Locomotor Activity In Response Research Articles

Acute nicotine exposure attenuates neurological deficits, ischemic injury and brain inflammatory responses and restores hippocampal long-term potentiation in ischemic stroke followed by lipopolysaccharide-induced sepsis-like state

Ischemic stroke is followed by an increased susceptibility to bacterial infections, which exacerbate histological stroke outcome, neurological deficits and memory impairment due to increased neuroinflammation and neurotransmitter dysfunction. Pharmacological activation of nicotinic acetylcholine receptors was suggested to mitigate brain inflammatory responses in ischemic stroke. The functional responses associated with nicotinic acetylcholine receptor activation were unknown. In this study, male NMRI mice subjected to transient intraluminal middle cerebral artery occlusion (MCAO) were intraperitoneally exposed to vehicle treatment or Escherichia coli lipopolysaccharide (LPS; 4 mg/kg)-induced sepsis-like state 24 h post-MCAO, followed by intraperitoneal administration of vehicle or nicotine (0.5 mg/kg) 30 min later. Over 96 h, rectal temperature, neurological deficits, spontaneous locomotor activity, working memory, ischemic injury, synaptic plasticity, and brain inflammatory responses were evaluated by temperature measurement, behavioral analysis, infarct volumetry, electrophysiological recordings, and polymerase-chain reaction analysis. LPS-induced sepsis induced hypothermia, increased general and focal neurological deficits, reduced spontaneous exploration behavior, reduced working memory, and increased infarct volume post-MCAO. Additional treatment with nicotine attenuated LPS-induced hypothermia, reduced neurological deficits, restored exploration behavior, restored working memory, and reduced infarct volume. Local field potential recordings revealed that LPS-induced sepsis decreased long-term potentiation (LTP) in the dentate gyrus post-MCAO, whereas concomitant nicotine exposure restored LTP in the contralateral dentate gyrus. LPS-induced sepsis increased microglial/ macrophage Iba-1 mRNA and astrocytic GFAP mRNA levels post-MCAO, whereas add-on nicotine treatment reduced astrocytic GFAP mRNA. Taken together, these findings indicate that acute nicotine exposure enhances functional stroke recovery. Future studies will have to evaluate the effects of (1) chronic nicotine exposure, a clinically relevant vascular risk factor, and (2) the cessation of nicotine exposure, which is widely recommended post-stroke, but might have detrimental effects in the early stroke recovery phase.

Effect of creatine administration on locomotor activity and stress response in olive flounder (Paralichthys olivaceus)

The creatine kinase system is crucial for maintaining cellular energy homeostasis and plays a role in regulating locomotor behavior in organisms, but its significance in the regulating the motionless behavior in olive flounder is limited. In the first experiment of this study, elevated levels of creatine kinase (CK) activity in the spinal cord were detected in the juvenile group (JG) flounder compared to the adult group (AG) flounder. In the second experiment, to further confirm the involvement of CK in the locomotor behavior, the adult flounder was given an intraperitoneal injection of creatine (150 mg/kg), while the flounder in the control group received a saline solution. After one week post-injection, the behavioral analysis revealed that the flounder in the creatine-treated group displayed higher levels of locomotor activity and a greater number of escape attempts in response to external stimuli when compared to the control group. However, the acute stress response, induced by intraperitoneal injection and characterized by tail beating, was significantly alleviated in the flounder in the creatine-treated group. Additionally, there was an upregulation of the UII and AchR genes in the spinal cord, as well as increased levels of UII and AchR in the muscle tissues of the creatine-treated flounder. However, a reduction in UI mRNA levels was observed in the brain of the flounder. Collectively, our data provide the evidence that the elevated enzyme activity and gene expression of creatine kinase play important roles in off-bottom swimming behavior in the JG flounder. Furthermore, administration of creatine improved the locomotor activity and alleviated the stress response in flounder, which is associated with regulation of the locomotor- and stress-related gene in the brain, spinal cord, and muscle.

