Alterations In Locomotor Behavior Research Articles

Behavioral risk models explain locomotor and balance changes when walking at virtual heights.

Walking in daily life requires humans to adapt to environments that can influence one's fear of falling and anxiety about a potential fall. In such environments, individuals may adopt compensatory locomotor and balance changes to maintain a constant expected risk function equal to the product of the probability of some event (e.g., a fall) and the cost of that event (e.g., injury or death). Here, we tested whether locomotor behaviors broadly align with this risk model in two experiments with height-related threats in immersive virtual reality. In Experiment 1, we examined how individuals change their locomotor trajectory while walking along a straight high-elevation walkway. In Experiment 2, we examined how individuals change trajectory and balance control during curved walking where the location of high elevation threat varied. Participants adopted two behaviors that decreased their probability of falling off the edge and aligned with the risk-based model: participants altered their proximity to perceived threats that pose high costs (e.g., a high-elevation ledge), and decreased mediolateral center of mass velocity when that was not possible. Taken together, our results suggest that individuals alter locomotor behavior to change the probability of falling based on the perceived cost of that fall.

Exposure of male adult zebrafish (Danio rerio) to triphenyl phosphate (TPhP) induces eye development disorders and disrupts neurotransmitter system-mediated abnormal locomotor behavior in larval offspring

Triphenyl phosphate (TPhP) is a widely used organophosphorus flame retardant, which has become ubiquitous in the environment. However, little information is available regarding its transgenerational effects. This study aimed to investigate the developmental toxicity of TPhP on F1 larvae offspring of adult male zebrafish exposed to various concentrations of TPhP for 28 or 60 days. The findings revealed significant morphological changes, alterations in locomotor behavior, variations in neurotransmitter, histopathological changes, oxidative stress levels, and disruption of Retinoic Acid (RA) signaling in the F1 larvae. After 28 and 60 days of TPhP exposure, the F1 larvae exhibited a myopia-like phenotype with pathological alterations in the lens and retina. The genes involved in the RA signaling pathway were down-regulated following parental TPhP exposure. Swimming speed and total distance of F1 larvae were significantly reduced by TPhP exposure, and long-term exposure to environmental levels of TPhP had more pronounced effects on locomotor behavior and neurotransmitter levels. In conclusion, TPhP induced histological and morphological alterations in the eyes of F1 larvae, leading to visual dysfunction, disruption of RA signaling and neurotransmitter systems, and ultimately resulting in neurobehavioral abnormalities. These findings highlight the importance of considering the impact of TPhP on the survival and population reproduction of wild larvae.

The topographical attenuation of cutaneous input is modulated at the ankle joint during gait.

The attenuation of sensory inputs via various methods has been demonstrated to impair balance control and alter locomotor behavior during human walking; however, the effects of attenuating foot sole sensation under distinct areas of the foot sole on lower extremity motor output remains poorly understood. Thus, the purpose of this study was to attenuate cutaneous feedback via regional hypothermia under five different areas of the foot sole and investigate the resultant modulation of kinematic and muscle activity during level walking. Electromyography from eight lower leg muscles, kinematics, and location of center of pressure was recorded from 48 healthy young adults completing walking trials with normal and reduced cutaneous sensation from bilateral foot soles. The results of this study highlight the modulatory response of the tibialis anterior in terminal stance (propulsion and toe-off) and medial gastrocnemius muscle throughout the entire stance phase of gait. The topographical organization of foot sole skin in response to the attenuation of cutaneous feedback from different areas of the foot sole significantly modified locomotor activity. Furthermore, the locomotor response to cutaneous attenuation under the same regions that we previously facilitated with tactile feedback do not oppose each other, suggesting different physiological changes to foot sole skin generate unique gait behaviors.

P14 Altered Locomotor Behavior Associated With Purkinje Cells and Astrocytes Dysfunctions in Rat With Acute Hepatic Encephalopathy Involving the Oxidative Stress and Neuroinflammation

P14 Altered Locomotor Behavior Associated With Purkinje Cells and Astrocytes Dysfunctions in Rat With Acute Hepatic Encephalopathy Involving the Oxidative Stress and Neuroinflammation

Sanguinarine exposure induces immunotoxicity and abnormal locomotor behavior in zebrafish.

