Yohimbine use in a natural setting: effects on posttraumatic stress disorder

Pharmacology of Herbal Sexual Enhancers: A Review of Psychiatric and Neurological Adverse Effects

Sexual enhancers increase sexual potency, sexual pleasure, or libido. Substances increasing libido alter the concentrations of specific neurotransmitters or sex hormones in the central nervous system. Interestingly, the same pathways are involved in the mechanisms underlying many psychiatric and neurological disorders, and adverse reactions associated with the use of aphrodisiacs are strongly expected. However, sexual enhancers of plant origin have gained popularity over recent years, as natural substances are often regarded as a safer alternative to modern medications and are easily acquired without prescription. We reviewed the psychiatric and neurological adverse effects associated with the consumption of herbal aphrodisiacs Areca catechu L., Argemone Mexicana L., Citrus aurantium L., Eurycoma longifolia Jack., Lepidium meyenii Walp., Mitragyna speciosa Korth., Panax ginseng C. A. Mey, Panax quinquefolius L., Pausinystalia johimbe (K. Schum.) Pierre ex Beille, Piper methysticum G. Forst., Ptychopetalum olacoides Benth., Sceletium tortuosum (L.) N. E. Brown, Turnera diffusa Willd. ex. Schult., Voacanga africana Stapf ex Scott-Elliot, and Withania somnifera (L.) Dunal. A literature search was conducted on the PubMed, Scopus, and Web of Science databases with the aim of identifying all the relevant articles published on the issue up to June 2020. Most of the selected sexual enhancers appeared to be safe at therapeutic doses, although mild to severe adverse effects may occur in cases of overdosing or self-medication with unstandardized products. Drug interactions are more concerning, considering that herbal aphrodisiacs are likely used together with other plant extracts and/or pharmaceuticals. However, few data are available on the side effects of several plants included in this review, and more clinical studies with controlled administrations should be conducted to address this issue.

Alpha2-adrenergic dysregulation in congenic DxH recombinant inbred mice selectively bred for a high fear-sensitized (H-FSS) startle response

Patients with anxiety disorders and posttraumatic stress disorder (PTSD) exhibit exaggerated fear responses and noradrenergic dysregulation. Fear-related responses to α₂-adrenergic challenge were therefore studied in DxH C3H/HeJ-like recombinant inbred (C3HLRI) mice, which are a DBA/2J-congenic strain selectively bred for a high fear-sensitized startle (H-FSS). C3HLRI mice showed an enhanced acoustic startle response and immobility in the forced swim test compared to DBA/2J controls. The α₂-adrenoceptor antagonist yohimbine (Yoh; 5.0 mg/kg) induced an anxiogenic and the α₂-adrenoceptor agonist clonidine (Clon; 0.1 mg/kg) an anxiolytic effect in the open field (OF) in C3HLRI but not DBA/2J mice. In auditory fear-conditioning, Yoh (5.0 mg/kg)-treated C3HLRI mice showed higher freezing during fear recall and extinction learning than DBA/2J mice, and a higher ceiling for the Yoh-induced deficit in fear extinction. No strain differences were observed in exploration-related anxiety/spatial learning or the Clon-induced (0.1 mg/kg) corticosterone surge. A global analysis of the behavioral profile of the two mouse strains based on observed and expected numbers of significant behavioral outcomes indicated that C3HLRI mice showed significantly more often fear- and stress-related PTSD-like behaviors than DBA/2J controls. The analysis of the robustness of significant outcomes based on false discovery rate (FDR) thresholds confirmed significant differences for the strain-Yoh-interactions in the OF center and periphery, the Yoh-induced general extinction deficit, strain differences in conditioned fear levels, and at the dose of 5.0 mg/kg for the Yoh-induced ceiling in freezing levels among others. The current findings are consistent with previous observations showing alterations in the central noradrenergic system of C3HLRI mice (Browne et al., 2014, Stress 17:471-83). Based on their behavioral profile and response to α₂-adrenergic stimulation, C3HLRI mice are a valuable genetic model for studying adrenergic mechanisms of anxiety disorders and potentially also of PTSD.

Sex differential effect of dexmedetomidine on fear memory extinction and anxiety behavior in adolescent rats

Exposure to stressful stimuli, including fear and anxiety, modulates the central noradrenergic system. Dexmedetomidine is a commonly used α2-adrenoreceptor agonist. Because the effect of fear acquisition varies between sexes, the present study was designed to investigate sex-related differences in the effects of dexmedetomidine on fear memory and anxiety-like behavior. We conducted a fear test and an elevated plus maze test in 6-8-week-old male and female rats. Two doses of dexmedetomidine (20 and 40 μg/kg) were injected intraperitoneally three times at 24 h intervals after the tests: after fear expression, extinction 1, and extinction 2. The repeated administration of dexmedetomidine showed significant acceleration of fear memory extinction in female rats but not in male rats; the effect increased proportionally to concentrations of dexmedetomidine. Compared to male rats, female rats treated with both concentrations of dexmedetomidine showed significant anxiolytic behavior after 1 week. Dexmedetomidine accelerated the fear memory extinction and reduced anxiety; it was more effective in female rats than in male rats. Our results suggest that dexmedetomidine may exert protective effects against fear-related and anxiety-like behaviors in rats with fear memory after repeated administration, and the sex-specific effects of dexmedetomidine should be considered.

