Citation:

Gilbert, M., K. Sanchez-Huerta, AND C. Wood. Developmental Hypothyroidism Reduces the Expression of Activity-Dependent Plasticity Genes in Denate Gyrus of the Adult Following Long Term Potentiation. Presented at Teratology Meeting, Bellevue, WA, June 28 - July 02, 2014.

Impact/Purpose:

This abstract will be presented at the Neurobehavioral Teratology Society Meeting, June 28-July 2, 2014, Bellevue, Washington

Description:

Disruption of thyroid hormone (TH) is a known effect of environmental contaminants. Neurotrophins including brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) have been implicated in brain dysfunction resulting from severe developmental TH insufficiency. Neurotrophins are also implicated in activity-dependent plasticity, a process critical for appropriate use-dependent connectivity in the developing brain and for memory formation in the adult. This study examined activity-induced expression of neurotrophin gene products in the hippocampus using the long-term potentiation (LTP) after developmental hypothyroidism induced by propylthiouracil (PTU). Pregnant rats were exposed to PTU (0 or I0ppm) via the drinking water from early gestation to weaning. Adult male offspring were anesthetized with urethane and implanted with electrodes in the dentate gyrus (00) and perforant path (PP). LTP was induced by PP stimulation and responses from 00 were monitored at 15m intervals until sacrifice of the animals 5 h later. The 00 was dissected from the stimulated and nonstimulated hemispheres for rtPCR analysis of the neurotrophins Bdnf, Ngf, Ntf3 and related genes Egrl, Arc, Klf9. We found no PTU-induced difference in basal levels of expression of any of these genes in the nonstimulated 00. LTP increased expression of Bdnf, Ngf, Arc and Klj9 in the control DG, and reduced expression of Ntf3. LTP in DG from PTU animals failed to increase expression of Bdnf, and although expression levels of Ngf, Arc and Klj9 were augmented, the magnitude of the fold change appeared diminished relative to controls. These data suggest that developmental hypothyroidism results in a reduced capacity to mount genomic responses required for synaptic plasticity despite lack of effect on basal levels of gene expression and return to normal thyroid.

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