First 3-D map of invertebrate nervous system
14 Feb 2011
A team of neurobiologists from the University of Freiburg
has created the first complete map of all axons that use dopamine as a
messenger in a vertebrate, in this case a Zebra fish.
The map identifies all projection possibilities, the so-called “projectome”
of every nerve cell for a class of messengers in the nervous system.
The research was published in the journal Nature Communications
in January .
Knowledge of which nerve cells send their connections,
called axons, into certain regions of the brain, is particularly
important for understanding the functioning of groups of nerves that
send out axons to modulate the activity of neural circuits in remote
regions of the brain.
One of these groups consists of nerve cells that use the molecule
dopamine as a messenger to control many types of behaviour. It is
precisely these neurons that die off in people afflicted with
Parkinson’s disease, a fact that demonstrates the central role they
play in medicine.
The scientists were able to create the first three-dimensional
projectome map of the intact brain of the zebrafish by combining the
selective genetic marking of individual nerve cells with high
resolution microscopy at the ZBSA.
A Zebrafish nervous system.
Source: Driever and Ryu.
The new map reveals important information on the possible
functioning of the brain. For instance, it illustrates that
dopaminergic neurons of the diencephalon connect distant regions of
the brain in previously unimagined ways — regions responsible for
higher brain functions in the telencephalon, physiological control
in the hypothalamus, the coordination of movement in the hindbrain
and the execution of movement in the spinal cord.
These neurons can be involved in effecting changes in basic
behavioural states following stress: active reactions like fight or
flight or passive reactions like freezing all activity.
In the same study, the scientists describe a new dopaminergic
system in another region of the zebrafish’s brain, the corpus
striatum, in which the loss of dopaminergic connections in Parkinson
patients is particularly severe. The authors speculate that this
system might compensate for the low amount of dopaminergic neurons
In conjunction with further neurobiological studies, the
projectome map opens up possibilities for a new understanding of
neural circuits in the brains of simple vertebrates like the
1. Tuan Leng Tay, Olaf Ronneberger, Soojin Ryu, Roland
Nitschke, and Wolfgang Driever. Comprehensive catecholaminergic
projectome analysis reveals single neuron integration of zebrafish
ascending and descending dopaminergic systems. Nature
Communications, 25 January 2011. doi: 10.1038/ncomms1171