Sanguinarine (C20H14NO4+), a plant alkaloid and pesticide, works well a fungicidal and insecticidal applications. The prospect that sanguinarine may have potentially toxic effects on aquatic organisms has been brought to light by its use in agriculture. The first evaluation of the immunotoxic and behavioral effects of sanguinarine exposure on larval zebrafish was done in this work. Firstly, zebrafish embryos exposed to sanguinarine had shorter body length, larger yolk sacs, and slower heart rates. Secondly, the number of innate immune cells was significantly reduced. Thirdly, alterations in locomotor behavior were observed as exposure concentrations increased. Total distance travelled, travel time, and mean speed were all reduced. We also found significant changes in oxidative stress-related indicators and a significant increase in apoptosis in the embryos. Further studies revealed aberrant expression of some key genes in the TLR immune signaling pathway including CXCL-c1c, IL8, MYD88, and TLR4. At the same time, the expression of the pro-inflammatory cytokine IFN-γ was upregulated. To sum up, our results suggest that sanguinarine exposure may cause immunotoxicity and aberrant behavior in larval zebrafish.

Metabolic exploration of the developmental abnormalities and neurotoxicity of Esculentoside B, the main toxic factor in Phytolaccae radix.

P: radix is a perennial herb, and its extracts have various biological properties that make it a potential candidate for the treatment of tumors, edema, and lymphatic stasis. However, the main factor contributing to its toxicity are not clear. Here, we used a zebrafish toxicological model to study the main toxicity factor of P. radix and explore the potential mechanisms involved. The results revealed that Esculentoside B was the major toxic factor of P. radix. Exposure of zebrafish larvae to Esculentoside B caused developmental abnormalities, neurotoxicity and altered locomotor behavior. The combination of AChE activity and the expression levels of genes relevant to CNS development demonstrated that Esculentoside B is neurotoxic to zebrafish larvae, impairs their CNS development, and that AChE may be a toxic target of Esculentoside B. Metabolomic analysis has revealed that Esculentoside B exposure can disrupt D-Amino acid metabolism, protein export, autophagy, and mTOR signaling pathways in zebrafish larvae. These findings provide insights into the molecular mechanisms underlying EsB-induced neurotoxicity in zebrafish, which can facilitate further research and development of P. radix for safe consumption.

Resveratrol-Mediated Reversal of Doxorubicin-Induced Osteoclast Differentiation

Secondary osteoporosis has been associated with cancer patients undertaking Doxorubicin (DOX) chemotherapy. However, the molecular mechanisms behind DOX-induced bone loss have not been elucidated. Molecules that can protect against the adverse effects of DOX are still a challenge in chemotherapeutic treatments. We investigated the effect and mechanism of DOX in osteoclast differentiation and used the Sirt 1 activator resveratrol (RES) to counteract DOX-induced effects. RAW 264.7 cells were differentiated into osteoclasts under cotreatment with DOX and RES, alone or combined. RES treatment inhibited DOX-induced osteoclast differentiation, reduced the expression of osteoclast fusion marker Oc-stamp and osteoclast differentiation markers Rank, Trap, Ctsk and Nfatc1. Conversely, RES induced the upregulation of antioxidant genes Sod 1 and Nrf 2 while DOX significantly reduced the FoxM1 expression, resulting in oxidative stress. Treatment with the antioxidant MitoTEMPO did not influence DOX-induced osteoclast differentiation. DOX-induced osteoclastogenesis was studied using the cathepsin-K zebrafish reporter line (Tg[ctsk:DsRed]). DOX significantly increased ctsk signal, while RES cotreatment resulted in a significant reduction in ctsk positive cells. RES significantly rescued DOX-induced mucositis in this model. Additionally, DOX-exposed zebrafish displayed altered locomotor behavior and locomotory patterns, while RES significantly reversed these effects. Our research shows that RES prevents DOX-induced osteoclast fusion and activation in vitro and in vivo and reduces DOX-induced mucositis, while improving locomotion parameters.

Dynorphin promotes stress-induced depressive behaviors by inhibiting ventral pallidal neurons in rats.

