Amphioxus Neurotransmitters

Note:  This page will record links to references which either discuss a neurotransmitter other than GABA or which discuss other neurotransmitters in addition to GABA.  For the references strictly about GABA, see Amphioxus GABA .   

Distribution of neuropeptide Y immunoreactivity in the central and peripheral
nervous systems of amphioxus (Branchiostoma lanceolatum Pallas).   
    "Immunocytochemistry techniques were employed to investigate the distribution of neuropeptide Y-like-immunoreactive (NPY-ir) cells and fibers in the central and peripheral nervous systems of adult amphioxus.  
     NPY-ir neurons of the commissural type were abundant in the brain and present but more scarce in the spinal cord. These neurons gave rise to conspicuous NPY-ir tracts that coursed along the entire length of the nerve cord. Some fibers exhibited conspicuous Herring body-like swellings.    
    In the peripheral nervous system, small NPY-ir neurons and a large number of thin, beaded NPY-ir fibers were observed in the atrial region, indicating the involvement of this substance in visceral regulation. A few NPY-ir fibers, possibly afferent to the spinal cord, coursed in the ventral branches of the spinal nerves of this region, whereas no NPY-ir fibers coursed in the preoral or velar nerves or in the dorsal branches of the other spinal nerves.  
    These results indicate that NPY is widely used as a neuroregulator/neurotransmitter in the central and peripheral nervous systems of this primitive chordate. In addition, this study demonstrates the presence of tall, thin NPY-ir cells in the putative adenohypophyseal homologue, the Hatschek's pit organ, which is located in the roof of the preoral cavity (vestibule)."  

232 Related citations:   
1 Cited by:   
See the paper.         

Distribution of tyrosine hydroxylase, dopamine, and serotonin in the central nervous system of amphioxus (Branchiostoma lanceolatum): implications for the evolution of catecholamine systems in vertebrates. (PubMed)
Only abstract available online.  I got PDF from the library. 
from the Abstract:       
    "The overall distribution of dopaminergic and serotoninergic systems is similar in amphioxus and vertebrate central nervous system and could be an ancestral character of chordates.  As assayed by high-performance liquid chromatrography and electrochemical detection, significant amounts of dopamine and octopamine, but not of noradrenaline, are present in amphioxus head. This finding is consistent with data obtained from most prostomian species. We conclude that the noradrenergic system is probably an innovation of vertebrates that appeared along with the neural crest and specific hindbrain nuclei."    
from the PDF:       
    "Gans and Northcutt (1983) originally proposed that the neural crest was a vertebrate innovation that accompanied the emergence of predator behavior in ancestral vertebrates."  

569 Related citations:   
The nervous system of amphioxus: structure, development, and evolutionary significance
    - Canadian Journal of Zoology     
The nervous system of amphioxus: structure, development, and evolutionary significance 
Searched for "GABA": See Amphioxus GABA  .

Endocrinology of protochordates - Canadian Journal of Zoology 
    See:  Evolution of Hormones
reports finding numerous neurotransmitters.  Although ostensibly about hormones, the article also summarizes the neurotransmitters found in protochordates.  They are: 
    Aspartate and

Free amino acids in the nervous system of the amphioxus Branchiostoma lanceolatum. A comparative study

    "The cephalochordate amphioxus is the closest invertebrate relative to vertebrates. In this study, using HPLC technique, free L-amino acids (L-AAs) and D-aspartic acid (D-Asp) have been detected in the nervous system of the amphioxus Branchiostoma lanceolatum. Among other amino acids glutamate, aspartate, glycine, alanine and serine are the amino acids found at the greatest concentrations. As it occurs in the nervous system of other animal phyla, glutamate (L-Glu) and aspartate (L-Asp) are present at very high concentrations in the amphioxus nervous system compared to other amino acids, whereas the concentration of taurine and gamma-aminobutyric acid (GABA) is very low. Interestingly, as it is the case in vertebrates, D-aspartic acid is present as an endogenous compound in amphioxus nervous tissues. The physiological function of excitatory amino acids, and D-aspartate in particular, are discussed in terms of evolution of the nervous system under an Evo-fun (Evolution of function) perspective."  

