Increased Retinal Metabolism Induced by Flicker in the Isolated Mouse Retina.

Area of Science:

• Ophthalmology
• Neuroscience
• Physiology

Background:

• Neurovascular coupling, the link between neural activity and blood flow, is observed in both the brain and retina.
• Increased blood flow in the retina, evoked by stimuli like flickering light, is a known phenomenon.
• However, the precise metabolic changes driving this increased retinal blood flow remain unquantified.

Purpose of the Study:

• To quantify the metabolic changes, specifically oxygen consumption, in different retinal layers during neural activation.
• To determine the relationship between metabolic demand and blood flow changes in the retina.

Main Methods:

• Isolated C57BL/6J mouse retinas were used, with oxygen supplied to both sides.
• Microelectrode recordings measured partial pressure of oxygen (PO2) in darkness and during 20-second intervals of 1 Hz flickering light.
• A four-layer oxygen diffusion model was employed to calculate oxygen consumption rates (QOR and QIR) in the outer and inner retina, respectively.

Main Results:

• Flickering light caused a PO2 increase in the outer retina and a decrease in the inner retina.
• Outer retinal oxygen consumption (QOR) decreased to 76 ± 14% of its dark-adapted level.
• Inner retinal oxygen consumption (QIR) increased by 6.4 ± 5.0%, with modeling suggesting a potential increase up to 45% under high illumination.

Conclusions:

• Retinal neural activation leads to regional changes in oxygen consumption, with decreased QOR and increased QIR.
• The observed increase in inner retinal oxygen consumption is comparable in magnitude to the potential increase in blood flow.
• These findings suggest that retinal blood flow is largely matched to the metabolic demands associated with neural activity.