Messenger molecules and receptor mRNA in the human trigeminal ganglion

The presence and distribution of neuromessenger molecules and receptor mRNA in human trigeminal ganglion was studied with immunocytochemical, in situ hybridisation and RT-PCR techniques. Immunofluorescence staining revealed that calcitonin gene-related peptide (CGRP) immunoreactive (-ir) neurons occurred in high numbers, constituting 36-40% of all nerve cell bodies in the ganglion. Accordingly, in situ hybridisation demonstrated CGRP mRNA in a large portion of the trigeminal neurons. A small number of the nerve cell bodies showed substance P (SP)-ir, (18%), nitric oxide synthase (NOS)-ir (15%), and pituitary adenylate cyclase activating peptide (PACAP)-ir (20%). Double immunostaining revealed that only few CGRP-ir neurons also were NOS-ir (less than 5%). The C-terminal flanking peptide of neuropeptide Y, C-PON, was not visible in any of the nerve cell bodies studied. Agarose gel electrophoresis of the RT-PCR products from the ganglia demonstrated the presence of mRNA corresponding to CGRP1, NPY Y1 and Y2, and VIP1 receptors. These results suggest both sympathetic and parasympathetic influence on the activity in the trigeminal ganglion.