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Ketamine and Psychedelic Drugs Change Structure of Neurons

ummary: A new study reveals psychedelics increase dendrites, dendritic spines and synapses, while ketamine may promote neuroplasticity. The findings could help develop new treatments for anxiety, depression and other related disorders.

Source: UC Davis.

A team of scientists at the University of California, Davis is exploring how hallucinogenic drugs impact the structure and function of neurons — research that could lead to new treatments for depression, anxiety, and related disorders. In a paper published on June 12 in the journal Cell Reports, they demonstrate that a wide range of psychedelic drugs, including well-known compounds such as LSD and MDMA, increase the number of neuronal branches (dendrites), the density of small protrusions on these branches (dendritic spines), and the number of connections between neurons (synapses). These structural changes suggest that psychedelics are capable of repairing the circuits that are malfunctioning in mood and anxiety disorders.

“People have long assumed that psychedelics are capable of altering neuronal structure, but this is the first study that clearly and unambiguously supports that hypothesis. What is really exciting is that psychedelics seem to mirror the effects produced by ketamine,” said David Olson, assistant professor in the Departments of Chemistry and of Biochemistry and Molecular Medicine, who leads the research team.

Ketamine, an anesthetic, has been receiving a lot of attention lately because it produces rapid antidepressant effects in treatment-resistant populations, leading the U.S. Food and Drug Administration to fast-track clinical trials of two antidepressant drugs based on ketamine. The antidepressant properties of ketamine may stem from its tendency to promote neural plasticity — the ability of neurons to rewire their connections.

“The rapid effects of ketamine on mood and plasticity are truly astounding. The big question we were trying to answer was whether or not other compounds are capable of doing what ketamine does,” Olson said.

Psychedelics show similar effects to ketamine

Olson’s group has demonstrated that psychedelics mimic the effects of ketamine on neurons grown in a dish, and that these results extend to structural and electrical properties of neurons in animals. Rats treated with a single dose of DMT — a psychedelic compound found in the Amazonian herbal tea known as ayahuasca — showed an increase in the number of dendritic spines, similar to that seen with ketamine treatment. DMT itself is very short-lived in the rat: Most of the drug is eliminated within an hour. But the “rewiring” effects on the brain could be seen 24 hours later, demonstrating that these effects last for some time.

Fairfax | NOVA Ketamine IV Ketamine for depression | Fairfax, Va 22306 | 703-844-0184
Fairfax | NOVA Ketamine IV Ketamine for depression | Fairfax, Va 22306 | 703-844-0184

Ketamine and Psychedelic Drugs Change Structure of Neurons

Summary: A new study reveals psychedelics increase dendrites, dendritic spines and synapses, while ketamine may promote neuroplasticity. The findings could help develop new treatments for anxiety, depression and other related disorders.

Source: UC Davis.

A team of scientists at the University of California, Davis is exploring how hallucinogenic drugs impact the structure and function of neurons — research that could lead to new treatments for depression, anxiety, and related disorders. In a paper published on June 12 in the journal Cell Reports, they demonstrate that a wide range of psychedelic drugs, including well-known compounds such as LSD and MDMA, increase the number of neuronal branches (dendrites), the density of small protrusions on these branches (dendritic spines), and the number of connections between neurons (synapses). These structural changes suggest that psychedelics are capable of repairing the circuits that are malfunctioning in mood and anxiety disorders.

“People have long assumed that psychedelics are capable of altering neuronal structure, but this is the first study that clearly and unambiguously supports that hypothesis. What is really exciting is that psychedelics seem to mirror the effects produced by ketamine,” said David Olson, assistant professor in the Departments of Chemistry and of Biochemistry and Molecular Medicine, who leads the research team.

Ketamine, an anesthetic, has been receiving a lot of attention lately because it produces rapid antidepressant effects in treatment-resistant populations, leading the U.S. Food and Drug Administration to fast-track clinical trials of two antidepressant drugs based on ketamine. The antidepressant properties of ketamine may stem from its tendency to promote neural plasticity — the ability of neurons to rewire their connections.

