The origin of dopaminergic systems in chordate brains: insights from amphioxus.

The origin of dopaminergic systems in chordate brains: insights from amphioxus. Int J Dev Biol. 2017;61(10-11-12):749-761 Authors: Zieger E, Lacalli TC, Pestarino M, Schubert M, Candiani S Abstract The basic anatomy of the central nervous system (CNS) is well conserved within the vertebrates and differs in significant ways from that of non-vertebrate chordates. Of the latter, amphioxus is of special interest, being the best available stand-in for the basal chordate condition. Immunohistochemical and gene expression studies on the developing CNS of amphioxus embryos and larvae are now sufficiently advanced that we can begin to assign specific neurotransmitter phenotypes to neurons identified by transmission electron microscopy (TEM), and then compare the distribution of cell types to that in vertebrate brains. Here, by monitoring tyrosine hydroxylase (TH) transcripts and protein, along with serial TEM, we identify a population of catecholamine-containing neurons in the anterior nerve cord of amphioxus larvae and describe their pattern of synaptic inputs and outputs. Inputs parallel those to the large paired neurons that control the larval escape response, suggesting that the TH+ system functions as an accessory excitatory and perhaps modulatory pathway in larval locomotion, with the added feature of recruiting an assortment of additional interneurons to the circuitry. The TH+ cells probably contain either L-DOPA or dopamine, and corre...
Source: International Journal of Developmental Biology - Category: Biology Tags: Int J Dev Biol Source Type: research