Expression of striatal D1 dopamine receptors coupled to inositol phosphate production and Ca2+ mobilization in Xenopus oocytes.
Expression of central nervous system receptors for dopamine was examined by injection of poly(A)+ RNA (mRNA) from rat striatum into oocytes from Xenopus laevis. Electrophysiological measurements in mRNA-injected oocytes indicated that addition of 100 microM dopamine induced an inward current (40-100 nA) that was consistent with the activation of endogenous Ca2(+)-dependent Cl- channels. This current was also elicited by addition of the selective D1 agonist SKF 38393 but not by the selective D2 agonist quinpirole. Prior addition of the dopaminergic antagonist cis-piflutixol completely abolished dopamine-induced currents but had no effect on currents produced by serotonin. Using 45Ca2+ efflux assays, addition of 100 microM dopamine to injected oocytes stimulated efflux 2- to 3-fold. This increase was mimicked by SKF 38393 and was blocked by the D1-selective antagonist (+)SCH 23390 but not by the D2-selective antagonist domperidone. No increase in 45Ca2+ efflux was seen with 100 microM quinpirole. Size fractionation of striatal mRNA yielded a single peak (2.5-3.0 kilobases) of D1 receptor-mediated 45Ca2+ efflux activity in injected oocytes. In addition, dopamine stimulation of oocytes injected with peak fractions and prelabeled with myo-[3H]inositol caused a 3-fold increase in [3H]inositol 1,4,5-triphosphate [( 3H]InsP3) formation. No effect on [3H]InsP3 production or 45Ca2+ efflux was observed, however, in injected oocytes incubated with 1 mM N6,O2'-dibutyryladenosine 3',5'-cyclic monophosphate. Thus, in addition to D1 receptors that stimulate adenylyl cyclase, rat striatum contains D1 receptors that can couple to InsP3 formation and mobilization of intracellular Ca2+.
Laboratory of Cell Biology, National Institute of Mental Health, National Institutes of Health, Bethesda, MD.
L C
LC
Mahan
R M
RM
Burch
F J
FJ
Monsma
D R
DR
Sibley
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003342:Corpus Striatum / Q000502:physiology*; D004298:Dopamine / Q000494:pharmacology*; D005260:Female; D007295:Inositol Phosphates / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008845:Microinjections; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D011061:Poly A / Q000235:genetics* / Q000302:isolation & purification; D012313:RNA / Q000235:genetics* / Q000302:isolation & purification; D012333:RNA, Messenger / Q000008:administration & dosage / Q000235:genetics* / Q000302:isolation & purification; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D017447:Receptors, Dopamine D1; D014982:Xenopus laevis
D007295:Inositol Phosphates; D012333:RNA, Messenger; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; D011061:Poly A; D012313:RNA; D002118:Calcium; D004298:Dopamine