Behavioural Effects of Manipulation of Basal Ganglia Neurotransmitters

Topographically organized dopaminergic projections from the extrapyramidal structures of the ventral mesencephalon (substantia nigra and ventral tegmental area) to the dorsal (body of caudate-putamen) and ventral (anterior-ventral caudate, nucleus accumbens, tuberculum olfactorium) striatum subserve sensorimotor integration in the rat. Selective depletion of DA impairs the animal's ability to integrate sensory input with motor output; in the dorsal striatum the exteroceptive sensory input and in the ventral or limbic striatum the interoceptive input principally related to motivation and affect. Grafts of fetal DA neurons to the damaged dorsal striatum reverse sensorimotor asymmetry and sensory neglect. A large number of other excitatory and inhibitory neurotransmitters, including recently discovered neuropeptides, contribute to the functional balance afforded by the DA neurons. This chemical heterogeneity of the basal ganglia offers the possibility that novel therapeutic approaches with drugs could be used to control the chemical imbalances in basal ganglia that are associated with a number of neurological and psychiatric conditions.