Serotonin-like immunoreactivity in the cat trigeminal ganglion.

The immunohistochemical distribution of serotonin-like immunoreactivity (SER-LI) has been established in networks of fine nerve fibers which arborize and wind profusely between non-immunoreactive sensory neurons in the cat trigeminal ganglion. Some of the varicose nerve fibers surround occasional non-immunoreactive sensory neurons like a woven basket. None of the sensory neurons display SER-LI. An extrinsic origin of intraganglionic fine nerve fibers has been suggested.