title: An immunohistochemical study on the distribution of vasotocin neurons in the brain of two weakly electric fish, Gymnotus omarorum and Brachyhypopomus gauderio.
abstract: Hypothalamic nonapeptides (arginin vasotocin-vasopressin, oxytocin-isotocin) are known to modulate social behaviors across vertebrates. The neuroanatomical conservation of nonapeptide systems enables the use of novel vertebrate model species to identify general strategies of their functional mechanisms. We present a detailed immunohistochemical description of vasotocin (AVT) cell populations and their projections in two species of weakly electric fish with different social structure, Gymnotus omarorum and Brachyhypopomus gauderio. Strong behavioral, pharmacological, and electrophysiological evidence support that AVT modulation of electric behavior differs between the gregarious B. gauderio and the solitary G. omarorum. This functional diversity does not necessarily depend on anatomical differences of AVT neurons. To test this, we focus on interspecific comparisons of the AVT system in basal non-breeding males along the brain. G. omarorum and B. gauderio showed similar AVT somata sizes and comparable distributions of AVT somata and fibers. Interestingly, AVT fibers project to areas related to the control of social behavior and electromotor displays in both species. We found that no gross anatomical differences in the organization of the AVT system account for functional differences between species, which rather shall depend on the pattern of activation of neurons embedded in the same basic anatomical organization of the AVT system.
authors.affiliation: Depto Histología y Embriología, Facultad de Medicina, Universidad de la República, Montevideo 11800, Uruguay; Unidad Bases Neurales de la Conducta, Departamento de Neurofisiología Celular y Molecular, IIBCE, Montevideo 11600, Uruguay.
authors.forename: Paula
authors.initials: P
authors.lastname: Pouso
authors.affiliation: Depto Histología y Embriología, Facultad de Medicina, Universidad de la República, Montevideo 11800, Uruguay.
authors.forename: Milka
authors.initials: M
authors.lastname: Radmilovich
authors.affiliation: Unidad Bases Neurales de la Conducta, Departamento de Neurofisiología Celular y Molecular, IIBCE, Montevideo 11600, Uruguay; Laboratorio de Neurociencias, Facultad de Ciencias, Universidad de la República, Montevideo 11400, Uruguay. Electronic address: asilva@fcien.edu.uy.
authors.forename: Ana
authors.initials: A
authors.lastname: Silva
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D004555:Electric Fish / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism*; D006608:Hierarchy, Social; D007031:Hypothalamus / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism*; D008297:Male; D009474:Neurons / Q000378:metabolism*; D014668:Vasotocin / Q000378:metabolism*
chemical_list: D014668:Vasotocin
keywords: AVT; Gymnotiform; Hypothalamic neuropeptide; Preoptic area