Feedback at the first synapse of vision!
Molecular mechanisms of horizontal cellto-cone feedback in the retina have been under debate. Feedback at the photoreceptor synapse is the first neuronal circuit computation in vision, which influences downstream activity patterns within the visual system.
The researchers show that Slc4a5, an electrogenic sodium-bicarbonate cotransporter specific to horizontal cells, is crucial for feedback. However, electroneutral bicarbonate transporter Slc4a3, which is also expressed in the horizontal cells, is not involved in the feedback.
They suggest that Slc4a5, through its voltage-dependent transport of bicarbonate, regulates pH in the synaptic cleft that mediates feedback.
Pharmacological blockage of bicarbonate transporters and buffering pH also abolished the feedback but blocking sodium-proton exchangers and GABA receptors did not.
