Dopamine-Glutamate Interactions in The Basal Ganglia

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In an attempt to formulate a working hypothesis of basal-ganglia functions, arguments are considered suggesting that the basal ganglia are involved in a process of response selection, i.e., in the facilitation of "wanted" and in the suppression of "unwanted" behavior. The meso-accumbal dopamine-system is considered to mediate natural and drug-induced reward and sensitization.

The meso-striatal dopamine-system seems to fulfill similar functions: It may mediate reinforcement which strengthens a given behavior when elicited subsequently, but which is not experienced as reward or hedonia. Glutamate as the transmitter of the corticofugal projections to the basal ganglia nuclei and of the subthalamic neurons is critically involved in basal ganglia functions and dysfunctions; for example Parkinson's disease can be considered to be a secondary hyperglutamatergic disease.

Additionally, glutamate is an essential factor in the plasticity response of the basal-ganglia. However, opposite to previous suggestions, the NMDA-receptor blocker MK-801 does not prevent psychostimulant-nor morphine-induced day-to-day increase (sensitization) of locomotion. Also the day-to-day increase of haloperidol-induced catalepsy was not prevented by MK-801.

Amino Acids, 1998, Vol 14, Iss 1-3, pp 5-10

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