Researcher Tony Pitts presented a study at the 2014 meeting of the International College of Neuropsychopharmacology (CINP) that described the neurobiology of an animal model of depression in rodents. In animal models, researchers provoke depression-like symptoms in animals with the hopes of finding neurobiological clues to human depression. Pitts’ studies explored the effects of acute stressors as well as more chronic long-term stressors such as learned helplessness.
In the rodents, acute stressors caused increased cell firing in the hippocampus, which caused increases in burst firing and an increase in the number of cells firing in the ventral tegmental area, which then led to increased activity in the nucleus accumbens (the brain’s reward center). However, after the stressor was over, there was an opponent process that resulted in a much more prolonged period of inhibition in the nucleus accumbens, with associated decreases in psychomotor activity and reward seeking. The rodents lost their preference for sucrose and engaged in less intracranial self-stimulation, pressing a bar to stimulate the brain pleasurably. These and other effects suggest an analogy to anhedonia (loss of pleasure in activities that were previously enjoyed), which is a key component of human depression.
In related studies, after experiencing periods of inescapable shocks, rodents developed learned helplessness, failing to avoid the area where shocks were delivered even when an exit was readily available. Rodents who had learned helplessness showed inhibited firing of cells in the ventral tegmental area, less activity in the nucleus accumbens, and apparent anhedonia. This inhibition was mediated via messages from the infralimbic prefrontal cortex (the equivalent to the subgenual cingulate cortex in humans, important for motivation) to the amygdala and then the GABAergic ventral pallidum, which decreased the number of dopaminergic cells firing in the ventral tegmental area. Blocking the amygdala input to this inhibitory pathway reversed the low dopamine firing and the anhedonia-like behaviors.
The anesthetic ketamine (which has rapid-acting antidepressant effects in humans) produces an immediate reversal of the learned helpless behavior in the rodents and increases the number of dopamine cells firing in the ventral tegmental area. Ketamine administered directly into the nucleus accumbens induces long-term potentiation (enhanced synaptic responsivity) and reverses helpless behavior and the long-term depression of neural firing that is associated with it.
Thus, when an acute stressor is over and the opponent process emerges, or following long-term chronic stressors such as learned helplessness, the excitatory path to the ventral tegmental area is absent, while the inhibitory path to the ventral tegmental area (via the infralimbic prefrontal cortex, amygdala, and ventral pallidum) predominates. Ketamine is able to re-activate the activating pathway and increase activity in the ventral tegmental area and the nucleus accumbens, changes that are associated with the reversal of learned helplessness and anhedonia.
Editor’s Note: In the previous BNN, we reported researcher Scott Russo’s findings that input from the intralaminar nucleus of the thalamus was critical to the depression-like behaviors seen in a different animal model of depression, social defeat stress, where repeated exposure to defeat by a larger, more aggressive animal produces behaviors that resemble human depression. Here in Pitts’ research, learned helplessness is induced by inescapable shocks. Both models share the finding that firing decreases in the reward area of the brain (the nucleus accumbens). However, the key part of the brain driving the low levels of activity in the nucleus accumbens and the associated depression-like behavior appear to be different in these two different models. The intralaminar nucleus of the thalamus plays a key role in the social defeat stress model, while the infralimbic cortex and the amygdala play key roles in the learned helplessness model. These data together suggest that part of the reason depression differs from person to person may be because the illness can be driven by different brain areas as a result of different kinds of stressors.
To study depression in humans, researchers look to rodents to learn more about behavior. Rodents who are repeatedly defeated by more aggressive animals often begin to exhibit behavior that resembles depression. At the 2014 meeting of the International College of Neuropsychopharmacology (CINP), researcher Andre Der-Avakian reported that in a recent study, repeated experiences of social defeat led to depressive behavior in a subgroup of animals (which he calls susceptible), but not in others (which he calls resilient). Among many biological differences, the resilient animals showed increases in neurogenesis in the dentate gyrus of the hippocampus.
