Medium spiny neuron
Type of GABAergic neuron in the striatum / From Wikipedia, the free encyclopedia
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Medium spiny neurons (MSNs), also known as spiny projection neurons (SPNs), are a special type of GABAergic inhibitory cell representing 95% of neurons within the human striatum, a basal ganglia structure.[1] Medium spiny neurons have two primary phenotypes (characteristic types): D1-type MSNs of the direct pathway and D2-type MSNs of the indirect pathway.[1][2][3] Most striatal MSNs contain only D1-type or D2-type dopamine receptors, but a subpopulation of MSNs exhibit both phenotypes.[1][2][3]
Medium spiny neuron | |
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Details | |
Location | Basal ganglia |
Shape | Spiny neuron |
Function | Inhibitory projection neuron |
Neurotransmitter | GABA |
Presynaptic connections | Dopaminergic: VTA, SNc Glutamatergic: PFC, hippocampus, amygdala, thalamus, other |
Postsynaptic connections | Other basal ganglia structures |
Identifiers | |
MeSH | D000094242 |
NeuroLex ID | nifext_141 |
Anatomical terms of neuroanatomy |
Direct pathway MSNs excite their ultimate basal ganglia output structure (such as the thalamus) and promote associated behaviors;[1] these neurons express D1-type dopamine receptors, adenosine A1 receptors, dynorphin peptides, and substance P peptides.[1][2] Indirect pathway MSNs inhibit their output structure and in turn inhibit associated behaviors;[1] these neurons express D2-type dopamine receptors, adenosine A2A receptors (A2A), DRD2–A2A heterotetramers, and enkephalin.[2][4] Both types express glutamate receptors (NMDAR and AMPAR), cholinergic receptors (M1 and M4)[5] and CB1 receptors are expressed on the somatodendritic area of both MSN types.[2][6] A subpopulation of MSNs contain both D1-type and D2-type receptors, with approximately 40% of striatal MSNs expressing both DRD1 and DRD2 mRNA.[1][2][3] In the nucleus accumbens (NAcc), these mixed-type MSNs that contain both D1-type and D2-type receptors are mostly contained in the NAcc shell.[1]
The dorsal striatal MSNs play a key role in initiating and controlling movements of the body, limbs, and eyes. The ventral striatal MSNs play a key role in motivation, reward, reinforcement, and aversion. Dorsal and ventral medium spiny neuron subtypes (i.e., direct D1-type and indirect D2-type) are identical phenotypes, but their output connections differ.[1][2]