Postembryonic development of the cerebellum in gymnotiform fish

Abstract

In contrast to adult mammals, adult teleost fish regularly generate new neurons and glial cells in many brain regions. A previous quantitative mapping of the proliferation zones in the brain of adult Apteronotus leptorhynchus (Teleostei, Gymnotiformes) has shown that 75% of all mitotically active cells are situated in the cerebellum (Zupanc and Horschke [1995] J. Comp. Neurol. 353:213-233). By employing the thymidine analogue 5-bromo-2'-deoxyuridine, we have, in the present study, investigated the postembryonic development of this brain region in detail. In the corpus cerebelli and the valvula cerebelli, the vast majority of newborn cells originate in the respective molecular layers. Within the first few days of their life, these cells migrate toward specific target areas, namely, the respective granule cell layers. In the caudal part of the cerebellum, the granule cell layer of the eminentia granularis pars medialis displays the highest mitotic activity. From there, the cells migrate through the adjacent molecular layer to the granule cell layer of the eminentia granularis pars posterior. Combination of retrograde-tracing techniques with immunohistochemistry for 5-bromo-2'-deoxyuridine showed that at least a portion of the newly generated cells develop into granule neurons. Many of the newly generated cells survive for long periods of time. A large fraction of these cells is added to the population of already existing cells, thus resulting in a permanent growth of the target areas and their associated structures.

Proliferative activity in the frog brain: A PCNA-immunohistochemistry analysis

“…In some other teleosts, the proliferation zones of the developing brain corresponded to the same areas as in the sole (see Wullimann and Puelles, 1999;Ekström et al, 2001;Wullimann and Mueller, 2004). In contrast with R. esculenta, in some teleostean fish species, however, the molecular layer of the cerebellum was described to contain proliferating cells (Zupanc et al, 1996;Ekström et al, 2001). In the gymnotiform teleost, Apteronotus leptorhynchus, Zupanc et al (1996) described that labeled cells in the molecular layer of the cerebellum ''migrate'' to the granular layer.…”

Environmental effects on fish neural plasticity and cognition

“…In contrast to mammals, where neurogenesis is limited in adulthood, this process continues throughout the brain during a fish's entire life (Zupanc et al , 2005). For example, adult neurogenesis in the mammalian brain is limited to a few regions, mainly the olfactory system and hippocampal formation (Gould et al , 1999; Gould & Gross, 2002), whereas proliferation and neurogenesis are widespread in the adult fish brain (Zupanc et al , 1996; Ekström et al, 2001; Zupanc, 2001; Candal et al, 2005; Kaslin et al, 2008). As far as is known, there are no other aspects of neural plasticity that continue to be high throughout a fish's life, creating an important avenue for further research.…”

Expression of GAP-43 mRNA in the Adult Carp Central Nervous System

“…Neurogenesis continues in adulthood in the optic tectum of the adult goldfish (Raymond and Easter, 1983) and in the cerebellum of the adult gymnoiform fish (Zupanc et al,1996). In the present study using in situ hybridization, we demonstrated that the brain and spinal cord of the adult carp contain many neurons which strongly express GAP-43 mRNA.…”