Noradrenergic Modulation of Fear Conditioning and Extinction

The locus coeruleus norepinephrine (LC-NE) system plays a broad role in learning and memory. Here we begin with an overview of the LC-NE system. We then consider how both direct and indirect manipulations of the LC-NE system affect cued and contextual aversive learning and memory. We propose that NE dynamically modulates Pavlovian conditioning and extinction, either promoting or impairing learning aversive processes under different levels of behavioral arousal. We suggest that under high levels of stress (e.g., during/soon after fear conditioning) the locus coeruleus (LC) promotes cued fear learning by enhancing amygdala function while simultaneously blunting prefrontal function. Under low levels of arousal, the LC promotes PFC function to promote downstream inhibition of the amygdala and foster the extinction of cued fear. Thus, LC-NE action on the medial prefrontal cortex (mPFC) might be described by an inverted-U function such that it can either enhance or hinder learning depending on arousal states. In addition, LC-NE seems to be particularly important for the acquisition, consolidation and extinction of contextual fear memories. This may be due to dense adrenoceptor expression in the hippocampus (HPC) which encodes contextual information, and the ability of NE to regulate long-term potentiation (LTP). Moreover, recent work reveals that the diversity of LC-NE functions in aversive learning and memory are mediated by functionally heterogeneous populations of LC neurons that are defined by their projection targets. Hence, LC-NE function in learning and memory is determined by projection-specific neuromodulation that accompanies various states of behavioral arousal.

Differences in trait impulsivity do not bias the response to pharmacological drug challenge in the rat five-choice serial reaction time task

RATIONALE

Maladaptive impulsivity is symptomatic of several neuropsychiatric disorders including schizophrenia, attention-deficit hyperactivity disorder (ADHD), and substance abuse disorders; paradigms designed to assess the underlying neurobiology of this behavior are essential for the discovery of novel therapeutic agents. Various models may be used to assess impulsivity as measured by the five-choice serial reaction time task (5-CSRTT), including variable inter-trial interval (ITI) sessions, the selection of extreme high and low impulsivity phenotypes from a large outbred population of rats, as well as pharmacological challenges.

OBJECTIVES

The aim of this study is to evaluate if pharmacological challenge models for impulsivity are biased by underlying differences in impulsivity phenotype.

METHODS

Extreme high and low impulsivity phenotypes were selected in the 5-CSRTT, and dose-dependent effects of various pharmacological challenges, namely MK-801, yohimbine, and cocaine, were evaluated on task performance, specifically accuracy and premature responses.

RESULTS

All three compounds increased premature responding, while a decrease in attentional performance occurred following MK-801 and yohimbine administration. No differences in drug-induced impulsivity between rats selected for high or low impulsivity or in parameters indicative of attentional performance could be determined.

CONCLUSIONS

Our findings indicate that different pharmacological challenges increase impulsivity on the 5-CSRTT, with modest effects on attention. These effects were not influenced by underlying differences in impulsivity phenotype, which is an important prerequisite to reliably use these challenge models to screen and profile compounds with putative anti-impulsive characteristics.

Monoamine Oxidase A Gene Methylation and Its Role in Posttraumatic Stress Disorder: First Evidence from the South Eastern Europe (SEE)-PTSD Study

BACKGROUND

Posttraumatic stress disorder is characterized by an overactive noradrenergic system conferring core posttraumatic stress disorder symptoms such as hyperarousal and reexperiencing. Monoamine oxidase A is one of the key enzymes mediating the turnover of noradrenaline. Here, DNA methylation of the monoamine oxidase A gene exonI/intronI region was investigated for the first time regarding its role in posttraumatic stress disorder risk and severity.

METHODS

Monoamine oxidase A methylation was analyzed via direct sequencing of sodium bisulfite-treated DNA extracted from blood cells in a total sample of N=652 (441 male) patients with current posttraumatic stress disorder, patients with remitted posttraumatic stress disorder, and healthy probands (comparison group) recruited at 5 centers in Bosnia-Herzegovina, Croatia, and the Republic of Kosovo. Posttraumatic stress disorder severity was measured by means of the Clinician-Administered Posttraumatic Stress Disorder Scale and its respective subscores representing distinct symptom clusters.

RESULTS

In the male, but not the female sample, patients with current posttraumatic stress disorder displayed hypermethylation of 3 CpGs (CpG3=43656362; CpG12=43656514; CpG13=43656553, GRCh38.p2 Assembly) as compared with remitted Posttraumatic Stress Disorder patients and healthy probands. Symptom severity (Clinician-Administered Posttraumatic Stress Disorder Scale scores) in male patients with current posttraumatic stress disorder significantly correlated with monoamine oxidase A methylation. This applied particularly to symptom clusters related to reexperiencing of trauma (cluster B) and hyperarousal (cluster D).

CONCLUSIONS

The present findings suggest monoamine oxidase A gene hypermethylation, potentially resulting in enhanced noradrenergic signalling, as a disease status and severity marker of current posttraumatic stress disorder in males. If replicated, monoamine oxidase A hypermethylation might serve as a surrogate marker of a hyperadrenergic subtype of posttraumatic stress disorder guiding personalized treatment decisions on the use of antiadrenergic agents.

Disciplined sleep for healthy living: Role of noradrenaline

Sleep is essential for maintaining normal physiological processes. It has been broadly divided into rapid eye movement sleep (REMS) and non-REMS (NREMS); one spends the least amount of time in REMS. Sleep (both NREMS and REMS) disturbance is associated with most altered states, disorders and pathological conditions. It is affected by factors within the body as well as the environment, which ultimately modulate lifestyle. Noradrenaline (NA) is one of the key molecules whose level increases upon sleep-loss, REMS-loss in particular and it induces several REMS-loss associated effects and symptoms. The locus coeruleus (LC)-NAergic neurons are primarily responsible for providing NA throughout the brain. As those neurons project to and receive inputs from across the brain, they are modulated by lifestyle changes, which include changes within the body as well as in the environment. We have reviewed the literature showing how various inputs from outside and within the body integrate at the LC neuronal level to modulate sleep (NREMS and REMS) and vice versa. We propose that these changes modulate NA levels in the brain, which in turn is responsible for acute as well as chronic psycho-somatic disorders and pathological conditions.

