Locomotor-regulatory Circuits in Brain / part 2

About 95% of striatal neurons are GABAergic medium spiny neurons (MSN). The striatum receives glutamatergic neuronal projections from cortex and dopaminergic projections from SNc. Dopamine receptors can be either excitatory (D₁R) or inhibitory (D₂R) and thus differentially modulate neurotransmission in response to endogenous dopamine. Presynaptic glutamate and dopamine receptors modulate neurotransmitter release, whereas postsynaptic receptors on soma and dendrites regulate neuronal excitability.


In addition, excitatory metabotropic glutamate receptors (mGluR; group I) act presynaptically to promote dopamine release and postsynaptically to enhance the excitability of striatal MSN; inhibitory mGluR (group II and III) also are expressed on striatal MSN. In addition, ionotropic N-methyl-D-aspartic acid (NMDA or look general information) and a-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors are expressed on striatal MSN, but their actions will not be discussed in this review.