Sex is an important variable in biomedical research. The zebrafish (Danio rerio) is increasingly utilized as a powerful new model organism in translational neuroscience and pharmacology. Mounting evidence indicates important sex differences in zebrafish behavioral and neuropharmacological responses. Here, we discuss the role of sex in zebrafish central nervous system (CNS) models, their molecular mechanisms, recent findings and the existing challenges in this field. We also emphasize the growing utility of zebrafish models in translational neuropharmacological research of sex differences, fostering future CNS drug discovery and the search for novel sex-specific therapies. Finally, we highlight the interplay between sex and environment in zebrafish models of sex-environment correlations as an important strategy of CNS disease modeling using this aquatic organism.

Sex differences in behavior and neuropharmacology of zebrafish.

Diabetes mellitus (DM) and chronic cerebral hypoperfusion(CCH)are both risk factors for cognitive impairment. However, whether DM and CCH can synergistically promote cognitive impairment and the related pathological mechanisms remain unknown. To investigate the effect of DM and CCH on cognitive function, rats fed with high-fat diet (HFD) and injected with low-dose streptozotocin (STZ) followed by bilateral common carotid artery occlusion (BCCAO) were induced to mimic DM and CCH in vivo and mouse BV2 microglial cells were exposed to hypoxia and/or high glucose to mimic CCH complicated with DM pathologies in vitro. To further explore the underlying mechanism, TREM-2-specific small interfering RNA and TREM-2 overexpression lentivirus were used to knock out and overexpress TREM-2, respectively. Cognitive deficits, neuronal cell death, neuroinflammation with microglial activation, and TREM-2-MAPK signaling were enhanced when DM was superimposed on CCH both in vivo and in vitro. Manipulating TREM-2 expression levels markedly regulated the p38 MAPK signaling and the inflammatory response in vitro. TREM-2 knockout intensified while TREM-2 overexpression suppressed the p38 MAPK signaling and subsequent pro-inflammatory mediator production under high glucose and hypoxia condition. These results suggest that TREM-2 negatively regulates p38 MAPK-mediated inflammatory response when DM was synergistically superimposed on CCH and highlight the importance of TREM-2 as a potential target of immune regulation in DM and CCH.

/pdf/trem-2-p38-mapk-signaling-regulates-neuroinflammation-during-169ritmsn1.pdf

TREM-2-p38 MAPK signaling regulates neuroinflammation during chronic cerebral hypoperfusion combined with diabetes mellitus.

In contrast to mammals, the adult zebrafish brain shows neurogenic activity in a multitude of niches present in almost all brain subdivisions. Irrespectively, constitutive neurogenesis in the adult zebrafish and mouse telencephalon share many similarities at the cellular and molecular level. However, upon injury during tissue repair, the situation is entirely different. In zebrafish, inflammation caused by traumatic brain injury or by induced neurodegeneration initiates specific and distinct neurogenic programs that, in combination with signaling pathways implicated in constitutive neurogenesis, quickly, and efficiently overcome the loss of neurons. In the mouse brain, injury-induced inflammation promotes gliosis leading to glial scar formation and inhibition of regeneration. A better understanding of the regenerative mechanisms occurring in the zebrafish brain could help to develop new therapies to combat the debilitating consequences of brain injury, stroke, and neurodegeneration. The aim of this review is to compare the properties of neural progenitors and the signaling pathways, which control adult neurogenesis and regeneration in the zebrafish and mammalian telencephalon.

/pdf/common-and-distinct-features-of-adult-neurogenesis-and-2vau9lhe9y.pdf

Common and Distinct Features of Adult Neurogenesis and Regeneration in the Telencephalon of Zebrafish and Mammals.