The centrality of fear extinction in linking risk factors to PTSD: A narrative review

Recent prospective studies in emergency services have identified impaired fear extinction learning and memory to be a significant predictor of Posttraumatic Stress Disorder (PTSD), complementing a wealth of cross-sectional evidence of extinction deficits associated with the disorder. Additional fields of research show specific risk factors and biomarkers of the disorder, including candidate genotypes, stress and sex hormones, cognitive factors, and sleep disturbances. Studies in mostly nonclinical populations also reveal that the aforementioned factors are involved in fear extinction learning and memory. Here, we provide a comprehensive narrative review of the literature linking PTSD to these risk factors, and linking these risk factors to impaired fear extinction. On balance, the evidence suggests that fear extinction may play a role in the relationship between risk factors and PTSD. Should this notion hold true, this review carries important implications for the improvement of exposure-based treatments, as well as strategies for the implementation of treatment.

Predator Stress-Induced CRF Release Causes Enduring Sensitization of Basolateral Amygdala Norepinephrine Systems that Promote PTSD-Like Startle Abnormalities

The neurobiology of post-traumatic stress disorder (PTSD) remains unclear. Intense stress promotes PTSD, which has been associated with exaggerated startle and deficient sensorimotor gating. Here, we examined the long-term sequelae of a rodent model of traumatic stress (repeated predator exposure) on amygdala systems that modulate startle and prepulse inhibition (PPI), an operational measure of sensorimotor gating. We show in rodents that repeated psychogenic stress (predator) induces long-lasting sensitization of basolateral amygdala (BLA) noradrenergic (NE) receptors (α1) via a corticotropin-releasing factor receptor 1 (CRF-R1)-dependent mechanism, and that these CRF1 and NE α1 receptors are highly colocalized on presumptive excitatory output projection neurons of the BLA. A profile identical to that seen with predator exposure was produced in nonstressed rats by intra-BLA infusions of CRF (200 ng/0.5 μl), but not by repeated NE infusions (20 μg/0.5 μl). Infusions into the adjacent central nucleus of amygdala had no effect. Importantly, the predator stress- or CRF-induced sensitization of BLA manifested as heightened startle and PPI deficits in response to subsequent subthreshold NE system challenges (with intra-BLA infusions of 0.3 μg/0.5 μl NE), up to 1 month after stress. This profile of effects closely resembles aspects of PTSD. Hence, we reveal a discrete neural pathway mediating the enhancement of NE system function seen in PTSD, and we offer a model for characterizing potential new treatments that may work by modulating this BLA circuitry.

SIGNIFICANCE STATEMENT

The present findings reveal a novel and discrete neural substrate that could underlie certain core deficits (startle and prepulse inhibition) that are observed in post-traumatic stress disorder (PTSD). It is shown here that repeated exposure to a rodent model of traumatic stress (predator exposure) produces a long-lasting sensitization of basolateral amygdala noradrenergic substrates [via a corticotropin-releasing factor (CRF)-dependent mechanism] that regulate startle, which is exaggerated in PTSD. Moreover, it is demonstrated that the sensitized noradrenergic receptors colocalize with CRF1 receptors on output projection neurons of the basolateral amygdala. Hence, this stress-induced sensitization of noradrenergic receptors on basolateral nucleus efferents has wide-ranging implications for the numerous deleterious sequelae of trauma exposure that are seen in multiple psychiatric illnesses, including PTSD.

Animal models in translational studies of PTSD

Understanding the neurobiological mechanisms of post-traumatic stress disorder (PTSD) is of vital importance for developing biomarkers and more effective pharmacotherapy for this disorder. The design of bidirectional translational studies addressing all facets of PTSD is needed. Animal models of PTSD are needed not only to capture the complexity of PTSD behavioral characteristics, but also to address experimentally the influence of variety of factors which might determine an individual's vulnerability or resilience to trauma, e.g., genetic predisposition, early-life experience and social support. The current review covers recent translational approaches to bridge the gap between human and animal PTSD research and to create a framework for discovery of biomarkers and novel therapeutics.

Differential effectiveness of tianeptine, clonidine and amitriptyline in blocking traumatic memory expression, anxiety and hypertension in an animal model of PTSD

Individuals exposed to life-threatening trauma are at risk for developing post-traumatic stress disorder (PTSD), a debilitating condition that involves persistent anxiety, intrusive memories and several physiological disturbances. Current pharmacotherapies for PTSD manage only a subset of these symptoms and typically have adverse side effects which limit their overall effectiveness. We evaluated the effectiveness of three different pharmacological agents to ameliorate a broad range of PTSD-like symptoms in our established predator-based animal model of PTSD. Adult male Sprague-Dawley rats were given 1-h cat exposures on two occasions that were separated by 10 days, in conjunction with chronic social instability. Beginning 24 h after the first cat exposure, rats received daily injections of amitriptyline, clonidine, tianeptine or vehicle. Three weeks after the second cat exposure, all rats underwent a battery of behavioral and physiological tests. The vehicle-treated, psychosocially stressed rats demonstrated a robust fear memory for the two cat exposures, as well as increased anxiety expressed on the elevated plus maze, an exaggerated startle response, elevated heart rate and blood pressure, reduced growth rate and increased adrenal gland weight, relative to the vehicle-treated, non-stressed (control) rats. Neither amitriptyline nor clonidine was effective at blocking the entire cluster of stress-induced sequelae, and each agent produced adverse side effects in control subjects. Only the antidepressant tianeptine completely blocked the effects of psychosocial stress on all of the physiological and behavioral measures that were examined. These findings illustrate the differential effectiveness of these three treatments to block components of PTSD-like symptoms in rats, and in particular, reveal the profile of tianeptine as the most effective of all three agents.

