Medium spiny neuron
![Confocal microscopy Z projection of medium spiny neurons (MSNs) in the mouse striatum. The neurons were labeled using the matrisome MSN mouse Gpr101-Cre[6] in combination with a dtTomato (red fluorescent protein) reporter. A 3D projection of the same neurons can be viewed here.](/Images/godic/202501/26/Z_MaxProjection_of_MediumSpinyNeurons_Gpr101Cre_dtTomato4027.jpg")
Medium spiny neurons (MSNs), also known as spiny projection neurons, are a special type of GABA-ergic inhibitory cell representing 95% of neurons within the human striatum, a structure located in the basal ganglia. Medium spiny neurons have two primary phenotypes (i.e., characteristic types): D1-type MSNs of the "direct pathway" and D2-type MSNs of the "indirect pathway".