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Characterization of synaptic circuits changes in ventral horn of embrionic spinal slices cultures from SOD1 G93A mice
Rančić, Vladimir
2011-04-11
Abstract
Amyotrophic lateral sclerosis (ALS) is a lethal neurodegenerative disease characterized
by loss of motoneurons. The discovery of mutations in the gene for the cytosolic Cu/Zn
superoxide dismutase in a small proportion of familiar ALS patients led to an animal
model in which the human mutant SOD1 is overexpressed in mice (G93A). For this study,
we employed the long term spinal cord organotypic cultures developed from G93A
embryonic mice and their wild type (WT) littermates, starting from the recent findings
emerged from a study by Avossa et al. (2006). These authors reported that G93A
organotypic spinal cultures exhibited increased vulnerability to AMPA glutamate receptormediated
excitotoxic stress, prior to clear disease appearance, besides showing a
significantly increased ratio between inhibitory and excitatory synapses, although they did
not express evident morphological differences, when compared to WT ones (Avossa et
al., 2006). The primary objective of this study was to investigate this early ALS stage to
understand how functional changes can predate morphological alterations. To that aim
we monitored spontaneous synaptic activity via patch clamping interneurons both in WT
and G93A spinal cultures after 7, 14 and 21 days of in vitro (DIV) growth. At 7 DIV, when
synchronous episodes of activity are normally detected in cultured spinal circuits, G93A
slices displayed bursting with a higher probability (83%) when compared to controls
(54%). Between 14 and 21 DIV, when bursting activity disappear, both in G93A and WT
slices, pharmacological dissection of glutamate, GABA and glycine mediated post
synaptic currents (PSCs), showed, in G93A, a significant reduction in GABAergic PSCs
and mPSCs in respect to WT. Upon pharmacological removal of the GABAergic
component, fast glycinergic events were unmasked and these events displayed a similar
frequency in both culture groups. Along with in vitro growth, we detected a progressive
reduction in the decay time constant of glycinergic PSCs, such process was significantly
faster in G93A. Thus, a shift in dynamic communication within spinal networks might be
involved in ALS progression.
Subjects
Publisher
Università degli studi di Trieste
Languages
en
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