Chronic treatment of the susceptible animals with the selective serotonin reuptake inhibitor (SSRI) antidepressant fluoxetine or the tricyclic antidepressant desipramine, which both increase neurogenesis, also reversed the depressive behavior in about half of the animals. A single injection of the anesthetic ketamine (which has rapid-acting antidepressant effects in humans) reversed social avoidance behavior in about 25% of the animals. One depression-like symptom was anhedonia (loss of pleasure from previously enjoyed activities), which researchers measured by observing to what extent the animals engaged in intracranial self-stimulation, pressing a bar to stimulate the brain pleasurably. The effectiveness of the drugs in inducing resilient behavior was related to the degree of anhedonia seen in the animals. The drugs worked less well in the more anhedonic animals (those who gave up the intracranial stimulation more easily, indicating that they experienced less reward from it.)
A limited number of atypical antipsychotics are approved by the Federal Drug Administration for the treatment of depression in patients with bipolar disorder. This is important to note, because the widely used traditional antidepressants that are highly effective in unipolar depression are not effective in bipolar depression. Here we review the status of the only three approved drug treatments for bipolar depression (olanzapine, quetiapine, and lurasidone) and highlight data on a promising new atypical antipsychotic, cariprazine.
At the 2014 meeting of the International College of Psychopharmacology, researcher Joseph Calabrese reviewed the efficacy of the latest atypical antipsychotic to receive FDA approval for bipolar depression, lurasidone. In monotherapy, both low (20–60mg/day) and high doses (80–120mg/day) showed higher response rates (53% and 51%, respectively) than placebo (30%). When added to either lithium or valproate, lurasidone response (57%) again exceeded that of placebo (42%). Calabrese also indicated that all of the other secondary outcome measures were also statistically significant, including score on the Clinical Global Impressions scale for bipolar disorder, time to response, percentage of remitters, time to remit, score on the Hamilton Anxiety scale, and a patient rated depression scale (QIDS).
Lurasidone is also approved for schizophrenia at higher doses (up to 160mg/day). At least twice as much of the drug is absorbed when food is in the stomach, so it is recommended that patients take it one to two hours after dinner or after a snack of 350 calories or more. The drug has an excellent side effects profile, as it is weight- and metabolically- neutral (i.e. it does not increase blood glucose, cholesterol, or triglycerides).
The atypical antipsychotic quetiapine has been FDA-approved for bipolar depression for a number of years. It consistently performs better than placebo in bipolar depression, and unlike lurasidone, quetiapine is also FDA-approved for mania, as well as for long-term prevention of both manic and depressive episodes as an adjunct to either lithium or valproate. Quetiapine is also superior to placebo for prevention of both manic and depressive episodes as a monotherapy, but is not FDA-approved for this indication. A good target dose for bipolar depression is 300mg/day of the extended release preparation taken several hours prior to bed time. Higher doses of 400 to 800mg/night are used for mania and schizophrenia. Quetiapine is also FDA-approved as an adjunct to antidepressants in unipolar depression. The drug has sedative side effects, perhaps because of its potent antihistamine effects. It can also increase weight, glucose, and cholesterol slightly more than placebo.
Olanzapine and Fluoxetine
Olanzapine (Zyprexa) and a combined preparation of olanzapine and fluoxetine (Symbyax) are also approved for bipolar depression, but many guidelines suggest that these be considered secondary treatments because they are associated with weight gain and adverse metabolic effects.
Cariprazine Effective in Bipolar Depression and Mania
At the 2014 meeting of the International College of Neuropsychopharmacology, researcher Suresh Durgam presented a poster on the first study of the atypical antipsychotic cariprazine in bipolar depression. There have also been three positive placebo-controlled studies of the drug in mania. It is a dopamine D2 and D3 partial agonist, with greater potency at the D3 receptor than the atypical antipsychotic aripiprazole (Abilify). In the large placebo-controlled eight-week study, doses of 1.5mg/day were superior to placebo, but higher (3mg) and lower doses (0.75mg) were not.
Another poster presented by the same research group also reported that augmentation of antidepressants with cariprazine in unipolar depression had results that were significantly better than placebo.
Editor’s Note: While all atypical antipsychotics that have been tested for mania have antimanic efficacy (lurasidone has not been studied in mania), their antidepressant profiles differ considerably. Only the three atypical antipsychotics noted above (olanzapine/fluoxetine, quetiapine, and lurasidone) are FDA-approved for bipolar depression, and in light of recent findings, cariprazine is likely to follow soon.
