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Enhanced muscarinic M1 receptor gene expression in the corpus striatum of streptozotocin-induced diabetic rats.

Gireesh G, Kumar TP, Mathew J, Paulose C - J. Biomed. Sci. (2009)

Bottom Line: We observed that insulin treatment brought back the decreased maximal velocity (Vmax) of acetylcholine esterase in the corpus striatum during diabetes to near control state.Real-time PCR experiment confirmed the increase in muscarinic M1 receptor gene expression and a similar reversal with insulin treatment.These results suggest the diabetes-induced changes of the cholinergic activity in the corpus striatum and the regulatory role of insulin on binding parameters and gene expression of total and muscarinic M1 receptors.

View Article: PubMed Central - HTML - PubMed

Affiliation: Molecular Neurobiology and Cell Biology Unit, Centre for Neuroscience, Cochin University of Science and Technology, Cochin-682022, Kerala, India. giri_ganga2000@yahoo.co.in

ABSTRACT
Acetylcholine (ACh), the first neurotransmitter to be identified, regulate the activities of central and peripheral functions through interactions with muscarinic receptors. Changes in muscarinic acetylcholine receptor (mAChR) have been implicated in the pathophysiology of many major diseases of the central nervous system (CNS). Previous reports from our laboratory on streptozotocin (STZ) induced diabetic rats showed down regulation of muscarinic M1 receptors in the brainstem, hypothalamus, cerebral cortex and pancreatic islets. In this study, we have investigated the changes of acetylcholine esterase (AChE) enzyme activity, total muscarinic and muscarinic M1 receptor binding and gene expression in the corpus striatum of STZ--diabetic rats and the insulin treated diabetic rats. The striatum, a neuronal nucleus intimately involved in motor behaviour, is one of the brain regions with the highest acetylcholine content. ACh has complex and clinically important actions in the striatum that are mediated predominantly by muscarinic receptors. We observed that insulin treatment brought back the decreased maximal velocity (Vmax) of acetylcholine esterase in the corpus striatum during diabetes to near control state. In diabetic rats there was a decrease in maximal number (Bmax) and affinity (Kd) of total muscarinic receptors whereas muscarinic M1 receptors were increased with decrease in affinity in diabetic rats. We observed that, in all cases, the binding parameters were reversed to near control by the treatment of diabetic rats with insulin. Real-time PCR experiment confirmed the increase in muscarinic M1 receptor gene expression and a similar reversal with insulin treatment. These results suggest the diabetes-induced changes of the cholinergic activity in the corpus striatum and the regulatory role of insulin on binding parameters and gene expression of total and muscarinic M1 receptors.

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Representative graph showing displacement analysis of [3H]QNB binding against pirenzepine in the corpus striatum of Control, Diabetic and Diabetic+Insulin treated group rats. Control (black circle), Diabetic (upward pointing black triangle), Insulin treated diabetic rats (downward pointing black triangle). Competition studies were carried out with 1 nM [3H]QNB in each tube with pirenzepine concentrations varying from 10-9 to 10-4 M. Data were fitted with iterative nonlinear regression software (Prism, GraphPad, San Diego, CA). Ki – The affinity of the receptor for the competing drug. EC50 is the concentration of the competitor that competes for half the specific binding.
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Figure 4: Representative graph showing displacement analysis of [3H]QNB binding against pirenzepine in the corpus striatum of Control, Diabetic and Diabetic+Insulin treated group rats. Control (black circle), Diabetic (upward pointing black triangle), Insulin treated diabetic rats (downward pointing black triangle). Competition studies were carried out with 1 nM [3H]QNB in each tube with pirenzepine concentrations varying from 10-9 to 10-4 M. Data were fitted with iterative nonlinear regression software (Prism, GraphPad, San Diego, CA). Ki – The affinity of the receptor for the competing drug. EC50 is the concentration of the competitor that competes for half the specific binding.

Mentions: In the displacement analysis, the competitive curve fitted to a one-site model in all the experimental conditions. Hill slopes were near unity confirming the one-site model. There were no changes in the log (EC50) values. The Ki value was decreased in diabetic condition (Fig 4 & Table 6).


