Patch-clamp capacitance measurements and Ca²⁺ imaging at single nerve terminals in retinal slices

Area of Science:

• Neuroscience
• Cell Biology
• Vision Science

Background:

• Vertebrate retinal neurons, including photoreceptors and bipolar cells, detect visual stimuli across a wide dynamic range.
• Ribbon-type active zones in these neurons enable sustained, high-throughput neurotransmitter release.
• ON-type mixed bipolar cell (Mb) terminals in goldfish are large and interconnected, making them ideal for studying ribbon synapses.

Purpose of the Study:

• To investigate the physiological properties of ribbon synapses in the vertebrate retina.
• To analyze short-term and long-term plasticity of both excitatory and inhibitory neurotransmitter release.
• To demonstrate a method for studying retinal microcircuit dynamics using brain slices.

Main Methods:

• Utilized the patch-clamp technique on goldfish retinal slices to record from Mb bipolar cell terminals.
• Measured presynaptic calcium currents, membrane capacitance changes (exocytosis), and reciprocal synaptic feedback inhibition.
• Employed the pre-embedding agar technique for slicing goldfish retina, including axotomized terminals for isolated input studies.

Main Results:

• Demonstrated that Mb bipolar cell terminals exhibit short-term plasticity of excitatory neurotransmitter release.
• Showed that GABAergic reciprocal feedback inhibition from amacrine cells undergoes paired-pulse depression, indicating vesicle pool depletion.
• Confirmed the utility of the brain-slice technique for analyzing synaptic transmission at ribbon synapses.

Conclusions:

• The experimental protocol provides direct access to study retinal synaptic physiology and microcircuit function.
• Findings contribute to understanding synaptic dynamics and neurotransmitter release mechanisms in the retina.
• The study highlights the importance of ribbon synapses in visual information processing.