Na(+) action potentials in human photoreceptors.
Mammalian photoreceptors are hyperpolarized by a light stimulus and are commonly thought to be nonspiking neurons. We used the whole-cell patch-clamp technique on surgically excised human retina to examine whether human photoreceptors can elicit action potentials. We discovered that human rod photoreceptors express voltage-gated Na(+) channels, and generate Na(+) action potentials, in response to membrane depolarization from membrane potentials of -60 or -70 mV. Na(+) spikes in human rods were elicited at the termination of a light response that hyperpolarized the potential well below -50 mV. This served to amplify the release of a neurotransmitter when a bright light is turned off, and thus selectively amplify the off response to the light signal.
Kawai
F
F
Department of Physiology, School of Medicine, Fujita Health University, Toyoake, Aichi 470-1192, Japan. fkawai@fujita-hu.ac.jp
Horiguchi
M
M
Suzuki
H
H
Miyachi
E
E
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000328:Adult; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008564:Membrane Potentials / Q000502:physiology; D008875:Middle Aged; D018377:Neurotransmitter Agents / Q000502:physiology; D018408:Patch-Clamp Techniques; D017948:Retinal Rod Photoreceptor Cells / Q000187:drug effects / Q000502:physiology*; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology
D018377:Neurotransmitter Agents; D015222:Sodium Channels; D013779:Tetrodotoxin