How are the D1 and D2 dopamine receptors expressed in the striatum?
The D1 dopamine receptor is predominantly expressed on the striatonigral neurons, whereas the D2 receptors are primarily found on the striatopallidal neurons.
MSNs in the direct pathway carry dopamine D1 receptors, while those in the indirect pathway carry D2 receptors.
Evidence suggests that in the striatum the D1 and D2 receptors have an excitatory and inhibitory action, respectively.