Interneurons in the rat striatum: relationships between parvalbumin neurons and cholinergic neurons.

A pre-embedding double-labeling immunocytochemical method was used to examine the synaptic relationships between cholinergic neurons and the parvalbumin immunoreactive (PV+) neurons. The PV+ neurons were labeled by silver-intensified colloidal gold particles, and the cholinergic neurons by immunoperoxidase reaction products. Cholinergic and PV+ axon terminals form synapses with both the somata and dendrites of PV+ neurons, as well as unlabeled medium-sized somata with round un-indented nuclei, a typical characteristic of the medium spiny projection neurons. These observations suggest that the PV+ and the cholinergic neurons have converging influences on both the projection neurons and the PV+ interneurons in the striatum.