“The rapid effects of ketamine on mood and plasticity are truly astounding. The big question we were trying to answer was whether or not other compounds are capable of doing what ketamine does,” Olson said.

Psychedelics show similar effects to ketamine

Olson’s group has demonstrated that psychedelics mimic the effects of ketamine on neurons grown in a dish, and that these results extend to structural and electrical properties of neurons in animals. Rats treated with a single dose of DMT — a psychedelic compound found in the Amazonian herbal tea known as ayahuasca — showed an increase in the number of dendritic spines, similar to that seen with ketamine treatment. DMT itself is very short-lived in the rat: Most of the drug is eliminated within an hour. But the “rewiring” effects on the brain could be seen 24 hours later, demonstrating that these effects last for some time.

image shows neurons under psychedelics and ketamine

Psychedelic drugs such as LSD and ayahuasca change the structure of nerve cells, causing them to sprout more branches and spines, UC Davis researchers have found. This could help in “rewiring” the brain to treat depression and other disorders. In this false-colored image, the rainbow-colored cell was treated with LSD compared to a control cell in blue. NeuroscienceNews.com image is credited to Calvin and Joanne Ly.

Behavioral studies also hint at the similarities between psychedelics and ketamine. In another recent paper published in ACS Chemical Neuroscience, Olson’s group showed that DMT treatment enabled rats to overcome a “fear response” to the memory of a mild electric shock. This test is considered to be a model of post-traumatic stress disorder (PTSD), and interestingly, ketamine produces the same effect. Recent clinical trials have shown that like ketamine, DMT-containing ayahuasca might have fast-acting effects in people with recurrent depression, Olson said.

These discoveries potentially open doors for the development of novel drugs to treat mood and anxiety disorders, Olson said. His team has proposed the term “psychoplastogen” to describe this new class of “plasticity-promoting” compounds.

“Ketamine is no longer our only option. Our work demonstrates that there are a number of distinct chemical scaffolds capable of promoting plasticity like ketamine, providing additional opportunities for medicinal chemists to develop safer and more effective alternatives,” Olson said.

 

Psychedelic drugs, ketamine change structure of neurons

Psychedelic drugs, ketamine change structure of neurons

Psychedelics as Possible Treatments for Depression and PTSD

A team of scientists at the University of California, Davis, is exploring how hallucinogenic drugs impact the structure and function of neurons — research that could lead to new treatments for depression, anxiety and related disorders.

In a paper published on June 12 in the journal Cell Reports, they demonstrate that a wide range of psychedelic drugs, including well-known compounds such as LSD and MDMA, increase the number of neuronal branches (dendrites), the density of small protrusions on these branches (dendritic spines) and the number of connections between neurons (synapses). These structural changes could suggest that psychedelics are capable of repairing the circuits that are malfunctioning in mood and anxiety disorders.

“People have long assumed that psychedelics are capable of altering neuronal structure, but this is the first study that clearly and unambiguously supports that hypothesis. What is really exciting is that psychedelics seem to mirror the effects produced by ketamine,” said David Olson, assistant professor in the departments of Chemistry and of Biochemistry and Molecular Medicine, who leads the research team.

Ketamine, an anesthetic, has been receiving a lot of attention lately because it produces rapid antidepressant effects in treatment-resistant populations, leading the U.S. Food and Drug Administration to fast-track clinical trials of two antidepressant drugs based on ketamine. The antidepressant properties of ketamine may stem from its tendency to promote neural plasticity — the ability of neurons to rewire their connections.

“The rapid effects of ketamine on mood and plasticity are truly astounding. The big question we were trying to answer was whether or not other compounds are capable of doing what ketamine does,” Olson said.

Psychedelics show similar effects to ketamine

Olson’s group has demonstrated that psychedelics mimic the effects of ketamine on neurons grown in a dish, and that these results extend to structural and electrical properties of neurons in animals. Rats treated with a single dose of DMT — a psychedelic compound found in the Amazonian herbal tea known as ayahuasca — showed an increase in the number of dendritic spines, similar to that seen with ketamine treatment. DMT itself is very short-lived in the rat: Most of the drug is eliminated within an hour. But the “rewiring” effects on the brain could be seen 24 hours later, demonstrating that these effects last for some time.

