S. Abu-raya et al., Characterization of pardaxin-induced dopamine release from pheochromocytoma cells: Role of calcium and eicosanoids, J PHARM EXP, 288(2), 1999, pp. 399-406
Citations number
43
Categorie Soggetti
Pharmacology & Toxicology
Journal title
JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS
Pardaxin, an excitatory neurotoxin, induced dopamine release from pheochrom
ocytoma (PC12) cells both in the presence and absence of extracellular calc
ium ([Ca](o)). In the presence of extracellular calcium, nifedipine, an L-t
ype calcium channel blocker, did not affect dopamine release, whereas 1,2-b
is (2-aminophenoxy) ethane N,N, N'N'-tetra-acetic acid (BAPTA), a chelator
of cytosolic calcium, and dantrolene, a blocker of calcium release from int
racellular stores, inhibited only partially (30-40%) pardaxin-induced dopam
ine release. In the absence of [Ca](o), BAPTA and dantrolene were ineffecti
ve. Pardaxin stimulated the arachidonic acid (AA) cascade in PC12 cells ind
ependently of [Ca](o). The phospholipase inhibitors mepacrine and bromophen
acyl bromide inhibited both pardaxin-induced AA release and pardaxin-induce
d dopamine release. Dopamine release induced by pardaxin also was blocked b
y the lipoxygenase inhibitors nordihydroguaiaretic acid, esculetin, and 2-(
12-hydroxydodeca-5,10-diynyl)-3,5,6-trimethyl-1,4-benzoquinone. Under these
conditions, a parallel reduction in 5-hydroxyeicosatetranoic acid release
also was observed. Suppression of pardaxin-induced dopamine release by inhi
bitors of phospholipase A, and lipoxygenase was more pronounced in calcium-
free medium. These results indicate the involvement of the lipoxygenase pat
hway in pardaxin-induced dopamine release and suggest the use of this toxin
as a novel pharmacological tool for investigating the mechanism of calcium
-independent neurotransmitter release.