Neuropeptide Y (NPY) Distribution in the Forebrain of Adult Spiny Eel, Macrognathus pancalus

In the present study, the distribution of neuropeptide Y (NPY)-immunoreactive neurons and fibers in the forebrain of adult spiny eel, Macrognathus pancalus , which is a bottom-dwelling nocturnal fish, was investigated. Serial Nissl-stained brain sections were used to demarcate forebrain regions and neuronal structures. NPY peptidecontaining cell bodies and fibers localized immunocytochemically were found widely distributed throughout the forebrain. The brain areas showing NPY distribution included predominant cell groups in the telencephalon (nucleus entopeduncularis, NE; nucleus of area ventralis telencephali, Vn), diencephalon (nucleus preopticus, pars parvocellularis, NPOp; nucleus preopticus, pars magnocellularis, NPOm; nucleus lateralis tuberis, NLT) and mesencephalon (midbrain tegmentum, MT). The important areas with only NPY-immunoreactive (-ir) fibers included olfactory bulb (OB), area dorsalis telencephali pars anterioris (Da), dorsal part of Dmd (Dmdd), ventral subdivision of Dl (Dlv), anterior subdivision of Dl (Dla), preoptic area (POA), optic tectum (OTec) and nucleus recessi lateralis (NRL). The pattern of NPY distribution in the forebrain of M. pancalus suggests its role in processing of many physiological functions (viz., feeding, daily activities, reproduction and other metabolic processes). The basic information on anatomical localization of NPY in eel will help to understand better the seasonal variations of NPY and its interaction with other reproductive hormones.