FMRFamide-like immunoreactivity in brain and pituitary of Xenotaca eisenii: (Ciprinidontoformes, Teleostei).

FMRFamide-immunoreactive neurons were determined immunocytochemically by means of the PAP-technique for unlabeled antibodies. FMRFamide-containing perikarya were found in the frontoventral telencephalon, in the valvula and corpus cerebelli, and in the rostral and caudal medulla oblongata. FMRFamide immunoreactive cells were localized in the anterio lobe of the pituitary. FMRFamide fibres occurred in the bulbus olfactorius, in the anterior, medial and lateral parts of the telencephalon, in the commissura anterior, beneath the nucleus praeopticus, beneath the nucleus dorsomedialis, ventrolis and anterior tuberis as well as in the caudal hypothalamus, surrounding the nucleus recessus lateralis and posterior. In the mesencephalon, FMRF-amide-containing fibres appeared in the dorsal tegmentum, in the torus semicircularis and in the deep layers of the tectum opticum. In the rhombencephalon, only few fibres were found in the cerebellum but a strong innervation occurred in the ventrolateral and dorsolateral medulla oblongata. The present results are discussed with those of other teleost species.