P. Dedeurwaerdere et al., D-FENFLURAMINE INCREASES STRIATAL EXTRACELLULAR DOPAMINE IN-VIVO INDEPENDENTLY OF SEROTONERGIC TERMINALS OR DOPAMINE UPTAKE SITES, Journal of neurochemistry, 65(3), 1995, pp. 1100-1108
The effect of various doses of the serotonin (5-HT) release-inducing a
gent d-fenfluramine (d-fenf) on extracellular dopamine (DA), 3,4-dihyd
roxyphenylacetic acid (DOPAC), and 5-hydroxyindoleacetic acid (5-HIAA)
was studied in vivo in the striatum of halothane-anesthetized rats, f
ollowing systemic and local administration. At 5 and 10 but not 2.5 mg
/kg, d-fenf administered intraperitoneally significantly increased DA
extracellular concentration and reduced DOPAC outflow. A concentration
-dependent enhancement of DA dialysate content was also found followin
g intrastriatal application (5, 10, 25, and 50 mu M). The bilateral ad
ministration of 5,7-dihydroxytryptamine into the dorsal raphe nucleus,
which markedly depleted 5-HT in the striatum, did not modify the effe
ct on extracellular DA concentration of 25 mu M d-fenf locally applied
into the striatum. The enhancement of extracellular DA level induced
by 25 mu M d-fenf was slightly but significantly reduced by the local
application of 25 mu M citalopram. The blockade of DA uptake sites by
nomifensine (0.1, 0.3, and 1 mu M) did not modify significantly the ef
fect of d-fenf. The rise of DA outflow induced by 25 mu M d-fenf was s
trongly reduced in the presence of 1 mu M tetrodotoxin (TTX) or by the
removal of Ca2+ from the perfusion medium. The results obtained show
that d-fenf increases the striatal extracellular DA concentration by a
Ca2+-dependent and TTX-sensitive mechanism that is independent of str
iatal 5-HT itself or DA uptake sites.