Properties of two types of calcium channels in clonal pituitary cells.

Matteson, D R; Armstrong, Clay M.

doi:10.1085/jgp.87.1.161

Cited by 271 publications

(192 citation statements)

References 20 publications

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“…Similar results were obtained from 6 other cells. We have not investigated the relationship between multiple exponential deactivation kinetics and different Ca current types, but a multiple exponential description of tail currents is considered indicative of multiple Ca channel types (Matteson and Armstrong, 1986). In any event, our data confirm that an actual decrease in Ca conductance had occurred.…”

Section: Efects Of Pkc Activators On Ca Currentsmentioning

confidence: 52%

Protein kinase C activators block specific calcium and potassium current components in isolated hippocampal neurons

1988

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Whole-cell voltage-clamp techniques were used to study the effects of the protein kinase C (PKC) activators phorbol esters and OAG on Ca and K currents in differentiated neurons acutely dissociated from adult hippocampus and in tissue-cultured neurons from fetal hippocampus. PKC activators had selective depressant effects on K currents, with persistent currents (IK and IK-Ca) being reduced and transient current (IA) being unaffected. In both cell types we recorded both high-voltage- activated, noninactivating (L-type) and high-voltage-activated, rapidly inactivating (N-type) Ca current. A low-voltage-activated, rapidly inactivating (T-type) Ca current was also recorded in tissue-cultured neurons but not in acutely dissociated neurons. PKC activators markedly reduced N-type current with less effect on L-type and no effect on T- type Ca current. Effects of PKC activators could be reversed with washing or with application of PKC inhibitors H-7 or polymyxin-B, an effect that could not be attributed to inhibition of cAMP-dependent protein kinase. The Ca/calmodulin inhibitor calmidazolium was ineffective in reversing the actions of PKC activators. Using whole- cell voltage-clamp techniques, we have demonstrated that hippocampal neurons possess 3 distinguishable components of calcium current. Distinct K currents were also observed. Our data strongly support the hypothesis that both Ca and K currents are selectively regulated by PKC and that these effects occur directly on the postsynaptic neuron.

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Section: Efects Of Pkc Activators On Ca Currentsmentioning

confidence: 52%

Protein kinase C activators block specific calcium and potassium current components in isolated hippocampal neurons

1988

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“…However, there are recent reports suggesting that CaV3.3 (α1I) channels close in a biexponential manner (15)(16)(17). It has been well established that GH3 cells contain two types of voltage-dependent Ca 2+ channels (L-and T-type channels) (8,18). The voltage dependence of deactivation was examined in a potential range (-120 to -60 mV) to avoid any interference by L-type Ca 2+ channels (18).…”

Section: Resultsmentioning

confidence: 99%

“…It has been well established that GH3 cells contain two types of voltage-dependent Ca 2+ channels (L-and T-type channels) (8,18). The voltage dependence of deactivation was examined in a potential range (-120 to -60 mV) to avoid any interference by L-type Ca 2+ channels (18). It is possible that the protocol used to measure tail currents was revealing L-type Ca 2+ channel deactivation along with T-type deactivation.…”

Section: Resultsmentioning

confidence: 99%

CaV 3.1 and CaV 3.3 account for T-type Ca2+ current in GH3 cells

Mudado

Rodrigues

Prado

et al. 2004

Braz J Med Biol Res

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T-type Ca 2+ channels are important for cell signaling by a variety of cells. We report here the electrophysiological and molecular characteristics of the whole-cell Ca 2+ current in GH3 clonal pituitary cells. The current inactivation at 0 mV was described by a single exponential function with a time constant of 18.32 ± 1.87 ms (N = 16). The I-V relationship measured with Ca 2+ as a charge carrier was shifted to the left when we applied a conditioning pre-pulse of up to -120 mV, indicating that a low voltage-activated current may be present in GH3 cells. Transient currents were first activated at -50 mV and peaked around -20 mV. The half-maximal voltage activation and the slope factors for the two conditions are -35.02 ± 2.4 and 6.7 ± 0.3 mV (prepulse of -120 mV, N = 15), and -27.0 ± 0.97 and 7.5 ± 0.7 mV (prepulse of -40 mV, N = 9). The 8-mV shift in the activation mid-point was statistically significant (P < 0.05). The tail currents decayed biexponentially suggesting two different T-type Ca 2+ channel populations. RT-PCR revealed the presence of α1G (CaV3.1) and α1I (CaV3.3) T-type Ca 2+ channel mRNA transcripts. Correspondence

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“…Tail currents resulting from the deactivation of calcium channels can be a sensitive measure of channel type and kinetics and have been useful in disclosing the existence of multiple channel types (Matteson & Armstrong, 1986). It is expected that the activation of a different channel type will be signalled by the presence of a new component in the tail current; likewise during inactivation the tail associated with the inactivating current, if it is indeed separate, should follow the decline of the inactivating component.…”

Section: Discussionmentioning

confidence: 99%

Inactivation kinetics of calcium current of acutely dissociated CA1 pyramidal cells of the mature guinea‐pig hippocampus.

Kay

1991

The Journal of Physiology

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SUMMARY1. The process of inactivation of the Ca21 current of acutely dissociated pyramidal cells from the CAl subfield of mature guinea-pig hippocampus was characterized.The decline of the current after rapid activation could be approximated well by the sum of two exponentials (time constants -200 ms and 2 s) and a constant offset.2. The time constants of inactivation exhibited a voltage dependence consistent with a voltage-dependent mechanism. However, under conditions which normally counteract Ca2+-dependent inactivation (viz. intracellular bis(O-aminophenoxy)-ethane-N,NNN'-tetraacetic acid (BAPTA) and external Ba2+) all three showed a U-shaped inactivation curve, characteristic of Ca2+-dependent inactivation.3. The rate of inactivation was found to increase with current at a given voltage; however. increasing external divalent ion concentrations did not accelerate inactivation.4. Calcium imaging experiments, using the Ca2+-sensitive probe, Fura-2, were performed to estimate the accumulation of Ca2+ in the presence of 10 mM-intracellular BAPTA. Under these conditions voltage steps which induced maximal Ca2+ currents lead to free Ca2+ concentrations of < 500 nm in the bulk of the cytoplasm.5. Elevation of the intracellular free Ca2+ concentration to above 1 ,UM suppressed all the components of the Ca2+ current. However, even at a concentration of 3 /tMCa2+ the U-shaped inactivation curve persisted. 6. Substitution of Ca2+ for Ba2+ led to an acceleration of inactivation through an increase in the proportion of the fast process of inactivation and an acceleration of both the fast and slow rates of inactivation.7. During the slow decline of Ca2+ current ('run-down') the proportion of all three components remained approximately constant and there was little change in the rate of inactivation.8. On the basis of the results I suggest that inactivation results from a dual process of voltage-and Ca2+-dependent inactivation. Ca2+-dependent inactivation seems to result from the accumulation of Ca2+ close to the channel mouth.

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Properties of two types of calcium channels in clonal pituitary cells.

Cited by 271 publications

References 20 publications

Protein kinase C activators block specific calcium and potassium current components in isolated hippocampal neurons

Protein kinase C activators block specific calcium and potassium current components in isolated hippocampal neurons

CaV 3.1 and CaV 3.3 account for T-type Ca2+ current in GH3 cells

Inactivation kinetics of calcium current of acutely dissociated CA1 pyramidal cells of the mature guinea‐pig hippocampus.

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