title: Insulin receptor signaling in rat hippocampus: a study in STZ (ICV) induced memory deficit model.
abstract: Brain insulin receptors (IRs) have been suggested as an important regulatory factor for cognitive functions but the involvement of IR signaling in memory deficit associated with neurodegenerative conditions is not yet explored. In the present study, IR gene expression was studied by RT-PCR and signaling pathways by immunoblotting in CA1, DG and CA3 subregions of hippocampus in intracerebroventricular (ICV) administered streptozotocin (STZ, 3mg/kg twice) induced memory deficit model in rat. The effect of pre- and post-treatment of donepezil (5mg/kg po) and melatonin (20mg/kg po) on signaling pathways were studied. Effect of LY294002 (ICV), a PI3 Kinase inhibitor, was also investigated on memory functions and Akt phosphorylation. An increased IR expression (both gene and protein), phosphorylation of Shc, Erk1/2, IRS-1 and Akt in CA1 and CA3 region of P2M fraction was observed after training as compared to control. STZ treated rats showed memory deficit and significant decrease in IR expression, phosphorylation of IRS-1 and Akt only in CA3 region as compared to trained group which were reversed by pre and post-treatment of melatonin but donepezil was effective only against memory deficit. LY294002 (3mM) treatment showed delayed learning and decrease in Akt phosphorylation. This study suggests that IR expression and its signaling pathways in hippocampal CA1 and CA3 regions are involved in memory functions and STZ (ICV) induced memory deficit. Hippocampal IR system might be playing an important role in regulation of memory functions, however only IR/IRS-1/Akt pathway in CA3 region is associated with STZ induced memory deficit.
authors.affiliation: Division of Pharmacology, Central Drug Research Institute, CSIR, Lucknow-226001, India.
authors.forename: Rahul
authors.initials: R
authors.lastname: Agrawal
authors.forename: Ethika
authors.initials: E
authors.lastname: Tyagi
authors.forename: Rakesh
authors.initials: R
authors.lastname: Shukla
authors.forename: Chandishwar
authors.initials: C
authors.lastname: Nath
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002867:Chromones / Q000494:pharmacology; D004195:Disease Models, Animal; D000077265:Donepezil; D015870:Gene Expression / Q000187:drug effects; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D007189:Indans / Q000494:pharmacology; D057967:Infusions, Intraventricular; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D008550:Melatonin / Q000494:pharmacology; D008568:Memory / Q000187:drug effects; D008569:Memory Disorders / Q000139:chemically induced / Q000378:metabolism*; D009025:Morpholines / Q000494:pharmacology; D018697:Nootropic Agents / Q000494:pharmacology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010880:Piperidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011972:Receptor, Insulin / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013311:Streptozocin / Q000008:administration & dosage
chemical_list: D001786:Blood Glucose; D002867:Chromones; D007189:Indans; D009025:Morpholines; D018697:Nootropic Agents; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010880:Piperidines; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D013311:Streptozocin; D000077265:Donepezil; D011972:Receptor, Insulin; D008550:Melatonin