Distribution of dynorphin A (1-17) in the cat brainstem: an immunocytochemical study.

We have studied the distribution of cell bodies and fibers containing dynorphin A (1-17) in the brainstem of the cat using an indirect immunoperoxidase technique. The highest density of cell bodies was observed in the nucleus of the trapezoid body, whereas a low density of perikarya was found in the inferior and superior colliculi, nucleus of the brachium of the inferior colliculus and in the alaminar and laminar spinal trigeminal nuclei. A moderate density of immunoreactive fibers was found in the nucleus of the solitary tract, dorsal nucleus of the raphe, area postrema, dorsal motor nucleus of the vagus and in the marginal nucleus of the brachium conjunctivum, whereas a low density of fibers was observed in the lateral tegmental field, laminar and alaminar spinal trigeminal nuclei, nucleus of the trapezoid body, nucleus coeruleus, brachium conjunctivum, Kölliker-Fuse nucleus, periaqueductal gray and in the inferior and superior colliculi. The highest density of fibers containing dynorphin A was visualized in the substatia nigra. The widespread distribution of dynorphin A (1-17) immunoreactive structures suggests that the peptide could be involved in respiratory, cardiovascular, nociceptive and auditory mechanisms.