Analyzing the neurotoxic effects of anatoxin-a and saxitoxin in zebrafish larvae

Global warming due to climate change, as well as freshwater eutrophication caused by anthropogenic activities are responsible, among other factors, for an increasing occurrence of harmful algal blooms (HABs) in aquatic systems. These can lead to the generation of cyanotoxins, secondary metabolites coming from cyanobacteria, producing adverse effects in living organisms including death. This research aims to study the effects that two neurotoxins, anatoxin-a (ATX-a) and saxitoxin (STX), have on living organisms. Once the stability of both compounds in water was determined for a 24 h period using ultra-high-performance liquid chromatography coupled to a triple quadrupole mass spectrometer (UPLC-MS/MS), zebrafish larvae were exposed to different levels of toxins (1 ng L−1, 10 ng L−1, 100 ng L−1 and 1 μg L−1) during 24 h. Behavioral studies including vibrational startle response (VSR), habituation to vibrational stimuli, basal locomotor activity (BLM) and visual motor response (VMR) were performed using Danio Vision system, and neurotransmitters (NTs) from 15-head pools of control and exposed zebrafish larvae were extracted and analyzed by UPLC-MS/MS. Both compounds induced hypolocomotion in the individuals, while 10 and 100 ng L−1 of ATX-a significantly increased methionine (120 % and 126 %, respectively) and glutamate levels (118 % and 129 %, respectively). Saxitoxin enhanced 3-metoxytyramine (3-MT) levels at 1 ng L−1 by 185 %. The findings of this study show that both studied cyanotoxins influence the behavior of zebrafish larvae as well as their metabolism.

Circadian variations influence anxiety-related behaviour, olfaction, and hedonic response in male Sprague–Dawley rats

IntroductionDespite the acknowledged impact of circadian rhythms on various aspects of life, behavioural tests with laboratory animals often overlook alignment with their natural activity patterns. This study aims to evaluate the influence of circadian variations on the results, validity, and reliability of different behavioural tests in rats. MethodsThree behavioural tests, the Light-Dark Box Test (LDB), assessing anxiety-related behaviour and locomotor activity; the Buried Pellet Test (BPT), revealing olfactory abilities and motivation issues; and the Sucrose Preference Test (SPT), studying the anhedonic response, were employed to encompass multiple daytime-dependent behavioural aspects in male Sprague-Dawley rats. ResultsOur findings underscore distinct circadian effects on locomotor activity, exploratory behaviour, olfactory acuity, motivation, and hedonic response. Notably, anxious behaviour remained unaffected by daytime conditions. Furthermore, decreased data variance was found to be correlated with conducting behavioural tests during the subjects’ active phase. DiscussionThis study demonstrates extensive circadian influences on nearly all parameters investigated, coupled with a significant reduction in data variability during the active phase. Emphasising the importance of aligning experimental timing with rats’ natural activity patterns, our results suggest that conducting tests during the active phase of the animals not only refines test sensitivity , reduces stress, and provides more representative data, but also contributes to ethical animal research (3 R) and improves test relevance. This, in turn, enhances the reliability and validity of experimental outcomes in behavioural research and promotes animal welfare.

5-hydroxytryptamine 2C/1A receptors modulate the biphasic dose response of the head twitch response and locomotor activity induced by DOM in mice.

