Switch to
| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
3
|
| pubmed:dateCreated |
1990-9-21
|
| pubmed:abstractText |
The effects of dopamine (DA) on voltage-dependent Ca2+ currents were investigated in cultured rat lactotroph cells using the patch clamp recording technique. Each recorded cell was identified by the reverse hemolytic plaque assay. In the whole-cell configuration, two types of Ca2+ currents, L and T, were characterized on the basis of their kinetics, voltage sensitivity, and pharmacology. The L component had a threshold of -25 mV, showed little inactivation during a 150-msec voltage step, and was maximal at +10 mV. Cadmium ions (100 microM) significantly reduced its amplitude (75%). The T component was activated at a membrane potential close to -50 mV, was maximal at -10 mV, and showed a voltage-dependent inactivation between -90 and -30 mV. It was quickly inactivated during a maintained depolarization (time constant, 27 ms at -30 mV) and was strongly reduced (80%) by nickel ions (100 microM). Bath application of DA (10 nM) caused a markedly general depression of inward Ca2+ currents, acting differently on the T- and L-type currents. DA application shifted the voltage-dependence of the L-type current activation toward depolarization values (8 mV) without modifying its time- and voltage-dependent inactivation. In contrast, DA enhanced the inactivation of the T-type current by accelerating its time-dependent inactivation (25% decrease in the time constant of inactivation) and by shifting the voltage-dependence of the T-type current inactivation toward hyperpolarizing values (-63 mV in control vs. -77 mV in the presence of DA). These effects of DA were dose-dependent and involved the activation of a D2 receptor type. They were mimicked by bromocriptine application (10 nM), whereas sulpiride (100 nM) blocked the DA-evoked response. The D1 antagonist SCH 23390 was ineffective up to 100 microM. All of these DA-induced modifications in Ca2+ currents were abolished using a GTP-free pipette solution or after pretreatment of cells with pertussis toxin, suggesting that DA can regulate the function of Ca2+ channels through GTP-binding proteins (G-proteins). Our results show that DA acts simultaneously by reducing both voltage-dependent Ca2+ currents on lactotroph cells. Thus, DA reduces the entry of Ca2+ ions across the surface membrane and thereby influences electrical activity and the cytosolic free Ca2+ concentration involved in both basal and evoked PRL release.
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| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
AIM
|
| pubmed:chemical |
http://linkedlifedata.com/resource/pubmed/chemical/Bromocriptine,
http://linkedlifedata.com/resource/pubmed/chemical/Cadmium,
http://linkedlifedata.com/resource/pubmed/chemical/Calcium Channels,
http://linkedlifedata.com/resource/pubmed/chemical/Cations, Divalent,
http://linkedlifedata.com/resource/pubmed/chemical/Guanosine Triphosphate,
http://linkedlifedata.com/resource/pubmed/chemical/Nickel,
http://linkedlifedata.com/resource/pubmed/chemical/Pertussis Toxin,
http://linkedlifedata.com/resource/pubmed/chemical/Prolactin,
http://linkedlifedata.com/resource/pubmed/chemical/Receptors, Dopamine,
http://linkedlifedata.com/resource/pubmed/chemical/Receptors, Dopamine D2,
http://linkedlifedata.com/resource/pubmed/chemical/Sulpiride,
http://linkedlifedata.com/resource/pubmed/chemical/Virulence Factors, Bordetella
|
| pubmed:status |
MEDLINE
|
| pubmed:month |
Sep
|
| pubmed:issn |
0013-7227
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| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:volume |
127
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
990-1001
|
| pubmed:dateRevised |
2003-11-14
|
| pubmed:meshHeading |
pubmed-meshheading:2167220-Animals,
pubmed-meshheading:2167220-Bromocriptine,
pubmed-meshheading:2167220-Cadmium,
pubmed-meshheading:2167220-Calcium Channels,
pubmed-meshheading:2167220-Cations, Divalent,
pubmed-meshheading:2167220-Cells, Cultured,
pubmed-meshheading:2167220-Dopamine,
pubmed-meshheading:2167220-Electric Conductivity,
pubmed-meshheading:2167220-Female,
pubmed-meshheading:2167220-Guanosine Triphosphate,
pubmed-meshheading:2167220-Kinetics,
pubmed-meshheading:2167220-Membrane Potentials,
pubmed-meshheading:2167220-Nickel,
pubmed-meshheading:2167220-Pertussis Toxin,
pubmed-meshheading:2167220-Pituitary Gland,
pubmed-meshheading:2167220-Prolactin,
pubmed-meshheading:2167220-Rats,
pubmed-meshheading:2167220-Rats, Inbred Strains,
pubmed-meshheading:2167220-Receptors, Dopamine,
pubmed-meshheading:2167220-Receptors, Dopamine D2,
pubmed-meshheading:2167220-Sulpiride,
pubmed-meshheading:2167220-Virulence Factors, Bordetella
|
| pubmed:year |
1990
|
| pubmed:articleTitle |
Dopamine inhibits two characterized voltage-dependent calcium currents in identified rat lactotroph cells.
|
| pubmed:affiliation |
INSERM U.176, 33077 Bordeaux, France.
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| pubmed:publicationType |
Journal Article
|