Discrimination, Stress and Reactivity to Alcohol Cues

Introduction: Our study investigated whether discrimination affects psychologi-cal/physiological stress and alcohol craving.

Method: Participants (N = 92) were asked to recall and write about (a) a neutral, (b) a negative, or (c) a discriminatory experience in the past and then completed a cue-reactivity procedure assessing their alcohol craving. In addition, we assessed levels of perceived stress before and after the discrimination manipulation, chronic substance use and craving, prior perceived discrimination, and strength of racial/ethnic identity.

Results: Results revealed a small effect in which the discrimination condition increased alcohol cue-elicited craving relative to the other conditions. Chronic craving moderated effects of discrimination on cortisol levels. Self-reported stress levels were increased in the discrimination and negative memory conditions relative to baseline. Strength of racial identity served as a protective factor for substance abuse in those who reported chronic high levels of discrimination.

Discussion: We discussed the direct link established between acute exposure to discrimination and craving, and experimental evidence for the relationship between discrimination and self-reported stress, but also addressed potential limitations of this work. It is further discussed how some individual differences factors (e.g., chronic craving) predict physiological stress in discriminatory settings. This work underscored the role of racial identity as a protective factor against alcohol abuse in individuals reporting high levels of discrimination.

Modeling consequences of prolonged strong unpredictable stress in zebrafish: Complex effects on behavior and physiology

Chronic stress is the major pathogenetic factor of human anxiety and depression. Zebrafish (Danio rerio) have become a novel popular model species for neuroscience research and CNS drug discovery. The utility of zebrafish for mimicking human affective disorders is also rapidly growing. Here, we present a new zebrafish model of clinically relevant, prolonged unpredictable strong chronic stress (PUCS). The 5-week PUCS induced overt anxiety-like and motor retardation-like behaviors in adult zebrafish, also elevating whole-body cortisol and proinflammatory cytokines - interleukins IL-1β and IL-6. PUCS also elevated whole-body levels of the anti-inflammatory cytokine IL-10 and increased the density of dendritic spines in zebrafish telencephalic neurons. Chronic treatment of fish with an antidepressant fluoxetine (0.1mg/L for 8days) normalized their behavioral and endocrine phenotypes, as well as corrected stress-elevated IL-1β and IL-6 levels, similar to clinical and rodent data. The CNS expression of the bdnf gene, the two genes of its receptors (trkB, p75), and the gfap gene of glia biomarker, the glial fibrillary acidic protein, was unaltered in all three groups. However, PUCS elevated whole-body BDNF levels and the telencephalic dendritic spine density (which were corrected by fluoxetine), thereby somewhat differing from the effects of chronic stress in rodents. Together, these findings support zebrafish as a useful in-vivo model of chronic stress, also calling for further cross-species studies of both shared/overlapping and distinct neurobiological responses to chronic stress.

Zebrafish models in neuropsychopharmacology and CNS drug discovery

Despite the high prevalence of neuropsychiatric disorders, their aetiology and molecular mechanisms remain poorly understood. The zebrafish (Danio rerio) is increasingly utilized as a powerful animal model in neuropharmacology research and in vivo drug screening. Collectively, this makes zebrafish a useful tool for drug discovery and the identification of disordered molecular pathways. Here, we discuss zebrafish models of selected human neuropsychiatric disorders and drug-induced phenotypes. As well as covering a broad range of brain disorders (from anxiety and psychoses to neurodegeneration), we also summarize recent developments in zebrafish genetics and small molecule screening, which markedly enhance the disease modelling and the discovery of novel drug targets.

Rest in The Zebrafish

The purpose and function of sleep has been the topic of discussion for several centuries. Though our understanding of the mechanisms underlying the propagation and maintenance of rest states has undergone significant improvement, much remains to be learned with regards to the effects of disrupted sleep on diseased states. A deeper understanding of the neural circuitry and associated phenotypes would allow for the identification of sleep-related pathologies as well as the development of therapies for individuals with sleep disorders. To this end, the zebrafish (danio rerio) pose a great advantage. In the adult animal, sleep is largely consolidated to dark phases. Sleep may be disrupted via environmental, pharmacological or genetic manipulations. Disrupted sleep rhythms in the adult animal are linked to changes in gene and protein expression, while behavioral measures of anxiety have produced mixed results. We propose that this variation is a result of the type of sleep disruption as well as the type of anxiety test employed. This beckons the need for further study of the effects of environmental and pharmacological manipulations on the sleep rhythms of the animal. Further, researchers must not rely solely on one test as a measure of stress or anxiety as it provides only a one-dimensional insight.

