Glycine input induces the synaptic facilitation in salamander rod photoreceptors.
Glycinergic synapses in photoreceptors are made by centrifugal feedback neurons in the network, but the function of the synapses is largely unknown. Here we report that glycinergic input enhances photoreceptor synapses in amphibian retinas. Using specific antibodies against a glycine transporter (GlyT2) and glycine receptor beta subunit, we identified the morphology of glycinergic input in photoreceptor terminals. Electrophysiological recordings indicated that 10 muM glycine depolarized rods and activated voltage-gated Ca(2+) channels in the neurons. The effects facilitated glutamate vesicle release in photoreceptors, meanwhile increased the spontaneous excitatory postsynaptic currents in Off-bipolar cells. Endogenous glycine feedback also enhanced glutamate transmission in photoreceptors. Additionally, inhibition of a Cl(-) uptake transporter NKCC1 with bumetanid effectively eliminated glycine-evoked a weak depolarization in rods, suggesting that NKCC1 maintains a high Cl(-) level in rods, which causes to depolarize in responding to glycine input. This study reveals a new function of glycine in retinal synaptic transmission.
Shen
Wen
W
College of Biomedical Science, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431, USA. wshen@fau.edu
Jiang
Zheng
Z
Li
Baoqin
B
D000818:Animals; D002034:Bumetanide / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D005998:Glycine / Q000378:metabolism* / Q000494:pharmacology*; D018684:Glycine Agents / Q000494:pharmacology; D007150:Immunohistochemistry; D012160:Retina / Q000187:drug effects* / Q000502:physiology; D051245:Retinal Bipolar Cells / Q000378:metabolism; D051248:Retinal Horizontal Cells / Q000378:metabolism; D017948:Retinal Rod Photoreceptor Cells / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000494:pharmacology; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism; D064506:Solute Carrier Family 12, Member 2; D013331:Strychnine / Q000494:pharmacology; D013569:Synapses / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors; D014562:Caudata / Q000502:physiology*
D015220:Calcium Channels; D018684:Glycine Agents; D049994:Sodium Potassium Chloride Symporter Inhibitors; D028021:Sodium-Potassium-Chloride Symporters; D064506:Solute Carrier Family 12, Member 2; D002034:Bumetanide; D018698:Glutamic Acid; D013331:Strychnine; D005998:Glycine