Endogenous dynorphin signaling via kappa opioid receptors (KORs) plays a key role in producing the depressive and aversive consequences of stress. We investigated the behavioral effects of the dynorphin/KOR system in the ventral pallidum (VP) and studied the underlying mechanisms. To investigate the effects of dynorphin on the VP, we conducted behavioral experiments after microinjection of drugs or shRNA and brain-slice electrophysiological recordings. Histological tracing and molecular biological experiments were used to identify the distribution of KORs and the possible sources of dynorphin projections to the VP. An elevated dynorphin concentration and increased KOR activity were observed in the VP after acute stress. Infusion of dynorphin-A into the VP produced depressive-like phenotypes including anhedonia and despair and anxiety behaviors, but did not alter locomotor behavior. Mechanistically, dynorphin had an inhibitory effect on VP neurons-reducing their firing rate and inhibiting excitatory transmission-through direct activation of KORs and modulation of downstream G-protein-gated inwardly rectifying potassium (GIRK) channels and high-voltage gated calcium channels (VGCCs). Tracing revealed direct innervation of VP neurons by dynorphin-positive projections; potential sources of these dynorphinergic projections include the nucleus accumbens, amygdala, and hypothalamus. Blockade of dynorphin/KOR signaling in the VP by drugs or viral knock-down of KORs significantly reduced despair behavior in rats. Endogenous dynorphinergic modulation of the VP plays a critical role in mediating depressive reactions to stress.

RCAN1 knockout and overexpression recapitulate an ensemble of rest-activity and circadian disruptions characteristic of Down syndrome, Alzheimer’s disease, and normative aging

BackgroundRegulator of calcineurin 1 (RCAN1) is overexpressed in Down syndrome (DS), but RCAN1 levels are also increased in Alzheimer’s disease (AD) and normal aging. AD is highly comorbid among individuals with DS and is characterized in part by progressive neurodegeneration that resembles accelerated aging. Importantly, abnormal RCAN1 levels have been demonstrated to promote memory deficits and pathophysiology that appear symptomatic of DS, AD, and aging. Anomalous diurnal rest-activity patterns and circadian rhythm disruptions are also common in DS, AD, and aging and have been implicated in facilitating age-related cognitive decline and AD progression. However, no prior studies have assessed whether RCAN1 dysregulation may also promote the age-associated alteration of rest-activity profiles and circadian rhythms, which could in turn contribute to neurodegeneration in DS, AD, and aging.MethodsThe present study examined the impacts of RCAN1 deficiency and overexpression on the photic entrainment, circadian periodicity, intensity and distribution, diurnal patterning, and circadian rhythmicity of wheel running in young (3–6 months old) and aged (9–14 months old) mice of both sexes.ResultsWe found that daily RCAN1 levels in the hippocampus and suprachiasmatic nucleus (SCN) of light-entrained young mice are generally constant and that balanced RCAN1 expression is necessary for normal circadian locomotor activity rhythms. While the light-entrained diurnal period was unaltered, RCAN1-null and RCAN1-overexpressing mice displayed lengthened endogenous (free-running) circadian periods like mouse models of AD and aging. In light-entrained young mice, RCAN1 deficiency and overexpression also recapitulated the general hypoactivity, diurnal rest-wake pattern fragmentation, and attenuated amplitudes of circadian activity rhythms reported in DS, preclinical and clinical AD, healthily aging individuals, and rodent models thereof. Under constant darkness, RCAN1-null and RCAN1-overexpressing mice displayed altered locomotor behavior indicating circadian clock dysfunction. Using the Dp(16)1Yey/+ (Dp16) mouse model for DS, which expresses three copies of Rcan1, we found reduced wheel running activity and rhythmicity in both light-entrained and free-running young Dp16 mice like young RCAN1-overexpressing mice. Critically, these diurnal and circadian deficits were rescued in part or entirely by restoring Rcan1 to two copies in Dp16 mice. We also found that RCAN1 deficiency but not RCAN1 overexpression altered protein levels of the clock gene Bmal1 in the SCN.ConclusionsCollectively, this study’s findings suggest that both loss and aberrant gain of RCAN1 precipitate anomalous light-entrained diurnal and circadian activity patterns emblematic of DS, AD, and possibly aging.

Using complex behavior to understand brain mechanisms in health and disease.

Using complex behavior to understand brain mechanisms in health and disease.

The Fly Homologue of MFSD11 Is Possibly Linked to Nutrient Homeostasis and Has a Potential Role in Locomotion: A First Characterization of the Atypical Solute Carrier CG18549 in Drosophila Melanogaster.

