Levothyroxin restores hypothyroidism-induced impairment of hippocampus-dependent learning and memory: Behavioral, electrophysiological, and molecular studies. Hippocampus 2009 Jan;19(1):66-78
Date
08/06/2008Pubmed ID
18680156DOI
10.1002/hipo.20476Scopus ID
2-s2.0-58149469365 (requires institutional sign-in at Scopus site) 130 CitationsAbstract
Hypothyroidism induces cognitive impairment in experimental animals and patients. Clinical reports are conflicting about the ability of thyroid hormone replacement therapy to fully restore the hypothyroidism-induced learning and memory impairment. In this study, we investigated the effects of L-thyroxin (thyroxin) treatment on hippocampus-dependent learning and memory in thyroidectomized adult rats. In the radial arm water maze (RAWM) task, thyroxin treated thyroidectomized animals made significantly fewer errors than the untreated hypothyroid animals in Trial 3 of the acquisition phase, short-term memory and long-term memory tests. In addition, the number of errors made by the thyroxin treated thyroidectomized animals was not different from that of the control group. Furthermore, the days-to-criterion (DTC) values for thyroxin treated thyroidectomized animals were not different from those of the control group but significantly lower than those of the untreated hypothyroid animals. In anesthetized rats, extracellular recording from hippocampal area CA1 of hypothyroid rats shows that thyroxin treatment restores impaired Late-phase long-term potentiation (L-LTP). Immunoblot analysis of signaling molecules, including cyclic-AMP response element binding protein (CREB), mitogen-activated protein kinases (MAPKp44/42; ERK1/2), in area CA1 revealed that thyroxin treatment reversed hypothyroidism-induced reduction of signaling molecules essential for learning and memory, and L-LTP. This study shows that thyroxin treatment reverses hypothyroidism-induced impairment of hippocampus-dependent cognition, and L-LTP, probably by restoring the levels of signaling molecule important for these processes.
Author List
Alzoubi KH, Gerges NZ, Aleisa AM, Alkadhi KAAuthor
Nashaat Gerges PhD Chair, Professor in the School of Pharmacy Administration department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AnimalsCyclic AMP Response Element-Binding Protein
Hippocampus
Hypothyroidism
Learning
Long-Term Potentiation
MAP Kinase Signaling System
Male
Maze Learning
Memory
Memory Disorders
Rats
Rats, Wistar
Thyroxine
Treatment Outcome
