Neuropeptides in the torus semicircularis of the carp (Cyprinus carpio).

The distribution of fibers and cell bodies containing neurotensin, neurokinin A, galanin, or somatostatin-28(1-12) immunoreactivity in the torus semicircularis of the carp was studied using an indirect immunoperoxidase technique. In this mesencephalic region, a high-density of galanin-immunoreactive fibers was found, whereas neurokinin A or somatostatin-28(1-12)-immunoreactive processes were observed at a moderate density and neurotensin-immunoreactive fibers at a low density. Cell bodies containing somatostatin-28(1-12) immunoreactivity were observed in both central and lateral nuclei. The torus semicircularis was not immunoreactive for dynorphin A. The presence of these neuropeptides in the carp torus semicircularis suggests that such neuroactive substances may be involved in auditory and visual mechanisms, as well as in the control of inputs arising from the lateral line system.