The phenylalkylamine hallucinogen (-)-2,5-dimethoxy-4-methylamphetamine (DOM) exhibits an inverted U-shaped dose-response curve for both head twitch response (HTR) and locomotor activity in mice. Accumulated studies suggest that HTR and locomotor hyperactivity induced by DOM are mainly caused by the activation of serotonin 5-hydroxytryptamine 2A receptor (5-HT2A receptor). However, the mechanisms underlying the biphasic dose response of HTR and locomotor activity induced by DOM, particularly at high doses, remain unclear. The primary objective of this study is to investigate the modulation of 5-HT2A/2C/1A receptors in HTR and locomotor activity, while also exploring the potential receptor mechanisms underlying the biphasic dose response of DOM. In this study, we employed pharmacological methods to identify the specific 5-HT receptor subtypes responsible for mediating the biphasic dose-response effects of DOM on HTR and locomotor activity in C57BL/6J mice. The 5-HT2A receptor selective antagonist (R)-[2,3-di(methoxy)phenyl]-[1-[2-(4-fluorophenyl)ethyl]piperidin-4-yl]methanol (M100907) (500µg/kg, i.p.) fully blocked the HTR at every dose of DOM (0.615-10mg/kg, i.p.) in C57BL/6J mice. M100907 (50µg/kg, i.p.) decreased the locomotor hyperactivity induced by a low dose of DOM (0.625, 1.25mg/kg, i.p.), but had no effect on the locomotor hypoactivity induced by a high dose of DOM (10mg/kg) in C57BL/6J mice. The 5-HT2C antagonist 6-chloro-5-methyl-1-[(2-[2-methylpyrid-3yloxy]pyrid-5yl)carbamoyl]indoline (SB242084) (0.3, 1mg/kg, i.p.) reduced the HTR induced by a dose of 2.5mg/kg DOM, but did not affect the response to other doses. SB242084 (1mg/kg, i.p.) significantly increased the locomotor activity induced by DOM (0.615-10mg/kg, i.p.) in mice. The 5-HT1A antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]N-(2-pyridinyl) cyclohexane carboxamide maleate (WAY100635) (1mg/kg, i.p.) increased both HTR and locomotor activity induced by DOM in mice. The 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (1mg/kg, i.p.) significantly reduced both the HTR and locomotor activity induced by DOM in mice. Additionally, pretreatment with the Gαi/o inhibitor PTX (0.25µg/mouse, i.c.v.) enhanced the HTR induced by DOM and attenuated the effect of DOM on locomotor activity in mice. Receptor subtypes 5-HT2C and 5-HT1A are implicated in the inverted U-shaped dose-response curves of HTR and locomotor activity induced by DOM in mice. The biphasic dose-response function of HTR and locomotor activity induced by DOM has different mechanisms in mice.

Multigenerational effects of alcohol: A behavioral study in three zebrafish populations

Fetal alcohol exposure can result in fetal alcohol spectrum disorder (FASD), which encompasses a range of cognitive and behavioral impairments. Although zebrafish have been used as a reliable model to study FASD, little is known about the ontogeny of this disorder and population differences in subsequent generations not directly exposed to alcohol. In this study, we evaluated the behavioral outcomes of zebrafish populations AB, Outbred (OB), and Tubingen (TU), offspring of parents exposed to alcohol during embryonic development. The offspring of adult fish with FASD (exposed to 1 % alcohol at the embryonic stage) was compared to the offspring of unexposed parental fish (0 % alcohol at the embryo phase). The behavioral profile of the offspring was assessed at 6 days post-fertilization (dpf) and 45 dpf. At 6dpf, the AB FASD offspring exhibited hyperactivity and increased time at the edge of the tank, while the TU and OB FASD offspring showed hypoactivity. At 45dpf, TU fish maintained the larval locomotor pattern, characterized by decreased average speed and total distance traveled and increased immobility. However, AB and OB fish did not show alterations in locomotor activity and anxiety-related responses at 45dpf. Our results demonstrate, for the first time, that FASD zebrafish offspring display behavioral differences, which were most evident during the early ontogenetic phase (6dpf) but may vary throughout animal ontogeny. TU fish exhibited the most consistent behavioral pattern across different developmental stages. These findings provide insights into the multigenerational and persistent behavioral consequences of embryonic alcohol exposure in zebrafish. Further research should focus on other features that can be inherited and the development of treatments for the offspring affected by it.

Analyzing the Effects of Age, Time of Day, and Experiment on the Basal Locomotor Activity and Light-Off Visual Motor Response Assays in Zebrafish Larvae.