The atypical antipsychotics NOT approved for bipolar depression include: aripiprazole (Abilify), risperidone (Risperidol), and ziprasidone (Geodon), with the first atypical antipsychotic clozapine and the most recent ones not yet formally tested as far as this editor is aware, including asenapine (Saphris), iloperidone (Fanapt), and paliperidone (Invega).
Only the atypical antipsychotics aripiprazole and quetiapine are FDA-approved as adjunctive treatments to antidepressants in unipolar depression, and cariprazine may soon be added to this list.
Raphael Mechoulam, who first synthesized THC, the main ingredient in marijuana, gave the history of marijuana and its receptors in the central nervous system in a plenary talk at the 2014 meeting of the International College of Neuropsychopharmacology. In Syria hundreds of years ago the drug was named ganzigunnu, meaning “the drug that takes away the mind.” It has also been called azalla, meaning “hand of the ghost.” Among the 100 compounds in marijuana, the best-known ingredient is delta-9-tetrahydrocannabinol (delta-9 THC), which produces most of the actions of the drug. There is another active ingredient, cannabidiol (CBD), which has calming and anti-anxiety effects, but is present in very low levels.
The brain has cannabinoid receptors that respond to ingredients in marijuana in addition to other chemicals produced in the brain. They modulate calcium ions and decrease the release of many neurotransmitters.
THC acts at CB-1 receptors, producing the high. The CB-1 receptor is synthesized on demand, post-synaptically, and is transferred to the pre-synaptic terminal where it decreases calcium and transmitter release. Consistent with marijuana’s appetite-stimulating properties (“the munchies”), if the CB-1 receptor is blocked in animals, they lose their appetite and die of hunger.
There are also low levels of CB-2 receptors in the brain, whose activation does not cause a high, and whose levels may increase dramatically in pathological situations. Activation of the CB-2 receptor is anti-inflammatory and, in the same way that the immune system acts against foreign proteins, CB-2 acts as a protector against non-proteins.
CBD does not bind to any cannabinoid receptors, but its actions are blocked by cannabinoid antagonists.
There are two chemicals in the brain (endogenous ligands) that act at cannabinoid receptors—anandamide and 2-arachidonoylglycerol (2-AG). They are soluble only in lipids (not in water), and have never been given to people. In animals, 2-AG has neuroprotective effects, decreases the size of a stroke by 60%, and increases recovery from stroke.
Marijuana and CBD in particular have also had beneficial effects in people. Marijuana decreases the nausea and vomiting associated with chemotherapy in children, has anti-inflammatory effects in rheumatoid arthritis (decreasing inflammatory marker TNF alpha), and has anti-diabetes and anti-convulsant effects.
In 2012, researcher F. Markus Leweke and colleagues showed that CBD was about as effective as the atypical antipsychotic amisulpiride in alleviating the psychotic symptoms of schizophrenia. CBD’s other effects include reducing anxiety and improving psoriasis by increasing DNA methylation (Pucci et al. 2013).
It seems possible that some of these myriad effects of marijuana and endogenous ligands at CB receptors could be exploited for clinical therapeutics, as Mechoulam endorses, but when and how that will take place remains an unanswered question.
Editor’s Note: Despite all these potential positives of CBD, it should be noted that its levels are very low in marijuana, and that heavy smoking of marijuana has substantial adverse effects. These include low motivation, a doubling of the risk of psychosis, a hastening of the onset of bipolar disorder and schizophrenia, and cognitive impairment, as well as some changes in brain structure seen via magnetic resonance imaging (MRI). It may be becoming legal in many states, but is a bad idea for those at high risk for mood, anxiety, or bipolar disorders or for schizophrenia.
In the clinic of researcher Eduard Vieta in Barcelona, a study was recently completed showing that antidepressant use in patients with bipolar disorder (where antidepressants are not effective) had dropped from around 50-60% in 2007 (in Baldessarini’s study) to about 30% in 2013 and 2014, and conversely lithium, anticonvulsants, and atypical antipsychotics, which have much more evidence of efficacy, were all used much more often, or about 60% of the time.
