Short daylight photoperiod alleviated alarm substance-stimulated fear response of zebrafish

Photoperiod has been well-documented to be involved in regulating many activities of animals. However, whether photoperiod takes part in mood control, such as fear response in fish and the underlying mode(s) of action remain unclear. In this study, adult zebrafish males and females (Danio rerio) were exposed to different photoperiods, Blank (12 h light: 12 h dark), Control (12 h light: 12 h dark), Short daylight (SD, 6 h light: 18 h dark) and Long daylight (LD, 18 h light: 6 h dark) for 28 days. After exposure, fear response of the fish was investigated using a novel tank diving test. After alarm substance administration, the onset to higher half, total duration in lower half and duration of freezing in SD-fish were significantly decreased, suggesting that short daylight photoperiod is capable of alleviating fear response in zebrafish. In contrast, comparing with the Control, LD didn't show significant effect on fear response of the fish. Further investigation revealed that SD increased the levels of melatonin (MT), serotonin (5-HT) and dopamine (DA) in the brain while decreased the plasma level of cortisol comparing to the Control. Moreover, the expressions of genes in MT, 5-HT and DA pathways and HPI axis were also altered consistently. Our data indicated that short daylight photoperiod might alleviate fear response of zebrafish probably through interfering with MT/5-HT/DA pathways and HPI axis.

Prazosin use in a patient with rare Neurobeachin gene deletion shows improvement in paranoid behavior: a case report

Background

Disruption of the Neurobeachin gene is a rare genetic mutation that has been implicated in the development of autism and enhanced long-term potentiation of the hippocampal CA1 region, causing a heightened conditioned fear response and impaired fear extinction. Prazosin, an alpha-1 receptor antagonist, has been used in patients with posttraumatic stress disorder to mitigate the increased alpha-1 activity involved in fear and startle responses. Here we report a case of a patient with a rare Neurobeachin gene deletion, who demonstrated marked and sustained improvement in paranoid behavior within days of prazosin initiation.

Case presentation

The patient is a 27-year-old White male with autism spectrum disorder, obsessive–compulsive disorder, and schizophrenia, with a chromosome 13q12 deletion including deletion of the Neurobeachin gene, who presented to the emergency department due to worsening functional status and profound weight loss as a result of only eating prepackaged foods. He had not showered or changed clothes in several months prior to presentation. He was hospitalized in the inpatient psychiatric unit for 2 months before prazosin was initiated. During that time, he demonstrated paranoia as evidenced by heightened sensitivity to doors opening, guarded interactions, and limited communication with providers and other patients. He also exhibited poor grooming habits, with aversion to showering, shaving, and changing clothes. Since initiating prazosin, he has demonstrated a brighter affect, initiates and maintains conversations, showers and changes clothes on a regular basis, and eats a variety of foods. At the time of this report, the patient was discharged to live in an apartment with a caregiver after a 7-month inpatient hospitalization.

Conclusions

Low-dose prazosin shows rapid and sustained improvement in paranoid behavior in a patient with a rare Neurobeachin gene deletion. Prazosin has a relatively favorable side effect profile with once-daily dosing and low cost. Prazosin may provide clinical improvement in patients with Neurobeachin gene deletions due to its theoretical attenuation in fear response through alpha-1 antagonism.

Role of Medial Prefrontal Cortical Neurons and Oxytocin Modulation in the Establishment of Social Buffering

Fear-related behaviors are rigidly controlled by the medial prefrontal cortex (mPFC). The mPFC is activated by the prosocial hormone oxytocin, which plays an important role in social buffering. We used a slice patch current-clamp recording in single- and pair-exposed rats who were subjected to electric shocks, to determine the cellular mechanism of the action of oxytocin in the mPFC under social buffering conditions. Pair-exposed rats showed a significant reduction in both freezing and passive avoidance behaviors compared to single-exposed rats. It was observed that input resistance in pyramidal neurons decreased in both single- and pair-exposed rats than na?ve rats, but input resistance in interneurons increased in pair-exposed rats than single-exposed rats. We found that the number of action potential (AP) spikes in the mPFC pyramidal neurons decreased significantly in pair-exposed rats than in single-exposed rats. The pyramidal neurons in the mPFC were similarly regulated by oxytocin in singleand pair-exposed rats, while the number of AP spikes in interneurons by oxytocin decreased in single-exposed rats, but there was no significant change in pair-exposed rats. Therefore, our findings reveal that a decrease in mPFC pyramidal neuronal activity in pair-exposed rats through social interaction induces a reduction in fear-related behavior via obstruction of fear-memory formation; however, no such reduction was observed in single-exposed rats. Moreover, we suggest that the oxytocin-mediated decrease in neuronal activity in the mPFC could facilitate social buffering.

