An immunohistochemically distinct population of cat ciliary ganglion cells.

In the cat ciliary ganglion, 16% and 23% respectively of the neurons are surrounded by nerve fibers immunoreactive to calcitonin gene-related peptide (CGRP) and somatostatin (SOM). One-third of the ganglion cell perikarya are immunoreactive to neuropeptide Y (NPY). Analysis of the coincidence of immunoreactivities shows a striking correlation. Practically all of the ganglion cells surrounded by CGRP-like immunoreactive (LI) nerve fibers also are surrounded by SOM-LI nerve processes and demonstrate NPY-LI perikarya. These observations define a subset of NPY-LI ciliary ganglion cells with a particular peptidergic input and perhaps a specific physiologic function.