Zebrafish models of autism spectrum disorder.

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder characterized by motor, social and cognitive deficits that develop early during childhood. The pathogenesis of ASD is not well characterized and involves a multifaceted interaction between genetic, neurobiological and environmental factors. Animal (experimental) models possess evolutionarily conserved behaviors and molecular pathways that are highly relevant for studying ASD. The zebrafish (Danio rerio) is a relatively new animal model with promise for understanding the pathogenesis of complex brain disorders and discovering novel treatments. As a highly social and genetically tractable organism, zebrafish have recently been applied to model a variety of deficits relevant to ASD. Here, we discuss the developing utility of zebrafish models of ASD, as well as current behavioral, toxicological and genetic models of ASD, and future directions of research in this field.

Adult zebrafish in CNS disease modeling: a tank that's half-full, not half-empty, and still filling.

The zebrafish (Danio rerio) is increasingly used in a broad array of biomedical studies, from cancer research to drug screening. Zebrafish also represent an emerging model organism for studying complex brain diseases. The number of zebrafish neuroscience studies is exponentially growing, significantly outpacing those conducted with rodents or other model organisms. Yet, there is still a substantial amount of resistance in adopting zebrafish as a first-choice model system. Studies of the repertoire of zebrafish neural and behavioral functions continue to reveal new opportunities for understanding the pathobiology of various CNS deficits. Although some of these models are well established in zebrafish, including models for anxiety, depression, and addiction, others are less recognized, for example, models of autism and obsessive-compulsive states. However, mounting data indicate that a wide spectrum of CNS diseases can be modeled in adult zebrafish. Here, we summarize recent findings using zebrafish CNS assays, discuss model limitations and the existing challenges, as well as outline future directions of research in this field.

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.

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.

Specification of variables predictive of victories in the sport of boxing: II. Further characterization of previous success.

Previous success, i.e., performance in the preceding bout and total number of wins and losses, was predictive of victory. Clarification of this effect was sought in examining whether the prior performance against a particular opponent or in a common location would be predictive of a victory in a bout against that opponent or in that locale. The career records of 739 male professional boxers who participated in contests held in the USA in November 2007 were collected from the BoxRec online database. Chi-squared tests and logistic regression analyses indicated that performance in the preceding bout, prior performance against the same opponent, and prior performance in a particular location were predictive of the outcome in a current bout.

Antidepressant efficacy screening of novel targets in the chick anxiety-depression model.

The chick anxiety-depression model is a hybrid simulation, which may prove useful as an early preclinical dual pharmacological screen for novel therapeutics. Separate dose-response studies were conducted with seven test compounds that have screened positive for antidepressant effects in rodent depression models and included prasterone (5.0-40.0 mg/kg), memantine (2.5-20.0 mg/kg), ketamine (1.0-10.0 mg/kg), mifepristone (50.0-400.0 mg/kg), DOV216,303 (5.0-20.0 mg/kg), CGP36742 (2.5-15.0 mg/kg), and antalarmin (1.0-30.0 mg/kg). Chicks aged 4-6 days posthatch received test compounds intramuscularly 15 min before social separation, in which distress vocalization rates were recorded. High rates of vocalization in the first phase (0-5 min) of social separation seem to model an anxiety-like state and lower rates of vocalization in the second phase (30-60 min) seem to model a depression-like state. Prasterone, memantine, ketamine, and DOV216,303 attenuated and CPG36742 enhanced the pattern of vocalizations in the first phase. Prasterone, ketamine, mifepristone, DOV216,303, and CPG36742 attenuated and memantine and antalarmin enhanced the pattern of vocalizations in the second phase. This pattern of drug effects parallels what clinical data exist, and highlights two important characteristics of this dual-screening assay. For the compounds tested, this chick model identified phase II and III clinical failures (e.g. memantine and antalarmin) and has the potential to reveal possible contraindications of compounds (i.e. CPG36742) in cases where anxiety symptoms are concomitant with a depressive episode.

Sex differences in working memory.

In two separate studies, sex differences in modal-specific elements of working memory were investigated by utilizing words and pictures as stimuli. Groups of men and women performed a free-recall task of words or pictures in which 20 items were presented concurrently and the number of correct items recalled was measured. Following stimulus presentation, half of the participants were presented a verbal-based distraction task. On the verbal working-memory task, performance of men and women was not significantly different in the no-distraction condition. However, in the distraction condition, women's recall was significantly lower than their performance in the no-distraction condition and men's performance in the distraction condition. These findings are consistent with previous research and point to sex differences in cognitive ability putatively resulting from functional neuroanatomical dissimilarities. On the visual working-memory task, women showed significantly greater recall than men. These findings are inconsistent with previous research and underscore the need for further research.

Specification of variables predictive of victories in the sport of boxing.

