My research group has been studying the effects of psychedelics on neuronal structure and function, and we found that these compounds cause neurons to grow. A lot. Many of these compounds are well-known and include lysergic acid diethylamide (LSD), psilocin (from magic mushrooms), N,N-dimethyltryptamine (DMT, from ayahuasca) and 3,4-methylenedioxymethamphetamine (MDMA, aka ecstasy).
These are among the most powerful drugs known to affect brain function, and our research shows that they can alter the structure of the brain as well. Changes in neuronal structure are important because they can impact how the brain is wired, and consequently, how we feel, think and behave.
Prior to our study, there were relatively few compounds known to have such drastic and rapid effects on neuronal structure. One of those compounds was ketamine – a dissociative anesthetic and quite possibly the best fast-acting antidepressant that we have available to us at the moment.
If you think of a neuron like a tree, then its dendrites would be the large branches, and its dendritic spines – which receive signals from other neurons – would be the small branches. Some of these small branches might have leaves, or synapses in the case of a neuron. In fact, neuroscientists often use terms like “arbor” and “pruning” much like a horticulturist would. When we grew neurons in a dish – which is not unlike growing a plant in a pot – and fed them psychedelic compounds, the neurons sprouted more dendritic branches, grew more dendritic spines, and formed more connections with neighboring neurons.
Thanks to studies on ketamine, slow-acting antidepressants and chronic stress models of depression, scientists now know that depression is not simply the result of a “chemical imbalance,” as pharmaceutical companies like to suggest. It is far more complicated and involves structural changes in key neural circuits that regulate emotion, anxiety, memory and reward.
One of the hallmarks of depression is the atrophy of neurons in the prefrontal cortex – a region of the brain that controls anxiety and regulates mood among other things. Basically, these branches and spines shrivel up, disconnecting from other neurons in the brain. One hypothesis for why ketamine is so effective is because it can rapidly regrow the arbors and spines of these critical neurons.