Zebrafish neurobehavioral phenomics for aquatic neuropharmacology and toxicology research

Zebrafish (Danio rerio) are rapidly emerging as an important model organism for aquatic neuropharmacology and toxicology research. The behavioral/phenotypic complexity of zebrafish allows for thorough dissection of complex human brain disorders and drug-evoked pathological states. As numerous zebrafish models become available with a wide spectrum of behavioral, genetic, and environmental methods to test novel drugs, here we discuss recent zebrafish phenomics methods to facilitate drug discovery, particularly in the field of biological psychiatry. Additionally, behavioral, neurological, and endocrine endpoints are becoming increasingly well-characterized in zebrafish, making them an inexpensive, robust and effective model for toxicology research and pharmacological screening. We also discuss zebrafish behavioral phenotypes, experimental considerations, pharmacological candidates and relevance of zebrafish neurophenomics to other 'omics' (e.g., genomic, proteomic) approaches. Finally, we critically evaluate the limitations of utilizing this model organism, and outline future strategies of research in the field of zebrafish phenomics.

The failure of anxiolytic therapies in early clinical trials: what needs to be done

INTRODUCTION

Anxiety spectrum disorders (ASDs) are highly prevalent psychiatric illnesses that affect millions of people worldwide. Strongly associated with stress, common ASDs include generalized anxiety disorder, panic, social anxiety, phobias and drug-abuse-related anxiety. In addition to ASDs, several other prevalent psychiatric illnesses represent trauma/stressor-related disorders, such as post-traumatic stress disorder and acute stress disorder. Anxiolytic drugs, commonly prescribed to treat ASDs and trauma/stressor-related disorders, form a highly heterogenous group, modulating multiple neurotransmitters and physiological mechanisms. However, overt individual differences in efficacy and the potential for serious side-effects (including addiction and drug interaction) indicate a need for further drug development. Yet, over the past 50 years, there has been relatively little progress in the development of novel anxiolytic medications, especially when promising candidate drugs often fail in early clinical trials.

AREAS COVERED

Herein, the authors present recommendations of the Task Force on Anxiolytic Drugs of the International Stress and Behavior Society on how to improve anxiolytic drug discovery. These recommendations cover a wide spectrum of aspects, ranging from methodological improvements to conceptual insights and innovation.

EXPERT OPINION

In order to improve the success of anxiolytic drugs in early clinical trials, the goals of preclinical trials may need to be adjusted from a clinical perspective and better synchronized with those of clinical studies. Indeed, it is important to realize that the strategic goals and approaches must be similar if we want to have a smoother transition between phases.

Gaining translational momentum: more zebrafish models for neuroscience research

Zebrafish (Danio rerio) are rapidly becoming a popular model organism in translational neuroscience and biological psychiatry research. Here we discuss conceptual, practical and other related aspects of using zebrafish in this field ("from tank to bedside"), and critically evaluate both advantages and limitations of zebrafish models of human brain disorders. We emphasize the need to more actively develop zebrafish models for neuroscience research focusing on complex traits.

