Patch-clamp recording of human retinal photoreceptors and bipolar cells

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21 Citations (Scopus)


Photoreceptors and retinal bipolar cells are considered as nonspiking neurons; however, we recently showed that human rod photoreceptors can generate sodium action potentials in response to membrane depolarization from membrane potentials of -60 or -70 mV (Kawai et al., Neuron30 [2001] 451). We performed patch-clamp recording of human cone photoreceptors and retinal bipolar cells to examine whether functional voltage-gated sodium channels are expressed in these cells as well as rod photoreceptors. Under current-clamp conditions, the injection of depolarizing current steps into a cone photoreceptor-induced marked action potentials. These action potentials were blocked by 1 μM tetrodotoxin, a voltage-gated sodium channel blocker. Under voltage-clamp conditions, depolarizing voltage steps-induced a fast transient inward current in several bipolar cells (n = 4/78). This current was activated from -70 to +20 mV (maximal at -10 mV) and inactivated within 5 ms. The 10-90% rise time of this current was shorter than another inward current (less than one-hundredth). These results indicate that human cones and bipolar cells express voltage-gated sodium channels as rod photoreceptors. Sodium channels may serve to amplify the release of a neurotransmitter and to accelerate the light-dark change in photosignals.

Original languageEnglish
Pages (from-to)317-322
Number of pages6
JournalPhotochemistry and Photobiology
Issue number2
Publication statusPublished - 03-2007

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Physical and Theoretical Chemistry


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