Function of a Neglected Structure in Neurons Revealed

September 9, 2009
Two-photon-microscopy of neuron. Source: FMI

Two-photon-microscopy of neuron. Source: FMI

Fifty years after it was originally discovered, scientists at the Friedrich Miescher Institute for Biomedical Research have elucidated the function of a microscopic network of tubules found in neurons. This structure modulates the strength of connections between two neurons, thereby contributing to our ability to learn and to adapt to new situations.

In the current online issue of the Proceedings of the National Academy of Sciences, Oertner’s group describes how the microscopic network of tubules known as the endoplasmic reticulum (ER) modulates the strength of connections between neurons. Neural connections play an important role in our ability to learn new information and constantly adapt to new conditions. In the brain, synaptic connections between neurons are thus continually formed, strengthened or weakened.

In addition, there are connections that remain stable – for example, when we store an important memory for many years. Connections of both types coexist, and their close proximity was one of the first key findings of Thomas Oertner’s study: the two types occur side by side on the same neuron and are individually controlled.

Observations and comparisons of individual dendritic spines and synapses are anything but routine. The findings just published were only possible thanks to a new method known as two photon microscopy. In this imaging technique, a pulsed infrared laser is used to excite fluorescence in a dye molecule in a cell. It is a gentle method of investigating cells, which yields unique, high-resolution images. Thomas Oertner’s research group is one of only a few worldwide that use this technique to optically stimulate and observe individual synapses, and to measure their activity. As equipment of this type cannot simply be purchased off the shelf, these innovative microscopes are custom-built and refined by Thomas Oertner himself. 

Original publication:
Holbro N et al. (2009) Differential distribution of endoplasmic reticulum controls metabotropic signaling and plasticity at hippocampal synapses. PNAS, 18 August 2009, doi: 10.1073/pnas.0905110106 -> Online publication