Behavioral studies also hint at the similarities between psychedelics and ketamine. In another recent paper published in ACS Chemical Neuroscience, Olson’s group showed that DMT treatment enabled rats to overcome a “fear response” to the memory of a mild electric shock. This test is considered to be a model of post-traumatic stress disorder, or PTSD, and interestingly, ketamine produces the same effect. Recent clinical trials have shown that like ketamine, DMT-containing ayahuasca might have fast-acting effects in people with recurrent depression, Olson said.

These discoveries potentially open doors for the development of novel drugs to treat mood and anxiety disorders, Olson said. His team has proposed the term “psychoplastogen” to describe this new class of “plasticity-promoting” compounds.

“Ketamine is no longer our only option. Our work demonstrates that there are a number of distinct chemical scaffolds capable of promoting plasticity like ketamine, providing additional opportunities for medicinal chemists to develop safer and more effective alternatives,” Olson said.

Additional co-authors on the Cell Reports “Psychedelics Promote Structural and Functional Neural Plasticity.” study are Calvin Ly, Alexandra Greb, Sina Soltanzadeh Zarandi, Lindsay Cameron, Jonathon Wong, Eden Barragan, Paige Wilson, Michael Paddy, Kassandra Ori-McKinney, Kyle Burbach, Megan Dennis, Alexander Sood, Whitney Duim, Kimberley McAllister and John Gray.

Olson and Cameron were co-authors on the ACS Chemical Neuroscience paper along with Charlie Benson and Lee Dunlap.

The work was partly supported by grants from the National Institutes of Health.

Psychedelics Promote Structural and Functional
Neural Plasticity

Below is the Intro and Discussion for the article:

Psychedelics Promote Structural and Functional neural Plasticity

Authors:

Calvin Ly, Alexandra C. Greb,
Lindsay P. Cameron, …,
Kassandra M. Ori-McKenney,
John A. Gray, David E. Olson
Correspondence
deolson@ucdavis.edu

In Brief
Ly et al. demonstrate that psychedelic
compounds such as LSD, DMT, and DOI
increase dendritic arbor complexity,
promote dendritic spine growth, and
stimulate synapse formation. These
cellular effects are similar to those
produced by the fast-acting
antidepressant ketamine and highlight
the potential of psychedelics for treating
depression and related disorders.

  • Highlights
     Serotonergic psychedelics increase neuritogenesis,
    spinogenesis, and synaptogenesis
  •  Psychedelics promote plasticity via an evolutionarily
    conserved mechanism
  •  TrkB, mTOR, and 5-HT2A signaling underlie psychedelicinduced
    plasticity
  •  Noribogaine, but not ibogaine, is capable of promoting
    structural neural plasticity

SUMMARY
Atrophy of neurons in the prefrontal cortex (PFC)
plays a key role in the pathophysiology of depression
and related disorders. The ability to promote
both structural and functional plasticity in the PFC
has been hypothesized to underlie the fast-acting
antidepressant properties of the dissociative anesthetic
ketamine. Here, we report that, like ketamine,
serotonergic psychedelics are capable of robustly
increasing neuritogenesis and/or spinogenesis both
in vitro and in vivo. These changes in neuronal structure
are accompanied by increased synapse number
and function, as measured by fluorescence microscopy
and electrophysiology. The structural changes
induced by psychedelics appear to result from stimulation
of the TrkB, mTOR, and 5-HT2A signaling
pathways and could possibly explain the clinical
effectiveness of these compounds. Our results underscore
the therapeutic potential of psychedelics
and, importantly, identify several lead scaffolds for
medicinal chemistry efforts focused on developing
plasticity-promoting compounds as safe, effective,
and fast-acting treatments for depression and
related disorders.

