Short-term plasticity in turtle dorsal horn neurons mediated by L-type Ca2+ channels

The lower thresholds and increased excitability of dorsal horn neurons in the neonatal rat suggest that inhibitory processing is less efficient in the immature spinal cord. This is unlikely to be explained by an absence of functional GABAergic inhibition because antagonism of γ-aminobutyric acid (GABA) type A receptors augments neuronal firing in vivo from the first days of life. However, it is possible that more subtle deficits in GABAergic signaling exist in the neonate, such as decreased reliability of transmission or greater depression during repetitive stimulation, both of which could influence the relative excitability of the immature spinal cord. To address this issue we examined monosynaptic GABAergic inputs onto superficial dorsal horn neurons using whole cell patch-clamp recordings made in spinal cord slices at a range of postnatal ages (P3, P10, and P21). The amplitudes of evoked inhibitory postsynaptic currents (IPSCs) were significantly lower and showed greater variability in younger animals, suggesting a lower fidelity of GABAergic signaling at early postnatal ages. Paired-pulse ratios were similar throughout the postnatal period, whereas trains of stimuli (1, 5, 10, and 20 Hz) revealed frequency-dependent short-term depression (STD) of IPSCs at all ages. Although the magnitude of STD did not differ between ages, the recovery from depression was significantly slower at immature GABAergic synapses. These properties may affect the integration of synaptic inputs within developing superficial dorsal horn neurons and thus contribute to their larger receptive fields and enhanced afterdischarge.

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Short-Term Plasticity in Hindlimb Motoneurons of Decerebrate Cats

Journal of Neurophysiology ◽

10.1152/jn.1998.80.4.2038 ◽

1998 ◽

Vol 80 (4) ◽

pp. 2038-2045 ◽

Cited By ~ 76

Author(s):

David J. Bennett ◽

Hans Hultborn ◽

Brent Fedirchuk ◽

Monica Gorassini

Keyword(s):

Threshold Level ◽

Short Term ◽

Muscle Stretch ◽

Warm Up ◽

Short Term Plasticity ◽

Dorsal Horn Neurons ◽

Current Ramp ◽

Inward Currents ◽

A Cell ◽

Decerebrate Cats

Bennett, David J., Hans Hultborn, Brent Fedirchuk, and Monica Gorassini. Short-term plasticity in hindlimb motoneurons of decerebrate cats. J. Neurophysiol. 80: 2038–2045, 1998. Cat hindlimb motoneurons possess noninactivating voltage-gated inward currents that can, under appropriate conditions, regeneratively produce sustained increments in depolarization and firing of the cell (i.e., plateau potentials). Recent studies in turtle dorsal horn neurons and motoneurons indicate that facilitation of plateaus occurs with repeated plateau activation (decreased threshold and increased duration; this phenomenon is referred to as warm-up). The purpose of the present study was to study warm-up in cat motoneurons. Initially, cells were studied by injecting a slow triangular current ramp intracellularly to determine the threshold for activation of the plateau. In cells where the sodium spikes were blocked with intracellular QX314, plateau activation was readily seen as a sudden jump in membrane potential, which was not directly reversed as the current was decreased (cf. hysteresis). With normal spiking, the plateau activation (the noninactivating inward current) was reflected by a steep and sustained jump in firing rate, which was not directly reversed as the current was decreased (hysteresis). Repetitive plateau activation significantly lowered the plateau activation threshold in 83% of cells (by on average 5 mV and 11 Hz with and without QX314, respectively). This interaction between successive plateaus (warm-up) occurred when tested with 3- to 6-s intervals; no interaction occurred at times >20 s. Plateaus initiated by synaptic activation from muscle stretch were also facilitated by repetition. Repeated slow muscle stretches that produced small phasic responses when a cell was hyperpolarized with intracellular current bias produced a larger and more prolonged responses (plateau) when the bias was removed, and the amplitude and duration of this response grew with repetition. The effects of warm-up seen with intracellular recordings during muscle stretch could also be recorded extracellularly with gross electromyographic (EMG) recordings. That is, the same repetitive stretch as above produced a progressively larger and more prolonged EMG response. Warm-up may be a functionally important form of short-term plasticity in motoneurons that secures efficient motor output once a threshold level is reached for a significant period. Finally, the finding that warm-up can be readily observed with gross EMG recordings will be useful in future studies of plateaus in awake animals and humans.

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Proton-Mediated Block of Ca2+ Channels during Multivesicular Release Regulates Short-Term Plasticity at an Auditory Hair Cell Synapse

Journal of Neuroscience ◽

10.1523/jneurosci.2304-14.2014 ◽

2014 ◽

Vol 34 (48) ◽

pp. 15877-15887 ◽

Cited By ~ 20

Author(s):

S. Cho ◽

H. von Gersdorff

Keyword(s):

Hair Cell ◽

Short Term ◽

Short Term Plasticity ◽

Cell Synapse ◽

Ca2 Channels

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Neurotransmitter Release Site Replenishment and Presynaptic Plasticity

International Journal of Molecular Sciences ◽

10.3390/ijms22010327 ◽

2020 ◽

Vol 22 (1) ◽

pp. 327

Author(s):

Sumiko Mochida

Keyword(s):

