Sodium Channels in Transient Retinal Bipolar Cells Enhance Visual Responses in Ganglion Cells

Ambient Light Regulates Sodium Channel Activity to Dynamically Control Retinal Signaling

“…Larval tiger salamanders were obtained from Charles Sullivan (Nashville, TN) and were kept in aquaria at 5°C on a 12 h light/dark cycle. Procedures for preparing and recording from salamander retinal slices were described previously (Ichinose et al, 2005). Light-and voltage-evoked responses were recorded from bipolar cells with axon terminals and ganglion cells with dendrites that ramified in the mid-inner plexiform layer (IPL) (Ichinose et al, 2005).…”

“…Procedures for preparing and recording from salamander retinal slices were described previously (Ichinose et al, 2005). Light-and voltage-evoked responses were recorded from bipolar cells with axon terminals and ganglion cells with dendrites that ramified in the mid-inner plexiform layer (IPL) (Ichinose et al, 2005). Using a gravity-fed system, the preparation was continually superfused at 2 ml/ min with a Ringer's solution containing the following (in mM): 112 NaCl, 2 KCl, 2 CaCl 2 , 1 MgCl 2 , 5 glucose, and 5 HEPES, adjusted to pH 7.75 with NaOH.…”

“…In the retina, sodium channels in a subset of bipolar cells boost light-evoked EPSPs (L-EPSPs) in dim-light conditions and amplify the excitatory drive to ganglion cells (Ichinose et al, 2005). Because bipolar cells have been implicated as sites of network adaptation (Green et al, 1975;Naka et al, 1979;Shapley and Enroth-Cugell, 1984;Smirnakis et al, 1997;Rieke, 2001;Baccus and Meister, 2002;PageMcCaw et al, 2004), the voltage-gated sodium channels in bipolar cells may regulate network adaptation by increasing retinal sensitivity in dim-light conditions (Fig.…”

Synaptic transmission at retinal ribbon synapses

“…100 ms, then decays with τ = 400 ms to a maintained plateau that is only 13% of peak depolarization. Ichinose et al (2005) showed that a TTX-sensitive Na current contributes to the initial peak. Sustained ON bipolar cells also show rolloff from peak depolarization, but the plateau voltage is ca.…”

Calcium spike-mediated digital signaling increases glutamate output at the visual threshold of retinal bipolar cells

“…While the classical view is that BCs operate with analog, graded potentials (Kaneko 1970;Werblin and Dowling 1969), a growing body of evidence suggests that certain BCs are capable of generating calcium (Ca 2ϩ ) or sodium (Na ϩ ) action potentials (Baden et al , 2013aDreosti et al 2011;Puthussery et al 2013;Saszik and DeVries 2012) and employ digital signals to process information at the second stage of the visual pathway (Baden et al 2013b). When present, voltage-gated Na ϩ currents amplify and speed up BC responses and subsequently enhance the temporal precision of postsynaptic GC signaling (Ichinose et al 2005;Puthussery et al 2013;Saszik and DeVries 2012). Less is understood concerning the role of Ca 2ϩ spike-mediated digital BC signaling.…”