Related Experiment Video
Updated: Jun 3, 2026
Dynamic Clamp Methods to Investigate Impaired Neuronal Excitability Associated with Autism
Published on: October 17, 2025
Enhanced long-term microcircuit plasticity in the valproic Acid animal model of autism
Guilherme Testa Silva1, Jean-Vincent Le Bé, Imad Riachi
1Laboratory of Neural Microcircuitry, Brain and Mind Institute, EPFL Lausanne, Switzerland.
Insights
Valproic acid (VPA) exposure in pregnant rats induced autistic-like behaviors in offspring. Long Term Microcircuit Plasticity (LTMP) expanded beyond normal minicolumnar limits, suggesting altered neocortical development in this autism model.
Area of Science:
- Neuroscience
- Developmental Neuroscience
- Autism Research
Background:
- Valproic acid (VPA) exposure during gestation causes autistic-like symptoms in offspring.
- VPA-induced autism models exhibit hyperreactive microcircuitry with increased glutamatergic synapse connectivity and NMDA receptor expression.
- Previous findings indicated these microcircuit changes were confined to minicolumnar dimensions (<50 μm).
Purpose of the Study:
- To investigate alterations in Long Term Microcircuit Plasticity (LTMP) in a VPA-induced rat model of autism.
- To determine if LTMP is modified in layer 5 pyramidal cells of the somatosensory cortex.
Main Methods:
- Multi-neuron patch-clamp recordings were performed on layer 5 pyramidal cells in somatosensory cortex slices from postnatal day 12-15 rats.
- Neuronal connectivity and synaptic properties were mapped before and after a 12-hour perfusion with 100 μM sodium glutamate.
- LTMP was assessed by re-patching the same neuronal clusters after glutamate exposure.
Main Results:
- Enhanced LTMP was observed specifically at inter-somatic distances exceeding minicolumnar dimensions.
- Hyperconnectivity within minicolumns appeared near saturation in VPA-treated animals.
- LTMP extended beyond the typical minicolumnar boundaries, driving increased hyperconnectivity.
Conclusions:
- Long Term Microcircuit Plasticity is altered in the VPA-induced autism model, expanding beyond typical minicolumnar limits.
- This suggests that the neocortex in this autism model remains highly plastic, with LTMP contributing to widespread hyperconnectivity.
- Findings support the hypothesis that aberrant synaptic plasticity contributes to the neurobiological underpinnings of autism.
Abstract:
A single intra-peritoneal injection of valproic acid (VPA) on embryonic day (ED) 11.5 to pregnant rats has been shown to produce severe autistic-like symptoms in the offspring. Previous studies showed that the microcircuitry is hyperreactive due to hyperconnectivity of glutamatergic synapses and hyperplastic due to over-expression of NMDA receptors. These changes were restricted to the dimensions of a minicolumn (<50 μm). In the present study, we explored whether Long Term Microcircuit Plasticity (LTMP) was altered in this animal model. We performed multi-neuron patch-clamp recordings on clusters of layer 5 pyramidal cells in somatosensory cortex brain slices (PN 12-15), mapped the connectivity and characterized the synaptic properties for connected neurons. Pipettes were then withdrawn and the slice was perfused with 100 μM sodium glutamate in artificial cerebrospinal fluid in the recording chamber for 12 h. When we re-patched the same cluster of neurons, we found enhanced LTMP only at inter-somatic distances beyond minicolumnar dimensions. These data suggest that hyperconnectivity is already near its peak within the dimensions of the minicolumn in the treated animals and that LTMP, which is normally restricted to within a minicolumn, spills over to drive hyperconnectivity across the dimensions of a minicolumn. This study provides further evidence to support the notion that the neocortex is highly plastic in response to new experiences in this animal model of autism.
Related Concept Videos
01:25Long-term Potentiation
Hebbian LTP
LTP can occur when presynaptic neurons...
01:35Long-term Potentiation