The Journal of Neuroscience, November 1, 2002, 22(21):9320-9330
Dopamine Activates Noradrenergic Receptors in the Preoptic Area
C. A.
Cornil1,
J.
Balthazart1,
P.
Motte3,
L.
Massotte2, and
V.
Seutin2
Center for Cellular and Molecular Neurobiology,
1 Research Group in Behavioral Neuroendocrinology and
2 Laboratory of Pharmacology, and 3 Department
of Life Sciences, Laboratory of Plant Cellular Biology, University of
Liège, B-4020 Liège, Belgium
Dopamine (DA) facilitates male sexual behavior and modulates
aromatase activity in the quail preoptic area (POA). Aromatase neurons
in the POA receive dopaminergic inputs, but the anatomical substrate
that mediates the behavioral and endocrine effects of DA is poorly
understood. Intracellular recordings showed that 100 µM
DA hyperpolarizes most neurons in the medial preoptic nucleus (80%) by
a direct effect, but depolarizes a few others (10%). DA-induced
hyperpolarizations were not blocked by D1 or D2 antagonists (SCH-23390
and sulpiride). Extracellular recordings confirmed that DA inhibits the
firing of most cells (52%) but excites a few others (24%). These
effects also were not affected by DA antagonists (SCH-23390 and
sulpiride) but were blocked by 
2-(yohimbine) and 1-(prazosin) noradrenergic receptor antagonists,
respectively. Two dopamine-
-hydroxylase (DBH) inhibitors (cysteine
and fusaric acid) did not block the DA-induced effects, indicating that
DA is not converted into norepinephrine (NE) to produce its effects. The pKB of yohimbine for the receptor involved in
the DA- and NE-induced inhibitions was similar, indicating that the two
monoamines interact with the same receptor. Together, these results
demonstrate that the effects of DA in the POA are mediated mostly by
the activation of 2 (inhibition) and 1
(excitation) adrenoreceptors. This may explain why DA affects the
expression of male sexual behavior through its action in the POA, which
contains high densities of 2-noradrenergic but limited
amounts of DA receptors. This study thus clearly demonstrates the
existence of a cross talk within CNS catecholaminergic systems between
a neurotransmitter and heterologous receptors.
Key words:
preoptic area; dopamine; noradrenergic receptors; extracellular recording; intracellular recording; quail
Copyright © 2002 Society for Neuroscience 0270-6474/02/22219320-11$05.00/0
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