Neurotransmitter Release ◽

Synaptic Vesicles ◽

High Speed ◽

Release Site ◽

Short Term ◽

Short Term Plasticity ◽

Multiple Protein ◽

Presynaptic Plasticity ◽

Presynaptic Plasma Membrane ◽

Ca2 Channels

An action potential (AP) triggers neurotransmitter release from synaptic vesicles (SVs) docking to a specialized release site of presynaptic plasma membrane, the active zone (AZ). The AP simultaneously controls the release site replenishment with SV for sustainable synaptic transmission in response to incoming neuronal signals. Although many studies have suggested that the replenishment time is relatively slow, recent studies exploring high speed resolution have revealed SV dynamics with milliseconds timescale after an AP. Accurate regulation is conferred by proteins sensing Ca2+ entering through voltage-gated Ca2+ channels opened by an AP. This review summarizes how millisecond Ca2+ dynamics activate multiple protein cascades for control of the release site replenishment with release-ready SVs that underlie presynaptic short-term plasticity.

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P/Q-type calcium channel ablation in a mice glycinergic synapse mediated by multiple types of Ca2+ channels alters transmitter release and short term plasticity

Neuroscience ◽

10.1016/j.neuroscience.2011.06.021 ◽

2011 ◽

Vol 192 ◽

pp. 219-230 ◽

Cited By ~ 12

Author(s):

B. Giugovaz-Tropper ◽

C. González-Inchauspe ◽

M.N. Di Guilmi ◽

F.J. Urbano ◽

I.D. Forsythe ◽

...

Keyword(s):

Calcium Channel ◽

Transmitter Release ◽

Short Term ◽

Short Term Plasticity ◽

Ca2 Channels

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Short-term swimming exercise attenuates the sensitization of dorsal horn neurons in rats with NGF-induced low back pain

European Journal of Pain ◽

10.1002/ejp.1230 ◽

2018 ◽

Vol 22 (8) ◽

pp. 1409-1418 ◽

Cited By ~ 2

Author(s):

G. de Azambuja ◽

U. Hortscht ◽

U. Hoheisel ◽

M.C. Oliveira Fusaro ◽

S. Mense ◽

...

Keyword(s):

Low Back Pain ◽

Back Pain ◽

Dorsal Horn ◽

Swimming Exercise ◽

Low Back ◽

Short Term ◽

Dorsal Horn Neurons

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Electrical Stimulation of the Anterior Cingulate Cortex Reduces Responses of Rat Dorsal Horn Neurons to Mechanical Stimuli

Journal of Neurophysiology ◽

10.1152/jn.00040.2005 ◽

2005 ◽

Vol 94 (1) ◽

pp. 845-851 ◽

Cited By ~ 37

Author(s):

Arun K. Senapati ◽

Stacey C. Lagraize ◽

Paula J. Huntington ◽

Hilary D. Wilson ◽

Perry N. Fuchs ◽

...

Keyword(s):

Spinal Cord ◽

Dorsal Horn ◽

Anterior Cingulate ◽

Spinal Cord Dorsal Horn ◽

Mechanical Stimuli ◽

Short Term ◽

Dorsal Horn Neurons ◽

Spinal Cord Dorsal ◽

Stimulation Of

The anterior cingulate cortex (ACC) is involved in the affective and motivational aspect of pain perception. Behavioral studies show a decreased avoidance behavior to noxious stimuli without change in mechanical threshold after stimulation of the ACC. However, as part of the neural circuitry of behavioral reflexes, there is no evidence showing that ACC stimulation alters dorsal horn neuronal responses. We hypothesize that ACC stimulation has two phases: a short-term phase in which stimulation elicits antinociception and a long-term phase that follows stimulation to change the affective response to noxious input. To begin testing this hypothesis, the purpose of this study was to examine the response of spinal cord dorsal horn neurons during stimulation of the ACC. Fifty-eight wide dynamic range spinal cord dorsal horn neurons from adult Sprague-Dawley rats were recorded in response to graded mechanical stimuli (brush, pressure, and pinch) at their respective receptive fields, while simultaneous stepwise electrical stimulations (300 Hz, 0.1 ms, at 10, 20, and 30 V) were applied in the ACC. The responses to brush at control, 10, 20, and 30 V, and recovery were 14.2 ± 1.4, 12.3 ± 1.2, 10.9 ± 1.2, 10.3 ± 1.1, and 14.1 ± 1.4 spikes/s, respectively. The responses to pressure at control, 10, 20, and 30 V, and recovery were 39.8 ± 4.7, 25.6 ± 3.0, 25.0 ± 3.0, 21.6 ± 2.4, and 34.2 ± 3.7 spikes/s, respectively. The responses to pinch at control, 10, 20, and 30 V, and recovery were 40.7 ± 3.8, 30.6 ± 3.1, 27.8 ± 2.8, 27.2 ± 3.2, and 37.4 ± 3.9 spikes/s, respectively. We conclude that electrical stimulation of the ACC induces significant inhibition of the responses of spinal cord dorsal horn neurons to noxious mechanical stimuli. The stimulation-induced inhibition begins to recover as soon as the stimulation is terminated. These results suggest differential short-term and long-term modulatory effects of the ACC stimulation on nociceptive circuits.

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