Neurokinin A, calcitonin gene-related peptide, and dynorphin A (1-8) in spinal dorsal horn contribute to descending inhibition evoked by nociceptive afferent pathways: an immunocytochemical study

Immunocytochemical technique was used to compare the contents of neurokinin A (NKA), calcitonin gene-related peptide (CGRP), and dynorphin A (1-8) (Dy nA) on two sides of the lumbar dorsal horn of rats in which the unilateral thoracic dorsalateral funiculus (DLF) was transected while formalin (0.2 ml , 0.5%) was injected equally into two hindpaws. The results showed that all the NKA-like. CGRP-like, and DynA (1-8)-like immunoreactivities were signi ficantly lower in the superficial laminae of the dorsal horn on the side ip silateral to the lesioned DLF than that on the side with intact DLF. This i mplies that peripheral noxious inputs activate the supraspinal descending i nhibitory systems which in turn modulate the transmission of noxious messag e at the spinal level by changing the release of related neuropeptides. (C) 2000 Elsevier Science B.V. All rights reserved.