Arecoline is a naturally occurring psychoactive alkaloid with partial agonism at nicotinic and muscarinic acetylcholine receptors. Arecoline consumption is widespread, making it the fourth (after alcohol, nicotine and caffeine) most used substance by humans. However, the mechanisms of acute and chronic action of arecoline in-vivo remain poorly understood. Animal models are a valuable tool for CNS disease modeling and drug screening. Complementing rodent studies, the zebrafish (Danio rerio) emerges as a promising novel model organism for neuroscience research. Here, we assessed the effects of acute and chronic arecoline on adult zebrafish behavior and physiology. Overall, acute and chronic arecoline treatments produced overt anxiolytic-like behavior (without affecting general locomotor activity and whole-body cortisol levels), with similar effects also caused by areca nut water extracts. Acute arecoline at 10 mg/L disrupted shoaling, increased social preference, elevated brain norepinephrine and serotonin levels and reduced serotonin turnover. Acute arecoline also upregulated early protooncogenes c-fos and c-jun in the brain, whereas chronic treatment with 1 mg/L elevated brain expression of microglia-specific biomarker genes egr2 and ym1 (thus, implicating microglial mechanisms in potential effects of long-term arecoline use). Finally, acute 2-h discontinuation of chronic arecoline treatment evoked withdrawal-like anxiogenic behavior in zebrafish. In general, these findings support high sensitivity of zebrafish screens to arecoline and related compounds, and reinforce the growing utility of zebrafish for probing molecular mechanisms of CNS drugs. Our study also suggests that novel anxiolytic drugs can eventually be developed based on arecoline-like molecules, whose integrative mechanisms of CNS action may involve monoaminergic and neuro-immune modulation.

Effects of acute and chronic arecoline in adult zebrafish: Anxiolytic-like activity, elevated brain monoamines and the potential role of microglia

Over recent decades, changes in zebrafish (Danio rerio) behaviour have become popular quantitative indicators in biomedical studies. The circadian rhythms of behavioural processes in zebrafish are known to enable effective utilization of energy and resources, therefore attracting interest in zebrafish as a research model. This review covers a variety of circadian behaviours in this species, including diurnal rhythms of spawning, feeding, locomotor activity, shoaling, light/dark preference, and vertical position preference. Changes in circadian activity during zebrafish ontogeny are reviewed, including ageing-related alterations and chemically induced variations in rhythmicity patterns. Both exogenous and endogenous sources of inter-individual variability in zebrafish circadian behaviour are detailed. Additionally, we focus on different environmental factors with the potential to entrain circadian processes in zebrafish. This review describes two principal ways whereby diurnal behavioural rhythms can be entrained: (i) modulation of organismal physiological state, which can have masking or enhancing effects on behavioural endpoints related to endogenous circadian rhythms, and (ii) modulation of period and amplitude of the endogenous circadian rhythm due to competitive relationships between the primary and secondary zeitgebers. In addition, different peripheral oscillators in zebrafish can be entrained by diverse zeitgebers. This complicated orchestra of divergent influences may cause variability in zebrafish circadian behaviours, which should be given attention when planning behavioural studies.

Circadian rhythms in zebrafish (Danio rerio) behaviour and the sources of their variability

Neuroinflammation and metabolic deficits contribute to the etiology of human affective disorders, such as anxiety and depression. The zebrafish (Danio rerio) has recently emerged as a powerful new model organism in CNS disease modeling. Here, we exposed zebrafish to 2% glucose and 10% cholesterol for 19 days to experimentally induce type 2 diabetes (DM) and to assess stress responses, microglia, inflammation and apoptosis. We analyzed zebrafish anxiety-like behavior in the novel tank and light-dark box (Days 15–16) tests, as well as examined their biochemical and genomic biomarkers (Day 19). Confirming DM-like state in zebrafish, we found higher whole-body glucose, triglyceride, total cholesterol, low-density lipoprotein levels and glucagon mRNA expression, and lower high-density lipoprotein levels. DM zebrafish also showed anxiety-like behavior, elevated whole-body cortisol and cytokines IFN-γ and IL-4, as well as higher brain mRNA expression of the glucocorticoid receptor, CD11b (a microglial biomarker), pro-inflammatory cytokines IL-6 and TNF-α (but not IL-1β or anti-inflammatory cytokines IL-4 and IL-10), GFAP (an astrocytal biomarker), neurotrophin BDNF, its receptors p75 and TrkB, as well as apoptotic Bax and Caspase-3 (but not BCl-2) genes. Collectively, this supports the overlapping nature of DM-related affective pathogenesis and emphasizes the role of peripheral and central inflammation and apoptosis in DM-related affective and neuroendocrine deficits in zebrafish.

