Voltage-Gated Ion Channels in Human Photoreceptors: Na+ and Hyperpolarization-Activated Cation Channels

  • Ei-ichi Miyachi
  • Fusao Kawai
Conference paper
Part of the Keio University International Symposia for Life Sciences and Medicine book series (KEIO, volume 11)


A light stimulus hyperpolarizes photoreceptors in biochemical processes in the outer segment and reduces the release of neurotransmitter by decreasing a Ca2+ influx at their synaptic terminals [1–6]. The photovoltage is shaped by voltage-gated channels in the inner segment [7–11]. Major voltage-gated currents measured in vertebrate photoreceptors are an L-type Ca2+ current, a delayed rectifier K+ current, a fast transient K+ current, and a hyperpolarization-activated cation current (h current) [7, 9, 10, 12]. Although mammalian photoreceptors are commonly thought to be nonspiking neurons [7, 9–11, 13], electrophysiological recordings with suction electrodes show that the termination of a light stimulus induces spike-like current responses in monkey photoreceptors [14]. This raises the possibility that primate photoreceptors may be able to generate action potentials. However, this hypothesis still remains uncertain, as there are few voltage recordings from primate photoreceptors [11, 15, 16]. Using the patch-clamp technique, we examined whether human rod photoreceptors can elicit action potentials, and also investigated the role of the voltage-gated currents for rod voltage responses.

Key words

Retina Photoreceptor Voltage-gated channel Sodium channel h channel 


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Copyright information

© Springer-Verlag Tokyo 2003

Authors and Affiliations

  • Ei-ichi Miyachi
    • 1
  • Fusao Kawai
    • 1
  1. 1.Department of PhysiologyFujita Health University School of MedicineToyoake, AichiJapan

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