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".