Zebrafish and conditioned place preference: a translational model of drug reward

Addiction and substance abuse are found ubiquitously throughout human society. In the United States, these disorders are responsible for amassing hundreds of billions of dollars in annual costs associated with healthcare, crime and lost productivity. Efficacious treatments remain few in number, the development of which will be facilitated by comprehension of environmental, genetic, pharmacological and neurobiological mechanisms implicated in the pathogenesis of addiction. Animal models such as the zebrafish (Danio rerio) have gained momentum within various domains of translational research, and as a model of complex brain disorders (e.g., drug abuse). Behavioral quantification within the conditioned place preference (CPP) paradigm serves as a measure of the rewarding qualities of a given substance. If the animal develops an increase in preference for the drug paired environment, it is inferred that the drug has positive-reinforcing properties. This paper discusses the utility of the zebrafish model in conjunction with the CPP paradigm and reports CPP behavior following acute exposure to 0.0%, 0.25%, 0.50%, and 1.00% alcohol, and 0 mg/L, 50 mg/L, 100 mg/L and 150 mg/L caffeine.

Aquatic toxicology of fluoxetine: understanding the knowns and the unknowns

Fluoxetine is one of the most prescribed psychotropic medications, and is an agent of increasing interest for environmental toxicology. Fish and other aquatic organisms are excellent models to study neuroactive small molecules like fluoxetine. However, prone to variance due to experimental factors, data obtained in these models need to be interpreted with caution, using proper experimental protocols, study designs, validated endpoints as well as well-established models and tests. Choosing the treatment protocol and dose range for fluoxetine and other serotonergic drugs is critical for obtaining valid test results and correct data interpretation. Here we discuss the value of aquatic models to study fluoxetine effects, based on prior high-quality research, and outline the directions of future translational studies in the field. We review fluoxetine-evoked phenotypes in acute vs. chronic protocols, discussing them in the contact of complex role of serotonin in behavioral regulation. We conclude that zebrafish and other aquatic models represent a useful in-vivo tool for fluoxetine pharmacology and (eco)toxicology research.

Modeling PTSD in the zebrafish: are we there yet?

Post-traumatic stress disorder is an anxiety disorder that can develop following one or more traumatic events that threaten one's safety or make the victim feel helpless. Currently there are an increasing number of cases in the population in part due to the number of soldiers returning from combat. The disorder is characterized by symptoms that include hypervigilance, sleep disturbances, social and cognitive degradation, and memory flashbacks. Most of the research has been centered on the human and rodent as subjects but recently another viable contender has emerged - the zebrafish (Danio rerio). The zebrafish is a strong comparative model with the ability to exhibit a wide variety of behaviors, complex learning, and neurobiological changes that can be extrapolated to the human condition. The zebrafish is an ideal organism to study pharmacological treatments as well as the neurological underpinnings of the disorder. Here we review a sampling of the human and rodent model literature on post-traumatic stress disorder focusing on symptomology, current treatments, and stress paradigms. We also make the argument for the inclusion of the zebrafish model in future studies investigating the causes, symptoms, and treatments of post-traumatic stress disorder.

Assessing attention in the zebrafish: Are we there yet?

Traditionally, rodent sustained attention models are used for studying the neurobiological underpinnings of attention, for assessing the disruptive and interactive effects of drugs and environmental toxins and for predicting the efficacy of pharmacotherapies for attention disorders. Virtually all-major psychiatric disorders are characterized by disturbances in attention or concentration. Additionally, many psychoactive drugs produce simultaneous effects on a variety of psychological processes. Behavioral measures in tasks designed to assess cognitive processes in rodents characterize and dissociate these multiple influences. While the zebrafish (Danio rerio) has been at the vanguard of neurobiological research and is increasing in popularity as a model organism for behavioral applications, their attentional capacity has not been fully assessed. Here we review some of the more popular animal models and discuss the utility of a choice discrimination zebrafish model.

Effects of acute alcohol intoxication and paroxetine on aggression in men

BACKGROUND

The purpose of this study was to examine the role of the serotonin (5-HT) system in alcohol-related aggression.

METHODS

Specifically, we experimentally examined the effects of 5-HT augmentation on alcohol-related aggression in men (n = 56). After consuming either alcohol (mean blood alcohol concentration of 0.10%) or a placebo (no alcohol) drink, and taking either 20 mg of paroxetine (Paxil) or a placebo pill, participants were provided the opportunity to administer electric shock to a (faux) opponent during a task disguised as a reaction-time game. Aggression was defined as the intensity of shock chosen and the frequency with which an extreme (clearly painful) shock was chosen. We predicted that 5-HT augmentation would be associated with lower aggressive behavior overall, and also reduce the aggression facilitating effects of acute alcohol intoxication.

