The Journal of Neuroscience, February 15, 2002, 22(4):1407-1413
Distinct Roles for Nigral GABA and Glutamate Receptors in the
Regulation of Dendritic Dopamine Release under Normal Conditions and in
Response to Systemic Haloperidol
William S.
Cobb and
Elizabeth D.
Abercrombie
Center for Molecular and Behavioral Neuroscience, Rutgers
University, Newark, New Jersey 07102
The regulation of dendritic dopamine release in the substantia
nigra (SN) likely involves multiple mechanisms. GABA and glutamate inputs to nigrostriatal dopamine neurons exert powerful influences on
dopamine neuron physiology; therefore, it is probable that GABA and
glutamate likewise influence dendritic dopamine release, at least under
some conditions. The present studies used in vivo microdialysis to determine the potential roles of nigral GABA and
glutamate receptors in the regulation of dendritic dopamine release
under normal conditions and when dopamine signaling in the basal
ganglia is compromised after systemic haloperidol administration. Nigral application of the GABAA receptor antagonist
bicuculline by reverse dialysis significantly increased spontaneous
dopamine efflux in the SN. However, spontaneous dopamine efflux in the SN was not significantly affected by local application of
the glutamate receptor antagonists
6-cyano-7-nitroquinoxaline-2,3-dione or
(±)-3-[2-carboxypiperazine-4-yl]-propyl-1-phosphonic
acid. Systemic haloperidol administration significantly
increased the extracellular dopamine measured in the SN. Blockade of
nigral GABAA receptors by local bicuculline application did
not alter this effect of systemic haloperidol, despite the
bicuculline-induced increase in spontaneous dendritic dopamine efflux.
In contrast, nigral application of either glutamate receptor antagonist
significantly attenuated the increases in dendritic dopamine efflux
elicited by systemic haloperidol. These data suggest that under normal conditions, activity of GABA afferents to SN dopamine neurons is an
important determinant of the spontaneous level of dendritic dopamine
release. Circuit-level changes in the basal ganglia involving an
increased glutamatergic drive to the SN appear to underlie the increase
in dendritic dopamine release that occurs in response to systemic
haloperidol administration.
Key words:
basal ganglia; dendritic dopamine release; microdialysis; Parkinson's disease; substantia nigra; subthalamic nucleus
Copyright © 2002 Society for Neuroscience 0270-6474/02/2241407-07$05.00/0