Compared to other sports, very little research has been conducted on which variables can predict victory in the sport of boxing. This investigation examined whether boxers' age, weight change from their preceding contest, country of origin, total number of wins, total number of losses, performance in their preceding contest, or the possession of a championship title was predictive of a winning performance in a given bout. A 1-mo. sample of male professional boxing records for all contests held in the USA (N = 400) were collected from the BoxRec online database. Logistic regression analysis indicated that only boxers' age, total number of wins and losses, and the performance in the preceding contest predicted significant variance in outcome.

Modeling the anxiety-depression continuum hypothesis in domestic fowl chicks.

Anxiety and depression are currently classified as separate clinical syndromes despite considerable similarities in their symptoms, pathophysiological substrates and response to treatment interventions. An alternative hypothesis views anxiety and depression along a temporal continuum, a construct that the current research attempts to model in a preclinical setting. In experiment 1, socially raised domestic fowl chicks separated from conspecifics demonstrated a pattern of distress vocalizations that sequentially models anxiety-like and depressive-like states. In addition, administration of the benzodiazepine anxiolytic chlordiazepoxide and the tricyclic antidepressant imipramine provided pharmacological validation for the model in that they were capable of dissociating the anxiety-like and depressive-like states. In experiment 2, corticosterone levels were quantified across the isolation test session to provide convergent validity to the model. These findings fit well with the human clinical literature on the anxiety-depression continuum perspective, and suggest the consideration of a nosology that emphasizes the inter-relatedness of these clinical states rather than their boundaries.

Modeling anxiety-like states: pharmacological characterization of the chick separation stress paradigm.

While previous research has sought to validate the chick separation stress paradigm as an anxiolytic screening assay, it is unknown whether the paradigm better models a nonspecific anxiety-like state or something similar to panic disorder or generalized anxiety disorder. To characterize the anxiety model pharmacologically, cockerels were administered drug probes that were either: (1) only effective for treating panic disorder (phenelzine 3.125-25.0 mg/kg), (2) effective for treating both panic disorder and generalized anxiety disorder (alprazolam 0.065-0.5 mg/kg; clonidine 0.1-0.25 mg/kg; imipramine 1.0-15.0 mg/kg), (3) only effective for treating generalized anxiety disorder (buspirone 2.5-10.0 mg/kg; trazodone 0.1-3.0 mg/kg) or (4) capable of exacerbating symptoms of panic disorder in humans (yohimbine 0.1-3.0 mg/kg). At 7 days after hatch, chicks received either vehicle or drug probe intramuscularly 15 min prior to social separation under a mirror (low-stress) or no-mirror (high-stress) condition for a 180-s observation period. Dependent measures were distress vocalizations to index separation stress and sleep-onset latency to index sedation. Phenelzine, alprazolam, imipramine and clonidine were able to attenuate distress vocalizations (at doses without significant sedation) whereas buspirone and trazodone did not. Paradoxically, yohimbine modestly attenuated distress vocalizations. These results suggest that the chick separation stress paradigm better models panic disorder than generalized anxiety disorder as an anxiolytic screen.

Antinociceptive profile of salvinorin A, a structurally unique kappa opioid receptor agonist.

Salvinorin A, is a structurally unique, non-nitrogenous, kappa opioid receptor (KOP) agonist. Given the role of KOPs in analgesic processes, we set out to determine whether salvinorin A has antinociceptive activity in thermal and chemo-nociceptive assays. The tail-flick assay was employed to investigate 1) salvinorin A's (0.5, 1.0, 2.0, and 4.0 mg/kg) dose-response and time-course (10, 20, and 30 min) effects in a thermal nociceptive assay, and 2) the ability for the KOP antagonist norBNI (10.0 mg/kg) to prevent salvinorin A antinociception. The hotplate assay was utilized as a second thermal nociceptive measure to test salvinorin A's dose-response effects. The acetic acid abdominal constriction assay was used to study salvinorin A's dose-response and time-course (over 30 min) effects in a chemo-nociceptive assay. Together, these studies revealed that salvinorin A produces a dose-dependent antinociception that peaked at 10 min post-injection but rapidly returned to baseline. Additionally, pretreatment with the KOP antagonist norbinaltorphimine (norBNI) reversed salvinorin A-induced antinociception. These findings demonstrate that salvinorin A produces a KOP mediated antinociceptive effect with a short duration of action.

Opioid receptor function in social attachment in young domestic fowl.

