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Published on: January 18, 2019
Ionic currents underlying spontaneous action potentials in isolated cerebellar Purkinje neurons
1Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Summary
Spontaneous firing in mouse Purkinje neurons relies on tetrodotoxin-sensitive sodium currents between spikes. Rapidly deactivating potassium currents promote high firing rates by enabling quick repolarization and restoring input resistance.
Area of Science:
- Neuroscience
- Electrophysiology
- Cell Biology
Background:
- Purkinje neurons are crucial for motor control and learning.
- Understanding the ionic mechanisms of their spontaneous activity is key to comprehending cerebellar function.
Purpose of the Study:
- To directly measure the ionic currents responsible for spontaneous action potential firing in mouse Purkinje neuron cell bodies.
- To elucidate the specific roles of sodium, calcium, and potassium currents in maintaining high-frequency firing.
Main Methods:
- Voltage-clamp and current-clamp electrophysiology on acutely dissociated mouse Purkinje neurons.
- Utilized prerecorded action potential trains as voltage commands.
- Employed ionic substitution (cobalt for calcium) and selective blockers (tetrodotoxin, mibefradil, cesium, TEA) to isolate ionic currents.
Main Results:
- Tetrodotoxin-sensitive sodium current was the largest inward current during the interspike interval.
- Calcium currents were present but their net effect was outward due to dominant calcium-dependent potassium currents.
- Potassium currents responsible for spike repolarization were rapidly activating and deactivating.
Conclusions:
- Spontaneous firing in Purkinje neuron cell bodies is primarily driven by tetrodotoxin-sensitive sodium current.
- High firing rates are facilitated by fast-deactivating potassium currents that allow for rapid repolarization and restoration of input resistance.
Related Concept Videos
01:41Action Potentials
Overview
01:14Action Potential
Neurons communicate by firing action potentials—the electrochemical signal that is propagated along the axon. The signal results in the release of neurotransmitters at axon terminals, thereby transmitting information to the nervous system. An action potential is a specific "all-or-none" change in membrane potential that results in a rapid spike in voltage.
Membrane potential in neurons
Neurons typically have a resting membrane potential of about -70 millivolts (mV). When they receive...
Membrane potential in neurons
Neurons typically have a resting membrane potential of about -70 millivolts (mV). When they receive...
01:19The Role of Ion Channels in Neuronal Computation
A postsynaptic neuron usually receives numerous impulses from several other presynaptic neurons. The axon hillock of the postsynaptic neuron integrates all these signals and determines the likelihood of firing an action potential.
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential.
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential.
01:24Generation of Action Potential in Skeletal Muscles
Every cell in the body maintains a membrane potential due to an uneven distribution of positive and negative charges across its plasma membrane. The membrane potential is measured in millivolts and quantifies the difference in charge across the membrane.
Like neurons, muscle cells are also regarded as excitable due to their capacity to change in response to stimuli, primarily due to voltage-gated ion channels embedded in their plasma membranes, which get activated by alterations in the cell's...
Like neurons, muscle cells are also regarded as excitable due to their capacity to change in response to stimuli, primarily due to voltage-gated ion channels embedded in their plasma membranes, which get activated by alterations in the cell's...
01:14Action Potential
Neurons communicate by firing action potentials—the electrochemical signal that is propagated along the axon. The signal results in the release of neurotransmitters at axon terminals, thereby transmitting information to the nervous system. An action potential is a specific "all-or-none" change in membrane potential that results in a rapid spike in voltage.
Membrane potential in neurons
Neurons typically have a resting membrane potential of about -70 millivolts (mV). When they receive...
Membrane potential in neurons
Neurons typically have a resting membrane potential of about -70 millivolts (mV). When they receive...
01:23Propagation of Action Potentials
The propagation of an action potential refers to the process by which a nerve impulse, or "action potential," travels along a neuron.
Neurons (nerve cells) have a resting membrane potential, with a slightly negative charge inside compared to outside. This is maintained by ion channels, such as sodium (Na+) and potassium (K+) channels, which control the flow of ions. When a stimulus, like a touch or a signal from another neuron, triggers the neuron, sodium channels open, allowing sodium ions to...
Neurons (nerve cells) have a resting membrane potential, with a slightly negative charge inside compared to outside. This is maintained by ion channels, such as sodium (Na+) and potassium (K+) channels, which control the flow of ions. When a stimulus, like a touch or a signal from another neuron, triggers the neuron, sodium channels open, allowing sodium ions to...