Substance P and dopamine form a "push-pull" system that diurnally regulates retinal gain

Area of Science:

• Neuroscience
• Vision Science
• Molecular Biology

Background:

• Retinal function is modulated by neurotransmitters like dopamine, which adjusts vision based on light.
• Dopamine release is light-dependent, regulating visual processing in a diurnal pattern.

Purpose of the Study:

• To investigate the role of substance P as a retinal modulator.
• To understand the interaction between substance P and the dopamine system in the retina.
• To elucidate how substance P affects visual signal processing and information flow.

Main Methods:

• Imaging glutamatergic synaptic transmission in larval zebrafish.
• Quantifying the effects of substance P on contrast sensitivity in ON and OFF visual channels.
• Analyzing changes in vesicle release patterns at bipolar cell synapses.
• Measuring the impact of substance P on visual information flow in bits.

Main Results:

• Substance P significantly decreases retinal contrast sensitivity up to 8-fold, particularly in the transient pathway.
• These effects are prominent in the morning and largely mediated by suppressing dopamine's amplification of visual signals.
• Substance P is largely inactive in the afternoon.
• Modulation of retinal gain by substance P alters synaptic vesicle release, shifting coding from release rate to amplitude via multivesicular release (MVR).
• Substance P reduces visual information flow by approximately 3-fold.

Conclusions:

• Substance P acts as a potent retinal modulator, interacting with the dopamine system.
• In the morning, substance P suppresses dopamine signaling, reducing visual information transmission.
• Substance P functions antagonistically to dopamine, contributing to the diurnal regulation of retinal processing.