Dopamine enhances a voltage-dependent transient K+ current in the MMQ cell, a clonal pituitary line expressing functional D2 dopamine receptors.
The influence of dopamine on voltage-dependent K+ current (IK) was studied in cultured MMQ cells using the whole-cell patch-clamp technique. IK in nearly all MMQ cells revealed a transient outward current component and inactivated during maintained depolarization lasting 60 ms. The transient component was inhibited by prepulse potentials more positive than -40 mV or by addition of 4 mM 4-aminopyridine to the bathing solution and was insensitive to the external Ca2+ concentration. Thus, this transient K+ current resembled the A-current (IA) found in other cells. Dopamine at 1 microM increased by 50% (P less than 0.001) the peak of IK evoked by a test potential to +80 mV and the response was prevented by pretreatment with 100 nM haloperidol, a D2 receptor antagonist. These data suggest that MMQ clonal pituitary cells possess a voltage-gated K+ A-current and that this current can be modulated by dopamine via D2 receptors.
Login
I S
IS
Department of Neurology, University of Virginia Health Sciences Center, Charlottesville 22908.
Pancrazio
J J
JJ
Kim
Y I
YI
D015761:4-Aminopyridine / Q000494:pharmacology; D002460:Cell Line; D004298:Dopamine / Q000494:pharmacology / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D011188:Potassium / Q000502:physiology*; D011954:Receptors, Dopamine / Q000187:drug effects / Q000502:physiology*; D017448:Receptors, Dopamine D2
D011954:Receptors, Dopamine; D017448:Receptors, Dopamine D2; D015761:4-Aminopyridine; D011188:Potassium; D004298:Dopamine