Current status on behavioral and biological markers of PTSD: a search for clarity in a conflicting literature

Extensive research has identified stereotypic behavioral and biological abnormalities in post-traumatic stress disorder (PTSD), such as heightened autonomic activity, an exaggerated startle response, reduced basal cortisol levels and cognitive impairments. We have reviewed primary research in this area, noting that factors involved in the susceptibility and expression of PTSD symptoms are more complex and heterogeneous than is commonly stated, with extensive findings which are inconsistent with the stereotypic behavioral and biological profile of the PTSD patient. A thorough assessment of the literature indicates that interactions among myriad susceptibility factors, including social support, early life stress, sex, age, peri- and post-traumatic dissociation, cognitive appraisal of trauma, neuroendocrine abnormalities and gene polymorphisms, in conjunction with the inconsistent expression of the disorder across studies, confounds attempts to characterize PTSD as a monolithic disorder. Overall, our assessment of the literature addresses the great challenge in developing a behavioral and biomarker-based diagnosis of PTSD.

A rodent "self-report" measure of methamphetamine craving? Rat ultrasonic vocalizations during methamphetamine self-administration, extinction, and reinstatement

Rats emit ultrasonic vocalizations (USVs) in a variety of contexts, and it is increasingly clear that USVs reflect more complex information than mere positive and negative affect states. We sought to examine USVs in a common model of addiction and relapse, the self-administration/reinstatement paradigm, in order to gain insight into subjective states experienced by rats during various types of methamphetamine seeking. We measured three subtypes of "50kHz" USVs [flats, trills, and non-trill frequency modulated (FM) USVs], as well as long and short duration "22kHz" USVs, during self-administration and extinction training, and during reinstatement elicited by cues, a methamphetamine prime, cues+prime, or the pharmacological stressor yohimbine. During self-administration and extinction, rats emitted many flats and FMs, (and short duration "22kHz" USVs on day 1 of self-administration), but few trills. In contrast, methamphetamine priming injections potently enhanced FMs and trills, and trill production was correlated with the degree of methamphetamine+cue-elicited reinstatement. Cues alone yielded increases only in flat USVs during reinstatement, though a subset of rats displaying strong cue-induced reinstatement also emitted long duration, aversion-related "22kHz" USVs. Although yohimbine administration caused reinstatement, it did not induce "22kHz" USVs in methamphetamine-experienced or methamphetamine-naïve rats (unlike footshock stress, which did induce long duration "22kHz" USVs). These findings demonstrate heterogeneity of rat USVs emitted during different types of methamphetamine seeking, and highlight their potential usefulness for gaining insight into the subjective states of rats in rodent models of drug addiction and relapse.

Emotional variability and sustained arousal during exposure

BACKGROUND AND OBJECTIVES

In traditional exposure therapy for phobias and anxiety disorders, reduction of fear responding is used as an index of learning. However, recent evidence in animal models suggests that sustained arousal and enhanced fear responding throughout exposure may actually predict better long-term outcomes (Rescorla, 2000).

METHODS

The effects of sustained arousal during exposure were investigated in a clinical analog sample of 59 participants fearful of public speaking. Participants completed exposure with or without the presence of additional excitatory stimuli which were intended to enhance arousal and fear responding throughout exposure.

RESULTS

Group assignment (exposure versus exposure with additional excitatory stimuli) did not significantly predict outcome at 1-week follow-up testing, as measured physiologically, subjectively, and behaviorally. A set of regression analyses investigating whether any exposure process measures predicted outcome indicated that sustained arousal throughout exposure as well as variability in subjective fear responding throughout exposure (e.g., Kircanski et al., 2011) predicted lower levels of fear at follow-up testing (p < 0.05; p < 0.001) after controlling for demographic variables as well as pre-exposure fear levels.

LIMITATIONS

The excitatory stimuli used failed to produce the intended effects. However, some participants did maintain elevated arousal throughout exposure and this predicted better outcomes at 1-week follow-up testing.

CONCLUSIONS

Sustained arousal throughout exposure as well as variability in subjective fear responding during exposure may be better predictors of long-term outcomes than habituation of fear across exposure.

Pharmacological treatment of PTSD - established and new approaches

A large proportion of humans will experience a traumatic event at least once in their lifetime, with up to 10% then going on to developing posttraumatic stress disorder (PTSD). In this review we will discuss established pharmacological interventions for PTSD as well as highlight novel therapeutic strategies undergoing extensive pre-clinical research as well as ongoing clinical research. Such strategies include prophylactic treatments and use of pharmacotherapy as adjunctive treatment with established trauma-focused psychological therapies. These potential treatment approaches include modulation of stress effects on memory consolidation after trauma (e.g., glucocorticoid, corticotropin-releasing factor and norepinephrine signalling modulators), as well as putative cognitive enhancers that target mechanisms of conditioned fear extinction and reconsolidation (e.g., glucocorticoid receptor modulators and modulators of glutamate signalling such as positive allosteric modulators of glutamate receptors, glycine transporter inhibitors, or glycine agonists). We will discuss evidence for and against these potential novel treatment strategies and their limitations. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.

The role of central noradrenergic dysregulation in anxiety disorders: evidence from clinical studies

The nature of the noradrenergic dysregulation in clinical anxiety disorders remains unclear. In panic disorder, the predominant view has been that central noradrenergic neuronal networks and/or the sympathetic nervous system was normal in patients at rest, but hyper-reactive to specific stimuli, for example carbon dioxide. These ideas have been extended to other anxiety disorders, which share with panic disorder characteristic subjective anxiety and physiological symptoms of excess sympathetic activity. For example, Generalized Anxiety Disorder is characterized by chronic free-floating anxiety, muscle tension, palpitation and insomnia. It has been proposed that there is chronic central hypersecretion of noradrenaline in Generalized Anxiety Disorder, with consequent hyporesponsiveness of central post-synaptic receptors. With regards to other disorders, it has been suggested that there is noradrenergic involvement or derangement, but a more specific hypothesis has not been enunciated. This paper reviews the evidence for noradrenergic dysfunction in anxiety disorders, derived from indirect measures of noradrenergic function in clinical populations.

The missing p in psychiatric training: why it is important to teach pain to psychiatrists

CONTEXT

Pain problems are exceedingly prevalent among psychiatric patients. Moreover, clinical impressions and neurobiological research suggest that physical and psychological aspects of pain are closely related entities. Nonetheless, remarkably few pain-related themes are currently included in psychiatric residency training.

