The Journal of Neuroscience, June 15, 2002, 22(12):5210-5218
Dopamine Modulates Excitability of Spiny Neurons in the Avian
Basal Ganglia
Long
Ding2 and
David J.
Perkel1
1 Departments of Zoology and Otolaryngology, University
of Washington, Seattle, Washington 98195-6115, and
2 Department of Neuroscience, University of Pennsylvania,
Philadelphia, Pennsylvania 19104
The neural substrate of vocal learning in songbirds is an
accessible system for studying motor learning and motor control in
vertebrates. In the so-called song system, the anterior forebrain pathway (AFP), which is essential for song learning, resembles the
mammalian basal ganglia-thalamocortical loop in its macroscopic organization, neuronal intrinsic properties, and microcircuitry. Area
X, the first station in the AFP, and the surrounding lobus parolfactorius (LPO), are both parts of the avian basal ganglia. Like
their mammalian counterparts, they receive dense dopaminergic innervation from the midbrain, but the physiological functions of this
projection remain unclear. In this study, we investigated the effect of
dopamine (DA) on excitability of spiny neurons in area X and LPO. We
recorded from neurons in brain slices of adult zebra finches and
Bengalese finches, using whole-cell and perforated-patch recording techniques in current-clamp configuration. We found that DA
modulates excitability in spiny neurons; activation of D1- and D2-like
DA receptors enhances and reduces excitability, respectively. These
effects are similar to those observed in the mammalian neostriatum,
with the main difference being that D1-like DA receptor activation
enhances excitability in avian spiny neurons at hyperpolarized states.
Our findings also indicate that some spiny neurons express both
receptor types and suggest that receptor colocalization in the entire
population can account for the spectrum of DA actions. The diversity of
DA actions enables the DA system to fine-tune the dynamics of the song
system and allows flexible control over song learning and production.
Key words:
dopamine; basal ganglia; songbird; excitability; song
learning; neuromodulation
Copyright © 2002 Society for Neuroscience 0270-6474/02/22125210-09$05.00/0
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