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Complex autonomous firing patterns of striatal low-threshold spike interneurons
Joseph A Beatty1, Matthew A Sullivan, Hitoshi Morikawa
1Department of Biology, University of Texas at San Antonio, San Antonio, Texas 78249, USA.
Journal of Neurophysiology
|May 11, 2012
Summary
Tonically active neurons (TANs) in the striatum exhibit complex firing patterns. Low-threshold spike (LTS) interneurons show autonomous firing, similar to cholinergic interneurons, but with distinct underlying mechanisms.
Area of Science:
- Neuroscience
- Cellular Neuroscience
Background:
- Tonically active neurons (TANs) in the striatum are crucial for sensorimotor learning, exhibiting firing patterns modulated by stimulus salience.
- Striatal cholinergic interneurons display intrinsic tonic firing, mimicking TAN activity in vivo.
- The identity of other striatal neurons contributing to TAN activity remains largely unknown.
Purpose of the Study:
- To investigate whether low-threshold spike (LTS) interneurons are among the neurons identified as TANs.
- To characterize the intrinsic firing properties and underlying mechanisms of LTS interneurons in the striatum.
- To compare the firing mechanisms of LTS interneurons with those of striatal cholinergic interneurons.
Main Methods:
- Utilized transgenic mice expressing green fluorescent protein under neuronal nitric oxide synthase or neuropeptide-Y promoters.
- Examined LTS interneurons in brain slices to identify their intrinsic firing patterns.
- Analyzed the ionic conductances and oscillatory mechanisms responsible for the observed firing behaviors.
Main Results:
- LTS interneurons exhibit autonomous firing with spontaneous transitions between regular, irregular, and burst firing modes, similar to cholinergic interneurons.
- Both LTS interneurons and cholinergic interneurons maintain tonic firing via persistent sodium currents.
- Distinct mechanisms underlie subthreshold oscillations: LTS interneurons rely on depolarization-activated noninactivating calcium currents, while cholinergic interneurons use hyperpolarization-activated potassium conductance.
- Sustained hyperpolarization induces bursting in LTS interneurons through a low-threshold, inactivating calcium conductance, differing from cholinergic interneuron bursting.
Conclusions:
- LTS interneurons share firing pattern similarities with cholinergic interneurons but possess unique intrinsic mechanisms.
- The complex firing patterns of LTS interneurons suggest a role in differential neurotransmitter release, including nitric oxide.
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