Chapter IV Structural and functional interactions in the striatum at the receptor level

Abstract

Abstract Dopamine is a neurotransmitter which has defied interpretation in part because of the multiplicity of its actions. In this chapter we focus on dopamine's actions in the striatum. We review evidence that the dopamine signal is time-specific but not spatially focused at the synaptic level. However, the distribution of different dopamine receptor subtypes may mean that naturally-released dopamine has pathway-specific actions. The actions of dopamine include, effects on glutamate receptors on nearby synapses, and modulation of postsynaptic ion channels. Both kinds of dopamine effects may be strongly dependent on prior membrane potential activity or on recent presynaptic activity. The effects of dopamine may also be divided into those immediate and reversible effects that occur in the presence of the agonist, and more persistent effects including both functional and structural synaptic plasticity. We suggest that the more immediate and reversible actions of dopamine are linked to initiation of movements, brought about by facilitation of striatal output by anticipatory firing of dopamine cells in response to incentive cues. The longer-lasting actions of dopamine may underlie the reward-related learning, by potentiation of corticostriatal synapses. This provides a framework for the coordinated action of dopamine in natural behavior. Both these dopamine effects are compromised by perturbations of the dopamine system as they occur in neurological disease, or as a consequence of dopaminergic drugs.