The Journal of Neuroscience, 2000, 20:RC69:1-6
RAPID COMMUNICATION
Activation of D2-Like Dopamine Receptors Reduces Synaptic Inputs
to Striatal Cholinergic Interneurons
Antonio
Pisani1,
Paola
Bonsi2,
Diego
Centonze1,
Paolo
Calabresi1, and
Giorgio
Bernardi1, 2
1 Clinica Neurologica, Dipartimento di Neuroscienze,
Università di Roma Tor Vergata, 00133 Rome, Italy, and
2 Istituto di Ricovero e Cura a Carattere
Scientifico S. Lucia, 00176 Rome, Italy
Dopamine (DA) plays a crucial role in the modulation of
striatal function. Striatal cholinergic interneurons represent an important synaptic target of dopaminergic fibers arising from the
substantia nigra and cortical glutamatergic inputs. By means of an
electrophysiological approach from corticostriatal slices, we isolated
three distinct synaptic inputs to cholinergic interneurons: glutamate-mediated EPSPs, GABAA-mediated potentials,
and Acetylcholine (ACh)-mediated IPSPs. We therefore explored whether
DA controls the striatal cholinergic activity through the modulation of
these synaptic potentials. We found that SKF38393, a D1-like
receptor agonist, induced a membrane depolarization (also see Aosaki et al., 1998) but had no effects on glutamatergic, GABAergic, and cholinergic synaptic potentials. Conversely, D2-like DA receptor activation by quinpirole inhibited both GABAA and
cholinergic synaptic potentials. These effects of quinpirole were
mimicked by
-conotoxin GVIA, blocker of N-type calcium channels. The
lack of effect both on the intrinsic membrane properties and on
exogenously applied GABA and ACh by quinpirole supports a presynaptic
site of action for the D2-like receptor-mediated inhibition. Moreover, the quinpirole-induced decrease in amplitude was accompanied by an
increase in paired pulse facilitation ratio (EPSP2/EPSP1), an index of
a decrease in transmitter release. Our findings demonstrate that DA
modulates the excitability of cholinergic interneurons through either
an excitatory D1-like-mediated postsynaptic mechanism or a presynaptic
inhibition of the GABAergic and cholinergic inhibitory synaptic potentials.
Key words:
dopamine; striatum; electrophysiology; GABA; acetylcholine; EPSP; IPSP
Copyright © 2000 Society for Neuroscience 0270-6474/00/$05.00/0