Acetylcholine and muscarinic receptor function in cerebral cortex of diabetic young and old male Wistar rats and the role of muscarinic receptors in calcium release from pancreatic islets

Abstract

We investigated acetylcholine esterase (AChE) activity, acetylcholine and muscarinic M1, M3 receptors kinetics in the cerebral cortex of young and old streptozotocin induced and insulin treated diabetic rats. The role of muscarinic receptors in intracellular calcium release from pancreatic islets was studied in vitro. Wistar rats of 7 and 90-weeks old were used. All studies were done in cerebral cortex. AChE assay was done by spectrophotometric method. Radioreceptor binding assays were done for Acetylcholine, Muscarinic M1 and M3 receptors using specific ligands. Calcium imaging was done using fluo4-AM in pancreatic cells. Ninety-weeks old control rats showed significantly decreased Vmax and increased Km for AChE compared to 7-weeks old control rats. An increased Vmax observed in both 7 and 90-weeks old diabetic groups with significant decrease in Km. Scatchard analysis using specific agonists showed significant decrease in the B (max) and K (d) of acetylcholine and muscarinic M1 receptors in 90-weeks old control rats compared to 7-weeks old control. Binding studies for M3 receptors showed no significant change compared to 7-weeks old control. Acetylcholine, muscarinic M1 and M3 receptor number significantly increased in 90-weeks old diabetic rat groups compared to their respective controls. Insulin treatment significantly reversed the binding parameters to near control compared to diabetic group. In vitro studies showed that acetylcholine through muscarinic M1 and M3 receptors' stimulated calcium release from the pancreatic islets. Thus our studies suggest that Insulin signaling play an important part in differentially regulating pancreatic cholinergic activity, and the diabetes mediated cortical dysfunctions with age.

Hormonal Signaling Systems of the Brain in Diabetes Mellitus

“…In the cerebral cortex of 7-week-old STZ rats the number of m 1 -MAChRs decreased by 28 %, while the number of m 3 -MAChRs increased by 30 %. In the cerebral cortex of 90-week-old diabetic rats the number of m 1 -and m 3 -MAChRs increased by 43 and 23 %, respectively, and the level of acetylcholine was significantly increased compared to control (Savitha et al, 2010). These alterations of m 1 -and m 3 -MAChR expression correlate with cholinergic hypofunction in short-term and prolonged STZ-induced DM.…”

Alterations of Hormone-Sensitive Adenylyl Cyclase System in the Tissues of Rats with Long-Term Streptozotocin Diabetes and the Influence of Intranasal Insulin

“…e degree of alterations and abnormalities in hormonal signaling systems is well correlated with the severity of T1DM and its complications [11,12]. As a result, at the later stages of the disease characterized by pronounced clinical symptoms, there are all reasons to expect the changes in these systems to be much expressed.…”

Decreased GABA receptor in the striatum and spatial recognition memory deficit in epileptic rats: Effect of Bacopa monnieri and bacoside-A

“…The sections were observed and photographed using confocal imaging system (Leica SP 5). The Pixel intensity of each image was calculated using LAS software from Lyca (Savitha et al, 2009a(Savitha et al, , 2009b.…”