Simple SummaryThe body is dependent on nutrients and ions to work normally. Within the hu-man body there is a group of proteins named transporters or solute carriers. These transporters are vital for the transport of nutrients such as glucose, amino acids, and fats, as well as ions such as sodium, calcium, and potassium. Despite being vital for normal physiology, as well as pathophysiology, a large number (approximately one third) of the transporters are orphans, where information about their expression and function is missing. Here, we aimed to begin to unravel the expression and function of one of these orphan transporters, MFSD11, by studying its orthologue in fruit flies (CG18549). We found that the fly orthologue is expressed in the brain of fruit flies and that it is possibly involved in metabolism and/or locomotion of the flies. The exact mechanism behind the observed behaviors is not fully understood, but our study provides new insights into the expression and function of CG18549. Clearly, these results, among others about the orphan transporters, provide a strong example as to why it is vital to fully characterize them and through that gain knowledge about the body during normal condition and disease.Cellular transport and function are dependent on substrate influx and efflux of various compounds. In humans, the largest superfamily of transporters is the SoLute Carriers (SLCs). Many transporters are orphans and little to nothing is known about their expression and/or function, yet they have been assigned to a cluster called atypical SLCs. One of these atypical SLCs is MFSD11. Here we present a first in-depth characterization of the MFSD11, CG18549. By gene expression and behavior analysis on ubiquitous and brain-specific knockdown flies. CG18549 knockdown flies were found to have altered adipokinetic hormone and adipokinteic hormone receptor expression as well as reduced vesicular monoamine transporter expression; to exhibit an altered locomotor behavior, and to have an altered reaction to stress stimuli. Furthermore, the gene expression of CG18549 in the brain was visualized and abundant expression in both the larvae and adult brain was observed, a result that is coherent with the FlyAtlas Anatomy microarray. The exact mechanism behind the observed behaviors is not fully understood, but this study provides new insights into the expression and function of CG18549. Clearly, these results provide a strong example as to why it is vital to fully characterize orphan transporters and through that gain knowledge about the body during normal condition and disease.

Transcriptome aberration associated with altered locomotor behavior of zebrafish (Danio rerio) caused by Waterborne Benzo[a]pyrene

Waterborne Benzo[a]pyrene (B[a]P) pollution is a global threat to aquatic organisms. The exposure to waterborne B[a]P can disrupt the normal locomotor behavior of zebrafish (Danio rerio), however, how it affect the locomotor behavior of adult zebrafish remains unclear. Herein, B[a]P at two concentrations (0.8 μg/L and 2.0 μg/L) were selected to investigate the molecular mechanisms of the affected locomotor behavior of zebrafish by B[a]P based on transcriptome profiling. Adverse effects of B[a]P exposure affecting locomotor behavior in zebrafish were studied by RNA sequencing, and the locomotion phenotype was acquired. The gene enrichment results showed that the differentially highly expressed genes (atp2a1, cdh2, aurka, fxyd1, clstn1, apoc1, mt-co1, tnnt3b, and fads2) of zebrafish are mainly enriched in adrenergic signaling in cardiomyocytes (dre04261) and locomotory behavior (GO:0007626). The movement trajectory plots showed an increase in the locomotor distance and velocity of zebrafish in the 0.8 μg/L group and the opposite in the 2.0 μg/L group. The results showed that B[a]P affects the variety of genes in zebrafish, including motor nerves, muscles, and energy supply, and ultimately leads to altered locomotor behavior.

Vapor exposure to Δ9-tetrahydrocannabinol (THC) slows locomotion of the Maine lobster (Homarus americanus)

RationaleDespite a long history of use in synaptic physiology, the lobster has been a neglected model for behavioral pharmacology. A restaurateur proposed that exposing lobster to cannabis smoke reduces anxiety and pain during the cooking process. It is unknown if lobster gill respiration in air would result in significant Δ9-tetrahydrocannabinol (THC) uptake and whether this would have any detectable behavioral effects. ObjectiveThe primary goal was to determine tissue THC levels in the lobster after exposure to THC vapor. Secondary goals were to determine if THC vapor altered locomotor behavior or nociception. MethodsTissue samples were collected (including muscle, brain and hemolymph) from Homarus americanus (N = 3 per group) following 30 or 60 min of exposure to vapor generated by an e-cigarette device using THC (100 mg/mL in a propylene glycol vehicle). Separate experiments assessed locomotor behavior and hot water nociceptive responses following THC vapor exposure. ResultsTHC vapor produced duration-related THC levels in all tissues examined. Locomotor activity was decreased (distance, speed, time-mobile) by 30 min inhalation of THC. Lobsters exhibit a temperature-dependent withdrawal response to immersion of tail, antennae or claws in warm water; this is novel evidence of thermal nociception for this species. THC exposure for 60 min had only marginal effect on nociception under the conditions assessed. ConclusionsVapor exposure of lobsters, using an e-cigarette based model, produces dose-dependent THC levels in all tissues and reduces locomotor activity. Hot water nociception was temperature dependent, but only minimal anti-nociceptive effect of THC exposure was confirmed.