Opioid systems are implicated in social attachment processes. This research sought to determine the functional contribution of each opioid receptor in modulating social attachment/separation distress. Following ICV administration of opiate probes, 7-day-old cockerels were isolated from conspecifics for a 3 min test period under either a mirror or no-mirror condition. Vocalizations served as the measure of separation-stress. Opioid receptor probes included: the mu agonist DAMGO (0.02, 0.19, 1.95 nmol), the mu antagonist CTOP (0.009, 0.09, 0.9 nmol), the delta agonist SNC80 (0.3, 1.0, 3.0 micromol), the delta antagonist naltrindole (0.2, 2.2, 22.2 nmol), the kappa agonist U50, 488 (1, 30, 100 nmol), the kappa antagonist norBNI (1.3, 13.6, 136.1 nmol), the NOP agonist N/OFQ (0.01, 0.1, 1.0 nmol), and the NOP antagonist UFP-101 (0.1, 1.0, 10.0 nmol). DAMGO attenuated separation distress vocalizations. No other drug probe enhanced or attenuated distress vocalizations. Further, the non-selective opiate antagonist naloxone (0.3, 8.3, 27.5 nmol) did not exacerbate distress vocalizations. These results suggest that only the mu receptor modulates social attachment in young domestic fowl.

High-performance liquid chromatographic determination of xanthohumol in rat plasma, urine, and fecal samples.

Xanthohumol (XN) is the major prenylated flavonoid in hop plants and as such a constituent of beer. Pharmacological studies have shown that XN possesses marked antioxidant and antiproliferative effects. In order to study the resorption and metabolism of this compound, reversed-phase high-performance liquid chromatography is used for the determination of XN in rat plasma, urine, and feces. In session one, rats receive either oral or intravenous (iv) administration (20 mg/kg body weight) of XN. In session two, rats receive oral administration of 50, 100, 200, 400, and 500 mg/kg body weight XN for bioavailability studies at various dose levels. Plasma, urine, and feces are collected at varying time points and assayed for their XN content. Plasma levels of XN fell rapidly within 60 min after iv administration; no XN is detected in plasma after oral administration in either session. XN and its metabolites are excreted mainly in feces within 24 h of administration. The method is a reliable tool for performing studies of XN in different biological material.

The chick separation stress paradigm: a validation study.

To expand the generalizability of the chick separation stress paradigm as a high-throughput anxiolytic screen, six positive drug probes (doses in mg/kg: meprobamate 15-120, pentobarbital 2.5-20.0, chlordiazepoxide 2.5-15.0, buspirone 2.5-10.0, imipramine 1-15, and clonidine 0.10-0.25) and five negative drug probes (amphetamine 0.5-4.0, scopolamine 0.2-1.6, caffeine 5-20, chlorpromazine 1-30, and haloperidol 0.03-1.00) were evaluated in the test. Seven-day-old chicks received intramuscular injections of either vehicle or drug probe 15 min prior to tests in either a mirror (low-stress) or a no-mirror (high-stress) condition for a 3-min observation period. The dependent measures were distress vocalizations to index separation stress and sleep onset latency to index sedation. All positive drug probes attenuated distress vocalizations in a dose-dependent manner, except buspirone. All positive drug probes affected sleep onset latency in a dose-dependent manner, except buspirone and imipramine. In all cases, the anxiolytic-like effect of positive drug probes was greater than its sedative effect. None of the negative drug probes affected either distress vocalizations or sleep onset latency, except for the highest dose of amphetamine, which caused pronounced stereotypy. These findings demonstrate that this anxiolytic screen is sensitive to a wide range of positive pharmacological probes and insensitive to a wide range of negative pharmacological probes.

Practice and incentive motivation in recognition of inverted faces.

In each of three experiments, participants received successive daily practice sessions on the task of recognizing inverted faces. In all practice sessions, an initial study series of 25 inverted faces was followed immediately by a test series of 17 pairs of inverted faces. Each test pair comprised a face from the study series and a new face. Completely new sets of faces were used in each session. Recognition of inverted faces did not improve across sessions in Exp. 1 but did improve in Exps. 2 and 3. Unlike Exp. 1, Exps. 2 and 3 employed an explicit incentive for improved performance. These results show that sufficiently motivated participants can become quite proficient at recognizing inverted faces. Implications of the results for the role of expertise at recognition in producing the inversion effect are discussed.

Corticosterone response in the chick separation-stress paradigm.

Corticosterone response to separation stress and its sensitivity to the anxiolytic, chlordiazepoxide (CDP), were examined in 7-day-old domestic fowl (Gallus gallus). Saline or CDP (8.0 mg/kg) was injected intramuscularly 30 min before tests. Chicks were placed in isolation either with or without mirrors for a 15-min observation period, in which distress vocalizations were recorded. After testing, chicks were euthanized and blood was collected for the corticosterone assay. Chicks tested in the No-Mirror condition displayed an increase in vocalizations that was attenuated by CDP. Similarly, corticosterone levels were highest in chicks tested in the No-Mirror condition; however, CDP only modestly attenuated corticosterone levels. The present findings demonstrate that corticosterone levels parallel the behavioral marker of distress vocalizations in this paradigm, but this biological marker may be less sensitive than the behavioral marker to benzodiazepine anxiolytic manipulations.