Slow depolarizing response from supporting cells in the goldfish saccule

Area of Science:

• Neuroscience
• Auditory Physiology
• Sensory Biology

Background:

• The saccular macula in goldfish is crucial for detecting sound.
• Understanding the cellular mechanisms of auditory transduction is essential.

Purpose of the Study:

• To investigate sound-evoked potentials within the goldfish saccular macula.
• To differentiate between cellular responses and identify the origin of observed potentials.

Main Methods:

• Intracellular and extracellular recordings were performed on anaesthetized goldfish saccular macula.
• Analysis of sound-evoked potentials, including microphonic potentials, nerve responses, and slow depolarization.
• Assessment of tetrodotoxin resistance and efferent stimulation effects.

Main Results:

• Intracellular recordings revealed three potentials: microphonic, nerve response, and a slow depolarization.
• The slow depolarization, unique to intracellular records, exhibited distinct time constants (30 ms rise, 200 ms fall) and low amplitude (5-6 mV).
• The nerve response was resistant to tetrodotoxin, suggesting it represents excitatory postsynaptic current in afferent fibers; efferent stimulation suppressed this response.

Conclusions:

• The slow depolarization is hypothesized to originate from supporting cells due to a rise in extracellular K+ concentration during sound stimulation.
• The tetrodotoxin-resistant nerve response likely reflects excitatory postsynaptic currents in afferent dendrites.
• Efferent pathways modulate auditory nerve activity in the saccular macula.