Differential sensitivity of synaptosomal calcium entry and endogenous dopamine release to omega-conotoxin.
The presynaptic neurotoxin omega-conotoxin (omega-CgTx) was tested for its ability to inhibit voltage-dependent calcium flux and transmitter release in rat brain synaptosomes. Conotoxin (0.001-10 microM) had no effect on calcium uptake or endogenous dopamine release from rat striatal synaptosomes in the absence of potassium depolarization. Fast-phase potassium stimulated calcium influx was only partially (20-30%) inhibited by conotoxin at concentrations between 1 nM and 10 microM. The fast-phase release of endogenous dopamine from the same synaptosomal preparation was inhibited by approximately 25% at 0.01 microM and by 60% at 10 microM. These results suggest that a subgroup of high affinity omega-CgTx-sensitive calcium channels may be involved in regulating the release of endogenous dopamine from brain synaptosomes.
Woodward
J J
JJ
Division of Pharmacology, College of Pharmacy, University of Texas, Austin 78712.
Rezazadeh
S M
SM
Leslie
S W
SW
D000818:Animals; D002118:Calcium / Q000493:pharmacokinetics* / Q000502:physiology; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D004298:Dopamine / Q000378:metabolism; D008978:Mollusk Venoms / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D020866:omega-Conotoxin GVIA
D008978:Mollusk Venoms; D020866:omega-Conotoxin GVIA; D011188:Potassium; D002118:Calcium; D004298:Dopamine