INTRODUCTION
Neuropsychiatric diseases, including mood and anxiety disorders,
are some of the leading causes of disability worldwide
and place an enormous economic burden on society (Gustavsson
et al., 2011; Whiteford et al., 2013). Approximately
one-third of patients will not respond to current antidepressant
drugs, and those who do will usually require at least 2–4 weeks
of treatment before they experience any beneficial effects
(Rush et al., 2006). Depression, post-traumatic stress disorder
(PTSD), and addiction share common neural circuitry (Arnsten,
2009; Russo et al., 2009; Peters et al., 2010; Russo and
Nestler, 2013) and have high comorbidity (Kelly and Daley,
2013). A preponderance of evidence from a combination of
human imaging, postmortem studies, and animal models suggests
that atrophy of neurons in the prefrontal cortex (PFC)
plays a key role in the pathophysiology of depression and
related disorders and is precipitated and/or exacerbated by
stress (Arnsten, 2009; Autry and Monteggia, 2012; Christoffel
et al., 2011; Duman and Aghajanian, 2012; Duman et al.,
2016; Izquierdo et al., 2006; Pittenger and Duman, 2008;
Qiao et al., 2016; Russo and Nestler, 2013). These structural
changes, such as the retraction of neurites, loss of dendritic
spines, and elimination of synapses, can potentially be counteracted
by compounds capable of promoting structural and
functional neural plasticity in the PFC (Castre´ n and Antila,
2017; Cramer et al., 2011; Duman, 2002; Hayley and Litteljohn,
2013; Kolb and Muhammad, 2014; Krystal et al., 2009;
Mathew et al., 2008), providing a general solution to treating
all of these related diseases. However, only a relatively small
number of compounds capable of promoting plasticity in the
PFC have been identified so far, each with significant drawbacks
(Castre´ n and Antila, 2017). Of these, the dissociative
anesthetic ketamine has shown the most promise, revitalizing
the field of molecular psychiatry in recent years.
Ketamine has demonstrated remarkable clinical potential as a
fast-acting antidepressant (Berman et al., 2000; Ionescu et al.,
2016; Zarate et al., 2012), even exhibiting efficacy in treatmentresistant
populations (DiazGranados et al., 2010; Murrough
et al., 2013; Zarate et al., 2006). Additionally, it has shown promise
for treating PTSD (Feder et al., 2014) and heroin addiction
(Krupitsky et al., 2002). Animal models suggest that its therapeutic
effects stem from its ability to promote the growth of dendritic
spines, increase the synthesis of synaptic proteins, and
strengthen synaptic responses (Autry et al., 2011; Browne and
Lucki, 2013; Li et al., 2010).

Like ketamine, serotonergic psychedelics and entactogens
have demonstrated rapid and long-lasting antidepressant and
anxiolytic effects in the clinic after a single dose (Bouso et al.,
2008; Carhart-Harris and Goodwin, 2017; Grob et al., 2011;
Mithoefer et al., 2013, 2016; Nichols et al., 2017; Sanches
et al., 2016; Oso´ rio et al., 2015), including in treatment-resistant
populations (Carhart-Harris et al., 2016, 2017; Mithoefer et al.,
2011; Oehen et al., 2013; Rucker et al., 2016). In fact, there
have been numerous clinical trials in the past 30 years examining
the therapeutic effects of these drugs (Dos Santos et al., 2016),
with 3,4-methylenedioxymethamphetamine (MDMA) recently
receiving the ‘‘breakthrough therapy’’ designation by the Food
and Drug Administration for treating PTSD. Furthermore, classical
psychedelics and entactogens produce antidepressant
and anxiolytic responses in rodent behavioral tests, such as
the forced swim test (Cameron et al., 2018) and fear extinction
learning (Cameron et al., 2018; Catlow et al., 2013; Young
et al., 2015), paradigms for which ketamine has also been shown
to be effective (Autry et al., 2011; Girgenti et al., 2017; Li et al.,
2010). Despite the promising antidepressant, anxiolytic, and
anti-addictive properties of serotonergic psychedelics, their
therapeutic mechanism of action remains poorly understood,
and concerns about safety have severely limited their clinical
usefulness.
Because of the similarities between classical serotonergic
psychedelics and ketamine in both preclinical models and clinical
studies, we reasoned that their therapeutic effects might
result from a shared ability to promote structural and functional
neural plasticity in cortical neurons. Here, we report that serotonergic
psychedelics and entactogens from a variety of chemical
classes (e.g., amphetamine, tryptamine, and ergoline) display
plasticity-promoting properties comparable to or greater than
ketamine. Like ketamine, these compounds stimulate structural
plasticity by activating the mammalian target of rapamycin
(mTOR). To classify the growing number of compounds capable
of rapidly promoting induced plasticity (Castre´ n and Antila,
2017), we introduce the term ‘‘psychoplastogen,’’ from the
Greek roots psych- (mind), -plast (molded), and -gen (producing).
Our work strengthens the growing body of literature indicating
that psychoplastogens capable of promoting plasticity
in the PFC might have value as fast-acting antidepressants
and anxiolytics with efficacy in treatment-resistant populations
and suggests that it may be possible to use classical psychedelics
as lead structures for identifying safer alternatives.