1 Cited by
See the PubMed abstract.     

    Full length paper. 
Note:  This study measured the free amino acids in amphioxus neural tube without claiming that they were functioning as neurotransmitters. 
     Table 1 

Major free L-amino acids and D-aspartate in the nervous system of the Amphioxus. Results are expressed in µmol/g tissue (mean ± SD). a from ref. [12]; b present work; c from ref. [13]; d from ref. [14]. For more details, see in the text.


By far the most prevalent amino acid neurotransmitter was L-Glutamate, which is excitatory.  They also found a little L-Aspartate, which they said is excitatory but which I don't remember as being important in humans.  They found only small quantities of GABA
and L-Glycine, which are inhibitory

N-methyl-D-aspartic acid (NMDA) in the nervous system of the amphioxus Branchiostoma lanceolatum.  
from the Abstract       
    NMDA (N-methyl-D-aspartic acid) is a widely known agonist for a class of glutamate receptors, the NMDA type. Synthetic NMDA elicits very strong activity for the induction of hypothalamic factors and hypophyseal hormones in mammals. Moreover, endogenous NMDA has been found in rat, where it has a role in the induction of GnRH (Gonadotropin Releasing Hormone) in the hypothalamus, and of LH (Luteinizing Hormone) and PRL (Prolactin) in the pituitary gland.
    In this study we show evidence for the occurrence of endogenous NMDA in the amphioxus Branchiostoma lanceolatum. A relatively high concentration of NMDA occurs in the nervous system of this species (3.08 +/- 0.37 nmol/g tissue in the nerve cord and 10.52 +/- 1.41 nmol/g tissue in the cephalic vesicle). As in rat, in amphioxus NMDA is also biosynthesized from D-aspartic acid (D-Asp) by a NMDA synthase (also called D-aspartate methyl transferase).
    Given the simplicity of the amphioxus nervous and endocrine systems compared to mammalian, the discovery of NMDA in this protochordate is important to gain insights into the role of endogenous NMDA in the nervous and endocrine systems of metazoans and particularly in the chordate lineage."  

83 Related citations
1 Cited by
See the PubMed abstract.           
Click on the active link, above.  

A neurochemical map of the developing amphioxus nervous system   

from the Abstract:   
Although the central nervous system (CNS) of amphioxus comprises only about 20,000 neurons (as compared to billions in vertebrates), the developmental genetics and neuroanatomy of amphioxus are strikingly vertebrate-like."      
we identified glutamatergic, GABAergic/glycinergic, serotonergic and cholinergic neurons in developing amphioxus. In addition to characterizing the distribution of excitatory and inhibitory neurons in the developing amphioxus CNS, we observed that cholinergic and GABAergic/glycinergic neurons are segmentally arranged in the hindbrain, whereas serotonergic, glutamatergic and dopaminergic neurons are restricted to specific regions of the cerebral vesicle and the hindbrain."  

92 Related citations:  
Figure 2. Schematic representation of the neural tube of amphioxus 14–18 hr neurulae showing expression of genes involved in the synthesis and/or transport of neurotransmitters."  
Figure 3. Schematic representation of the neural tube of amphioxus 20–24 hr neurulae of showing expression of genes involved in the synthesis and/or transport of neurotransmitters. "  
Figure 12. Comparison of neurotransmitter cell types in amphioxus embryos with the distribution of ventrolateral neurons in amphioxus larvae."  
    "Our neurochemical map of the amphioxus CNS reveals that the developing amphioxus nervous system is characterized by a strict regionalization and segmented organization of discrete groups of neuronal cell types. At the neurula stage, GABAergic/glycinergic as well as cholinergic neurons show a segmented distribution in the hindbrain, while glutamatergic, serotonergic and dopaminergic neurons are detectable in very restricted groups of neurons with precise locations along the anteroposterior axis of the CNS."  
My summary of neurotransmitters identified in amphioxus:   
glutamatergic - glutamate
    GABAergic/glycinergic -
GABA /glycine
    serotonergic - serotonin 
    cholinergic - 
dopaminergic - dopamine 

CotA Neurochemical Map/Amph
140713 - 1400  modified