Interactions between excitatory amino acids and dopamine systems in the forebrain: implications for schizophrenia and...

The midbrain dopamine neurones innervate not only the dorsal and ventral sectors of the striatum but also limbic structures and fronto-temporal association cortex. The forebrain structures providing and receiving dopaminergic input are highly interconnected. The dopamine pathways are now seen to provide modulation of widespread limbo- and cortico-striatal circuits involved in motivated behaviour. The nucleus accumbens is a pivotal structure of this ventral striatal system, whereas the caudate putamen of the dorsal striatum integrates sensori-motor coordination. These striatal sectors have access to complex parallel output pathways of the pallidal and the thalamo-cortical motor systems. Excitatory amino acids are now known to play an important role as neurotransmitters in the dorsal and ventral forebrain circuits and in the output pathways associated with dopamine neurones. Current drug treatment of both schizophrenia and Parkinson's disease focus on drugs which modify dopamine activity in the brain. Glutamatergic mechanisms may provide interesting alternative pharmacological targets for the treatment of such disorders.