Editor’s Note: Hopefully these data from Spain will soon be matched by similar data in the US showing that evidenced-based treatments for bipolar depression are in fact being used instead of antidepressants, which can have adverse effects, such as switching into mania or cycle acceleration.
At the 2014 meeting of the International College of Neuropsychopharmacology, researcher Rieva et al. reported that 60% of bipolar patients with comorbid alcohol abuse have attempted suicide, and 48% of bipolar patients with cocaine abuse have attempted suicide. Thus, both of these comorbidities deserve specific attention and treatment. Unfortunately there are currently no Federal Drug Administration–approved drugs for bipolar patients with these comorbidities. The most promising treatments, based on data in patients with primary addictions, are the nutritional supplement N-acetylcysteine and topiramate, which have both performed better than placebo in studies of alcohol and cocaine abuse disorders.
In a symposium at the 2014 meeting of the International College of Neuropsychopharmacology, four researchers shared insights on children who are at high risk for bipolar disorder because they have a parent with the disorder.
Researcher John Nurnberger has been studying 350 children of parents with bipolar disorder in the US and 141 control children of parents with no major psychiatric disorder, following the participants into adolescence. He found a major affective disorder in 23.4% of the children with parents who have bipolar disorder and 4.4% of the controls. Of the at-risk children, 8.5% had a bipolar diagnosis versus 0% of the controls.
Nurnberger found that disruptive behavior disorders preceded the onset of mood disorders, as did anxiety disorders. These diagnoses predicted the later onset of bipolar disorder in the at-risk children, but not in the controls. A mood disorder in early adolescence predicted a substance abuse disorder later in adolescence among those at risk.
In genome-wide association studies, the genes CACNA1C and ODZ4 are consistently associated with risk of bipolar disorder, but with a very small effect size. Therefore, Nurnberger used 33 different gene variants to generate a total risk score and found that this measure was modestly effective in identifying relative risk of developing bipolar disorder. He hopes that using this improved risk calculation along with family history and clinical variables will allow better prediction of the risk of bipolar onset in the near future.
Researcher Ann Duffy reported on her Canadian studies of children who have a parent with bipolar disorder and thus are at high risk for developing the disorder. In contrast to the studies of Nurnberger et al. and many others in American patients, she found almost no childhood onset of bipolar disorder before late adolescence or early adulthood. She found that anxiety disorders emerge first, followed by depression, and then only much later bipolar disorder. Bipolar disorder occurred with comorbid substance abuse disorders in only about 10-20% of cases in 1975, but substance abuse increased to 50% of bipolar cases in 2005. The incidence of comorbid substance disorder and the year at observation correlated strongly, indicating a trend toward increased substance abuse over the 30-year period.
Duffy found that having parents who were ill as opposed to recovered was associated with a more rapid onset of mood disorder in the offspring, usually in early adulthood. Duffy emphasized the need to intervene earlier in children of parents with bipolar disorder, but this is rarely done in clinical practice. Read more
In an earlier BNN we mistakenly attributed the protocol developed by David Bakish, a renowned Canadian psychopharmacologist, to another doctor named Vaishali P. Bakshi. Our apologies to both individuals.
Dr. David Bakish is Medical Director at the Ottawa Psychopharmacology Clinic and a Former Professor of Psychiatry at the University of Ottawa in Ottawa, Ontario. He shared with this editor his novel treatment strategy for patients with exceptionally profound degrees of post-traumatic stress disorder (PTSD), which, particularly among military veterans, can be compounded by traumatic brain injury. He has had a distinguished academic career with an extensive CV and credentials including membership in the International College of Neuropsychopharmacology (CINP), the Royal College of Physicians and Surgeons of Canada, and the Canadian and European Colleges of Neuropsychopharmacology. Most importantly he has had great success in treating large numbers of patients with severe PTSD. Treatment options based on placebo-controlled clinical trials are sometimes insufficient for the treatment of seriously ill patients. FDA-approved treatment for PTSD consists of serotonin-selective antidepressants, while exposure therapies (in which the patient is gradually exposed to more of the stimuli that triggered symptoms) are the recommended psychotherapy, but these methods often leave patients highly disabled. We relay Dr. Bakish’s treatment strategy with several caveats.