High-glucose/high-cholesterol diet in zebrafish evokes diabetic and affective pathogenesis: The role of peripheral and central inflammation, microglia and apoptosis.

The role of intraspecies variation in fish neurobehavioral and neuropharmacological phenotypes in aquatic models.

OBJECTIVE
To observe the effect of five-element music therapy of traditional Chinese medicine (TCM) on the clinical symptoms and the quality of life in the patients with suboptimal health status (SHS) of liver stagnation and spleen deficiency and explore the corresponding specificity changes in the temperature of acupoints when zangfu functions are of dysfunction and recovered to be balanced, separately.


METHODS
Sixty patients with SHS of liver stagnation and spleen deficiency were randomized into an observation group and a control group, 30 cases in each one. In the control group, the conventional health education was provided. In the observation group, on the base of the therapeutic regimen as the control group, the patients received the five-element music therapy to pacify the liver qi and strengthen the spleen functions, once every two days, 30 min each time, 3 treatments a week. The course of treatment consisted of 4 weeks. Before and after treatment, the TCM syndrome score and the MOS 36-item short form healthy survey (SF-36) score were compared between the two groups and the clinical therapeutic effect was evaluated. Using infrared thermal imaging, the temperature at the acupoints of the affected organs (liver, spleen), the related organs (gallbladder, stomach) and the other non-related zangfu organs (pericardium, lung) was detected before and after treatment in the two groups.


RESULTS
After treatment, the TCM syndrome scores were reduced when compared with those before treatment in the two groups (P<0.01, P<0.05); the reduction in the observation group was larger than that of the control group (P<0.01). The score of each domain for the SF-36 in the observation group and the score of role-emotional domain in the control group were all increased when compared with the scores before treatment (P<0.01, P<0.05); and the score of each domain for the SF-36 in the observation group was higher than that in the control group (P<0.01). The total effective rate was 66.7% (20/30) in the observation group, which was higher than 10.0% in the control group (3/30, P<0.05). In the observation group, the temperature of the yuan-primary point, the back-shu point and the front-mu point related to the liver, as well as those related to the gallbladder after treatment was reduced when compared with the temperature before treatment; and the changes were larger than those of the control group (P<0.01). The temperature of the yuan-primary point, the back-shu point and the front-mu point related to the spleen, as well as the back-shu point and the front-mu point related to the stomach in the observation group was increased when compared with the temperature before treatment (P<0.01); and the changes were larger than those of the control group (P<0.01). For the temperature of the non-specific points related to the liver and spleen, as well as the yuan-primary point, the back-shu point and the front-mu point related to the pericardium and the lung, there was no significant differences when compared with the temperature at the above-mentioned acupoints before and after treatment (P>0.05).


CONCLUSION
TCM five-element music therapy associated with the conventional health education may effectively relieve the clinical symptoms and improve the quality of life in the patients with suboptimal health status of liver stagnation and sleep deficiency; and the therapeutic effect is better than the simple health education. The changes in the temperature of acupoints may reflect the functional regulation of the related zangfu organs in the body.

[Regulatory effect of five-element music therapy of traditional Chinese medicine for suboptimal health status of liver stagnation and spleen deficiency based on the temperature changes of acupoints].

Jia Jia Wang

Papers

High-glucose/high-cholesterol diet in zebrafish evokes diabetic and affective pathogenesis: The role of peripheral and central inflammation, microglia and apoptosis.

The role of intraspecies variation in fish neurobehavioral and neuropharmacological phenotypes in aquatic models.

[Regulatory effect of five-element music therapy of traditional Chinese medicine for suboptimal health status of liver stagnation and spleen deficiency based on the temperature changes of acupoints].