Mechanisms involved in tributyltin-enhanced aggressive behaviors and fear responses in male zebrafish

Tributyltin (TBT), an aromatase inhibitor, has been found to disrupt gametogenesis and reproductive behavior in several fish species. However, whether TBT is capable of affecting other behaviors such as aggressive behavior and fear response in fish and the underlying mode(s) of action remain unclear. To study aggressive behavior, adult zebrafish (Danio rerio) males were continuously exposed to two nominal concentrations of TBT (TBT-low, 100 ng/L and TBT-high, 500 ng/L) for 28 days. To study the fear response, the fish were divided into four groups (Blank and Control, 0 ng/L TBT; TBT-low, 100 ng/L; and TBT-high, 500 ng/L). The fish were then treated with DW (Blank) or with alarm substance (AS) (Control, TBT-low and TBT-high). After exposure, the aggressive behavior of the fish was tested using the mirror test (mirror-biting frequency, approaches to the mirror and duration in approach zone).and fighting test (fish-biting frequency) The mirror-biting frequency, approaches to the mirror, duration in approach zone and fish-biting frequency of the TBT-exposed fish increased significantly compared to those of the control fish, indicating enhanced aggressive behavior. The fear response parameters tested using the novel tank dive test (onset time to the higher half, total duration in the lower half and the frequency of turning) of the TBT-exposed fish were also significantly increased after AS administration, suggesting an enhanced fear response. Further investigation revealed that TBT treatment elevated the plasma level of 11-ketotestosterone (11-KT) and decreased the plasma level of estradiol (E2) in a concentration-dependent manner. Moreover, TBT up-regulated the mRNA levels of ar, c-fos and bdnf1, and suppressed the expression of btg-2 in fish. In addition, exposure to AS increased the plasma level of cortisol and down-regulated the mRNA expression levels of genes involved in 5-HT synthesis (such as tph1b and pet1) in both control and TBT-treated fish. AS significantly suppressed the mRNA level of tph1b, tph2, pet1 and npy in the TBT-high group compared to the control fish. The present study demonstrates that TBT enhances aggressive behavior and fear responses in male zebrafish probably through altering plasma levels of 11-KT, E2 and cortisol and altering the expression of genes involved in the regulation of aggressive behavior (ar, c-fos, bdnf1 and btg-2) and fear responses (tph1b, tph2, pet1 and npy). The present study greatly extends our understanding of the behavioral toxicity of TBT to fish.

Variability in response to severe stress: highly reactive rats exhibit changes in fear and anxiety-like behavior related to distinct neuronal co-activation patterns

There is an important individual variability in development of posttraumatic stress disorder (PTSD) and this feature needs to be better addressed in preclinical studies. Previously we showed that only rats that explored the context before a foot shock (delayed shock group) exhibited long-lasting behavioral changes. In this study the delayed shock group was segregated using the freezing response upon re-exposure to the shock-paired context and we investigated whether higher reactivity would be related to behavioral alterations and to activation of brain regions using Fos immunoreactivity. The latter allowed the analysis of co-activity patterns among brain regions within each group, by creating connectivity maps. High responder rats (HR) displayed heightened freezing response upon context re-exposure, anxiety-like behavior, impaired exploratory behavior and fear sensitization. Fos analysis showed that HR displayed a negative correlation between the medial prefrontal cortex and the ventral hippocampus (vHPC) after the first context re-exposure. After the second context re-exposure, HR displayed reduced Fos expression in vHPC CA1 area, whereas low responders (LR) showed increased Fos in the paraventricular nucleus of the thalamus. Pearson correlation analyses revealed positive associations between freezing and Fos in the dorsal the periaqueductal gray and vHPC after exposure to unfamiliar acoustic stimulus in a novel environment. Thus, assessment of individual variability allowed the identification of a subset of reactive animals that displayed behavioral modifications relevant to PTSD. Fos correlation and network analyses revealed co-activity patterns in HR rats that may point out to associations of brain areas relevant to the behavioral outcomes.

Association of open field behavior with blood and semen characteristics in roosters: an alternative animal model

INTRODUCTION

The paucity of literature is addressed regarding the correlation between open field as an individual behavioral trait on reproductive capacity in animals.

MATERIALS AND METHODS

To address this, Nine-month-old indigenous roosters were housed in individual cages. Each animal was observed twice a week for ten minutes before feeding in an open field apparatus for two weeks (7:00-12:00PM).