Most of Bakish’s suggestions are “off-label” treatments for the treatment of PTSD or traumatic brain injury, i.e. treatments that are not FDA-approved for these purposes. In some of these instances, there is no controlled research to support the use of these drugs in patients with PTSD. Thus the ideas noted here are anecdotal, based on his personal experience, and have not been tested in controlled clinical trials. Accordingly, patients with their physicians must make their own decisions about any of the strategies reported in this or other issues of the BNN.
Bakish’s typical treatment algorithm goes well beyond the usual treatment guidelines to find solutions for hard-to-treat patients. Bakish first addresses sleep disturbance, which is almost universal in PTSD. He suggests the anticonvulsant levetiracetam (Keppra), for the hyperarousal and sleep disorder. He uses starting at doses of 125mg per night and increases by 125mg every three weeks. Read more
Researcher Murray Raskind has conducted a series of controlled studies, all with the same conclusion—the alpha-1 antagonist prazosin, used to treat high blood pressure, works for post-traumatic stress disorder (PTSD), especially in preventing nightmares. In his latest study, 67 soldiers were randomly assigned to either prazosin or placebo for 15 weeks. Doses were slowly titrated (to avoid low blood pressure and dizziness) to a possible maximum dose of 5mg at midmorning and 20mg at bedtime for men and 2mg at midmorning and 10mg at bedtime for women over a period of 6 weeks, based on whether the patients continued to experience nightmares.
Raskind found that prazosin was effective for trauma nightmares, sleep quality, global functioning, total score on a scale of PTSD symptoms, and hyperarousal. Side effects were minimal. Raskin concluded that prazosin “is effective for combat-related PTSD with trauma nightmares in active-duty soldiers, and benefits are clinically meaningful.”
At the 2014 meeting of the International College of Neuropsychopharmacology, researcher Joseph Zohar presented a poster on the effects of early post-stressor intervention with the drug agomelatine in animals who showed behavioral and molecular responses to stress that served as a model of post-traumatic stress disorder (PTSD).
Agomelatine is available clinically as an antidepressant in Canada and Europe (but not in the US), and can also reduce anxiety and re-synchronize circadian rhythms. Agomelatine is a melatonin (MT1/MT2) receptor agonist and a serotonin 5HT2C antagonist (increasing dopamine and norepinephrine in the frontal cortex).
Long-term behavioral, molecular and structural effects of the drug were assessed in animals. Adult male Sprague-Dawley rats were exposed to the scent of a predator for 10 minutes, and one hour later they were treated acutely for this stress with agomelatine (50mg/kg i.p.) or placebo.
Agomelatine decreased the prevalence of extreme, PTSD-like behavioral and molecular responses to the stressor, such as freezing in place and increased corticosterone. Agomelatine also normalized decreases in brain-derived neurotrophic factor (BDNF) observed in the dentate gyrus of the hippocampus, the cortex (layer III), and the basolateral amygdala. In line with this, agomelatine-treated stressed animals displayed significantly increased number and length of dendrites at glutamate synapses in the hippocampus (including the dentate gyrus and CA1) and reversed the hippocampal neuronal retraction observed in the rats who were given the placebo.
Agomelatine also affected the expression of clock genes in the rats, which regulate biorhythms. These genes lead to the production of the major clock gene proteins Per1 and Per2. Agomelatine normalized Per1 increases in three parts of the brain: the CA3, another glutamate synapse near the dentate gyrus; the suprachiasmatic nucleus over the optic chiasm, important for circadian rhythms; and the basolateral amygdala. Per2, a protein that also drives circadian rhythms, increased in the CA1 synapse of the hippocampus, the suprachiasmatic nucleus and the basolateral amygdala of the stressed rats.
The researchers concluded that the data provide “initial evidence that a single dose of agomelatine administered in the acute aftermath of stress promotes recovery while promoting enhanced neuronal and synaptic plasticity and connectivity in the secondary prevention of PTSD in this model.”