DISCUSSION
Classical serotonergic psychedelics are known to cause
changes in mood (Griffiths et al., 2006, 2008, 2011) and brain
function (Carhart-Harris et al., 2017) that persist long after the
acute effects of the drugs have subsided. Moreover, several
psychedelics elevate glutamate levels in the cortex (Nichols,
2004, 2016) and increase gene expression in vivo of the neurotrophin
BDNF as well as immediate-early genes associated with
plasticity (Martin et al., 2014; Nichols and Sanders-Bush, 2002;
Vaidya et al., 1997). This indirect evidence has led to the
reasonable hypothesis that psychedelics promote structural
and functional neural plasticity, although this assumption had
never been rigorously tested (Bogenschutz and Pommy,
2012; Vollenweider and Kometer, 2010). The data presented
here provide direct evidence for this hypothesis, demonstrating
that psychedelics cause both structural and functional changes
in cortical neurons.

Prior to this study, two reports suggested
that psychedelics might be able
to produce changes in neuronal structure.
Jones et al. (2009) demonstrated that DOI
was capable of transiently increasing the
size of dendritic spines on cortical neurons,
but no change in spine density was
observed. The second study showed
that DOI promoted neurite extension in a
cell line of neuronal lineage (Marinova
et al., 2017). Both of these reports utilized
DOI, a psychedelic of the amphetamine
class. Here we demonstrate that the ability
to change neuronal structure is not a
unique property of amphetamines like
DOI because psychedelics from the ergoline,
tryptamine, and iboga classes of compounds also promote
structural plasticity. Additionally, D-amphetamine does not increase
the complexity of cortical dendritic arbors in culture,
and therefore, these morphological changes cannot be simply
attributed to an increase in monoamine neurotransmission.
The identification of psychoplastogens belonging to distinct
chemical families is an important aspect of this work because
it suggests that ketamine is not unique in its ability to promote
structural and functional plasticity. In addition to ketamine, the
prototypical psychoplastogen, only a relatively small number of
plasticity-promoting small molecules have been identified previously.
Such compounds include the N-methyl-D-aspartate
(NMDA) receptor ligand GLYX-13 (i.e., rapastinel), the mGlu2/3
antagonist LY341495, the TrkB agonist 7,8-DHF, and the muscarinic
receptor antagonist scopolamine (Lepack et al., 2016; Castello
et al., 2014; Zeng et al., 2012; Voleti et al., 2013). We
observe that hallucinogens from four distinct structural classes
(i.e., tryptamine, amphetamine, ergoline, and iboga) are also
potent psychoplastogens, providing additional lead scaffolds
for medicinal chemistry efforts aimed at identifying neurotherapeutics.
Furthermore, our cellular assays revealed that several
of these compounds were more efficacious (e.g., MDMA) or more potent (e.g., LSD) than ketamine. In fact, the plasticity-promoting
properties of psychedelics and entactogens rivaled that
of BDNF (Figures 3A–3C and S3). The extreme potency of LSD
in particular might be due to slow off kinetics, as recently proposed
following the disclosure of the LSD-bound 5-HT2B crystal
structure (Wacker et al., 2017).
Importantly, the psychoplastogenic effects of psychedelics in
cortical cultures were also observed in vivo using both vertebrate
and invertebrate models, demonstrating that they act through an
evolutionarily conserved mechanism. Furthermore, the concentrations
of psychedelics utilized in our in vitro cell culture assays
were consistent with those reached in the brain following systemic
administration of therapeutic doses in rodents (Yang
et al., 2018; Cohen and Vogel, 1972). This suggests that neuritogenesis,
spinogenesis, and/or synaptogenesis assays performed
using cortical cultures might have value for identifying
psychoplastogens and fast-acting antidepressants. It should
be noted that our structural plasticity studies performed in vitro
utilized neurons exposed to psychedelics for extended periods
of time. Because brain exposure to these compounds is often
of short duration due to rapid metabolism, it will be interesting
to assess the kinetics of psychedelic-induced plasticity.
A key question in the field of psychedelic medicine has been
whether or not psychedelics promote changes in the density of
dendritic spines (Kyzar et al., 2017). Using super-resolution
SIM, we clearly demonstrate that psychedelics do, in fact, increase
the density of dendritic spines on cortical neurons, an effect
that is not restricted to a particular structural class of compounds.
Using DMT, we verified that cortical neuron spine
density increases in vivo and that these changes in structural
plasticity are accompanied by functional effects such as
increased amplitude and frequency of spontaneous EPSCs.

