Medium Spiny Neuron

Neuron spinosum medium

The projection neuron of the striatum, spiny, silent until excited, and split into two populations with opposing functions in action selection.

Function

GABAergic projection neurons that split into two populations with opposite effects on movement: D1-receptor-expressing 'direct pathway' MSNs facilitate movement and encode reward; D2-receptor-expressing 'indirect pathway' MSNs suppress competing actions. This dual architecture is the computational core of action selection in the basal ganglia.

Morphology

A medium-sized soma (~14 µm) with dendrites densely studded with spines, hence the name. The spines receive converging glutamatergic input from cortex and thalamus and dopaminergic input from the substantia nigra.

Specification

  • Neurotransmitter: GABA
  • Co-transmitters: Substance P / Dynorphin (D1 / direct pathway); Enkephalin (D2 / indirect pathway)
  • Receptors: D1 (Direct pathway); D2 (Indirect pathway)
  • Location: Striatum, caudate nucleus and putamen.
  • Projections: Globus pallidus; Substantia nigra
  • Firing: Up/Down states; Silent at rest
  • Markers: PPP1R1B/DARPP-32; DRD1 + TAC1/Substance P + PDYN (direct); DRD2 + PENK + ADORA2A (indirect); FOXP1/FOXP2/BCL11B
  • Developmental origin: Lateral ganglionic eminence
  • Disease: Selective MSN death, particularly of D2 indirect-pathway neurons, drives the chorea of Huntington's disease.
  • Cell Ontology: CL:1001474

References

  1. Kravitz AV et al. (2010). Regulation of parkinsonian motor behaviours by optogenetic control of basal ganglia circuitry.. Nature 466: 622–626 PMID 20613723
  2. Reiner A, Albin RL, Anderson KD, D'Amato CJ, Penney JB, & Young AB (1988). Differential loss of striatal projection neurons in Huntington disease.. Proc Natl Acad Sci USA 85: 5733–5737 PMID 2456581

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