BMAA and MCLR Interact to Modulate Behavior and Exacerbate Molecular Changes Related to Neurodegeneration in Larval Zebrafish.

Exposure to toxins produced by cyanobacteria (ie, cyanotoxins) is an emerging health concern due to their increasing prevalence and previous associations with neurodegenerative diseases including amyotrophic lateral sclerosis. The objective of this study was to evaluate the neurotoxic effects of a mixture of two co-occurring cyanotoxins, β-methylamino-l-alanine (BMAA) and microcystin leucine and arginine (MCLR), using the larval zebrafish model. We combined high-throughput behavior-based toxicity assays with discovery proteomic techniques to identify behavioral and molecular changes following 6 days of exposure. Although neither toxin caused mortality, morphological defects, nor altered general locomotor behavior in zebrafish larvae, both toxins increased acoustic startle sensitivity in a dose-dependent manner by at least 40% (p < .0001). Furthermore, startle sensitivity was enhanced by an additional 40% in larvae exposed to the BMAA/MCLR mixture relative to those exposed to the individual toxins. Supporting these behavioral results, our proteomic analysis revealed a 4-fold increase in the number of differentially expressed proteins in the mixture-exposed group. Additionally, prediction analysis reveals activation and/or inhibition of 8 enriched canonical pathways (enrichment p-value < .01; z-score≥|2|), including ILK, Rho Family GTPase, RhoGDI, and calcium signaling pathways, which have been implicated in neurodegeneration. We also found that expression of TDP-43, of which cytoplasmic aggregates are a hallmark of amyotrophic lateral sclerosis pathology, was significantly upregulated by 5.7-fold following BMAA/MCLR mixture exposure. Together, our results emphasize the importance of including mixtures of cyanotoxins when investigating the link between environmental cyanotoxins and neurodegeneration as we reveal that BMAA and MCLR interact in vivo to enhance neurotoxicity.

Effect of hyperbaric oxygen on chemotherapy-induced neuropathy in male and female rats.

Chemotherapeutic agents can cause peripheral neuropathy, a deleterious side effect of cancer treatment. Hyperbaric oxygen (HBO2) treatment has shown great potential for decreasing pain in numerous clinical pain conditions and in preclinical studies. This study was designed to test whether HBO2 might also be useful for treating chemotherapy-induced peripheral neuropathy. Male and female Sprague-Dawley rats were injected with 1 mg/kg paclitaxel or vehicle every other day for 7 days to induce allodynia, followed by either one single, or four daily 60-min exposures to HBO2 or room air. Mechanical and cold allodynia as well as locomotor behavior and body weight were assessed intermittently for several weeks. Estrous cycling was also tracked in female rats. Paclitaxel caused pronounced mechanical allodynia in both sexes that was completely reversed by either one or four treatments of HBO2. Females in all treatment groups showed greater cold acetone scores than males, and acetone scores were not reliably reduced by HBO2 treatment. Neither paclitaxel nor HBO2 treatment altered locomotor behavior or estrous cycling. We conclude that HBO2 treatment was highly effective at reducing mechanical allodynia in paclitaxel-treated rats without affecting weight gain, locomotion, or estrous cycling, suggesting that HBO2 may be effective for treating chemotherapy-induced neuropathic pain without producing significant side effects.

Graphene oxide-induced neurotoxicity on neurotransmitters, AFD neurons and locomotive behavior in Caenorhabditis elegans

