Spiny and aspiny types of neuropeptide Y immunoreactive neurons in the monkey neostriatum

The present study demonstrates the existence of two types of neurons with neuropeptide Y (NPY) immunoreactivity in the neostriatum of the monkey (Macacus fuscatus) by using the avidin-biotin-immunoperoxidase method. One type, accounted for about 80% of striatal NPY cells, corresponded to the medium-sized aspiny type neurons. The other type resembled the medium-sized, spiny type II neurons. These findings suggest that there are at least two functional subpopulations of NPY neurons in the monkey neostriatum.