OBJECTIVES

To provide clinical and scientific rationale for psychiatric-training enrichment with basic tenets of pain medicine and to raise the awareness and sensitivity of physicians, scientists, and educators to this important yet unmet clinical and public health need.

RESULTS

We present 3 lines of translational research evidence, extracted from a comprehensive literature review, in support of our objectives. First, the neuroanatomical and functional overlap between pain and emotion/reward/motivation brain circuitry suggests integration and mutual modulation of these systems. Second, psychiatric disorders are commonly associated with alterations in pain processing, whereas chronic pain may impair emotional and neurocognitive functioning. Third, given its stressful nature, pain may serve as a functional probe for unraveling pathophysiological mechanisms inherent in psychiatric morbidity.

CONCLUSIONS

Pain training in psychiatry will contribute to deeper and more sophisticated insight into both pain syndromes and general psychiatric morbidity regardless of patients' pain status. Furthermore, it will ease the artificial boundaries separating psychiatric and medical formulations of brain disorders, thus fostering cross-fertilizing interactions among specialists in various disciplines entrusted with the care of patients experiencing pain.

Posttraumatic stress disorder in children and adolescents: a review of psychopharmacological treatment

PTSD in children and adolescents differs from the adult disease. Therapeutic approaches involve both psychotherapy and psychopharmacotherapy.

OBJECTIVES

The current paper aims at reviewing studies on psychopharmacological treatment of childhood and adolescent PTSD. Additionally, developmental frameworks for PTSD diagnosis and research along with an experimental model of quenching and kindling in the context of stress exposure are presented. We conducted an extensive literature search of reviews on psychopharmacotherapy as well as studies on psychopharmacological treatment for PTSD among children and adolescents. We used the database PubMed and focused on the time period of the last 10 years up to January 2009. Pertinent earlier papers were also included.There are a limited number of studies specifically assessing the psychopharmacological treatment of PTSD in children and adolescents. The vast majority of them lack verification in RCTs. Only the use of imipramine, divalproex sodium and sertraline were already evaluated in RCTs. Future studies should take into account developmental approaches to the diagnosis and treatment of PTSD in children and adolescents. In this context, different underlying neurobiological patterns, which are reflected in distinct clinical symptomatology, require a precise investigation and a symptom-orientated psychopharmacological approach.

Therapeutic utility of non-peptidic CRF1 receptor antagonists in anxiety, depression, and stress-related disorders: evidence from animal models

Adaptive responding to threatening stressors is of fundamental importance for survival. Dysfunctional hyperactivation of corticotropin releasing factor type-1 (CRF(1)) receptors in stress response system pathways is linked to stress-related psychopathology and CRF(1) receptor antagonists (CRAs) have been proposed as novel therapeutic agents. CRA effects in diverse animal models of stress that detect anxiolytics and/or antidepressants are reviewed, with the goal of evaluating their potential therapeutic utility in depression, anxiety, and other stress-related disorders. CRAs have a distinct phenotype in animals that has similarities to, and differences from, those of classic antidepressants and anxiolytics. CRAs are generally behaviorally silent, indicating that CRF(1) receptors are normally in a state of low basal activation. CRAs reduce stressor-induced HPA axis activation by blocking pituitary and possibly brain CRF(1) receptors which may ameliorate chronic stress-induced pathology. In animal models sensitive to anxiolytics and/or antidepressants, CRAs are generally more active in those with high stress levels, conditions which may maximize CRF(1) receptor hyperactivation. Clinically, CRAs have demonstrated good tolerability and safety, but have thus far lacked compelling efficacy in major depressive disorder, generalized anxiety disorder, or irritable bowel syndrome. CRAs may be best suited for disorders in which stressors clearly contribute to the underlying pathology (e.g. posttraumatic stress disorder, early life trauma, withdrawal/abstinence from addictive substances), though much work is needed to explore these possibilities. An evolving literature exploring the genetic, developmental and environmental factors linking CRF(1) receptor dysfunction to stress-related psychopathology is discussed in the context of improving the translational value of current animal models.

Pharmacological facilitation of fear extinction and the search for adjunct treatments for anxiety disorders--the case of yohimbine

There is current interest in identifying drugs that facilitate fear extinction, as this form of learning is the basis of certain cognitive therapies for anxiety disorders. Following an initial report several years ago that the alpha2-adrenoreceptor antagonist yohimbine facilitated extinction in mice, more recent studies have shown mixed effects or even impairment. It has become clear that the effect of yohimbine on extinction depends on a number of factors, including genetic background, contextual variables and the presence of competing behaviors. To what extent theses effects of yohimbine are mediated through the alpha2-adrenoreceptor, as opposed to other sites of action, is also uncertain. More work is needed before this drug can be approved as a pharmacological adjunct for extinction-based therapies. More generally, the case of yohimbine may serve as a model for the development of other extinction facilitators.

The effects of yohimbine and amphetamine on fear expression and extinction in rats

RATIONALE

Psychostimulants, such as yohimbine and amphetamine, can enhance learning and memory. Extinction of conditioned fear involves new learning, so we asked whether psychostimulants could enhance this learning. Previous work suggests that yohimbine facilitates extinction, using freezing as a fear measure. However, psychostimulant-induced alterations in locomotion can confound freezing measurements. Furthermore, the effects of amphetamine on fear extinction have never been examined.

OBJECTIVE

We evaluated the effectiveness of yohimbine and amphetamine in enhancing fear extinction. In addition to freezing, we measured bar-press suppression, which is less sensitive to changes in locomotion. We asked: Do psychostimulants reduce fear during extinction training when drug is present? Does learning extinction with psychostimulants result in better extinction retention?

MATERIALS AND METHODS

Rats received fear conditioning on day 1 followed by partial extinction training on days 2 and 3. Yohimbine (1.0, 2.0, or 5.0 mg/kg, i.p.), amphetamine (1.0 mg/kg, i.p.), or vehicle were injected prior to extinction on day 2.

