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Trophic factor-induced excitatory synaptogenesis involves postsynaptic modulation of nicotinic acetylcholine
Melanie A Woodin1, David W Munno, Naweed I Syed
1Respiratory and Neuroscience Research Groups, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
Summary
Trophic factors promote excitatory synapse formation by acting on the postsynaptic neuron. This study shows these factors modulate nicotinic acetylcholine receptors, essential for excitatory synaptogenesis.
Area of Science:
- Neuroscience
- Cell Biology
- Synaptic Plasticity
Background:
- Neurotrophic factors are crucial for neuronal development.
- Their exact role in synapse formation and plasticity requires further elucidation.
- Previous work indicated trophic factors are necessary for excitatory, but not inhibitory, synapse formation.
Purpose of the Study:
- To define the cellular mechanisms of trophic factor-induced excitatory synaptogenesis.
- To investigate the specific site (presynaptic vs. postsynaptic) of trophic factor action.
- To understand the molecular pathways involved in trophic factor-mediated synapse formation.
Main Methods:
- Utilized soma-soma synapses between identified Lymnaea neurons (VD4 and RPeD1) in cell culture.
- Manipulated Lymnaea brain-conditioned medium (CM) concentrations to observe synapse development.
- Examined the effects of trophic factors on receptor tyrosine kinases and nicotinic acetylcholine receptors (nAChRs) in the postsynaptic cell (RPeD1).
- Assessed synaptic responses using cholinergic antagonists.
Main Results:
- In defined media (DM), mutually inhibitory synapses formed between VD4 and RPeD1.
- In the presence of CM, a biphasic synapse (excitatory followed by inhibitory) developed.
- Trophic factor-induced excitatory synapse formation required postsynaptic activation of receptor tyrosine kinases.
- Modulation of postsynaptic nAChRs in RPeD1 was sufficient to mediate trophic factor effects on excitatory synaptogenesis.
Conclusions:
- Trophic factors act postsynaptically to promote excitatory synapse formation.
- This action involves the activation of receptor tyrosine kinases and modulation of nAChRs.
- Provides direct evidence for the postsynaptic role of trophic factors in excitatory synaptogenesis.