Development of galanin-like immunoreactivity in the brain of the brown trout (Salmo trutta fario), with some observations on sexual dimorphism.
The development of galanin-like immunoreactive (GAL-ir) cells and fibers was investigated in the brain of brown trout embryos, alevins, juveniles, and adults (some spontaneously releasing their gametes). The earliest GAL-ir neurons appeared in the preoptic region and the primordial hypothalamic lobe of 12-mm embryos. After hatching, new GAL-ir neurons appeared in the lateral, anterior, and posterior tuberal nuclei, and in late alevins, GAL-ir neurons appeared in the area postrema. In juveniles, further GAL-ir populations appeared in the nucleus subglomerulosus and magnocellular preoptic nucleus. The GAL-ir neuronal groups present in juveniles were also observed in sexually mature adults, although the area postrema of males lacked immunoreactive neurons. Moreover, spawning males exhibited GAL-ir somata in the olfactory bulb and habenula, which were never observed in adult females or in developing stages. In adults, numerous GAL-ir fibers were observed in the ventral telencephalon, preoptic area, hypothalamus, neurohypophysis, mesencephalic tegmentum, ventral rhombencephalon, and area postrema. Moderate to low GAL-ir innervation was seen in the olfactory bulbs, dorsomedial telencephalon, epithalamus, medial thalamus, optic tectum, cerebellum, and rhombencephalic alar plate. There were large differences among regions in the GAL-ir innervation establishment time. In embryos, GAL-ir fibers appeared in the preoptic area and hypothalamus, indicating early expression of galanin in hypophysiotrophic centers. The presence of galanin immunoreactivity in the olfactory, reproductive, visual, and sensory-motor centers of the brain suggest that galanin is involved in many other brain functions. Furthermore, the distribution of GAL-ir elements observed throughout trout development indicates that galaninergic system maturation continues until sexual maturity.
Rodríguez
Miguel Angel
MA
Department of Cell Biology and Ecology, Faculty of Biology, University of Santiago de Compostela, 15706 Santiago de Compostela, Spain.
Anadón
Ramón
R
Rodríguez-Moldes
Isabel
I
D000818:Animals; D001921:Brain / Q000196:embryology / Q000254:growth & development / Q000378:metabolism*; D002452:Cell Count; D004625:Embryo, Nonmammalian / Q000502:physiology; D005260:Female; D044089:Galanin-Like Peptide; D007150:Immunohistochemistry; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D012727:Sex Characteristics; D013116:Spinal Cord / Q000196:embryology / Q000254:growth & development / Q000378:metabolism; D014337:Trout / Q000196:embryology / Q000254:growth & development / Q000378:metabolism*
D044089:Galanin-Like Peptide; D009419:Nerve Tissue Proteins