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Synaptically triggered action potentials in dendrites
W Regehr1, J S Kehoe, P Ascher
1Department of Physiology, University of Pennsylvania, Philadelphia 19104-6085.
Neuron
|July 1, 1993
Summary
Action potentials in pyramidal cells initiate in apical dendrites, not somata. This finding challenges previous assumptions about neuronal electrical signaling and action potential generation.
Area of Science:
- Neuroscience
- Cellular Electrophysiology
Background:
- Pyramidal cells are key neuronal components in the cerebral cortex.
- The precise initiation site of action potentials in pyramidal cells remains a subject of investigation.
Purpose of the Study:
- To test the hypothesis that action potentials originate in the apical dendrites of pyramidal neurons.
Main Methods:
- Voltage clamp recordings from Layer V pyramidal cell somata in rat motor cortex slices.
- Application of hyperpolarization and tetrodotoxin to basal dendrites and soma.
- Stimulation via synaptic input, voltage steps, and direct electrical stimulation.
Main Results:
- Synaptic input to apical dendrites evoked small synaptic currents at the soma.
- Tetrodotoxin and hyperpolarization blocked later spike components but not the initial synaptically triggered Na+ spike in the apical dendrite.
- Similar Na+ spikes were observed following voltage steps or direct stimulation, independent of somatic or basal dendritic conditions.
Conclusions:
- Sodium (Na+) action potentials are initiated in the apical dendrite of pyramidal cells.
- This apical dendritic initiation occurs in response to synaptic input.
- Findings suggest a revised understanding of action potential generation in cortical pyramidal neurons.