The recent availability of commercial platforms for behavioral analyses in zebrafish larvae based on video-tracking technologies has exponentially increased the number of studies analyzing different behaviors in this model organism to assess neurotoxicity. Among the most commonly used assays in zebrafish larvae are basal locomotor activity (BLA) and visual motor responses (VMRs). However, the effect of different intrinsic and extrinsic factors that can significantly alter the outcome of these assays is still not well understood. In this work, we have analyzed the influence of age (5-8 days post-fertilization), time of day (8:00, 10:00, 12:00, 14:00; 16:00, 18:00, and 20:00 h), and experiment (three experiments performed at different days) on BLA and VMR results (4004 analyses for each behavior) in 143 larvae. The results from both behaviors were adjusted to a random-effects linear regression model using generalized least squares (GLSs), including in the model the effect of the three variables, the second-way interactions between them, and the three-way interaction. The results presented in this manuscript show a specific effect of all three intrinsic factors and their interactions on both behaviors, supporting the view that the most stable time period for performing these behavioral assays is from 10:00 am to 04:00 pm, with some differences depending on the age of the larva and the behavioral test.

Methamphetamine effects in zebrafish (Danio rerio) depend on behavioral endpoint, dose and test session duration

Research using zebrafish (Danio rerio) has begun to provide novel information in many fields, including the behavioral pharmacology of drug use and misuse. There have been limited studies on the effects of methamphetamine in adult zebrafish and the parameters of exposure (dose, test session length) have not been well-documented. Behavior following drug exposure is generally measured during relatively short sessions (6–10 min is common) in a novel tank environment. Many procedural variables (isolation, netting, novel tank) elicit anxiety-like behavior that is most apparent during the initial portion of a test session. This anxiety-like behavior might mask the initial effects of methamphetamine. During longer test sessions, these anxiety-like responses would be expected to habituate and drug effects should become more apparent. To test this idea, we measured several locomotor activity responses for 50-min following a range of methamphetamine doses (0.1–3.0 mg/L via immersion in methamphetamine solution). Methamphetamine failed to alter swimming velocity, distance travelled, or freezing time. In contrast, methamphetamine produced a dose-dependent decrease in time spent in the bottom of the tank, an increase in the number of visits to the top of the tank, and an increase in the number of transitions along the sides of the tank. The effects of methamphetamine were apparent 10–20 min following exposure and generally persisted throughout the session. These findings indicate that longer test sessions are required to measure methamphetamine-induced changes in behavior in zebrafish, as has been shown in other laboratory animals. The results also suggest that anxiety-like responses associated with various procedural aspects (netting, isolation, novel test apparatus) likely interfere with the ability to observe many behavioral effects of methamphetamine in zebrafish. Based on the current results, habituation to testing procedures to reduce anxiety-like behaviors is recommended in determining the effects of methamphetamine in zebrafish.

Established sensitization of ethanol-induced locomotor activity is not reversed by psilocybin or the 5-HT2A receptor agonist TCB-2 in male DBA/2J mice

RationalePsychedelic drugs, which share in common 5-HT2A receptor agonist activity, have shown promise in treating alcohol-use disorders (AUDs). Repeated exposure to ethanol (EtOH) induces molecular and behavioural changes reflective of neuroadaptations that may contribute to addiction. Psychedelic drugs can induce neuroplasticity also, raising the possibility that their potential clinical effects in AUD may involve an action to reverse or offset effects of long-term changes induced by EtOH. This possibility was examined by investigating whether psilocybin, or the 5-HT2A receptor agonist TCB-2, counteracted established sensitization of EtOH-induced locomotor activity. MethodsMale DBA/2J mice received repeated injections of 2.2 g/kg EtOH to induce a sensitized locomotor activity response. In two experiments separate groups of mice were then injected with psilocybin (0, 0.3 and 1 kg/kg) or TCB-2 (0, 1 and 3 mg/kg) on 5 consecutive days. Next, mice were challenged with 1.8 g/kg EtOH and locomotor activity measured for 15 min. ResultsRelative to naïve controls, previously sensitized mice showed enhanced locomotor activity to the challenge dose. Despite reducing locomotor activity in their own right psilocybin and TCB-2 did not alter the strength of this sensitized response. ConclusionPsilocybin and TCB-2 at behaviourally effective doses did not reverse sensitization of EtOH-induced activity. This suggests that mechanisms involved in mediating short-term reductions in EtOH intake by psilocybin or TCB-2 may not involve a capacity of these drugs to offset enduring changes in behaviour and any underlying neural adaptations induced by repeated intermittent exposure to EtOH.

