Synapses

Subject – Science and Tech

Context – NCBS: Zebrafish study reveals how the brain makes its connections

Concept –

Neurons, or nerve cells, in the brain connect by means of junctions known as synapses through which they transmit signals.
Recent work by researchers at the National Centre of Biological Sciences, Bengaluru, has thrown light on what stimulates these synapses to form.
There are two types of synapses – chemical and electrical.
In chemical synapses, there is a space of about 20 nanometres between two neurons, and the way they communicate is this:
- One neuron converts electrical signal into chemical signals and this chemical is released into the synaptic space and the receiving neuron converts the chemical signal back into an electrical signal.
As far as the electrical synapse goes, this is not the way it operates. In these synapses, the two neurons have a physical connection and the conversion of electrical to chemical need not occur, and they communicate directly.
Electrical synapses are like a physical wire, communication is faster but they are also fewer in number.
It was shown that electrical synapses are formed before chemical synapses, they are like a blueprint in which neurons make a handshake. This results in the making of chemical synapses.

Research on organisms such as leeches showed that if you remove electrical synapses, the chemical synapses do not form. However, the mechanism of how it happens in higher organisms such as vertebrates was not known.
Researchers from TIFR-National Centre of Biological Sciences, Bengaluru, have chosen Zebrafish as a model organism to study this process.
- Zebrafish are transparent and neuron development in larval zebrafish can be observed from day to day by injecting a dye or by engineering the fish to express fluorescent proteins.
- How nerve-end connections known as synapses form is highlighted in this study of Purkinje neurons in the cerebellum of knockout zebrafish.