17 Mar 2016

Using light and electricity to study individual brain cells

From Our Changing World, 9:34 pm on 17 March 2016
False colour image of a rat brain

Optogentics in action - using light to study the brain. This is an immunocytochemical image of a rat brain slice (cut horizontally) showing intense expression of endocannabinoid receptors (red), particularly in regions with dopamine-producing neurons (green), and associated with movement. Photo: Peter Freestone / University of Auckland

Light is a hot topic in biology at the moment and Peter Freestone, a post-doctoral researcher at the University of Auckland, is pioneering the use of optogenetics or light-based technology in New Zealand.

He is studying individual brain cells to find out how they communicate with each other, and he hopes that the research will improve our understanding of what happens to the brain of someone with Parkinson’s disease.

Peter is particularly interested in how two-way communication happens between neurons, and the role that endocannabinoids play in this.

“Endocannabinoids are cannabis-like substances that are produced naturally within the brain, and I’m looking to see how they control the flow of information between two cells.”

Brain cells communicate by passing a chemical neurotransmitter such as dopamine, glutamate or GABA across a synapse. Peter says this signal from ‘cell A’ might cause ‘cell B’ to increase in activity or quieten down.

“Endocannabinoids work in the opposite direction. ‘Cell B’ communicates back with ‘cell A’, and says ‘I heard your signal and I’m going to turn your signal off or maybe turn your signal up a little bit more.’ Endocannabinoids … are actually known as retrograde, because they’re going in the opposite direction from the normal flow.”

Peter says his ‘cell B’ are the ones that produce dopamine, and in particular ones that produce endocannabinoids especially a kind known as NADA.

Dopamine is an important neurotransmitter, and what happens in the brains of people with Parkinson’s disease is that the cells that produce dopamine degenerate so there is less dopamine.

“We are interested in the dopamine cells, as we want to see what signal they get in and see if we can somehow rescue or help the cells that survive and get them to produce more dopamine in [brains affected by Parkinsons].”

Man in front of a large microscope

Peter Freestone stands in front of the microscope he uses to work with individual brain cells. Photo: RNZ / Alison Ballance

Interesting fact: there are about 86 billion neurons or brain cells in a human brain.

Peter works with rat brains, and he studies slices of brain under a powerful microscope using electricity and light. A technique known as electrophysiology allows him to record the electrical activity of individual brain cells.


Optogenetics is a relatively new technique in neuroscience, and it involves the use of light to control individual brain cells. The benefit of optogenetics is that it solves the problem of trying to isolate single neurons within a tightly interconnected network, and allows a very high level of precision.

Electrical stimulation, such as deep brain stimulation, and drugs are more general in their effect and activate whole areas of the brain

Brain cells don’t usually respond to light, but scientists identified a light-sensitive protein in simple single-celled organisms that are able to photosynthesise that can be introduced into brain cells, and enables them to respond to blue light. Cells without the protein won’t respond to the light.

Although it is a long way off, Peter sees a future in which optogenetics becomes a treatment as well as an experimental tool. He believes it could replace deep brain stimulation as a treatment for Parkinson’s disease.

In this Our Changing World summer science podcast, science communication student Steve Banks finds out about living with Parkinson’s disease.