SPINAL PROJECTIONS TO THE PARABRACHIAL NUCLEUS ARE SUBSTANCE P-IMMUNOREACTIVE

SUBSTANCE P plays an important role in nociceptive processing in the s pinal cord. Substance P is also present in several supraspinal regions , such as the pontine parabrachial nucleus, a major relay for autonomi c regulation. In this study we examined in the cat with an immunogold method the presence of substance P-like immunoreactivity in spinoparab rachial terminals that were labelled by anterograde transport of uncon jugated and lectin-conjugated horseradish peroxidase. We found that de nse core vesicles in anterogradely labelled terminals were substance P -immunoreactive. Taken together with previous observations that noxiou s stimuli increase preprotachykinin expression in ascending nociceptiv e pathways from the spinal dorsal horn, the present finding provides e vidence that substance P is involved in nociceptive processing also in the brain stem.