellar glutamate receptor subunits and glutamate transporter. Cerebellar dysfunction is associated with seizure generation, motor deficits and memory impairment. We found an up regulation in NMDA receptor number and gene expression of N-methyl-d-aspartic acid (NMDA(R1)), NMDA(2B), metabotrophic glutamate 5 (mGlu(5)) glutamate receptor subunits in experimental rats. The glutamate content was shown to be increased with decreased glutamate aspartate transporter (GLAST) gene expressions indicating lower reuptake of glutamate. The enhanced gene expression of NMDA(R1), NMDA(2B), mGlu(5) glutamate receptors were confirmed by immunohistochemistry studies. At the second messenger level, the IP3 content and IP3 receptors were enhanced in the cerebellum of both hypoglycaemic and diabetic rats increased. The present study showed that the enhanced glutamate content activates NMDA receptors, increasing the inositol triphosphate (IP3) content which mediates Ca(2+) overload in cells causing cell damage and neurodegeneration. Our results also showed that the enhanced glutamate receptor activity were more prominent in hypoglycaemic group compared to diabetic group. Further the neurodegeneration by the up regulation of glutamate receptor activity causing motor dysfunction was demonstrated by the Rotarod test. Thus our results suggest that enhanced NMDA receptor mediated neurodegeneration affect the motor learning and memory ability of an individual.

Antihyperglycemic and insulin secretory activity of Costus pictus leaf extract in streptozotocin induced diabetic rats and in in vitro pancreatic islet culture

AIM OF THE STUDY The leaves of Costus pictus D. Don were used extensively for its antihyperglycemic activity by the people in Kerala, India. In the present study, the antihyperglycemic and insulin secretory activity of an aqueous extract of Costus pictus leaf extract was investigated in streptozotocin induced diabetic rats. MATERIALS AND METHODS Oral Glucose Tolerance Test was done to determine the effective dose of Costus pictus extract. Aqueous extract of Costus pictus leaves was given orally to the diabetic rats for 14 days. The insulin secretory action of the leaf extract was investigated using isolated pancreatic islets from rat. Liver glucose uptake activity was measured using D-[14C] glucose. RESULTS The oral administration of an aqueous extract of Costus pictus at a dose of 250 mg/kg body weight significantly decreased the blood glucose with significant increase in plasma insulin level in diabetic rats at the end of 14 days treatment. The Costus pictus leaf extract significantly increased glucose induced insulin secretion at both 4 mM and 20 mM glucose concentrations which represents normal physiological and diabetic condition respectively. The decreased glucose uptake activity of the liver of diabetic rats was reverted to near normal levels after the treatment with Costus pictus leaf extract. CONCLUSION Our results suggest the glucose lowering effect of Costus pictus to be associated with the potentiation of insulin release from pancreatic islets and enhancement of peripheral utilization of glucose.

Cholinergic and GABAergic receptor functional deficit in the hippocampus of insulin-induced hypoglycemic and streptozotocin-induced diabetic rats

Neurotransmitter receptor functional regulation plays an important role in controlling the excitability and responsiveness of hippocampal neurons. Deregulation of its function is associated with seizure generation, motor deficits, and memory impairment. In the present study we investigated the changes in hippocampal cholinergic and GABA receptor binding and gene expression in insulin-induced hypoglycemic and streptozotocin-induced diabetic rats. Expression of cholinergic enzymes; acetylcholine esterase (AChE) and choline acetyltransferase (ChAT) upregulated and downregulated, respectively, in diabetic group, which was further exacerbated by hypoglycemia. Total muscarinic receptor, muscarinic M1, and GABA maximal binding (B(max)) significantly decreased in hypoglycemic and diabetic rats. In hypoglycemic group, the B(max) showed further decline compared with diabetes. Muscarinic M3 receptor B(max) and gene expression upregulated in hypoglycemic and diabetic group. Alpha7 nicotinic acetylcholine receptor (α7 nAChR) expression significantly downregulated in hypoglycemic and diabetic rats. Gene expression of glutamate decarboxylase (GAD), GABAAα1, and GABAB in hypoglycemic and diabetic rats downregulated, with more significant decrease in hypoglycemic group. Present findings show altered cholinergic, muscarinic, nicotinic receptor expression and thereby function. Decreased GABA receptor expression is associated with decline in GABAergic neurotransmission. Thus cholinergic receptor dysfunction and decreased GABAergic neuroprotective inhibitory function in the hippocampus of hypoglycemic and diabetic rats account for the increased vulnerability of hippocampus predisposing to neuronal damage, which is suggested to contribute to cognitive impairment and memory deficit reported in hypoglycemia and diabetes. Also, recurrent hypoglycemia in diabetes exacerbates the hippocampal dysfunction induced by diabetes, which has clinical significance in diabetes therapy.