We specifically designed these experiments
to mimic previous studies of ketamine
(Li et al., 2010) so that we might
directly compare these two compounds,
and, to a first approximation, they appear
to be remarkably similar. Not only do they
both increase spine density and neuronal
excitability in the cortex, they seem to
have similar behavioral effects. We have
shown previously that, like ketamine,
DMT promotes fear extinction learning
and has antidepressant effects in the
forced swim test (Cameron et al., 2018). These results, coupled
with the fact that ayahuasca, a DMT-containing concoction, has
potent antidepressant effects in humans (Oso´ rio et al., 2015;
Sanches et al., 2016; Santos et al., 2007), suggests that classical
psychedelics and ketamine might share a related therapeutic
mechanism.
Although the molecular targets of ketamine and psychedelics
are different (NMDA and 5-HT2A receptors, respectively), they
appear to cause similar downstream effects on structural plasticity
by activating mTOR. This finding is significant because ketamine is
known to be addictive whereas many classical psychedelics are
not (Nutt et al., 2007, 2010). The exact mechanisms by which these
compounds stimulate mTOR is still not entirely understood, but
our data suggest that, at least for classical psychedelics, TrkB
and 5-HT2A receptors are involved. Although most classical psychedelics
are not considered to be addictive, there are still significant
safety concerns with their use in medicine because they
cause profound perceptual disturbances and still have the potential
to be abused. Therefore, the identification of non-hallucinogenic
analogs capable of promoting plasticity in the PFC could
facilitate a paradigm shift in our approach to treating neuropsychiatric
diseases. Moreover, such compounds could be critical to
resolving the long-standing debate in the field concerning whether
the subjective effects of psychedelics are necessary for their therapeutic
effects (Majic et al., 2015  ). Although our group is actively
investigating the psychoplastogenic properties of non-hallucinogenic
analogs of psychedelics, others have reported the therapeutic
potential of safer structural and functional analogs of ketamine
(Moskal et al., 2017; Yang et al., 2015; Zanos et al., 2016).
Our data demonstrate that classical psychedelics from several
distinct chemical classes are capable of robustly promoting the
growth of both neurites and dendritic spines in vitro, in vivo, and across species. Importantly, our studies highlight the similarities
between the effects of ketamine and those of classical serotonergic
psychedelics, supporting the hypothesis that the clinical
antidepressant and anxiolytic effects of these molecules might
result from their ability to promote structural and functional plasticity
in prefrontal cortical neurons. We have demonstrated that
the plasticity-promoting properties of psychedelics require
TrkB, mTOR, and 5-HT2A signaling, suggesting that these key
signaling hubs may serve as potential targets for the development
of psychoplastogens, fast-acting antidepressants, and anxiolytics.
Taken together, our results suggest that psychedelics
may be used as lead structures to identify next-generation neurotherapeutics
with improved efficacy and safety profiles.

Also below is a great article on DMT and neuroplasticity:

 

Dark Classics in Chemical Neuroscience N,N-Dimethyltryptamine DMT