title: Distribution of somatostatin (SRIF) in the brain and pituitary of Eigenmannia lineata (Gymnotiformes, Teleostei). An immunohistochemical study.
abstract: Somatostatin-immunoreactive (SRIFi) cells in the brain and pituitary of the weakly-electric teleost Eigenmannia lineata were identified immunohistochemically by the use of unlabelled antibodies and the peroxidase-antiperoxidase technique. Several groups of neurons and fibres were immunostained in Eigenmannia's brain. Intensely SRIFi neurons occurred in the nucleus entopeduncularis, in the nucleus preaeopticus, and in the nucleus dorsolateralis between the commissura posterior and the nucleus glomerulosus, the latter two structures being completely devoid of immunoreactive elements. Few weakly-immunoreactive perikarya were found scattered in the nucleus ventromedialis and in the nucleus lateralis tuberis anterior and posterior. In the medullary electric organ pacemaker nucleus (pm) the large relay-neurons sometimes were immunoreactive while the smaller pacemaker-neurons were SRIF-negative and did not contain any immunoreactive vesicles. SRIFi fibres appeared in the dorsomedial and in the ventrolateral parts of the bulbus olfactorius. Telencephalic SRIFi fibres were found in the area dorsalis telencephali pars medialis below the ventricular wall and in the caudal pars lateralis. Diencephalic immunoreactive fibres were located below the preoptic nuclei, in the dorsomedial diencephalon, lateral to the nucleus dorsomedialis and ventromedialis, and as a bundle adjacent to the dorsomedial part of the nucleus recessus lateralis. SRIFi fibres coursing in the pituitary stalk led to the adenohypophysis. SRIFi mesencephalic fibres were only found in the rostral tectum opticum. In the anterior medulla oblongata SRIF-fibre-bundles occurred mediolaterally to the midline, and dorsolaterally below the lumen of the 4th ventricle. Only a few fibres were found in the corpus cerebelli, while an intensely immunostained medullary bundle occurred laterally to the pacemaker nucleus, connecting to the spinal medulla. The results of our study suggest that SRIF is a neurotransmitter or neuromodulator in the brain of Eigenmannia, also occurring in some parts of the electrosensory and electromotor system. The present results are compared to those in other teleost brains.
authors.affiliation: Institute for Anatomy, University of Regensburg, FRG.
authors.forename: U
authors.initials: U
authors.lastname: Bonn
authors.forename: B
authors.initials: B
authors.lastname: König
mesh_terms: D000818:Animals; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D004555:Electric Fish / Q000033:anatomy & histology / Q000378:metabolism*; D007150:Immunohistochemistry; D010455:Peptides / Q000378:metabolism*; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism*
chemical_list: D010455:Peptides; C029993:somatostatin-like peptides