Researchers observed synaptic transmission in a live animal for the first time using a new technique that employs genetics and the physics of light.
Neurons in the brain communicate by transmitting chemical signals to each other through synapses, but studying this process in live animals has proven to be extremely difficult, the Ecole Polytechnique Federale de Lausanne reported.
In order to get around this roadblock the researchers used a technique called "optogenetics" to control the activity of specific neurons in live animals in real time. This allowed the research team to study hundreds of types of neuron types, providing insight into higher brain functions such as thought and language.
In optogenetics the gene of a light-sensitive protein is inserted into live neurons. When light is shined onto these neurons an "electrical channel" opens up, allowing electrical ions to flow into the cell. This electrical flow changes the voltage balance of the neurons, which allows researchers to control neural activity as if "switching a light on and off."
The researchers used optogenetics to stimulate single neurons of anesthetized mice, targeting a sensory-processing region of the brain called the barrel cortex. When the researchers shined blue light onto the neurons that contained the light-sensitive proteins while measuring the electrical signals in neighboring neurons.
The technique allowed the team to look at activity in small connector neurons called "interneurons." The team recorded and analyzed synaptic transmissions from the light-sensitive neurons to interneurons. They also used an advanced imaging technique (two-photon microscopy) to identify each interneuron, revealing the ins and outs of neuronal transmissions.
"This is a proof-of-concept study," said Aurélie Pala, who received her PhD for this work. "Nonetheless, we think that we can use optogenetics to put together a larger picture of connectivity between other types of neurons in other areas of the brain."
The findings were published in a recent edition of the journal Neuron.
