An immunocytochemical mapping of methionine-enkephalin-Arg6-Gly7-Leu8 in the cat brainstem

The distribution of methionine-enkephalin-Arg6-Gly7-Leu8-immunoreactive cell bodies and fibres was studied in the brainstem of the cat using an indirect immunoperoxidase technique. In the mesencephalon, immunoreactive cell bodies were observed in the periaqueductal grey, the dorsal raphe nucleus, the central and pericentral nuclei of the inferior colliculus and the pericentral division of the dorsal tegmental nucleus. In the pons, immunoreactive cell bodies were observed in the dorsolateral division of the pontine nucleus; below the central division of the dorsal tegmental nucleus; above the dorsolateral division of the pontine nucleus, and close to the superior cerebellar peduncle. In the medulla oblongata, immunoreactive cell bodies were observed in the laminar spinal trigeminal nucleus and in the lateral tegmental field; the dorsal motor nucleus of the vagus; the prepositus hypoglossal nucleus; the medial nucleus of the solitary tract; the rostral division of the cuneate nucleus, and close to the parvocellular division of the alaminar spinal trigeminal nucleus. The highest (moderate) density of immunoreactive fibres was observed in the periaqueductal grey; the parvocellular and magnocellular divisions of the alaminar spinal trigeminal nucleus; the laminar spinal trigeminal nucleus; the rostral division of the cuneate nucleus; the dorsal motor nucleus of the vagus; the lateral nucleus of the solitary tract, and in the midline between the central divisions of the reticulotegmental pontine nucleus. The widespread distribution of methionine-enkephalin-Arg6-Gly7-Leu8 in the cat brainstem indicates that the peptide might be involved in several physiological functions.