RESULTS

Yohimbine dose-dependently reduced freezing during extinction training on day 2, whereas bar-press suppression was reduced at the highest dose only. When tested drug-free, yohimbine-treated rats showed equivalent levels of freezing and suppression to controls. Amphetamine also decreased freezing during extinction, but did not decrease suppression. During the drug-free test, there was no difference between amphetamine-treated rats and controls in either measure.

CONCLUSIONS

Although yohimbine and amphetamine are capable of decreasing freezing, neither drug strengthened retention of fear extinction. Based on these rodent findings, psychostimulants may not be suitable adjuncts to extinction-based therapies for the treatment of anxiety disorders.

Effects of yohimbine and hydrocortisone on panic symptoms, autonomic responses, and attention to threat in healthy adults

RATIONALE

Research in rodents and non-human primates implicates the noradrenergic system and hypothalamic-pituitary-adrenal axis in stress, anxiety, and attention to threat. Few studies examine how these two neurochemical systems interact to influence anxiety and attention in humans.

OBJECTIVE

The objective of this paper is to examine the effects of exogenous yohimbine and hydrocortisone, as well as their combination (Y + H), on panic symptoms and attention to social threat cues.

METHODS

Thirty-two healthy adults underwent a pharmacological challenge in which they were blindly randomized to either yohimbine, hydrocortisone, Y + H, or placebo. Thirty minutes after drug infusion, attention to threat was measured using the dot probe task, a visual attention task that presents angry, happy, and neutral faces and measures the degree of attention allocated towards or away from the emotional faces. Panic and autonomic measures were assessed before and 30 min after drug infusion.

RESULTS

There was a significant increase in panic symptoms in the yohimbine and Y + H groups, but not in the hydrocortisone or placebo groups. Yohimbine resulted in a greater increase in panic symptoms than Y + H. On the dot probe task, the placebo group exhibited an attention bias to angry faces, whereas this bias was absent after yohimbine. When collapsing across groups, increased panic symptoms was associated with less attention to angry faces.

CONCLUSIONS

Exogenous hydrocortisone may attenuate noradrenergic-induced panic symptoms. The inverse relationship between panic symptoms and attention to angry faces extends prior research demonstrating attention modulation by stressful conditions.

Acute episodes of predator exposure in conjunction with chronic social instability as an animal model of post-traumatic stress disorder

People who are exposed to horrific, life-threatening experiences are at risk for developing post-traumatic stress disorder (PTSD). Some of the symptoms of PTSD include persistent anxiety, exaggerated startle, cognitive impairments and increased sensitivity to yohimbine, an alpha(2)-adrenergic receptor antagonist. We have taken into account the conditions known to induce PTSD, as well as factors responsible for long-term maintenance of the disorder, to develop an animal model of PTSD. Adult male Sprague-Dawley rats were administered a total of 31 days of psychosocial stress, composed of acute and chronic components. The acute component was a 1-h stress session (immobilization during cat exposure), which occurred on Days 1 and 11. The chronic component was that on all 31 days the rats were given unstable housing conditions. We found that psychosocially stressed rats had reduced growth rate, reduced thymus weight, increased adrenal gland weight, increased anxiety, an exaggerated startle response, cognitive impairments, greater cardiovascular and corticosterone reactivity to an acute stressor and heightened responsivity to yohimbine. This work demonstrates the effectiveness of acute inescapable episodes of predator exposure administered in conjunction with daily social instability as an animal model of PTSD.

Noradrenergic signaling in infralimbic cortex increases cell excitability and strengthens memory for fear extinction

Emotional arousal strengthens memory. This is most apparent in aversive conditioning, in which the stress-related neurotransmitter norepinephrine (NE) enhances associations between sensory stimuli and fear-inducing events. In contrast to conditioning, extinction decreases fear responses, and is thought to form a new memory. It is not known, however, whether NE is necessary for extinction learning. Previous work has shown that the infralimbic prefrontal cortex (IL) is a site of extinction consolidation. Here, we show that blocking noradrenergic beta-receptors in IL before extinction training impaired retrieval of extinction the following day, consistent with a weakened extinction memory. We further found that the sequelae of beta-receptor activation, including protein kinase A (PKA), gene transcription and translation in IL, are necessary for extinction. To determine whether activation of this cascade modulates IL excitability, we measured the response of IL pyramidal neurons to injected current. NE increased the excitability of IL neurons in a beta-receptor- and PKA-dependent manner. We suggest that NE released in IL during fear extinction activates a PKA-mediated molecular cascade that strengthens extinction memory. Thus, emotional arousal evoked by conditioned fear paradoxically promotes the subsequent extinction of that fear, thereby ensuring behavioral flexibility.

PTSD and stress sensitisation: a tale of brain and body Part 1: human studies

Post-traumatic stress disorder (PTSD) is a chronic, debilitating psychiatric disorder that can follow exposure to extreme stressful experiences. It is characterised by hyperarousal and increased startle responses, re-experiencing of the traumatic event, withdrawal or avoidance behaviour and emotional numbing. The focus of this review is on aspects that have received less attention. PTSD develops only in a substantial minority of people exposed to traumatic stress, and possible individual traits that increase vulnerability are discussed. An overview is given of the wide variety of physiological disturbances that accompany PTSD and may contribute to disability, including neuroendocrine, cardiovascular, gastrointestinal and immune function and pain sensitivity. Brain imaging and pharmacological studies have generated some insight into the circuitry that may be involved in the generation of PTSD symptoms. Major limitations of human studies so far are the issue of causality and our lack of understanding of the underlying molecular substrates in the brain, which are easier to address in relevant animal models and will be discussed in a companion paper.

