Immunoreactivity of NOS, CGRP, PACAP, SP and VIP in the trigeminal nucleus caudalis and in the cervical spinal cord C1 and C2 of the cat

The aim of the present study was to map the presence of neurotransmitters and nitric oxid synthase (NOS) in the trigeminal nucleus caudalis and cervical spinal cord of cat. Immunocytochemistry was used to map the presence of neuronal NOS, calcitonin gene-related peptide (CGRP), pituitary adenylate cyclase activating peptide (PACAP), substance P (SP) and vasoactive intestinal peptide (VIP). The superior sagittal sinus (SSS) was stimulated electrically for 2h (0.3 Hz, 0.25 ms duration, 120 V) to examine if this would lead to depletion of the neurotransmitters. Numerous SP- and CGRP-positive nerve fibers (but no cells) were found in the trigeminal nucleus caudalis (TNC) and in Rexed lamina I and II° of the dorsal horn at C1/C2 level of the spinal cord. Moderate amounts of PACAP- and NOS-positive nerve fibers were also seen in these areas while there were only few VIP-positive fibers. There was no observable difference in the amount of immunoreactivity of NOS or the neuropeptides between stimulated and control cats. The stimulation resulted in marked c-fos immunoreactivity in the same regions of the TNC. The bipolar trigeminal neurons project to the TNC and C1/C2 areas with fibers containing neuropeptides and NOS. Stimulation of the SSS for 2 h was not sufficient to cause noticeable depletion.