Synapse formation and function: insights from identified leech neurons in culture

Area of Science:

• Neuroscience
• Cell Biology
• Molecular Signaling

Background:

• Identified leech neurons in culture retain physiological properties and form specific synapses.
• Synapse formation and characteristics depend on neuronal identity and cell contact regions.
• Retzius cells form inhibitory chemical synapses with pressure-sensitive (P) cells using serotonin (5-HT).

Purpose of the Study:

• To investigate the signals underlying synapse formation and function using identified leech neurons in culture.
• To characterize the properties of chemical and electrical synapses formed between cultured leech neurons.
• To elucidate the nature of synaptogenic signals that modify neuronal properties during synapse development.

Main Methods:

• Individual identification and culturing of leech central nervous system neurons.
• Direct electrophysiological and imaging approaches to study synapse formation and function.
• Analysis of neurotransmitter release (serotonin), calcium dependence, and synaptic plasticity.

Main Results:

• Cultured leech neurons form functional chemical or electrical synapses, or no synapse, based on cell type and contact region.
• Retzius cells release serotonin (5-HT) in a quantal, calcium-dependent manner, exhibiting activity-dependent plasticity.
• Synapse formation involves anterograde and retrograde signals affecting calcium currents, 5-HT responses, and neurite outgrowth.
• Contact with Retzius cells induces localized transmitter responses in P cells, signaled by tyrosine phosphorylation.

Conclusions:

• Cultured leech neurons provide a powerful model for studying synapse development and molecular signaling.
• Serotonin (5-HT) plays a key role in inhibitory neurotransmission and synaptic plasticity in leech neurons.
• Tyrosine phosphorylation is an early signaling event in synapse formation, mediating cell-specific responses.