QBI researchers have found that general anaesthetics act on the brain in a more complex way than previously thought. The discovery could lead to improved drugs for surgery.

Though general anaesthesia is commonly used during medical procedures worldwide to put patients into an unconscious state, little is known about how the drugs actually work.

Associate Professor Bruno van Swinderen said his team has overturned previous understanding of what general anaesthetics do to the brain, finding the drugs did much more than induce sleep.

"We looked at the effects of propofol – one of the most common general anaesthetic drugs used during surgery - on synaptic release," he said.

Synaptic release is the mechanism by which neurons – or nerve cells – communicate with each other.

"We know from previous research that general anaesthetics including propofol act on sleep systems in the brain, much like a sleeping pill," Associate Professor van Swinderen said.

"But our study found that propofol also disrupts presynaptic mechanisms, probably affecting communication between neurons across the entire brain in a systematic way that differs from just being asleep. In this way it is very different than a sleeping pill."

General anaesthetics interrupt brain communication pathways

PhD student Adekunle Bademosi said the discovery was focused on an important protein involved in communication between neurons.

"We found that propofol restricts the movement of a key protein (syntaxin1A) required at the synapses of all neurons. This restriction leads to decreased communication between neurons in the brain," he said.

Associate Professor van Swinderen said the finding contributed to understanding how general anaesthetics worked, and could explain why people experienced grogginess and disorientation after coming out of surgery.

"We think that widespread disruption to synaptic connectivity – the brain's communication pathways – is what makes surgery possible, although effective anaesthetics such as propofol do put you to sleep first," he said.



Representation of thousands of tracked syntaxin1A molecules in a neuron exposed to propofol (Credit: QBI).​

General anaesthetic risk to children and older people

"The discovery has implications for people whose brain connectivity is vulnerable, for example in children whose brains are still developing or for people with Alzheimer's or Parkinson's disease,” Associate Professor van Swinderen said.

"It has never been understood why general anaesthesia is sometimes problematic for the very young and the old. This newly discovered mechanism may be a reason."

Associate Professor van Swinderen said more research was needed to determine if general anaesthetics had any lasting effects in these vulnerable groups of people.

"Studying these effects in model systems such as rats and flies allows us to address these questions by manipulating the likely mechanisms involved, which we can't do in humans."

The research involved Professor Frederic Meunier's laboratory at QBI, where super-resolution microscopy techniques enabled the researchers to understand how the anaesthetic worked on single cells. Dr Victor Anggono, whose laboratory at QBI focuses on synaptic mechanisms, was a partner in the study.

The research is published in Cell Reports.