Communication between neurons, or nerve cells, is the cellular basis for thinking, decision making, and control of muscular movements. Neurons are cells with a particular shape: they possess two types of long ramification, called the axon and the dendrites. The axon of one neuron is in contact with the dendrites of other neurons. These contacts are termed synapses. Each neuron forms thousands of synapses with other neurons. Neurons communicate by sending electric signals along their axons
When a signal reaches a synapse, it triggers the release of neurotransmitters, which are small molecules that diffuse in the intercellular space and activate receptor on the surface of the other cell forming the synapse. In turn, activated receptors generate electric signals of variable intensity. The signals coming from every synapses of a neuron passively converge to the base of its axon and are summed up. If the resulting signal is intense enough, the axon will actively propagate the signal further; otherwise, the signal will stop there.
I am interested in the fine structure, or the architecture, of synapses because it defines the framework in which the synaptic events take place. Electron microscopy (EM) has been used for more than 50 years for this purpose. However, specimens are usually dehydrated prior EM observation and this generates several distortions. Our goal is to provide a better picture of the synapse that reflects its native, intact structure. We can achieve that by applying cryo-electron microscopy of vitreous sections (CEMOVIS), a recently developed technique where specimens can be observed without dehydration. We have already shown that the space between the two cells, termed the synaptic cleft, contains a high density of regularly arranged molecules. To get further insights, we want to obtain three dimensional images of model synapses by using a method termed cryo-electron tomography. This should notably allow us to decipher the arrangement of the cellular skeleton at the synapse and of the scaffold holding receptors in place. These are highly involved in the regulation of synaptic transmission.