Presence of monoaminergic neurons in the spinal cord and intestine of the lamprey, Lampetra japonica.

It is said that the lamprey has no commissural sympathetic chain (NICOL, 1952; JOHNELS, 1956), although visceral efferents from the vagus are described (JOHNELS, 1956). It is not clear whether the visceral efferents coming from the spinal cord emerge from the dorsal or ventral roots or both. AYERS (1921, 1930) found the visceral efferents emerging from the ventral roots in Amphioxus and Myxinoid and suggested the presence of similar visceral efferents in the lamprey. GOODRICH (1930) stated that the visceral efferents arise from the dorsal root nerves in the lamprey. On the other hand, JOHNELS (1956) described the presence of visceral efferents emerging from both the dorsal and ventral roots. It is not certain whether the monoaminergic nerve fibers are present in these spinal efferents. If they exist, then it seems probable that the monoaminergic neurons might be present in the spinal cord of the lamprey. These observations were made to prove the presence of monoaminergic neurons in the lamprey spinal cord. In mammalian intestinal wall, no adrenergic neuronal somata seem to be present, although the adrenergic fibers are found around the neurons of the plexus of Auerbach and in the muscle layer (NORBERG, 1964; HOLLANDS and VANOV, 1965). The presence of neuronal somata and fibers in the intestinal wall and that of the ganglion dorsal to the caudal end part of the ureter have been described in the lamprey (JOHNELS, 1956). It is not clear, however, whether the monoaminergic neural elements exist in these tissues. In the present study, these tissues were examined by using the Falck-Hillarp method for the demonstration of cells containing biogenic monoamines (FALCK and OWMAN, 1965).