NMDA and AMPA receptor mediated excitotoxicity in cerebral cortex of streptozotocin induced diabetic rat: ameliorating effects of curcumin.

Functional activity of neurotransmitter receptor and their sensitivity to regulation are altered in DM. We evaluated the neuroprotective effect of curcumin in glutamate mediated excitotoxicity in cerebral cortex of streptozotocin induced diabetic rats. Gene expression studies in diabetic rats showed a down regulation of glutamate decarboxylase mRNA leading to accumulation of glutamate. Radioreceptor binding assays showed a significant increase in α-amino-3-hydroxy-5-methyl-4-isoxazole propionate and N-methyl-D-aspartate receptors density which was confirmed by immunohistochemical studies. Decreased glutathione peroxidases gene expression indicates enhanced oxidative stress in diabetic rats. This leads to decreased expression of glutamate aspartate transporter, which in turn reduces glutamate transport. All these events lead to excitotoxic neuronal death in the cerebral cortex, which was confirmed by the increased expression of caspase 3, caspase 8 and BCL2-associated X protein. Curcumin and insulin treatment reversed these altered parameters to near control. We establish, a novel therapeutic role of curcumin by reducing the glutamate mediated excitotoxicity in cerebral cortex of diabetes through modulating the altered neurochemical parameters.

Hypoglycemia induced changes in cholinergic receptor expression in the cerebellum of diabetic rats.

Glucose homeostasis in humans is an important factor for the functioning of nervous system. Hypoglycemia and hyperglycemia is found to be associated with central and peripheral nerve system dysfunction. Changes in acetylcholine receptors have been implicated in the pathophysiology of many major diseases of the central nervous system (CNS). In the present study we showed the effects of insulin induced hypoglycemia and streptozotocin induced diabetes on the cerebellar cholinergic receptors, GLUT3 and muscle cholinergic activity. Results showed enhanced binding parameters and gene expression of Muscarinic M1, M3 receptor subtypes in cerebellum of diabetic (D) and hypoglycemic group (D + IIH and C + IIH). α7nAchR gene expression showed a significant upregulation in diabetic group and showed further upregulated expression in both D + IIH and C + IIH group. AchE expression significantly upregulated in hypoglycemic and diabetic group. ChAT showed downregulation and GLUT3 expression showed a significant upregulation in D + IIH and C + IIH and diabetic group. AchE activity enhanced in the muscle of hypoglycemic and diabetic rats. Our studies demonstrated a functional disturbance in the neuronal glucose transporter GLUT3 in the cerebellum during insulin induced hypoglycemia in diabetic rats. Altered expression of muscarinic M1, M3 and α7nAchR and increased muscle AchE activity in hypoglycemic rats in cerebellum is suggested to cause cognitive and motor dysfunction. Hypoglycemia induced changes in ChAT and AchE gene expression is suggested to cause impaired acetycholine metabolism in the cerebellum. Cerebellar dysfunction is associated with seizure generation, motor deficits and memory impairment. The results shows that cerebellar cholinergic neurotransmission is impaired during hyperglycemia and hypoglycemia and the hypoglycemia is causing more prominent imbalance in cholinergic neurotransmission which is suggested to be a cause of cerebellar dysfunction associated with hypoglycemia.

