Calcium channels in isolated rat dorsal horn neurones, including labelled spinothalamic and trigeminothalamic cells

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Abstract

Single isolated neurones were prepared from the spinal trigeminal nucleus and the dorsal horn of cervical spinal cord of the rat. Spinothalamic and trigeminothalamic neurones were identified using rhodamine-labelled fluorescent latex microspheres. Calcium currents in these cells were examined by the whole-cell patch-clamp technique. Three types of calcium currents, transient (T) and slow inactivating (N and L) types, were identified by their sensitivities to inorganic blockers and rates or inactivation at two different holding potentials (temperature = 21-25°C). From a holding potential of -100 mV, the I(Ca,T) began to activate at -60 mV. The current reached its maximum amplitude around -30 mV and was inactivated completely when the cell was held more positive than -60 mV. The time constant of the inactivation was between 10 and 50 ms. The slow inactivating component of I(Ca) was dissociated into two components by eliciting I(Ca) from two holding potentials of -100 and of -40 mV. The current (I(Ca,L)) activated from -40 mV was characterized by positive activation potentials and a very slow inactivation (time constant, 700-4000 ms). The current (I(Ca,N)) elicited from a holding potential of -100 mV started to activate at -30 mV and inactivated slowly with time constants ranging between 400 and 1000 ms. Compared with the I(Ca,T), the activation curve for I(Ca,N) was shifted about 30 mV in the depolarizing direction. I(Ca,N) inactivated over a broader range of potentials, and its inactivation and activation curves overlapped. Cadmium blocked I(Ca,T) at a concentration 24 times higher than that which was needed to block slow inactivating currents. The apparent dissociation constant of nickel for I(Ca,T) is twofold lower than that for the slow inactivating currents. Nimodipine (2 μM) decreased the slow inactivating currents, but had no effect on I(Ca,T). (-)-Bay K 8644 (200 nM) increased both I(Ca,N) and I(Ca,L) and shifted the current activation in the hyperpolarizing direction. This result is different from that obtained in sensory and sympathetic neurones in which I(Ca,N) is insensitive to Bay K 8644.

Original languageEnglish (US)
Pages (from-to)161-177
Number of pages17
JournalJournal of Physiology
Volume411
StatePublished - 1989

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Posterior Horn Cells
Calcium Channels
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester
Spinal Trigeminal Nucleus
Calcium
Neurons
Nimodipine
Rhodamines
Latex
Patch-Clamp Techniques
Sensory Receptor Cells
Nickel
Cadmium
Microspheres
Temperature
Direction compound

ASJC Scopus subject areas

  • Physiology

Cite this

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title = "Calcium channels in isolated rat dorsal horn neurones, including labelled spinothalamic and trigeminothalamic cells",
abstract = "Single isolated neurones were prepared from the spinal trigeminal nucleus and the dorsal horn of cervical spinal cord of the rat. Spinothalamic and trigeminothalamic neurones were identified using rhodamine-labelled fluorescent latex microspheres. Calcium currents in these cells were examined by the whole-cell patch-clamp technique. Three types of calcium currents, transient (T) and slow inactivating (N and L) types, were identified by their sensitivities to inorganic blockers and rates or inactivation at two different holding potentials (temperature = 21-25°C). From a holding potential of -100 mV, the I(Ca,T) began to activate at -60 mV. The current reached its maximum amplitude around -30 mV and was inactivated completely when the cell was held more positive than -60 mV. The time constant of the inactivation was between 10 and 50 ms. The slow inactivating component of I(Ca) was dissociated into two components by eliciting I(Ca) from two holding potentials of -100 and of -40 mV. The current (I(Ca,L)) activated from -40 mV was characterized by positive activation potentials and a very slow inactivation (time constant, 700-4000 ms). The current (I(Ca,N)) elicited from a holding potential of -100 mV started to activate at -30 mV and inactivated slowly with time constants ranging between 400 and 1000 ms. Compared with the I(Ca,T), the activation curve for I(Ca,N) was shifted about 30 mV in the depolarizing direction. I(Ca,N) inactivated over a broader range of potentials, and its inactivation and activation curves overlapped. Cadmium blocked I(Ca,T) at a concentration 24 times higher than that which was needed to block slow inactivating currents. The apparent dissociation constant of nickel for I(Ca,T) is twofold lower than that for the slow inactivating currents. Nimodipine (2 μM) decreased the slow inactivating currents, but had no effect on I(Ca,T). (-)-Bay K 8644 (200 nM) increased both I(Ca,N) and I(Ca,L) and shifted the current activation in the hyperpolarizing direction. This result is different from that obtained in sensory and sympathetic neurones in which I(Ca,N) is insensitive to Bay K 8644.",
author = "Li-Yen Huang",
year = "1989",
language = "English (US)",
volume = "411",
pages = "161--177",
journal = "Journal of Physiology",
issn = "0022-3751",
publisher = "Wiley-Blackwell",

