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09:09
Electrophysiological Investigations of Retinogeniculate and Corticogeniculate Synapse Function
Published on: August 7, 2019
Electrical and chemical synapses between relay neurons in developing thalamus
Seung-Chan Lee1, Scott J Cruikshank, Barry W Connors
1Department of Neuroscience, Division of Biology and Medicine, Brown University, Providence, RI 02912, USA.
The Journal of Physiology
|May 12, 2010
Summary
Electrical synapses are common between developing thalamic relay neurons but decrease with age. Connexin36 (Cx36) is crucial, but other proteins also contribute to these vital neural circuit connections.
Area of Science:
- Neuroscience
- Developmental Biology
- Cellular Neuroscience
Background:
- Gap junction-mediated electrical synapses are vital for neural circuit synchronization and development.
- Thalamic relay neurons are key inputs to the neocortex, but electrical synapses between them remain uncharacterized.
- The ventrobasal nucleus (VBN) of the thalamus processes somatosensory information.
Purpose of the Study:
- To investigate the presence and developmental trajectory of electrical synapses between thalamic relay neurons.
- To identify the molecular players, specifically connexins, involved in VBN neuron electrical coupling.
- To understand the interplay between electrical and chemical synaptic transmission during VBN development.
Main Methods:
- Extracellular and patch-clamp recordings from pairs of VBN relay neurons in acute brain slices from developing rats and mice.
- Electrophysiological analysis of electrical coupling strength and properties.
- Investigation of electrical synapses in connexin36 (Cx36) knockout mice.
- Analysis of Cx36 expression using a beta-galactosidase reporter system.
Main Results:
- Electrical synapses were prevalent between VBN relay neurons in the first postnatal week, declining sharply by the second week.
- Cx36 knockout mice showed reduced electrical coupling, indicating Cx36's primary role, with contributions from other gap junction proteins.
- Cx36 expression in VBN neurons mirrored the developmental decline in electrical coupling.
- A shift from electrical to chemical synaptic communication was observed, with disynaptic inhibition emerging as electrical coupling decreased.
Conclusions:
- Thalamic relay neurons primarily utilize electrical synapses during early development.
- Electrical coupling between VBN neurons is largely dependent on Cx36 but not exclusively.
- A developmental transition occurs where electrical synapses diminish, and a chemical inhibitory circuit matures.
- These findings reveal a critical developmental plasticity in thalamic circuit communication.
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