INCREASED GLUTAMATE RECEPTOR GENE EXPRESSION IN THE CEREBRAL CORTEX OF INSULIN INDUCED HYPOGLYCEMIC AND STREPTOZOTOCIN-INDUCED DIABETIC RATS

Hypoglycemia causes brain fuel deprivation, resulting in functional brain failure and brain death. It is a serious complication of insulin therapy in diabetic patients. A single intrafemoral dose of streptozotocin was administered to induce diabetes. Hypoglycemia was induced by appropriate doses of insulin s.c. in control and diabetic rats. Glutamate content and glutamate receptor kinetics were studied using [3H]glutamate. [3H]MK 801 was used to study the NMDA receptor kinetics. NMDA2B and metabotropic glutamate receptor (mGluR) 5 subunits receptor gene expressions were done using real time PCR. There was a significant (P<0.001) increase in the glutamate content in the cerebral cortex of hypoglycemic and diabetic rats when compared with control with more glutamate content in the hypoglycemic group. Scatchard analysis using [3H]glutamate and [3H]MK 801 in the cerebral cortex showed a significant (P<0.001) increase in the maximal binding (Bmax) in both hypoglycemic and diabetic rats when compared with control with no significant change in equilibrium dissociation constant. The glutamate and NMDA receptor binding parameters were significantly (P<0.001) enhanced in the hypoglycemic rats compared with hyperglycemic rats. Real time PCR analysis also showed a significant increase (P<0.001) in the gene expression of NMDA2B and mGluR5 subunits of glutamate receptor. This increased gene expression of NMDA2B and mGluR5 glutamate receptor subunits confirmed the enhanced mRNA of receptor subunits and subsequently at the protein level from the receptor kinetic studies. The enhanced glutamate receptors were more prominent in hypoglycemic group which is of significance in this study. Up-regulation of glutamate leads to Ca2+ overload in cells, potentially leading to cell damage and death. This functional damage during hypoglycemia is suggested to contribute to cognitive and memory deficits which has immense clinical relevance in the therapeutic management of diabetes.

Oxidative Stress Induced NMDA Receptor Alteration Leads to Spatial Memory Deficits in Temporal Lobe Epilepsy: Ameliorative Effects of Withania somnifera and Withanolide A

In the present study we investigate the effect of Withania somnifera (WS) root extract and Withanolide A (WA) in restoring spatial memory deficit by inhibiting oxidative stress induced alteration in glutamergic neurotransmission. We demonstrate significant cellular loss in hippocampus of epileptic rats, visualized through decreased TOPRO stained neurons. Impaired spatial memory was observed in epileptic rats after Radial arm maze test. Treatment with WS and WA has resulted in increased number of TOPRO stained neurons. Enhanced performance of epileptic rats treated with WS and WA was observed in Radial arm maze test. The antioxidant activity of WS and WA was studied using superoxide dismutase (SOD) and Catalase (CAT) assays in the hippocampus of experimental rats. The SOD activity and CAT activity decreased significantly in epileptic group, treatment with WS and WA significantly reversed the enzymatic activities to near control. Real time gene expression studies of SOD and GPx showed significant up-regulation in epileptic group compared to control. Treatment with WS and WA showed significant reversal to near control. Lipid peroxidation quantified using TBARS assay, significantly increased in epileptic rats. Treatment with WS and WA showed significant reversal to near control. NMDA receptor expression decreased in epileptic rats. The treatment with WS and WA resulted in physiological expression of NMDA receptors. This data suggests that oxidative stress effects membrane constitution resulting in decreased NMDA receptor density leading to impaired spatial memory. Treatment with WS and WA has ameliorated spatial memory deficits by enhancing antioxidant system and restoring altered NMDA receptor density.