Developmental expression patterns of acetylcholinesterase and cholineacetyltransferase in zebrafish retina

ABSTRACT

During recent years a key role as morphogen has been postulated for the neurotransmitter acetylcholine in the developing Central Nervous System. Acetylcholine released from growing axons regulates growth, differentiation and plasticity. The acetylcholine distribution is frequently defined by acetylcholinesterase and choline acetyltransferase expression patterns. The cholinergic/cholinoceptive system in the adult zebrafish retina has been described. Nevertheless, there are no data regarding the developing retina. The acetylcholinesterase and choline acetyltransferase distribution patterns during zebrafish retinal development are very similar. In both cases the first positive elements appear in the plexiform layers and in later stages reactive amacrine cells have been observed in the ganglion cell layer and inner nuclear layer. In the adult retina a cholinergic and cholinoceptive neuropile band is observed in the inner plexiform layer. Displaced amacrine cells and amacrine cells positive to both markers have been observed. Transient expressions of choline acetyltransferase in the optic nerve and outer plexiform layer and of acetylcholinesterase in amacrine cells and displaced amacrine cells are observed during retinal development coinciding with the arrangement of the pioneering retinal projections into the optic tectum. The mature distribution pattern of the cholinergic/ cholinoceptive system in the adult retina is conserved along the phylogenetic scale, thus it seems to be a primary feature acquired relatively early during the evolution of vertebrates (AU)

RESUMEN

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