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Substance P Depolarizes Lamprey Spinal Cord Neurons by Inhibiting Background Potassium Channels.

Thörn Pérez C, Hill RH, Grillner S - PLoS ONE (2015)

Bottom Line: Substance P is endogenously released in the adult lamprey spinal cord and accelerates the burst frequency of fictive locomotion.Hyperpolarizing steps induced inward currents during whole-cell voltage clamp that were reduced by substance P.These background K+ channels are pH sensitive and are selectively blocked by anandamide and AVE1231.

View Article: PubMed Central - PubMed

Affiliation: Nobel Institute for Neurophysiology, Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.

ABSTRACT
Substance P is endogenously released in the adult lamprey spinal cord and accelerates the burst frequency of fictive locomotion. This is achieved by multiple effects on interneurons and motoneurons, including an attenuation of calcium currents, potentiation of NMDA currents and reduction of the reciprocal inhibition. While substance P also depolarizes spinal cord neurons, the underlying mechanism has not been resolved. Here we show that effects of substance P on background K+ channels are the main source for this depolarization. Hyperpolarizing steps induced inward currents during whole-cell voltage clamp that were reduced by substance P. These background K+ channels are pH sensitive and are selectively blocked by anandamide and AVE1231. These blockers counteracted the effect of substance P on these channels and the resting membrane potential depolarization in spinal cord neurons. Thus, we have shown now that substance P inhibits background K+ channels that in turn induce depolarization, which is likely to contribute to the frequency increase observed with substance P during fictive locomotion.

No MeSH data available.


Related in: MedlinePlus

A1. Experimental arrangement of the isolated spinal cord.A2.Photomicrograph of a patched neuron exposed by slicing the spinal cord on the ventral side. The micropipette is shown to the left of the cell. B1. Current traces from voltage steps (-30 to -130) applied to a spinal neuron in the presence of TTX (1 μM) and Kynurenic acid (2 mM). B2. The current-voltage (I-V) relationship with reversal potential at ~60 mV at control conditions, ~50 mV with high extracellular K+ and ~64 mV with low K+ (Control: 2.1 mM, Low: 1 mM and high: 6 mM). C. Membrane potential changes with different extracellular concentrations of K+ during current clamp recording (Control: 2.1 mM, Low: 1 mM and high: 6 mM, single star = p < 0.05, n = 3). D. Current measurements from hyperpolarizing voltage steps (-70 and -100 mV) under voltage clamp during application of different extracellular K+ concentrations (2.1, 6 and 1 mM). Holding potential was -60 mV.
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pone.0133136.g001: A1. Experimental arrangement of the isolated spinal cord.A2.Photomicrograph of a patched neuron exposed by slicing the spinal cord on the ventral side. The micropipette is shown to the left of the cell. B1. Current traces from voltage steps (-30 to -130) applied to a spinal neuron in the presence of TTX (1 μM) and Kynurenic acid (2 mM). B2. The current-voltage (I-V) relationship with reversal potential at ~60 mV at control conditions, ~50 mV with high extracellular K+ and ~64 mV with low K+ (Control: 2.1 mM, Low: 1 mM and high: 6 mM). C. Membrane potential changes with different extracellular concentrations of K+ during current clamp recording (Control: 2.1 mM, Low: 1 mM and high: 6 mM, single star = p < 0.05, n = 3). D. Current measurements from hyperpolarizing voltage steps (-70 and -100 mV) under voltage clamp during application of different extracellular K+ concentrations (2.1, 6 and 1 mM). Holding potential was -60 mV.

Mentions: Animals were anesthetized with tricaine methanesulfonate (MS 222, 100 mg/l; Sigma–Aldrich, Sweden), decapitated, and the spinal cord was dissected and kept at 4–8°C in a saline solution of the following composition (in mM): 137.9 NaCl, 2.1 KCl, 2.6 CaCl2, 1.8 MgCl2, 4 glucose, 5 HEPES. The pH was adjusted to 7.4 with 1 M NaOH. The osmolarity was adjusted to 270 mOsm with distilled water. The spinal cord and musculature of approximately 8 segments were pinned down to a Sylgard chamber. The protective meninx primitiva was removed and the spinal cords were isolated and placed in a cooled microslicer with the ventral side up. A horizontal layer of about 40 μm above the gray matter was removed from the ventral surface to facilitate visibility and penetration of the patch electrode into the tissue (Fig 1A). The spinal cords were then pinned to a cooled sylgard-lined chamber. Solutions of pharmacological agents were bath-applied at a perfusion rate of 1 ml/min into a chamber volume of 1ml.


