Light-evoked changes in extracellular pH in frog retina.

Area of Science:

• Neuroscience
• Retinal Physiology
• Extracellular pH Dynamics

Background:

• Extracellular pH changes are crucial for neuronal function.
• Understanding light-induced pH shifts in the retina is key to comprehending visual processing.

Purpose of the Study:

• To investigate light-induced changes in extracellular H+ concentration (delta pH0) in frog retina.
• To elucidate the spatial and temporal characteristics of these pH changes.
• To explore the role of carbonic anhydrase in retinal pH buffering.

Main Methods:

• Intraretinal H(+)-sensitive double-barreled microelectrodes were used in frog eyecup and isolated retina preparations.
• Small-spot and diffuse retinal illumination, as well as flicker stimulation, were employed.
• Tetrodotoxin (TTX) was used to assess the involvement of action potentials.
• Carbonic anhydrase inhibitors (acetazolamide, methazolamide) were applied.

Main Results:

• Prominent pH increases (alkalinizations) were observed in the inner plexiform layer at light onset and offset.
• pH changes were enhanced by flicker stimulation and showed spatial profiles similar to field potentials.
• Surround antagonism of pH changes was observed and blocked by TTX, indicating independence from action potentials.
• Diffuse illumination in the subretinal space caused a small pH increase, potentially linked to photoreceptor lactate production.
• Inhibition of carbonic anhydrase increased both proximal and distal retinal pH changes.

Conclusions:

• Light induces significant extracellular pH changes in the frog retina, primarily in the inner plexiform layer.
• These pH dynamics are influenced by stimulus properties and are independent of action potentials.
• Carbonic anhydrase plays a crucial role in buffering retinal pH.