The Journal of Neuroscience, November 1, 2002, 22(21):9150-9154
BRIEF COMMUNICATION
D-Amphetamine Fails to Increase Extracellular
Dopamine Levels in Mice Lacking
1b-Adrenergic Receptors:
Relationship between Functional and Nonfunctional Dopamine Release
Agnès
Auclair1,
Susanna
Cotecchia2,
Jacques
Glowinski1, and
Jean-Pol
Tassin1
1 Institut National de la Santé et de la
Recherche Médicale U 114, Collège de France, 75231 Paris
Cedex 05, France, and 2 Institut de Pharmacologie et de
Toxicologie, CH-1005 Lausanne, Switzerland
It was found recently that locomotor and rewarding effects of
psychostimulants and opiates were dramatically decreased or suppressed
in mice lacking
1b-adrenergic receptors [
1b-adrenergic receptor
knock-outs (
1bAR-KOs)] (Drouin et al., 2002). Here we show that
blunted locomotor responses induced by 3 and 6 mg/kg D-amphetamine in
1bAR-KO mice [
84 and
74%,
respectively, when compared with wild-type (WT) mice] are correlated
with an absence of D-amphetamine-induced increase in
extracellular dopamine (DA) levels in the nucleus accumbens of
1bAR-KO mice. Moreover, basal extracellular DA levels in the nucleus
accumbens are lower in
1bAR-KO than in WT littermates (
28%;
p < 0.001).
In rats however, prazosin, an
1-adrenergic antagonist, decreases
D-amphetamine-induced locomotor hyperactivity without
affecting extracellular DA levels in the nucleus accumbens, a finding
related to the presence of an important nonfunctional release of DA
(Darracq et al., 1998). We show here that local
D-amphetamine releases nonfunctional DA with the same
affinity but a more than threefold lower amplitude in C57BL6/J mice
than in Sprague Dawley rats. Altogether, this suggests that a
trans-synaptic mechanism amplifies functional DA into nonfunctional DA release.
Our data confirm the presence of a powerful coupling between
noradrenergic and dopaminergic neurons through the stimulation of
1b-adrenergic receptors and indicate that nonfunctional DA release
is critical in the interpretation of changes in extracellular DA
levels. These results suggest that
1b-adrenergic receptors may be
important therapeutic pharmacological targets not only in addiction but
also in psychosis because most neuroleptics possess anti-
1-adrenergic properties.
Key words:
1b-adrenergic receptor; D-amphetamine; dopamine; microdialysis; rats; mice
Copyright © 2002 Society for Neuroscience 0270-6474/02/22219150-05$05.00/0