Psychoendokrinologie der Angst

Zusammenfassung. Ätiologie, Symptomatik und Verlauf von Angststörungen sind multikausal zu erklären. Ein Teilaspekt der psychobiologischen Erklärungsansätze von Angststörungen sind endokrine Auffälligkeiten, anhand derer bestimmte Unterformen pathologischer Angst charakterisiert werden können. Vor allem die Hypothalamus-Hypophysen-Nebennierenrinde-Achse und das sympathiko-adrenomedulläre System werden im Zusammenhang mit Emotionsregulation und pathologischer Angst untersucht. Beide Hormonsysteme spielen bei der Anpassung an individuelle Belastungssituationen eine bedeutende Rolle und beeinflussen die psychobiologische Anpassung an angstauslösende Situationen nachhaltig. In dieser Überblicksarbeit werden endokrine Dysregulationen der o.g. Hormonsysteme für verschiedene Unterformen von Angststörungen aufgezeigt und bzgl. ihrer ätiologischen Bedeutsamkeit, auch unter Berücksichtigung genetischer Befunde, diskutiert. Darüber hinaus werden erste therapeutische Ansätze, bei denen psychoendokrinologische Methoden genutzt werden, aufgezeigt.

Single and repeated immobilization stress differentially trigger induction and phosphorylation of several transcription factors and mitogen-activated protein kinases in the rat locus coeruleus

The locus coeruleus (LC) is a critical stress-responsive location that mediates many of the responses to stress. We used immunoblotting and immunohistochemistry to investigate changes in induction and phosphorylation of several transcription factors and kinases in the LC that may mediate the stress-triggered induction of tyrosine hydroxylase (TH) transcription. Rats were exposed to single or repeated immobilization stress (IMO) for brief (5 min), intermediate (30 min) or sustained (2 h) duration. Single IMO elicited rapid induction of c-Fos and phosphorylation of cyclic AMP response element-binding protein (CREB) without changing the expression of early growth response (Egr)1, Fos-related antigen (Fra)-2 or phosphorylated activating transcription factor-2. Repeated IMO triggered increased phosphorylation and levels of CREB along with transient induction of c-Fos and increased Fra-2 expression. Several mitogen-activated protein kinases were activated by repeated IMO, shown by increased phosphorylation of p38, c-Jun N-terminal kinase (JNK)1/2/3 and extracellular signal-regulated kinase (ERK1/2). ERK1 was the major isoform expressed, and ERK2 the predominant isoform phosphorylated. Repeated IMO elicited hyperphosphorylation of ERK1/2 selectively in TH immunoreactive neurons, with substantial nuclear localization. These distinct alterations in transcriptional pathways following repeated compared with single stress may be involved in mediating long-lasting neuronal remodeling and are implicated in the mechanisms by which acute beneficial responses to stress are converted into prolonged adaptive or maladaptive responses.

Noradrenergic mechanisms in the pathophysiology of post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is a serious psychiatric illness that may develop in individuals after exposure to a traumatic event. Recent data suggest that trauma and/or long-term stressors can cause alterations in the functioning of neuroanatomical structures and neural networks throughout the central nervous system. Specifically, dysregulation in central and perhaps, peripheral noradrenergic neural networks has been implicated as the cause of specific symptom clusters in the pathophysiology of PTSD. In this review, both clinical and preclinical data are presented to highlight types of noradrenergic dysfunction observed in individuals with PTSD. Additionally, the role of noradrenaline dysregulation in the acquisition/initiation, and maintenance of hyperarousal and reexperiencing symptom clusters in PTSD will be addressed.

Glucocorticoid effects on memory retrieval require concurrent noradrenergic activity in the hippocampus and basolateral amygdala

Previous findings indicate that administration of abeta-adrenoceptor antagonist systemically blocks glucocorticoid impairment of memory retrieval. Here, we report that beta-adrenoceptor activation in the hippocampus and the basolateral complex of the amygdala (BLA) is implicated in the impairing effects of glucocorticoids on memory retrieval. The specific glucocorticoid receptor (GR) agonist 11beta,17beta-dihydroxy-6,21-dimethyl-17alpha-pregna-4,6-trien-20yn-3-one (RU 28362) (15 ng) infused into the hippocampus of male Sprague Dawley rats 60 min before water maze retention testing, 24 hr after training, impaired probe trial retention performance, as assessed by quadrant search time and initial latency to cross the platform location. Because we found previously that RU 28362 infused into the hippocampus does not affect water maze acquisition or immediate recall, the findings suggest that the GR agonist-induced retention impairment was attributable to a selective influence on long-term memory retrieval. Likewise, systemic injections of the beta1-adrenoceptor partial agonist xamoterol (3.0 or 10.0 mg/kg, s.c.) 60 min before the probe trial dose-dependently impaired retention performance. The beta-adrenoceptor antagonist propranolol (2.0 mg/kg) administered subcutaneously before retention testing did not affect retention performance alone, but blocked the memory retrieval impairment induced by concurrent intrahippocampal infusions of RU 28362. Pretest infusions of the beta1-adrenoceptor antagonist atenolol into either the hippocampus (1.25 microg in 0.5 microl) or the BLA (0.5 microg in 0.2 microl) also prevented the GR agonist-induced memory retrieval impairment. These findings suggest that glucocorticoids impair retrieval of long-term spatial memory by facilitating noradrenergic mechanisms in the hippocampus, and additionally, that norepinephrine-mediated BLA activity is critical in enabling hippocampal glucocorticoid effects on memory retrieval.

