Enkephalin-immunoreactive perikarya in the cat raphe dorsalis.

The serotonin-containing nucleus raphe dorsalis (RD) of the cat contains numerous leucine-enkephalin immunoreactive cells, throughout its rostral-caudal extent. The distribution of the enkephalin neurons closely parallels the cytoarchitectural boundaries of the RD, as described in previous Nissl preparations. Enkephalin perikarya are most numerous along the midline of the RD, but also extend ventrally, into the dorsal portion of the nucleus centralis superior, and laterally, into the 'wings' of the rostral RD, at the level of the IV nucleus. The possible contribution of these enkephalin cells to endogenous pain control systems is discussed.