Synapses Finally Revealed in 3D

In a groundbreaking, new study, scientists were able to use a new type of electron microscopy, known as electron cryotomography, to image the connections between individual neurons for the first time. The work is presented in amazing details, and features representations of all the vesicles and filaments that can be found inside synapses. The team behind this achievement was based at the Max Planck Institute of Biochemistry, in Germany, and was led by Spanish physicist Ruben Fernandez-Busnadiego, AlphaGalileo reports.

The innovative, new imaging method can yield this unprecedented level of detail because it is able to basically freeze the sample it is analyzing with such speed, that all processes going on inside the structure are immortalized before they can stop or disintegrate. “We used electron cryotomography, a new technique in microscopy based on ultra-fast freezing of cells, in order to study and obtain three-dimensional images of synapses, the cellular structure in which the communication between neurons takes place in the brains of mammals,” Fernandez-Busnadiego tells SINC.

The expert has also been the lead author of a new scientific paper detailing the team's methodology, which appears on the front cover of the January issue of the respected scientific Journal of Cell Biology. “Thanks to the use of certain pharmacological treatments and the advanced 3D imaging analysis method we have developed, it is possible to observe the huge range of filamentous structures that are within the presynaptic terminal and interact directly with the synaptic vesicles, as well as to learn about their crucial role in responding to the electrical activity of the brain,” he adds.

Information transfer between neurons is done in a relatively straightforward, yet complicated manner. The end of the neuron transporting data (encoded in an electrical signal) uses what are known as presynaptic emitter release neurotransmitters in the space between the nerve cells sending the data and the ones receiving it. These neurotransmitters are in fact a collection of chemicals, which are “packed” inside small vesicles, each no bigger than 40 nanometers in diameter. Specialized postsynaptic receptors on the receiving neurons collect the vesicles, break them apart, and then process the chemicals, generating the same electric impulse in the second nerve cells. This happens countless times per second.