Activation of alpha2 adrenergic receptors suppresses fear conditioning: expression of c-Fos and phosphorylated CREB in mouse amygdala

alpha(2) adrenergic agonists such as dexmedetomidine generally suppress noradrenergic transmission and have sedative, analgesic, and antihypertensive properties. Considering the importance of the neurotransmitter norepinephrine in forming memories for fearful events, we have investigated the acute and chronic effects of dexmedetomidine on discrete cue and contextual fear conditioning in mice. When administered before training, dexmedetomidine (10-20 microg/kg, i.p.) selectively suppressed discrete cue fear conditioning without affecting contextual memory. This behavioral change was associated with a decrease in memory retrieval-induced expression of c-Fos and P-CREB in the lateral, basolateral, and central nuclei of the amygdala. Dexmedetomidine's action on discrete cue memory did not occur in alpha(2A) adrenoceptor knockout (KO) mice. When dexmedetomidine was administered after training, it suppressed contextual memory, an effect that did not occur in alpha(2A) adrenoceptor KO mice. We conclude that dexmedetomidine, acting at alpha(2A) adrenoceptors, must be present during the encoding process to decrease discrete cue fear memory; however, its ability to suppress contextual memory is likely the result of blocking the consolidation process. The ability of alpha(2) agonists to suppress fear memory may be a valuable property clinically in order to suppress the formation of memories during stressful situations.

Augmentation of the noradrenergic system in alpha-2 adrenergic receptor deficient mice: anatomical changes associated with enhanced fear memory

We have investigated sensitivity to the conditioned fear procedure of mice is influenced by the genetic deletion of alpha2A adrenoceptors (ARs). We observed a heightened freezing response in the discrete cue memory test in alpha2A AR knockout (alpha2A AR KO) mice and in D79N mice, a transgenic mouse strain with functionally impaired alpha2A ARs. No significant differences in contextual memory were observed between control and alpha2A AR KO or D79N mice suggesting a minimal role for the noradrenergic system in contextual memory. We speculated that the increased freezing response of the alpha2A AR KO and D79N mice in the discrete cue setting was due to increased release of norepinephrine evoked by the unconditioned footshock stimulus. In alpha2A AR KO mice we measured a doubling in the number of noradrenergic neurons in the locus coeruleus (LC) and a large increase in the cell volume of tyrosine hydroxylase positive neurons, likely due to selective preservation of large, multipolar neurons in the subcoeruleus. Hyperplasia of the noradrenergic neurons in the nucleus tractus solitarius, A5 and A7, was also observed. Alpha2A AR KO mice exhibit greater c-Fos expression in the LC compared to wild type mice suggesting that the LC neurons in the alpha2A AR KO mice were spontaneously more active. This study suggests that alpha2A ARs are involved in the development of the central noradrenergic system and raises the possibility that alterations in alpha2A AR expression may contribute to variations in fear and stress responses.

Post-traumatic stress disorder in women: current concepts and treatments

In the US, 13% of women develop post-traumatic stress disorder (PTSD) during their lifetime. An accurate diagnosis of PTSD requires screening for trauma and symptoms of PTSD. Current research in the neurobiologic and psychologic responses to traumatic stress supports the use of pharmacologic and psychosocial interventions. Selective serotonin reuptake inhibitors are the current first-line pharmacotherapy. Efficacious psychosocial interventions include exposure therapy and cognitive processing therapy.

Pre-exercise administration of yohimbine may enhance the efficacy of exercise training as a fat loss strategy by boosting lipolysis

The natural alpha-2 antagonist yohimbine promotes sympathetic activity by central as well as peripheral mechanisms, and yet in moderate doses dose not usually raise heart rate, increase blood pressure, or induce anxiety (in contrast to sympathomimetic drugs such as ephedrine). Administered prior to exercise, it boosts lipolysis and serum FFA levels both during and following exercise; blockade of adipocyte alpha-2 adrenoreceptors makes at least a modest contribution to this pro-lipolytic activity. These considerations suggest that pre-exercise administration of yohimbine will lower the respiratory quotient during and following exercise, thus promoting fat loss. Since yohimbine can potentiate postprandial insulin secretion, its bariatric benefits should be greatest if administered on a schedule that minimizes postprandial yohimbine activity. A possible synergism of yohimbine and caffeine should be explored. Pre-exercise yohimbine administration has the potential to down-regulate the lipoprotein lipase activity of visceral adipocytes, increase lipolysis in refractory gynoid fat depots, and improve the impaired lipolytic response to exercise in the elderly.

Chronic psychosocial stress impairs learning and memory and increases sensitivity to yohimbine in adult rats

BACKGROUND

It is well known that intense and prolonged stress can produce cognitive impairments and hippocampal damage and increase noradrenergic activity in humans. This study investigated the hypothesis that chronic psychosocial stress would affect behavior, drug sensitivity, and hippocampal-dependent learning and memory in rats. The work provides a novel connection between animal and human studies by evaluating the effects of stress on a rat's response to yohimbine, an alpha(2) adrenergic receptor antagonist.

METHODS

Rats were exposed to a cat for 5 weeks and randomly housed with a different group of cohorts each day (psychosocial stress). The effects of the stress manipulations were then assessed on open field behavior, spatial learning and memory in the radial arm water maze and the behavioral response to a low dose of yohimbine (1.5 mg/kg).

RESULTS

Stressed rats displayed impaired habituation to a novel environment, heightened anxiety, and increased sensitivity to yohimbine. In addition, the stressed rats exhibited impaired learning and memory.

CONCLUSIONS

There are commonalities between the current findings on stressed rats and from studies on traumatized people. Thus, psychosocial stress manipulations in rats may yield insight into the basis of cognitive and neuroendocrine disturbances that commonly occur in people with anxiety disorders.

Post-traumatic stress disorder: a review of recent findings

This article provides an update on recent findings in post-traumatic stress disorder (PTSD) with reference to pertinent epidemiologic, etiologic, diagnostic, and treatment advances in the past year. New studies serve to confirm high prevalence rates in the general population (7% to 12%), and high rates of secondary mood, anxiety, and substance use disorders. Recent substantive evidence has highlighted 1) the unique pattern of biological alteration in PTSD that distinguishes it from the normative stress response, and 2) the role of constitutional risk factors and trauma-related factors in determining disease expression after trauma exposure. The emergence of consistent data suggesting that medications (selective serotonin reuptake inhibitors) and psychotherapies (cognitive-behavior therapy) are effective in reducing core symptoms and improving quality of life, has reinforced optimism and more widespread use of these interventions in patients with PTSD.