Graphene oxide (GO) and graphene-based nanomaterials have been widely applied in recent years, but their potential health risk and neurotoxic potentials remain poorly understood. In this study, neurotoxic potential of GO and its underlying molecular and cellular mechanism were investigated using the nematode, Caenorhabditis elegans. Deposition of GO in the head region and increased reactive oxygen species (ROS) was observed in C. elegans after exposure to GO. The neurotoxic potential of GO was then investigated, focusing on neurotransmitters contents and neuronal activity using AFD sensory neurons. The contents of all neurotransmitters, such as, tyrosine, tryptophan, dopamine, tyramine, and GABA, decreased significantly by GO exposure. Decreased fluorescence of Pgcy-8:GFP, a marker of AFD sensory neuron, by GO exposure suggested GO could cause neuronal damage on AFD neuron. GO exposure led decreased expression of ttx-1 and ceh-14, genes required for the function of AFD neurons also confirmed possible detrimental effect of GO to AFD neuron. To understand physiological meaning of AFD neuronal damage by GO exposure, locomotive behavior was then investigated in wild-type as well as in loss-of-function mutants of ttx-1 and ceh-14. GO exposure significantly altered locomotor behavior markers, such as, speed, acceleration, stop time, etc., in wild-type C. elegans, which were mostly rescued in AFD neuron mutants. The present study suggested the GO possesses neurotoxic potential, especially on neurotransmitters and AFD neuron in C. elegans. These findings provide useful information to understand the neurotoxic potential of GO and other graphene-based nanomaterials, which will guide their safe application.

Differences in Depressive‐ and Anxiety‐like effects in S426A/S430A Mutant and Wild‐type Mice Following the Induction of Neuropathic Pain

Clinically, chronic pain has been associated with increases in anxiety‐ and depressive‐like symptoms, concomitant with the severity and duration of pain. Pursuant to the on‐going opioid crisis, novel therapeutic approaches, including the use of cannabinoids, have been investigated for the management of chronic pain. We have previously demonstrated that mice expressing a desensitization form of the cannabinoid type‐1 (CB1) receptor (S426A/S430A) show delayed tolerance and heightened sensitivity to the anti‐nociceptive effects of Δ9‐tetrahydrocannabinol (Δ9‐THC). In addition to analgesia, cannabinoids have been implicated in mediating affect in select mood disorders. Therefore, the purpose of the present study was to examine whether the induction of chronic neuropathic pain would alter anxiety and/or depressive‐like phenotypes in either wild‐type and/or S426A/S430A mutant mice, and whether the severity of these symptoms correlated with either basal allodynia or Δ9‐THC‐induced anti‐allodynic responses. Male and female wild‐type and S426A/S430A mice were assessed for alterations in locomotor behavior, anxiety‐like (elevated plus maze; open field) and depressive‐like (forced swim test) behaviors before and after the induction of cisplatin‐evoked neuropathic pain. Mice were also assessed to see whether basal pain levels correlated with either anxiety‐ and/or depressive‐like behaviors, and whether increased anxiety‐ and/or depressive‐like symptoms correlated with the degree of anti‐allodynia produced following pretreatment with Δ9‐THC. All mice showed evidence of neuropathic pain following repeated cisplatin‐treatment. Interestingly, the S426A/S430A mutation caused female (but not male) mice to exhibit reduced anxiety‐like behavior prior to the induction of cisplatin pain but caused them to be more susceptible to anxiety and depressive‐like symptoms once they exhibited cisplatin‐evoked pain. Pretreatment with Δ9‐THC was also able to completely reverse allodynia in male and female mutant, but not wild‐type, mice. Taken together, these results highlight the importance of understanding the role that sex may have in the potential clinical use of cannabinoids to modulate both affective and sensory aspects of chronic pain.Support or Funding InformationPenn State University College of Medicine Department of Anesthesiology &amp; Perioperative MedicineThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A protective role of autophagy in TDCIPP-induced developmental neurotoxicity in zebrafish larvae

