CHEMICAL ANATOMY OF PRIMATE BASAL GANGLIA

This paper provides an overview of the anatomical and functional organ ization of the most prominent chemospecific neuronal systems that comp ose the basal ganglia in primates. Emphasis is placed on the heterogen eity and diversity of small-molecule transmitters, neuroactive peptide s and proteins used by basal ganglia neurons. Dopaminergic, serotonine rgic and cholinergic neuronal systems are shown to comprise multiple s ubsystems organized according to highly specific patterns. These subsy stems differentially regulate gene expression of several neuroactive p eptides, including tachykinins, enkephalins, dynorphin, somatostatin, and neuropeptide Y, that are used by distinct subsets of basal ganglia neurons. Glutamatergic excitatory inputs establish distinct functiona l territories within the basal ganglia, and neurons in each of these t erritories act upon other brain neuronal systems through a GABAergic d isinhibitory output mechanism. A striking complementary pattern of dis tribution of the calcium-binding proteins parvalbumin and calbindin D- 28k is noted in all basal ganglia components. The limbic system-associ ated membrane protein (LAMP) is confined chiefly to basal ganglia sect ors that are anatomically and functionally related to limbic system st ructures; these may serve as functional interfaces between the basal g anglia and the limbic sytem. The functional status of the various basa l ganglia chemospecific systems in neurodegenerative diseases, such as Parkinson's disease and Huntington's chorea, is examined. It is concl uded that these multiple transmitter-related systems cannot be analyze d separately as they form highly complex and interactive neuronal netw orks. These complexities should be taken into account to reach a bette r understanding of the functions of primate basal ganglia in health an d disease.