V. Chaparrohuerta et al., NITRIC-OXIDE INVOLVEMENT IN REGULATING THE DOPAMINE TRANSPORT IN THE STRIATAL REGION OF RAT-BRAIN, Neurochemistry international, 31(4), 1997, pp. 607-616
Spontaneous [H-3]dopamine ([H-3]DA) overflow was measured from striata
l slices in the presence of different glutamate (Glu) receptor agonist
s such as N-methyl-D-aspartate (NMDA), kainate (KA) and quisqualate (Q
A) and their corresponding antagonists, Dizocilpine maleate (MK-801),
D-gamma-glutamylaminomethanesulfonic acid (GAMS) and 6-cyano-7-nitroqu
inoxaline 2,3-dione (CNQX), respectively. [H-3]DA uptake and release i
n the presence of L-Arginine (L-Arg) and N-G-nitro-arginine (L-N-Arg),
an inhibitor of nitric oxide (NO) synthesis were also evaluated. L-N-
Arg alone or combined with L-Arg significantly reduced [H-3]DA uptake
at 10 and 100 mu M from 33% to 44% from striatal slices. Whereas, in b
rain synaptosomal fractions L-Arg induced a biphasic effect on that [H
-3]DA uptake in a dose dependent manner, and L-N-Arg showed an absolut
e inhibition in 80-90% of this [H-3]DA uptake at 1-500 mu M. The amino
acids, lysine, valine and histidine (100 mu M) had a little effect in
hibitory on [H-3]DA uptake from synaptosomal fractions. Glu agonists,
NMDA (10 mu M) and KA (10 mu M) importantly increased the spontaneous
[H-3]DA overflow, which was blocked by MK-801 (10 mu M) and GAMS (10 m
u M), respectively. QA had no effect on [H-3]DA release. L-Arg (10-200
mu M) potentiated the spontaneous [H-3]DA overflow in a dose dependen
t fashion from striatal slices, being reverted by 10 mu M L-N-Arg alon
e or in combination with all other compounds; whereas, lysine, histidi
ne and valine did not modify that spontaneous [H-3]DA overflow. Result
s support the hypothesis related to the participation of NO on DA tran
sport possibly synthesized at the dopaminergic (DAergic) terminals in
the striatum; also that L-Arg concentration may determine alternative
mechanisms to regulate the DAergic activity at the striatum. (C) 1997
Elsevier Science Ltd.