Paired-pulse plasticity in the strength and latency of light-evoked lateral inhibition to retinal bipolar cell terminals.
Synapses in the inner plexiform layer of the retina undergo short-term plasticity that may mediate different forms of adaptation to regularities in light stimuli. Using patch-clamp recordings from axotomized goldfish Mb bipolar cell (BC) terminals with paired-pulse light stimulation, we isolated and quantified the short-term plasticity of GABAergic lateral IPSCs (L-IPSCs). Bright light stimulation evoked ON and OFF L-IPSCs in axotomized BCs, which had distinct onset latencies (∼50-80 and ∼70-150 ms, respectively) that depended on background light adaptation. We observed plasticity in both the synaptic strength and latency of the L-IPSCs. With paired light stimulation, latencies of ON L-IPSCs increased at paired-pulse intervals (PPIs) of 50 and 300 ms, whereas OFF L-IPSC latencies decreased at the 300 ms PPI. ON L-IPSCs showed paired-pulse depression at intervals <1 s, whereas OFF L-IPSCs showed depression at intervals ≤1 s and amplitude facilitation at longer intervals (1-2 s). This biphasic form of L-IPSC plasticity may underlie adaptation and sensitization to surround temporal contrast over multiple timescales. Block of retinal signaling at GABA(A)Rs and AMPARs differentially affected ON and OFF L-IPSCs, confirming that these two types of feedback inhibition are mediated by distinct and convergent retinal pathways with different mechanisms of plasticity. We propose that these plastic changes in the strength and timing of L-IPSCs help to dynamically shape the time course of glutamate release from ON-type BC terminals. Short-term plasticity of L-IPSCs may thus influence the strength, timing, and spatial extent of amacrine and ganglion cell inhibitory surrounds.
The Vollum Institute, Oregon Health and Science University, Portland, Oregon 97239, USA.
Evan
E
Vickers
Mean-Hwan
MH
Kim
Jozsef
J
Vigh
Henrique
H
von Gersdorff
D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D019771:Axotomy; D055592:Biophysical Phenomena / Q000502:physiology; D004347:Drug Interactions; D004558:Electric Stimulation; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D006054:Goldfish; D066298:In Vitro Techniques; D053444:Inhibitory Postsynaptic Potentials; D008027:Light; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010721:Phosphinic Acids / Q000494:pharmacology; D017785:Photons; D017729:Presynaptic Terminals / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D011724:Pyridazines / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D012160:Retina / Q000166:cytology; D051245:Retinal Bipolar Cells / Q000145:classification / Q000166:cytology* / Q000187:drug effects; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors
C101879:(1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid; D000779:Anesthetics, Local; D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D010721:Phosphinic Acids; D011724:Pyridazines; D011725:Pyridines; D011810:Quinoxalines; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D013779:Tetrodotoxin; C049853:gabazine