Psilocybin Induces Long Lasting Modifications to Brain Connections
Psilocybin and Dendritic Spines
In this video, Samuel Costella, a neuropharmacologist, discusses a recent study investigating the effects of psilocybin on dendritic spines in rodents. Psilocybin is a classical psychedelic that has shown promise in the treatment of depression and may promote synaptic plasticity.
Dendritic Spines and Neurons
- Dendritic spines are parts of neurons that receive chemical signals from other neurons.
- Neurons have axons and dendrites. Once a neuron gets excited enough, it fires an action potential resulting in an electrical signal that propagates away from the cell body through a projection of the neuron known as the axon.
- Ultimately, it reaches the axon terminals which are known as synaptic boutons where it also triggers the release of neurotransmitters to the synaptic cleft.
- The postsynaptic part or the part that receives the chemical neurotransmitters belongs to the dendrite of another neuron and it is called the dendritic spine.
Plasticity and Depression
- Changes in synaptic structure including dendritic spines and synapse formation are crucial in bringing about adaptiveness or plasticity of the brain.
- A synaptic atrophy of prefrontal cortex is often seen in patients suffering from major depression similar deficits emerge in brains of rodents subjected to chronic stress.
- Rapid acting antidepressants like ketamine have been shown to promote structural plasticity and reverse synaptic deficits caused by chronic stress through an increase in rate of spine formation.
Psilocybin and Dendritic Spines
- A single dose of psilocybin is capable of facilitating the growth of dendritic spines in the layer 5 neurons of the medial frontal cortex of the mouse.
- Approximately half of the new spines remained stable for 7 days and 30 to 40 percent remain persistent after 34 days suggesting that functional synapses are also formed.
- The authors suggest that these persistent changes could underlie the positive effects of psychedelics in the treatment of depression.
- The blockade of 5ht2a receptors which are thought to be primary pharmacological targets of classical psychedelics would modify effects on dendritic spines. However, catancerin pretreatment was not sufficient to abolish structural remodeling.