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T1 - Calcium channels in isolated rat dorsal horn neurones, including labelled spinothalamic and trigeminothalamic cells

AU - Huang, Li-Yen

PY - 1989

Y1 - 1989

N2 - Single isolated neurones were prepared from the spinal trigeminal nucleus and the dorsal horn of cervical spinal cord of the rat. Spinothalamic and trigeminothalamic neurones were identified using rhodamine-labelled fluorescent latex microspheres. Calcium currents in these cells were examined by the whole-cell patch-clamp technique. Three types of calcium currents, transient (T) and slow inactivating (N and L) types, were identified by their sensitivities to inorganic blockers and rates or inactivation at two different holding potentials (temperature = 21-25°C). From a holding potential of -100 mV, the I(Ca,T) began to activate at -60 mV. The current reached its maximum amplitude around -30 mV and was inactivated completely when the cell was held more positive than -60 mV. The time constant of the inactivation was between 10 and 50 ms. The slow inactivating component of I(Ca) was dissociated into two components by eliciting I(Ca) from two holding potentials of -100 and of -40 mV. The current (I(Ca,L)) activated from -40 mV was characterized by positive activation potentials and a very slow inactivation (time constant, 700-4000 ms). The current (I(Ca,N)) elicited from a holding potential of -100 mV started to activate at -30 mV and inactivated slowly with time constants ranging between 400 and 1000 ms. Compared with the I(Ca,T), the activation curve for I(Ca,N) was shifted about 30 mV in the depolarizing direction. I(Ca,N) inactivated over a broader range of potentials, and its inactivation and activation curves overlapped. Cadmium blocked I(Ca,T) at a concentration 24 times higher than that which was needed to block slow inactivating currents. The apparent dissociation constant of nickel for I(Ca,T) is twofold lower than that for the slow inactivating currents. Nimodipine (2 μM) decreased the slow inactivating currents, but had no effect on I(Ca,T). (-)-Bay K 8644 (200 nM) increased both I(Ca,N) and I(Ca,L) and shifted the current activation in the hyperpolarizing direction. This result is different from that obtained in sensory and sympathetic neurones in which I(Ca,N) is insensitive to Bay K 8644.

AB - Single isolated neurones were prepared from the spinal trigeminal nucleus and the dorsal horn of cervical spinal cord of the rat. Spinothalamic and trigeminothalamic neurones were identified using rhodamine-labelled fluorescent latex microspheres. Calcium currents in these cells were examined by the whole-cell patch-clamp technique. Three types of calcium currents, transient (T) and slow inactivating (N and L) types, were identified by their sensitivities to inorganic blockers and rates or inactivation at two different holding potentials (temperature = 21-25°C). From a holding potential of -100 mV, the I(Ca,T) began to activate at -60 mV. The current reached its maximum amplitude around -30 mV and was inactivated completely when the cell was held more positive than -60 mV. The time constant of the inactivation was between 10 and 50 ms. The slow inactivating component of I(Ca) was dissociated into two components by eliciting I(Ca) from two holding potentials of -100 and of -40 mV. The current (I(Ca,L)) activated from -40 mV was characterized by positive activation potentials and a very slow inactivation (time constant, 700-4000 ms). The current (I(Ca,N)) elicited from a holding potential of -100 mV started to activate at -30 mV and inactivated slowly with time constants ranging between 400 and 1000 ms. Compared with the I(Ca,T), the activation curve for I(Ca,N) was shifted about 30 mV in the depolarizing direction. I(Ca,N) inactivated over a broader range of potentials, and its inactivation and activation curves overlapped. Cadmium blocked I(Ca,T) at a concentration 24 times higher than that which was needed to block slow inactivating currents. The apparent dissociation constant of nickel for I(Ca,T) is twofold lower than that for the slow inactivating currents. Nimodipine (2 μM) decreased the slow inactivating currents, but had no effect on I(Ca,T). (-)-Bay K 8644 (200 nM) increased both I(Ca,N) and I(Ca,L) and shifted the current activation in the hyperpolarizing direction. This result is different from that obtained in sensory and sympathetic neurones in which I(Ca,N) is insensitive to Bay K 8644.

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