Thyroid hormone (T3)-induced up-regulation of voltage-activated sodium current in cultured postnatal hippocampal neurons requires secretion of soluble factors from glial cells.
We have previously shown that treatment with the thyroid hormone T(3) increases the voltage-gated Na(+)current density (Nav-D) in hippocampal neurons from postnatal rats, leading to accelerated action potential upstrokes and increased firing frequencies. Here we show that the Na(+) current regulation depends on the presence of glial cells, which secrete a heat-instable soluble factor upon stimulation with T(3). The effect of conditioned medium from T(3)-treated glial cells was mimicked by basic fibroblast growth factor (bFGF), known to be released from cerebellar glial cells after T(3) treatment. Neutralization assays of astrocyte-conditioned media with anti-bFGF antibody inhibited the regulation of the Nav-D by T(3). This suggests that the up-regulation of the neuronal sodium current density by T(3) is not a direct effect but involves bFGF release and satellite cells. Thus glial cells can modulate neuronal excitability via secretion of paracrinely acting factors.
Niederkinkhaus
Vanessa
V
Department of Molecular Neurobiochemistry, Ruhr-University Bochum, NC7-170, Universitätsstrasse 150, D-44780 Bochum, Germany.
Marx
Romy
R
Hoffmann
Gerd
G
Dietzel
Irmgard D
ID
D000818:Animals; D001253:Astrocytes / Q000166:cytology; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism*; D008954:Models, Biological; D009457:Neuroglia / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000378:metabolism; D014284:Triiodothyronine / Q000378:metabolism*; D015854:Up-Regulation
D015222:Sodium Channels; D014284:Triiodothyronine; D016222:Fibroblast Growth Factor 2; D012964:Sodium