Embryonic and larval development of the basal ganglia connections in the brain of Xenopus laevis
International Journal of Developmental Biology
Recently, the afferent and efferent connections of the components of the amphibian basal ganglia, I.e., the striatum and the nucleus accumbens, have been studied in the brain of adult anurans and urodeles (Marin et aI., 1995(Marin et aI., , 1996. Significant differences in connections between the nucleus accumbens and the striatum were demonstrated, suggesting the presence of functional subdivisions. Moreover, those studies strongly supported the notion that a common pattern of connectivity
... ts among tetrapod vertebrates. The aim of the present study was to establish the temporal sequence of appearance of striatal and accumbal connections in amphibians so that the comparison with other amniotes allows to gain more insight into the evolution of the basal ganglia of vertebrates. To reach this goal, the anuran Xenopus laevis has been selected because of the existence of an accurate timetable of development (Nieuwkoop and Faber, , 967) and the existence of recent hodological data of basal ganglia connections in the adult brain of this species. The methodology used in this study is based on the neuronal transport of low molecular weight (3kD) biotinylated dextranamines (BOA). Shortly, at appropriate times, embryos and larvae anesthetized in MS222 were cooled to a body temperature of 40C and perfused transcardially with iced Ringer's solution. The brains were then removed and placed in fresh iced Ringer's solution. Applications of BDA were made unilaterally within the striatum (Fig.1) or the nucleus accumbens. After '5-24 h at 150C in continuously oxygenated Ringer's solution the brains were fixed in 4% parformaldehyde. Following crioprotection, the brains were cut on a freezing microtome and free-floating sections were reacted with avidin-biotin complex for BOA visualization.