RESULTS

The results indicated that alcohol intoxication increased aggression, particularly under low provocation. Paroxetine decreased aggression, particularly during high provocation. These effects, however, occurred independently of each other.

CONCLUSIONS

The effect of alcohol on extreme aggression was moderated by previous aggression history, with more aggressive individuals showing greater alcohol-related increases in extreme aggression.

Role of brain norepinephrine in the behavioral response to stress

The brain noradrenergic system is activated by acute stress. The post-synaptic effects of norepinephrine (NE), exerted at a cellular or neural circuit level, have been described as modulatory in nature, as NE facilitates responses evoked in target cells by both excitatory and inhibitory afferent input. Over the past few years, we have undertaken a series of studies to understand how these cellular modulatory effects of NE, elicited by acute stress, might translate into modulation of the behavioral-affective components of the whole-animal response to stress. Using microdialysis, we have demonstrated that acute immobilization stress activates NE release in a number of stress-related limbic forebrain target regions, such as the central and medial amygdala, lateral bed nucleus of the stria terminalis, medial prefrontal cortex, and lateral septum. Using microinjections of adrenergic antagonist drugs directly into these regions, we have shown that this stress-induced release of NE facilitates a number of anxiety-like behavioral responses that are mediated in these regions, including stress-induced reduction of open-arm exploration on the elevated plus-maze, stress-induced reduction of social interaction behavior, and activation of defensive burying behavior by contact with an electrified probe. Dysregulation of the brain noradrenergic system may be a factor in determining vulnerability to stress-related pathology, or in the interaction of genetic vulnerability and environmental sensitization. Compared to outbred Sprague-Dawley rats, we have shown that the modulatory effect of NE is deficient in Wistar-Kyoto rats, which also exhibit attenuated behavioral reactivity to acute stress, as well as increased vulnerability to stress-induced gastric ulcers and exaggerated activation of the hypothalamic-pituitary-adrenal (HPA) stress axis. Further, repeated exposure to mild intermittent cold stress resulted in a much greater sensitization of both the brain noradrenergic system and the HPA axis in Wistar-Kyoto rats compared to Sprague-Dawley rats. The recruitment of a robust noradrenergic facilitatory influence following repeated cold exposure in this previously deficient strain resulted in an aberrant HPA response, which may be illustrative of the kinds of neurobiological changes that may contribute to the development of stress-related neuropsychiatric disorders such as depression, post-traumatic stress disorder, or other anxiety disorders in predisposed or susceptible individuals. On the other side of the same issue, regulatory alterations in noradrenergic neurotransmission, or in the stress-modulatory functions of NE, may be important in the behavioral effects of chronic antidepressant drug treatment. We present recent preliminary results addressing the effects of chronic treatment with the selective NE reuptake inhibitor, desipramine, on acute behavioral reactivity to stress. A better understanding of the role of NE in adaptive responses to acute stress, the pathological consequences of prolonged, repeated or severe stress, and the mechanisms of action of drugs used to treat stress-related diseases, may contribute to the future development of more effective strategies for the treatment or even prevention of such disorders.

Administration of the galanin antagonist M40 into lateral septum attenuates shock probe defensive burying behavior in rats

