Chronic stimulation of D2 dopamine receptors specifically inhibits calcium but not potassium currents in rat lactotrophs.
The present study examines the effect of chronic dopamine treatment, known to inhibit prolactin release from anterior pituitary, on two Ca2+ and K+ currents in cultured rat lactotrophs. K+ and Ca2+ currents were recorded using the whole-cell mode of the patch-clamp technique. The two types of voltage-dependent Ca2+ currents are called SD and FD (slowly deactivating and fast deactivating current component, respectively) and the two types of voltage-dependent K+ currents, IA and IK. All current types were isolated by tail current analysis. The amplitude of both normalized calcium components depended on the length of the culture (n = 48) while normalized amplitudes of both potassium currents remained constant (n = 9). Incubation of cells during 72 h with 50 microM of Actinomycin D, an inhibitor of mRNA synthesis, suggested that this increase in Ca2+ currents involved the synthesis of proteins. Long-lasting D2 receptor stimulation (8 days; 10 nM RU 24213) prevented this selective effect through activation of a pertussis toxin-sensitive G protein. We also examined whether cyclic adenosine-3',5'-cyclic-monophosphate (cyclic AMP) or Ca2+/phospholipid-dependent protein kinase (protein kinase C) could affect this development of channel activity.(ABSTRACT TRUNCATED AT 250 WORDS)
INSERM, Unité 176, Bordeaux, France.
P M
PM
Lledo
J M
JM
Israel
J D
JD
Vincent
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004298:Dopamine / Q000502:physiology; D015259:Dopamine Agents / Q000494:pharmacology; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000502:physiology; D037342:Pertussis Toxin; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects*; D017448:Receptors, Dopamine D2; D015290:Second Messenger Systems / Q000502:physiology; D013268:Stimulation, Chemical; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D002121:Calcium Channel Blockers; D015259:Dopamine Agents; D015221:Potassium Channels; D011954:Receptors, Dopamine; D017448:Receptors, Dopamine D2; D010566:Virulence Factors, Bordetella; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D004298:Dopamine