Enhanced muscarinic M1 receptor gene expression in the corpus striatum of streptozotocin-induced diabetic rats.

Gireesh G, Kumar TP, Mathew J, Paulose C - J. Biomed. Sci. (2009)

Representative graph showing displacement analysis of [3H]QNB binding against pirenzepine in the corpus striatum of Control, Diabetic and Diabetic+Insulin treated group rats. Control (black circle), Diabetic (upward pointing black triangle), Insulin treated diabetic rats (downward pointing black triangle). Competition studies were carried out with 1 nM [3H]QNB in each tube with pirenzepine concentrations varying from 10-9 to 10-4 M. Data were fitted with iterative nonlinear regression software (Prism, GraphPad, San Diego, CA). Ki – The affinity of the receptor for the competing drug. EC50 is the concentration of the competitor that competes for half the specific binding.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2682793&req=5

Figure 4: Representative graph showing displacement analysis of [3H]QNB binding against pirenzepine in the corpus striatum of Control, Diabetic and Diabetic+Insulin treated group rats. Control (black circle), Diabetic (upward pointing black triangle), Insulin treated diabetic rats (downward pointing black triangle). Competition studies were carried out with 1 nM [3H]QNB in each tube with pirenzepine concentrations varying from 10-9 to 10-4 M. Data were fitted with iterative nonlinear regression software (Prism, GraphPad, San Diego, CA). Ki – The affinity of the receptor for the competing drug. EC50 is the concentration of the competitor that competes for half the specific binding.
Mentions: In the displacement analysis, the competitive curve fitted to a one-site model in all the experimental conditions. Hill slopes were near unity confirming the one-site model. There were no changes in the log (EC50) values. The Ki value was decreased in diabetic condition (Fig 4 & Table 6).

Bottom Line: We observed that insulin treatment brought back the decreased maximal velocity (Vmax) of acetylcholine esterase in the corpus striatum during diabetes to near control state.Real-time PCR experiment confirmed the increase in muscarinic M1 receptor gene expression and a similar reversal with insulin treatment.These results suggest the diabetes-induced changes of the cholinergic activity in the corpus striatum and the regulatory role of insulin on binding parameters and gene expression of total and muscarinic M1 receptors.

View Article: PubMed Central - HTML - PubMed

Affiliation: Molecular Neurobiology and Cell Biology Unit, Centre for Neuroscience, Cochin University of Science and Technology, Cochin-682022, Kerala, India. giri_ganga2000@yahoo.co.in

ABSTRACT
Acetylcholine (ACh), the first neurotransmitter to be identified, regulate the activities of central and peripheral functions through interactions with muscarinic receptors. Changes in muscarinic acetylcholine receptor (mAChR) have been implicated in the pathophysiology of many major diseases of the central nervous system (CNS). Previous reports from our laboratory on streptozotocin (STZ) induced diabetic rats showed down regulation of muscarinic M1 receptors in the brainstem, hypothalamus, cerebral cortex and pancreatic islets. In this study, we have investigated the changes of acetylcholine esterase (AChE) enzyme activity, total muscarinic and muscarinic M1 receptor binding and gene expression in the corpus striatum of STZ--diabetic rats and the insulin treated diabetic rats. The striatum, a neuronal nucleus intimately involved in motor behaviour, is one of the brain regions with the highest acetylcholine content. ACh has complex and clinically important actions in the striatum that are mediated predominantly by muscarinic receptors. We observed that insulin treatment brought back the decreased maximal velocity (Vmax) of acetylcholine esterase in the corpus striatum during diabetes to near control state. In diabetic rats there was a decrease in maximal number (Bmax) and affinity (Kd) of total muscarinic receptors whereas muscarinic M1 receptors were increased with decrease in affinity in diabetic rats. We observed that, in all cases, the binding parameters were reversed to near control by the treatment of diabetic rats with insulin. Real-time PCR experiment confirmed the increase in muscarinic M1 receptor gene expression and a similar reversal with insulin treatment. These results suggest the diabetes-induced changes of the cholinergic activity in the corpus striatum and the regulatory role of insulin on binding parameters and gene expression of total and muscarinic M1 receptors.

Show MeSH
Related in: MedlinePlus