Galanin (GAL) has been implicated in modulating anxiety, although a precise role remains unclear. Previous studies revealed anxiolytic effects, anxiogenic effects, or no effect, depending on the test, brain region, route of drug administration and context. We have shown previously that microinjection of the GAL antagonist M40 into central amygdala blocked an anxiolytic response to acute stress on the elevated plus maze when rats were pretreated with yohimbine, suggesting an anxiolytic effect of GAL. By contrast, we also showed that microinjection of M40 into the lateral bed nucleus of the stria terminalis attenuated anxiety-like behavioral responses to stress on the plus maze and social interaction tests, implying an anxiogenic effect for GAL. The behavioral response to stress on both these tests is a reduction of an ongoing behavior (open-arm exploration or social interaction, respectively). To better understand the anxiety-modulating role of GAL, it is also important to ascertain its effect on a response that represents an activation rather than suppression of behavior. Thus, in this study, we investigated an active behavioral response to acute stress in rats, the shock-probe defensive burying response. Bilateral microinjections of M40 into lateral septum (LS), a region important to this response and innervated by GAL, dose-dependently decreased burying without affecting immobility. No change was seen in hindpaw withdrawal latency on a thermosensitivity assay, suggesting that the reduction in burying behavior was not attributable to changes in cutaneous pain sensitivity. These results indicate that in LS, GAL facilitates the active anxiety-like behavioral response on the defensive burying test, similar to its facilitatory effect on anxiety-like stress-induced suppression of behavior in the lateral bed nucleus. These results highlight the fact that, rather than a unified system-like role in modulating anxiety, the effects of GAL can be either facilitating or attenuating, and are region-specific, context-specific and response-specific.

Galanin and perseveration

Galanin is a 29/30 amino acid neuropeptide that has been shown to impair learning and memory task performance and also have roles in somatosensation, stress responses, sexual behavior, and feeding regulation. However, little is known about galanin involvement in higher cognitive processes, especially executive processes. Perseveration is a classic sign of frontal cortex damage and failure of executive control. Galanin has been shown to disrupt the performance of maze delayed alternation tasks and the operant, spatial delayed nonmatch-to-position (DNMTP) working memory task, tests especially sensitive to perseverative responding. To better understand this potential involvement of galanin in executive control, the present study tested the hypothesis that galanin induces perseveration. The first experiment examined the effects of galanin (10, 20 microg i.c.v.) on the performance of a simple operant response alternation task in which stimuli were assigned to one of two spatially distinct locations to produce extended sequences of presentations to one location, separated by a 10-s intertrial interval. The second experiment looked at the effects of galanin (5, 20 microg i.c.v.) on the performance of non-delayed match-to-position and nonmatch-to-position conditional discrimination operant tasks in which a minimal 1.0 s time interval separated responses. Finally, the effects of galanin (10, 20 microg i.c.v.) on delayed match-to-position (DMTP) performance were examined to determine whether response alternation (i.e., nonmatching) was critical to observing a galanin-induced impairment in this task. Galanin reduced the rate of trial completion in all the tasks, but did not alter simple or conditional discrimination accuracy. Galanin (10 microg) impaired DMTP performance in a delay-independent manner. Together, these data suggest that galanin does not produce perseveration, but are consistent with a galanin-induced decrease in reinforcer strength.

One for all or one for one: does co-transmission unify the concept of a brain galanin "system" or clarify any consistent role in anxiety?

Galanin (GAL) is a potential target for novel antidepressant or anti-anxiety drug development. However, no integrated role for a "brain galanin system" in anxiety has yet emerged. It is possible that such a function may be revealed by examining the interaction of GAL with norepinephrine (NE), with which it is prominently co-localized. We showed previously that enhancing stress-activation of the NE system by yohimbine (YOH) pretreatment induced the release of GAL in central amygdala (CeA) to exert an anxiolytic effect on the elevated plus-maze. However, it remained to be demonstrated conclusively that GAL was co-released from NE terminals in CeA in this context, or if a multi-synaptic circuit activated GAL release from another afferent to CeA, or from local GAL neurons in the vicinity of CeA. In studies presented at the Third International Symposium on Galanin and Its Receptors, we utilized a combination of behavioral pharmacological approaches, testing the effects of YOH on the behavioral response to stress on the plus-maze after lesioning NE afferents to CeA with 6-OHDA, and anatomical approaches to identify GAL afferents to CeA that are activated in the context of stress with yohimbine pretreatment, to address these alternatives. Our results suggest that GAL was not co-released from noradrenergic terminals innervating CeA to exert an anxiolytic influence when noradrenergic activation was amplified by yohimbine pretreatment. Rather, it most likely originated from GAL neurons immediately adjacent to CeA that were activated by a non-noradrenergic afferent arising from elsewhere in the brain, itself activated by increasing NE activity. Thus, any role for brain GAL in anxiety remains region-specific, pathway specific, response specific and context-specific, which is likely to continue to present challenges to the development of novel agents targeting brain GAL for treatment of depression or anxiety.

