Voltage-dependent dye coupling at a rectifying electrotonic synapse of the crayfish

Area of Science:

• Neuroscience
• Cell Biology
• Synaptic Physiology

Background:

• The crayfish giant motor synapse exhibits two states of ionic coupling.
• Junctional conductance varies with membrane potential, being low at rest and high upon polarity reversal.

Purpose of the Study:

• To investigate junctional permeability using the intercellular tracer Lucifer Yellow.
• To determine if dye transfer is sensitive to junctional polarization and conductance states.

Main Methods:

• Ionophoretic injection of Lucifer Yellow into presynaptic (lateral giant axon) or postsynaptic (giant motor fibre) cells.
• Observation of dye spread under different junctional polarization conditions (resting vs. reversed polarity).

Main Results:

• In the high conductance state (reversed polarity), Lucifer Yellow spread bidirectionally between neurons.
• In the low conductance state (resting polarity), dye spread occurred from the giant axon to the giant motor fibre, but not vice versa.

Conclusions:

• Dye transfer at the crayfish giant motor synapse is sensitive to junctional polarization, mirroring ionic coupling behavior.
• Permeability is significantly higher in the high conductance state, with observed asymmetry in the low conductance state.