Dopamine presynaptically and heterogeneously modulates nucleus accumbens medium-spiny neuron GABA synapses in vitro.
BACKGROUND
The striatal complex is the major target of dopamine action in the CNS. There, medium-spiny GABAergic neurons, which constitute about 95% of the neurons in the area, form a mutually inhibitory synaptic network that is modulated by dopamine. When put in culture, the neurons reestablish this network. In particular, they make autaptic connections that provide access to single, identified medium-spiny to medium-spiny neuron synaptic connections.


RESULTS
We examined medium-spiny neuron autaptic connections in postnatal cultures from the nucleus accumbens, the ventral part of the striatal complex. These connections were subject to presynaptic dopamine modulation. D1-like receptors mediated either inhibition or facilitation, while D2-like receptors predominantly mediated inhibition. Many connections showed both D1 and D2 modulation, consistent with a significant functional colocalization of D1 and D2-like receptors at presynaptic sites. These same connections were subject to GABAA, GABAB, norepinephrine and serotonin modulation, revealing a multiplicity of modulatory autoreceptors and heteroreceptors on individual varicosities. In some instances, autaptic connections had two components that were differentially modulated by dopamine agonists, suggesting that dopamine receptors could be distributed heterogeneously on the presynaptic varicosities making up a single synaptic (i.e. autaptic) connection.


CONCLUSIONS
Differential trafficking of dopamine receptors to different presynaptic varicosities could explain the many controversial studies reporting widely varying degrees of dopamine receptor colocalization in medium-spiny neurons, as well as more generally the diversity of dopamine actions in target areas. Longer-term changes in the modulatory actions of dopamine in the striatal complex could be due to plasticity in the presynaptic distribution of dopamine receptors on medium-spiny neuron varicosities.
Geldwert
Daron
D
Department of Neuroscience, NYS Psychiatric Institute, 1051 Riverside Drive, Unit 62, New York, NY 10032, USA. dgeldwert@aol.com
Norris
J Madison
JM
Feldman
Igor G
IG
Schulman
Joshua J
JJ
Joyce
Myra P
MP
Rayport
Stephen
S
D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D049229:Dendritic Spines / Q000187:drug effects / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism* / Q000494:pharmacology; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D018755:GABA Agonists / Q000494:pharmacology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009434:Neural Pathways / Q000187:drug effects / Q000378:metabolism; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology; D009714:Nucleus Accumbens / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D051381:Rats; D017207:Rats, Sprague-Dawley; D011940:Receptor Aggregation / Q000187:drug effects / Q000502:physiology; D017447:Receptors, Dopamine D1 / Q000187:drug effects / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000187:drug effects / Q000378:metabolism; D018079:Receptors, GABA / Q000187:drug effects / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D018491:Dopamine Agonists; D018492:Dopamine Antagonists; C073804:FM1 43; D018755:GABA Agonists; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D018079:Receptors, GABA; D005680:gamma-Aminobutyric Acid; D004298:Dopamine