Tris (1, 3-dichloro-2-propyl) phosphate (TDCIPP), an extensively used organophosphorus flame retardant, is frequently detected in various environmental media and biota, and has been demonstrated as neurotoxic. Autophagy has been proposed as a protective mechanism against toxicant-induced neurotoxicity. The purpose of the present study was to investigate the effect of TDCIPP exposure on autophagy, and its role in TDCIPP-induced developmental neurotoxicity. Zebrafish embryos (2–120 h post-fertilization [hpf]) were exposed to TDCIPP (0, 5, 50 and 500 μg/l) and a model neurotoxic chemical, chlorpyrifos (CPF, 100 μg/l). The developmental endpoints, locomotive behavior, cholinesterase activities, gene and protein expression related to neurodevelopment and autophagy were measured in the larvae. Our results demonstrate that exposure to TDCIPP (500 μg/l) and CPF causes developmental toxicity, including reduced hatching and survival rates and increased malformation rate (e.g., spinal curvature), as well as altered locomotor behavior. The expression of selected neurodevelopmental gene and protein markers (e.g., mbp, syn2a, and α1-tubulin) was significantly down-regulated in CPF and TDCIPP exposed zebrafish larvae. Treatment with CPF significantly inhibits AChE and BChE, while TDCIPP (0–500 μg/l) exerts no effects on these enzymes. Furthermore, the conversion of microtubule-associated protein I (LC3 I) to LC3 II was significantly increased in TDCIPP exposed zebrafish larvae. In addition, exposure to TDCIPP also activates transcription of several critical genes in autophagy (e.g. Becn1, atg3, atg5, map1lc3b and sqstm1). To further investigate the role of autophagy in TDCIPP induced developmental neurotoxicity, an autophagy inducer (rapamycin, Rapa, 1 nM) and inhibitor (chloroquine, CQ, 1 μM) were used. The results demonstrate that the hatching rate, survival rate, and the expression of mbp and а1-tubulin proteins were all significantly increased in larvae treated with TDCIPP (500 μg/l) and Rapa compared to TDCIPP alone. In contrast, co-treatment with the autophagy inhibitor CQ results in exacerbated neurodevelopmental toxicity. Taken together, our results confirm that exposure to TDCIPP induces autophagy, which plays a protective role in TDCIPP-induced developmental neurotoxicity in zebrafish embryos and larvae.

Effects of intracerebroventricular injection of vitamin B12 on formalin-induced muscle pain in rats: Role of cyclooxygenase pathway and opioid receptors.

Vitamin B12 modulates pain at the local and peripheral levels. This study has investigated the effects of intracerebroventricular (ICV) injection of vitamin B12 on themuscle pain. We used diclofenac (cyclooxygenase inhibitor) and naloxone (opioid receptors antagonist) to clarify the possible mechanisms. For ICV injections, a guide cannula was implanted in the left lateral ventricle of the brain. Muscle pain was induced by intramuscular injection of formalin (2.50%; 50 µl) in the right gastrocnemius muscle and the number of paw flinching was recorded at 5-min blocks for 60 min. Locomotor activity was performed using an open-field test. Formalin induced a biphasic pain. Vitamin B12 (1.25, 2.50, 5.00 and 10.00 µg per rat) and diclofenac (12.50 and 25.00 µg per rat) significantly reduced both phases pain intensity. Significant antinociceptive effects were observed after combined treatments of diclofenac (6.25 and 12.50 µg per rat) with vitamin B12 (0.63 and 2.50 µg per rat), respectively. Prior ICV injection of naloxone (10.00 µg per rat) prevented vitamin B12 (10.00 µg per rat) and diclofenac (25.00 µg per rat) induced antinociceptive effects. All the above-mentioned chemicals did not alter locomotor behavior in an open-field test. The present results showed that the cyclooxygenase pathway and opioid receptors may be involved in the central antinociceptive effect of vitamin B12. In addition, opioid receptors might be involved in diclofenac-induced antinociception.

Role of neurexin2a in lead-induced locomotor defect in developing zebrafish

Low-dose chronic lead (Pb) exposure interferes with the development of the nervous system, which may lead to learning disabilities, behavioral abnormalities, and mental retardation. Neurexins (Nrxns) are synaptic cell-adhesion molecules associated with neurological disorders. We hypothesized that Pb can affect the expression of nrxns during synapse formation and alter the phenotype behavior. Here, apoptosis, nrxns mRNA expression, and alterations of locomotion were examined after exposure to Pb in zebrafish embryos/larvae. To confirm the function of nrxn2a, rescue experiments were performed using β-nrxn2a mRNA microinjection. Pb exposure increased apoptosis and altered locomotor behavior in zebrafish larvae. Quantitative PCR showed that among several synaptic adhesion molecules, only nrxn2a were affected by Pb exposure. Moreover, exposure to Pb at 10μmol/L upregulated mRNA expression of nrxn1a and nrxn3a at 24h post fertilization (hpf) and downregulated expression at 48 hpf, whereas the expression remained unchanged at 72 hpf. Only the two isoforms of nrxn2a were downregulated by Pb at 10μmol/L at all three time points. Rescue experiments showed that β-nrxn2a mRNA injection recovered the decreased locomotor activity and the increased apoptosis induced by Pb. In addition, overexpression of β-nrxn2a mRNA upregulated α-nrxn2a. These data indicated that Pb inhibited the expression of nrxn2a genes, which play a critical role in neural development, and further altered the behavior of zebrafish embryos/larvae.