Substance P Depolarizes Lamprey Spinal Cord Neurons by Inhibiting Background Potassium Channels.

Thörn Pérez C, Hill RH, Grillner S - PLoS ONE (2015)

A1. Experimental arrangement of the isolated spinal cord.A2.Photomicrograph of a patched neuron exposed by slicing the spinal cord on the ventral side. The micropipette is shown to the left of the cell. B1. Current traces from voltage steps (-30 to -130) applied to a spinal neuron in the presence of TTX (1 μM) and Kynurenic acid (2 mM). B2. The current-voltage (I-V) relationship with reversal potential at ~60 mV at control conditions, ~50 mV with high extracellular K+ and ~64 mV with low K+ (Control: 2.1 mM, Low: 1 mM and high: 6 mM). C. Membrane potential changes with different extracellular concentrations of K+ during current clamp recording (Control: 2.1 mM, Low: 1 mM and high: 6 mM, single star = p < 0.05, n = 3). D. Current measurements from hyperpolarizing voltage steps (-70 and -100 mV) under voltage clamp during application of different extracellular K+ concentrations (2.1, 6 and 1 mM). Holding potential was -60 mV.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4510128&req=5

pone.0133136.g001: A1. Experimental arrangement of the isolated spinal cord.A2.Photomicrograph of a patched neuron exposed by slicing the spinal cord on the ventral side. The micropipette is shown to the left of the cell. B1. Current traces from voltage steps (-30 to -130) applied to a spinal neuron in the presence of TTX (1 μM) and Kynurenic acid (2 mM). B2. The current-voltage (I-V) relationship with reversal potential at ~60 mV at control conditions, ~50 mV with high extracellular K+ and ~64 mV with low K+ (Control: 2.1 mM, Low: 1 mM and high: 6 mM). C. Membrane potential changes with different extracellular concentrations of K+ during current clamp recording (Control: 2.1 mM, Low: 1 mM and high: 6 mM, single star = p < 0.05, n = 3). D. Current measurements from hyperpolarizing voltage steps (-70 and -100 mV) under voltage clamp during application of different extracellular K+ concentrations (2.1, 6 and 1 mM). Holding potential was -60 mV.
Mentions: Animals were anesthetized with tricaine methanesulfonate (MS 222, 100 mg/l; Sigma–Aldrich, Sweden), decapitated, and the spinal cord was dissected and kept at 4–8°C in a saline solution of the following composition (in mM): 137.9 NaCl, 2.1 KCl, 2.6 CaCl2, 1.8 MgCl2, 4 glucose, 5 HEPES. The pH was adjusted to 7.4 with 1 M NaOH. The osmolarity was adjusted to 270 mOsm with distilled water. The spinal cord and musculature of approximately 8 segments were pinned down to a Sylgard chamber. The protective meninx primitiva was removed and the spinal cords were isolated and placed in a cooled microslicer with the ventral side up. A horizontal layer of about 40 μm above the gray matter was removed from the ventral surface to facilitate visibility and penetration of the patch electrode into the tissue (Fig 1A). The spinal cords were then pinned to a cooled sylgard-lined chamber. Solutions of pharmacological agents were bath-applied at a perfusion rate of 1 ml/min into a chamber volume of 1ml.

Bottom Line: Substance P is endogenously released in the adult lamprey spinal cord and accelerates the burst frequency of fictive locomotion.Hyperpolarizing steps induced inward currents during whole-cell voltage clamp that were reduced by substance P.These background K+ channels are pH sensitive and are selectively blocked by anandamide and AVE1231.

View Article: PubMed Central - PubMed

Affiliation: Nobel Institute for Neurophysiology, Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.

ABSTRACT
Substance P is endogenously released in the adult lamprey spinal cord and accelerates the burst frequency of fictive locomotion. This is achieved by multiple effects on interneurons and motoneurons, including an attenuation of calcium currents, potentiation of NMDA currents and reduction of the reciprocal inhibition. While substance P also depolarizes spinal cord neurons, the underlying mechanism has not been resolved. Here we show that effects of substance P on background K+ channels are the main source for this depolarization. Hyperpolarizing steps induced inward currents during whole-cell voltage clamp that were reduced by substance P. These background K+ channels are pH sensitive and are selectively blocked by anandamide and AVE1231. These blockers counteracted the effect of substance P on these channels and the resting membrane potential depolarization in spinal cord neurons. Thus, we have shown now that substance P inhibits background K+ channels that in turn induce depolarization, which is likely to contribute to the frequency increase observed with substance P during fictive locomotion.

No MeSH data available.


Related in: MedlinePlus