Psilocybin spurs growth of neural connections lost in depression in vivo

New findings from Yale University, US, have revealed how a single dose of psilocybin, a naturally occurring compound found in some mushrooms, given to mice prompted an immediate and long-lasting increase in connections between neurons.

The psychedelic drug psilocybin has been studied as a potential treatment for depression for years. However, exactly how it works in the brain and how long beneficial results might last has remained unclear.

“We not only saw a 10 percent increase in the number of neuronal connections, but also they were on average about 10 percent larger, so the connections were stronger as well,” said Associate Professor Alex Kwan, senior author of the paper published in the journal Neuron.

Previous laboratory experiments have shown promise that psilocybin, as well as the anaesthetic ketamine, can decrease depression. The new research found that these compounds increase the density of dendritic spines, small protrusions found on nerve cells which aid in the transmission of information between neurons. Chronic stress and depression are known to reduce the number of these neuronal connections.

Using a laser-scanning microscope, Kwan and first author Ling-Xiao Shao, a postdoctoral associate in the Yale School of Medicine, imaged dendritic spines in high resolution and tracked them for multiple days in living mice. They found increases in the number of dendritic spines and in their size within 24 hours of administration of psilocybin. These changes were still present a month later. Also, mice subjected to stress showed behavioural improvements and increased neurotransmitter activity after being given psilocybin.

It may be the novel psychological effects of psilocybin itself that spurs the growth of neuronal connections, Kwan suggested. “It was a real surprise to see such enduring changes from just one dose of psilocybin,” he said. “These new connections may be the structural changes the brain uses to store new experiences.”