Assessment of new functional roles for galanin in the CNS

There is considerable evidence that galanin plays an important role in food intake, nociception, stress reactivity, sexual behavior, and learning. However, its involvement in other important behavioral processes, especially higher cognition, has not been systematically investigated. This review summarizes our recent efforts to explore the role of galanin in executive processes as well as in fundamental motivational and motor productive processes that are essential to the behavioral assessment of cognitive constructs in rodents. Our work points to a role in reward processes and physiological water balance regulation, and argues against a role for galanin in fine motor production and maintenance, simple visual discrimination, and perseveration.

Memory facilitation by methylene blue: Dose-dependent effect on behavior and brain oxygen consumption

Methylene blue administered post-training improves memory retention in avoidance and appetitive tasks, and restores spatial memory impaired by an inhibitor of cytochrome oxidase. Methylene blue may improve memory retention by increasing brain oxygen utilization. We investigated which doses improve memory without nonspecific behavioral effects, and whether methylene blue enhances brain oxygen consumption. Different doses were evaluated 24 h after administration in wheel running, feeding, open field habituation and object recognition tests. The 1-10 mg/kg methylene blue-treated rats were not different from saline-treated rats in locomotion or feeding behavior. The 50-100 mg/kg doses decreased running wheel behavior. The 4 mg/kg dose improved behavioral habituation and object memory recognition. Dose-dependent effects of methylene blue on brain oxygen consumption revealed that low concentrations increased brain oxygen consumption in vitro and 24 h after in vivo administration. Therefore, methylene blue doses that increase brain oxygen consumption also facilitate memory retention.

Construct validity of an operant signal detection task for rats

Many psychoactive drugs produce simultaneous effects on a variety of psychological processes. Behavioral measures in tasks designed to assess cognitive processes in rodents should be able to characterize and dissociate these multiple influences. The present study evaluated how error measures in a classic two-choice operant spatial signal detection paradigm were affected by procedural manipulations of the motivational state of the rat, stimulus properties, and alterations of the inter-trial interval. The experiments were conducted in a two lever operant chamber in which a cue lamp was mounted over each lever. The rats were trained to respond quickly to a short illumination of one of the cue lamps at one of three durations (100, 300 or 1000 ms), presented in a random order. The procedural manipulations were (1) to allow pre-session water access to the normally water-restricted subjects, (2) to vary the intertrial interval (ITI) between sessions, (3) to reduce the intensity of the discriminative stimuli, and (4) to manipulate the variability of the ITI within a session. Stimulus duration-dependent decreases of detection accuracy were observed following pre-session water access and when the intertrial interval was decreased. A reduction of stimulus intensity resulted in decreased accuracy at all stimulus durations. Varying the ITI within the session produced stimulus duration-independent alterations of detection accuracy but no change in the frequency of errors of omission. These findings show that distinct patterns of performance deficits result from manipulating different components of this task and that errors of omission and commission often co-vary and raise questions about the definitions of vigilance and sustained attention as these constructs apply to signal detection tasks that present spatially distinct stimuli.

Regulation of feeding by galnon

Galanin is a neuropeptide that has been implicated in multiple bioactivities, inter alia eating disorders. In this study, we have examined the effects of galnon, a novel low molecular weight galanin receptor ligand. Previous studies have shown that galnon acts as a systemically active, blood-brain barrier crossing agonist on galanin signaling both in vitro and in vivo, inhibiting pentylenetetrazole-induced seizures. Here, intracerebroventricular (10-20 microg) and intraperitoneal (1.5-5 mg/kg) administration of galnon induced a strong, dose-dependent reduction of food intake in rats and mice. This reduction in feeding occurred without reducing general activity and was shown to be attenuated by an intracerebroventricular administration of M35, a peptide galanin antagonist. These data demonstrate that galnon is a promising tool for studies of the involvement of galanin in feeding disorders and other behavioral processes.