Immunohistochemical distribution of neuropeptide Y in the mesencephalon and rhombencephalon of carp, Cyprinus carpio L. (Cyprinidae: Teleostei)

The localization of neuropeptide Y (NPY)-immunoreactive elements was investigated in the mesencephalon and rhombencephalon of carp, Cyprinus carpio, by using antisera raised against porcine NPY and the immunoperoxidase technique. Concurrently, to identify the distribution of NPY-immunoreactivity, we developed an atlas of the studied areas based on Nissl-stained sections. The NPY-immunoreactive (NPY-ir) elements were located in many zones of the mesencephalon and rhombencephalon. In the mesencephalon, positive fibers were the most abundant elements while neurons were scarce. The rhombencephalon rostral part was characterized by a low to moderate fiber density, distributed in the ventro-medial and ventro-lateral region. Differently the caudal part of the rhombencephalon exhibited several NPY-ir elements. In particular, a high density of immunoreactivity was located in the gustatory area at the level of the nucleus (n.) originis nervi glossopharyngei, in the n. nervi vagi, and in the vagal lobe. The latter can be considered a valid neuroanatomical model for the study of gustatory signal processing in vertebrates. Our results regarding the primary gustatory centers give neuroanatomical support to the view that NPY may act as a neurotransmitter and/or a neuromodulator in a wide neural network for feeding behavior control.