[Immunohistochemical observation of neurotransmitters in rat and human pterygopalatine ganglia].

Immunohistochemical studies were performed to determine the distribution of neuropeptides and tyrosine hydroxylase in rat and human pterygopalatine ganglia. In the rat pterygopalatine ganglion, the most commonly found peptide in ganglion cells was vasoactive intestinal polypeptide (VIP) (99%) followed by neuropeptide Y (NPY) (54%) and enkephalin (ENK) (11%). Substance P (SP)-, calcitonin gene-related peptide (CGRP)-, ENK-, and NPY-immunoreactive (IR) varicose nerve fibers were found around ganglion cells. SP- and CGRP-IR varicosities were in synaptic contact with somatic spines or somata of ganglion cells. The combination of retrograde labeling and immunohistochemical study revealed that some of the ganglion cells projecting to the nasal mucosa were surrounded by SP-IR fibers. These results indicate that SP- and CGRP-IR axon collaterals of the trigeminal ganglion cells may form direct synaptic contact with ganglion cells projecting to the nasal mucosa. ENK-IR varicosities were probably derived from parasympathetic preganglionic neurons. In the human pterygopalatine ganglion, almost all ganglion cells were VIP-IR. They were not, however, immunoreactive with other peptides investigated in this study. VIP-, SP- and CGRP-IR varicose nerve fibers were found around ganglion cells. A few NPY- and ENK-IR varicose fibers were also observed around ganglion cells. The origins of these peptide-IR varicose nerve fibers are still unknown, but it is suggested that the human pterygopalatine ganglion is innervated by a greater variety of peptide-IR nerve fibers than that of the rat and forms different neuronal circuit.