title: An intriguing pitfall in chemical neuroanatomy: specific populations of unspecifically immunoreactive neurons in the brain of the mormyrid fish Gnathonemus petersii.
abstract: The present paper describes the location, morphology, ultrastructure and immunocytochemical properties of neurons in the brain of the mormyrid fish Gnathonemus petersii, that appear to be unspecifically immunoreactive to a number of secondary or tertiary antibodies used in immunohistochemical procedures, including rabbit-anti-mouse immunoglobulins (IGGs), rabbit peroxidase-anti-peroxidase IGGs, and rabbit-anti-sheep or sheep peroxidase-anti-peroxidase IGGs. Unspecifically immunoreactive (UI) cells have typically neuronal morphological and ultrastructural characteristics, and occur at four specific locations in the mormyrid brain. A small rhombencephalic group is located rostrolateral to the efferent octaval nucleus, between the fasciculus longitudinalis medialis and the decussation of the lateral lemniscus. A mesencephalic cluster of cells is located in the dorsal midbrain tegmentum against the tractus telencephalo-mesencephalicus. In addition, dispersed UI neurons were observed in the nucleus lateralis of the torus semicircularis and in the preoptic region above the optic chiasm. Remarkably, UI cells are clearly present in a substantial number of brains investigated, but not detectable in others. The present findings point to a curious pitfall in chemical neuroanatomy, the functional significance of which is unknown at present. In several previous studies using the brain of G. petersii, UI cells were abusively included in the description of monoaminergic cell groups. Similar cells have until now not been reported in other vertebrate brains.
authors.affiliation: Department of Anatomy and Embryology, University of Nijmegen, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Meek
authors.forename: T G
authors.initials: TG
authors.lastname: Hafmans
authors.forename: H W
authors.initials: HW
authors.lastname: Joosten
mesh_terms: D000818:Animals; D001921:Brain / Q000166:cytology*; D001923:Brain Chemistry; D005399:Fishes / Q000033:anatomy & histology / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D007150:Immunohistochemistry; D008636:Mesencephalon / Q000737:chemistry / Q000166:cytology; D008854:Microscopy, Electron; D009474:Neurons / Q000737:chemistry / Q000166:cytology* / Q000276:immunology / Q000648:ultrastructure; D011301:Preoptic Area / Q000737:chemistry / Q000166:cytology; D012249:Rhombencephalon / Q000737:chemistry / Q000166:cytology