Reference : Calcium Release from Internal Stores Is Required for the Generation of Spontaneous Hyper...
Scientific journals : Article
Human health sciences : Pharmacy, pharmacology & toxicology
http://hdl.handle.net/2268/8795
Calcium Release from Internal Stores Is Required for the Generation of Spontaneous Hyperpolarizations in Dopaminergic Neurons of Neonatal Rats
English
Seutin, Vincent mailto [Université de Liège - ULg > Département des sciences biomédicales et précliniques > Pharmacologie >]
Mkahli, F. [> > > >]
Massotte, Laurent mailto [Université de Liège - ULg > Département des sciences biomédicales et précliniques > Département des sciences biomédicales et précliniques >]
Dresse, Albert mailto [Université de Liège - ULg > Services généraux (Faculté de médecine) > Relations académiques et scientifiques (Médecine) >]
Jan-2000
Journal of Neurophysiology
83
1
192-7
Yes (verified by ORBi)
International
0022-3077
[en] We recently have demonstrated the existence of spontaneous hyperpolarizations in midbrain dopaminergic neurons of neonatal but not adult rats. These events are mediated by the opening of apamin-sensitive K(+) channels after a rise in the intracellular concentration of Ca(2+). They are resistant to tetrodotoxin in most cases and are probably endogenous (i.e., not synaptically activated). Here their mechanism was investigated. Cyclopiazonic acid (10 microM), a specific inhibitor of endoplasmic reticulum Ca(2+) ATPases, reversibly abolished the events. Caffeine, which promotes Ca(2+) release from intracellular stores, had concentration-dependent effects. At 1 mM, it markedly and steadily increased the frequency and the amplitude of the hyperpolarizations. At 10 mM, it induced a transient increase in their frequency followed by their cessation. All these effects were quickly reversible. Ryanodine (10 microM), which decreases the conductance of Ca(2+) release channels, irreversibly blocked the spontaneous hyperpolarizations. Dantrolene (100 microM), a blocker of Ca(2+) release from sarcoplasmic reticulum of striated muscle, did not affect the events. On the other hand, Cd(2+) (100-300 microM), a broad antagonist of membrane voltage-gated Ca(2+) channels, significantly reduced the amplitude and the frequency of the hyperpolarizations. However, when the frequency of the events was increased by 1 mM caffeine, Cd(2+) affected them to a smaller extent, whereas cyclopiazonic acid still abolished them. We conclude that internal stores are the major source of Ca(2+) ions that induce the K(+) channel openings underlying the spontaneous hyperpolarizations of these neurons.
http://hdl.handle.net/2268/8795

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