Related Experiment Videos
Na(+) action potentials in human photoreceptors.
F Kawai1, M Horiguchi, H Suzuki
1Department of Physiology, School of Medicine, Fujita Health University, Toyoake, Aichi 470-1192, Japan. fkawai@fujita-hu.ac.jp
Neuron
|June 8, 2001
Summary
Human rod photoreceptors can generate electrical spikes, called action potentials, when stimulated by light. This finding challenges the long-held belief that these cells are nonspiking neurons.
Area of Science:
- Neuroscience
- Ophthalmology
- Cellular Biology
Background:
- Mammalian photoreceptors typically hyperpolarize in response to light.
- Photoreceptors are widely considered to be nonspiking neurons in mammals.
Purpose of the Study:
- To investigate whether human photoreceptors are capable of generating action potentials.
- To determine the mechanism and functional significance of potential spiking in human photoreceptors.
Main Methods:
- Whole-cell patch-clamp recordings were performed on surgically excised human retina.
- Membrane potentials and voltage-gated channel activity were analyzed during light stimulation.
Main Results:
- Human rod photoreceptors express voltage-gated sodium (Na+) channels.
- Depolarization to -60 or -70 mV induced Na+ action potentials in human rods.
- These Na+ spikes occurred at the termination of light responses, below -50 mV.
Conclusions:
- Human rod photoreceptors can generate Na+ action potentials, contradicting the nonspiking neuron model.
- Spiking in rods amplifies neurotransmitter release upon cessation of bright light.
- This mechanism selectively enhances the 'off' response to visual signals.