Experimental acute hyperthyroidism disrupts hippocampal long-term potentiation but not paired pulse facilitation in adult rats

Abstract

Event Abstract Back to Event Experimental acute hyperthyroidism disrupts hippocampal long-term potentiation but not paired pulse facilitation in adult rats A. S. Artis1*, C. Süer1, N. Dolu1 and L. Sahin1 1 Erciyes University Medical Faculty, Physiology Department, Turkey Manipulations of thyroid hormones have been shown to influence learning and memory. The main paradigm currently used to investigate hyperthyroidism is the administration of thyroxin to adult normothyroid animals. To date, however, there is a lack of electrophysiological data to complement results from behavioral studies. In the present study, we therefore tested the effects of L-thyroxine on paired-pulse facilitation and long-term potentiation in rats. The experiments were carried out on rats between the ages of 9-10 months and were approved by the Erciyes University Committee on Ethics in Animal Experimentation. The experimental animals were randomly divided into a hyperthyroid group and a control group (n=6 in each group). All rats in the hyperthyroid group were injected with thyroxine (0.1 mg/kg/day, ip, 14 days). At the 15th day, stimulating and recording electrodes were introduced in the medial perforant path and dentate gyrus, respectively. Field excitatory postsynaptic potentials (fEPSP) in response to electrical stimulation of perforant pathway were recorded from dentate gyrus using a voltage/current amplifier. fEPSP amplitudes were plotted relative to increasing current of the electrical stimulus to obtain input-output relationship. Paired pulse facilitation was measured from evoked responses of paired pulses with inter-pair intervals between 20-160 ms. Long-term potentiation was induced by four sets of tetanic trains after a baseline recording of fEPSP. Compared to controls, the thyroxine-treated rats showed a significantly attenuated response during input-output relationship and lower efficacy of long-term potentiation. No significant differences were found in paired pulse facilitation. These results provide in vivo evidence that administration of L-thyroxine leads to changes in the excitability of dentate gyrus neurons in adult rats. We hypothesize that this could be due to reduced expression of the NR1-NR2A subgroups of NMDA-type glutamate receptors, which are known to play a role in long term potentiation. To test this hypothesis it will be necessary to combine behavioral and electrophysiological measurements with studies of receptor binding or Western blot analysis. Conference: 2nd NEUROMED Workshop, Fez, Morocco, 10 Jun - 12 Jun, 2010. Presentation Type: Oral Presentation Topic: Oral Session 3: The plastic brain: implications for learning and education Citation: Artis AS, Süer C, Dolu N and Sahin L (2010). Experimental acute hyperthyroidism disrupts hippocampal long-term potentiation but not paired pulse facilitation in adult rats. Front. Neurosci. Conference Abstract: 2nd NEUROMED Workshop. doi: 10.3389/conf.fnins.2010.12.00031 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 04 Jun 2010; Published Online: 04 Jun 2010. * Correspondence: A. S Artis, Erciyes University Medical Faculty, Physiology Department, Kayseri, Turkey, aseda@yahoo.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers A. S Artis C. Süer N. Dolu L. Sahin Google A. S Artis C. Süer N. Dolu L. Sahin Google Scholar A. S Artis C. Süer N. Dolu L. Sahin PubMed A. S Artis C. Süer N. Dolu L. Sahin Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.