RESULTS

Interestingly, it was found that rooster's semen characteristics were correlated with their open field behavior. On the other hand, plasma glucose level as a blood attribute was more correlated with semen characteristics. The open field monitoring also revealed that the roosters with the lowest delay to their first pace had the highest sperm forward motility and lower sperm abnormality. The heterophil to lymphocyte ratio (H:L) was found to be low when pace bout and pace numbers were 20 and 35, respectively. The negative correlation between H:L ratio and semen characteristics (live sperm percentage, sperm concentration, and membrane integrity) may be an indication of poor reproductive performance in fearful roosters with higher H:L ratio.

CONCLUSIONS

The data suggested a relationship between open field behavior indices and some reproductive parameters in roosters. The results might be applicable for selection of more reproductive animals. Hence, the rooster may also be useful model for similar studies in other species.

Foraging decisions in wild versus domestic Mus musculus: What does life in the lab select for?

What does domestication select for in terms of foraging and anti-predator behaviors? We applied principles of patch use and foraging theory to test foraging strategies and fear responses of three strains of Mus musculus: wild-caught, control laboratory, and genetically modified strains. Foraging choices were quantified using giving-up densities (GUDs) under three foraging scenarios: (1) patches varying in microhabitat (covered versus open), and initial resource density (low versus high); (2) daily variation in auditory cues (aerial predators and control calls); (3) patches with varying seed aggregations. Overall, both domestic strains harvested significantly more food than wild mice. Each strain revealed a significant preference for foraging under cover compared to the open, and predator calls had no detectable effects on foraging. Both domestic strains biased their harvest toward high quality patches; wild mice did not. In terms of exploiting favorable and avoiding unfavorable distributions of seeds within patches, the lab strain performed best, the wild strain worst, and the mutant strain in between. Our study provides support for hypothesis that domestic animals have more energy-efficient foraging strategies than their wild counterparts, but retain residual fear responses. Furthermore, patch-use studies can reveal the aptitudes and priorities of both domestic and wild animals.

Identification of the CART neuropeptide circuitry processing TMT-induced predator stress

Abundance of cocaine- and amphetamine-regulated transcript (CART) neuropeptide in the limbic areas like the olfactory system, central nucleus of amygdala (CeA), ventral bed nucleus of stria terminalis (vBNST) and the hypothalamus suggests involvement of the peptide in emotive processing. We examined the role of CART in mediating fear, a strong emotion with profound survival value. Rats, exposed to 2,4,5-trimethyl-3-thiazoline (TMT), a predator related cue extracted from fox feces, showed significant increase in freezing, escape and risk assessment behavior, whereas grooming was reduced. Neuronal activity was up-regulated in the CeA and vBNST in terms of increased immunoreactivity in CART elements and c-Fos expression. Increased expression of both the markers was also seen in some discrete magnocellular as well as parvicellular subdivisions of the paraventricular nucleus (PVN). However, CART containing mitral cells in the main or accessory olfactory bulb did not respond. CART antibody was stereotaxically injected bilaterally into the CeA to locally immunoneutralize endogenous CART. On exposure to TMT, these rats showed reduced freezing, risk assessment and escape behavior while grooming was restored to normal value. We suggest that the CART signaling in the CeA and vBNST, but not in the olfactory system, might be an important component of the innate fear processing, and expression of stereotypic behavior, while CART in the PVN subdivisions might mediate the neuroendocrine response to predator stress.

FGF2 blocks PTSD symptoms via an astrocyte-based mechanism. Behav Brain Res. 2013;256:472-480. [PMID: 24013012 DOI: 10.1016/j.bbr.2013.08.048]

Although posttraumatic stress disorder (PTSD) is characterized by traumatic memories or experiences and increased arousal, which can be partly alleviated by antidepressants, the underlying cellular mechanisms are not fully understood. As emerging studies have focused on the critical role of astrocytes in pathological mood disorders, we hypothesized that several 'astrocyte-related' mechanisms underlying PTSD exist. In the present study, using the single prolonged stress (SPS) model, we investigated the effects of intraperitoneal FGF2 on SPS-induced PTSD behavior response as well as the astrocytic activation after FGF2 administration in SPS rats. Behavioral data showed that intraperitoneal FGF2 inhibited SPS-induced hyperarousal and anxiety behavior; however, immunohistochemistry showed that SPS-induced astrocytic inhibition was activated by intraperitoneal FGF2. Quantitative western blotting showed that intraperitoneal FGF2 up-regulated glial fibrillary acidic protein (GFAP), but not NeuN, expression in the hippocampus. We suggest that intraperitoneal FGF2 could block the SPS-induced fear response and anxiety behavior in PTSD via astrocyte-based but not neuron-based mechanisms.