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Updated: May 30, 2026
Identification of Specific Sensory Neuron Populations for Study of Expressed Ion Channels
Published on: December 24, 2013
Multiple T-type Ca2+ current subtypes in electrophysiologically characterized hamster dorsal horn neurons: possible
Wen-hsin Ku1, Stephen P Schneider
1Dept. of Physiology, Michigan State Univ., East Lansing, MI 48824-3320, USA.
Insights
Transient, low-threshold calcium currents (I(T)) significantly influence how hamster spinal dorsal horn neurons fire. These currents are crucial for distinguishing between different sensory input frequencies.
Area of Science:
- Neuroscience
- Electrophysiology
- Calcium Channels
Background:
- Spinal dorsal horn neurons play a critical role in processing sensory information.
- Transient, low-threshold calcium currents (I(T)) are known to influence neuronal excitability.
Purpose of the Study:
- To investigate the role of I(T) in the firing properties of hamster spinal dorsal horn neurons.
- To determine the relationship between I(T) expression and neuronal firing patterns.
Main Methods:
- Whole-cell patch-clamp recordings were performed on hamster spinal dorsal horn neurons.
- Neuronal firing properties were analyzed under current-clamp conditions.
- The effects of Ni(2+) and mibefradil on I(T) were examined.
- Single-cell RT-PCR was used to identify calcium channel subtypes.
Main Results:
- I(T) was widely expressed in Rexed's laminae I-IV and correlated with firing patterns.
- Neurons with phasic firing exhibited significantly larger I(T) compared to tonically firing neurons.
- Ramp-activated I(T) was sensitive to depolarization slope and blocked by Ni(2+).
- Two components of I(T) (fast and slow) were identified, with the fast component linked to Ca(V)3.1 channels.
Conclusions:
- I(T) significantly contributes to the firing properties of spinal dorsal horn neurons.
- The fast component of I(T) may enhance responses to rapid depolarization in phasic-firing neurons.
- I(T) likely plays a role in discriminating between high- and low-frequency sensory inputs.
Abstract:
Whole cell patch-clamp recordings were used to investigate the contribution of transient, low-threshold calcium currents (I(T)) to firing properties of hamster spinal dorsal horn neurons. I(T) was widely, though not uniformly, expressed by cells in Rexed's laminae I-IV and correlated with the pattern of action potential discharge evoked under current-clamp conditions: I(T) in neurons responding to constant membrane depolarization with one or two action potentials was nearly threefold larger than I(T) in cells responding to the same activation with continuous firing. I(T) was evoked by depolarizing voltage ramps exceeding 46 mV/s and increased with ramp slope (240-2,400 mV/s). Bath application of 200 μM Ni(2+) depressed ramp-activated I(T). Phasic firing recorded in current clamp could only be activated by membrane depolarizations exceeding ∼43-46 mV/s and was blocked by Ni(2+) and mibefradil, suggesting I(T) as an underlying mechanism. Two components of I(T), "fast" and "slow," were isolated based on a difference in time constant of inactivation (12 ms and 177 ms, respectively). The amplitude of the fast subtype depended on the slope of membrane depolarization and was twice as great in burst-firing cells than in cells having a tonic discharge. Post hoc single-cell RT-PCR analyses suggested that the fast component is associated with the Ca(V)3.1 channel subtype. I(T) may enhance responses of phasic-firing dorsal horn neurons to rapid membrane depolarizations and contribute to an ability to discriminate between afferent sensory inputs that encode high- and low-frequency stimulus information.
