Neurokinin A-like immunoreactivity in the cat brainstem.

We have studied the distribution of neurokinin A-like immunoreactive cell bodies and fibers in the cat brainstem. The densest clusters of perikarya containing the peptide were observed in the periaqueductal gray, inferior colliculus, postpyramidal nucleus of the raphe, medial nucleus of the solitary tract and in the lateral reticular nucleus. By contrast, the interpeduncular nucleus, magnocellular part of the red nucleus, central tegmental field, cuneiform nucleus, dorsal tegmental nucleus, nucleus sagulum and the medial and inferior vestibular nuclei had the lowest density, whereas a moderate density of immunoreactive cell bodies was found in the superior colliculus, medial division of the dorsal nucleus of the raphe, nucleus incertus, locus coeruleus and in the Kölliker-Fuse area. The highest density of immunoreactive fibers was observed in the substantia nigra, periaqueductal gray, marginal nucleus of the brachium conjunctivum, medial vestibular nucleus, medial nucleus of the solitary tract, laminar spinal trigeminal nucleus, inferior colliculus, medial division of the dorsal nucleus of the raphe, locus coeruleus, dorsal tegmental nucleus and in the spinal trigeminal tract. A moderate density of immunoreactive fibers was found in the dorsal motor nucleus of the vagus and in the postpyramidal nucleus of the raphe and a low density in the cuneiform nucleus, Kölliker-Fuse area, nucleus sagulum, inferior and superior central nuclei, lateral reticular nucleus and in the lateral and magnocellular tegmental fields.