title: Hypothyroidism impairs late LTP in CA1 region but not in dentate gyrus of the intact rat hippocampus: MAPK involvement.
abstract: Thyroid hormone activates extracellular signal-regulated kinases (ERK1 and ERK2), which are important in late long-term potentiation (L-LTP). The aim of this study was to determine the possible mechanism underlying the impairment of L-LTP as a result of hypothyroidism. We investigated the effect of hypothyroidism on L-LTP of the two associative pathways in the hippocampus: the Schaffer collateral synapses and the perforant path synapses. We also examined the effect of hypothyroidism on ERK1 and ERK2 levels in both the CA1 and dentate gyrus (DG) regions of the hippocampus. Electrophysiological recordings from hippocampi of anesthetized rats show that hypothyroidism impairs L-LTP in CA1 region, but not in the DG. Western blot analysis of the CA1 region shows that hypothyroidism decreases phosphorylated ERK1 and ERK2 levels without affecting their total levels. In the DG of the hypothyroid rat, however, there was no significant change in the levels of phosphorylated or total ERKs. The correlation between the effect of hypothyroidism on L-LTP and enzyme levels suggests that hypothyroidism-induced impairment of L-LTP in CA1 may be due to decreased levels of phosphorylated ERK1 and ERK2.
authors.affiliation: Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas 77204-5515, USA.
authors.forename: Nashaat Z
authors.initials: NZ
authors.lastname: Gerges
authors.forename: Karim A
authors.initials: KA
authors.lastname: Alkadhi
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D018891:Dentate Gyrus / Q000201:enzymology / Q000503:physiopathology; D015536:Down-Regulation / Q000502:physiology; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D006624:Hippocampus / Q000201:enzymology* / Q000503:physiopathology; D007037:Hypothyroidism / Q000150:complications* / Q000503:physiopathology; D017774:Long-Term Potentiation / Q000502:physiology*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008297:Male; D008569:Memory Disorders / Q000201:enzymology* / Q000209:etiology* / Q000503:physiopathology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009434:Neural Pathways / Q000201:enzymology / Q000503:physiopathology; D010766:Phosphorylation; D017729:Presynaptic Terminals / Q000201:enzymology; D051381:Rats; D017208:Rats, Wistar; D009435:Synaptic Transmission / Q000502:physiology
chemical_list: D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases