Cell-specific contact selects transmitter responses in an identified leech neuron

Area of Science:

• Neuroscience
• Cell Biology
• Neurophysiology

Background:

• Leech Retzius (R) neurons form Cl-dependent synapses with pressure-sensitive (P) neurons.
• P cells exhibit an extrasynaptic, cationic response to 5-hydroxytryptamine (5-HT).
• This 5-HT response is modulated by neuronal contact.

Purpose of the Study:

• To investigate the cellular specificity of 5-HT response selection in leech P cells.
• To determine the factors influencing the reduction of extrasynaptic 5-HT responses upon neuronal contact.

Main Methods:

• Primary neuronal cultures of identified leech neurons.
• Electrophysiological recordings to assess neuronal responses to 5-HT.
• Co-culture experiments pairing P cells with various identified neurons.

Main Results:

• Contact with non-synaptic sensory cells did not alter P cell 5-HT responses.
• Interaction with non-serotonergic partners also failed to modify P cell 5-HT responses.
• Contact with serotonergic neurons that do not form chemical synapses with P cells did not alter its 5-HT responses.
• Selective reduction of the extrasynaptic 5-HT response in P cells was specifically induced by contact with its known serotonergic synaptic partner.

Conclusions:

• Neuronal recognition and subsequent synapse formation between leech R and P neurons specifically alter P cell responses to 5-HT.
• The selective reduction of extrasynaptic 5-HT responses is a specific outcome of interaction with the appropriate serotonergic partner.
• This phenomenon highlights a mechanism for refining neuronal communication during synapse development.