Neuropeptide Y in the carp torus semicircularis: an immunocytochemical study

The presence of neuropeptide Y-like immunoreactivity in the torus semicircularis of the teleost fish Cyprinus carpio was studied using an indirect immunoperoxidase technique. In general, both the nuclei lateralis and centralis of the torus semicircularis showed a high density of immunoreactive fibers from rostral to caudal levels. In particular, in the nucleus lateralis a low density of immunoreactive fibers was only found in the subependymal layer, whereas this was high in the small cell, fibrillar and disperse cells layers. Similarly, the nucleus centralis showed a low density of immunoreactive fibers in the fibrillar cortex, and a high density in the cellular region. Moreover, a moderate density of fusiform or round-ovoid cell bodies containing neuropeptide Y-like immunoreactivity was found in the cellular region of the nucleus centralis. These neurons were located dorsally or near to the lateral lemniscus, and situated perpendicular, parallel or oblique to the surface, showing one or two long and relatively unbranching dendritic trunks. The localization of neuropeptide Y-like immunoreactivity in both nuclei--lateralis and centralis--of the carp torus semicircularis suggests that this peptide is involved in the control of visual, auditive, and lateral line mechanisms, as well as in the control of feeding.