Sex-specific variations in spatial reference memory acquisition: Insights from a comprehensive behavioral test battery in C57BL/6JRj mice

Sex differences in declarative memory are described in humans, revealing a female or a male advantage depending on the task. Specifically, spatial memory (i.e., spatial navigation) is typically most efficient in men. This sexual dimorphism has been replicated in male rats but not clearly in mice. In this study, sex differences in spatial memory were assessed in thirty-six C57BL/6 J mice (Janvier Labs; i.e., C57BL/6JRj mice), a widely used mouse substrain. Both male and female mice (12 weeks-old) were subjected to standard behavioral paradigms: the elevated plus maze, the open field test, the novel object and place tests, the forced swimming test, and the water maze test for spatial navigation. Across assessment, no sex differences were found in measures of locomotor activity, emotional and behavioral responses, and object and place recognition memories. In the water maze, male mice were faster in learning the platform location in the reference memory training and used more spatial strategies during the first training days. However, both sexes reached a similar asymptotic performance and performed similarly in the probe trial for long-term memory consolidation. No sex differences were found in the cued training, platform inversion sessions, or spatial working memory sessions. Hippocampal expression of the brain-derived neurotrophic factor was similar in both sexes, either in basal conditions or after performing the behavioral training battery. Importantly, female mice were not more variable than males in any measure analyzed. This outcome encourages the investigation of sex differences in animal models and the usefulness of including female mice in behavioral research.

Ethopharmacological evaluation of antidepressant-like effect of serotonergic psychedelics in C57BL/6J male mice.

Serotonergic psychedelics such as psilocybin, lysergic acid diethylamide, and DOI exert a hallucinatory effect through serotonin 5-HT2A receptor (5-HT2A) activation. Recent studies have revealed that serotonergic psychedelics have therapeutic potential for neuropsychiatric disorders, including major depressive and anxiety-related disorders. However, the involvement of 5-HT2A in mediating the therapeutic effects of these drugs remains unclear. In this study, we ethopharmacologically analyzed the role of 5-HT2A in the occurrence of anxiolytic- and antidepressant-like effects of serotonergic psychedelics such as psilocin, an active metabolite of psilocybin, DOI, and TCB-2 in mice 24h post-treatment. Mice with acute intraperitoneal psychedelic treatment exhibited significantly shorter immobility times in the forced swimming test (FST) and tail-suspension test (TST) than vehicle-treated control mice. These effects were eliminated by pretreatment with volinanserin, a 5-HT2A antagonist. Surprisingly, the decreasing immobility time in the FST in response to acute psilocin treatment was sustained for at least three weeks. In the novelty-suppressed feeding test (NSFT), the latency to feed, an indicator of anxiety-like behavior, was decreased by acute administration of psilocin; however, pretreatment with volinanserin did not diminish this effect. In contrast, DOI and TCB-2 did not affect the NSFT performance in mice. Furthermore, psilocin, DOI, and TCB-2 treatment did not affect the spontaneous locomotor activity or head-twitch response, a hallucination-like behavior in rodents. These results suggest that 5-HT2A contributes to the antidepressant effects of serotonergic psychedelics rather than anxiolytic effects.

Differential locomotor activity responses to day-time light intensity in juvenile and adult solitary Cape mole-rats, Georychus capensis (Rodentia: Bathyergidae)

ABSTRACT The Cape mole-rat (Georychus capensis) is a solitary, strictly subterranean rodent that is responsive to light and entrains to photic cues despite having a reduced visual system. Circadian entrainment is maintained throughout life, but age can alter the amplitude of the response and re-entrainment time. Mole-rats are long-lived for their size which raises questions regarding the robustness of their circadian rhythms and how impacts their locomotor activity rhythms. The locomotor activity rhythms of juvenile and adult Cape mole-rats were investigated. They were exposed to pre-experimental and post-experimental control cycles under fluorescent lights, six 12 h light:12 h dark cycles of decreasing intensities and a constant dark cycle (DD). All animals exhibited more activity during the dark phases of all light regimes. Juveniles were more active than adults and displayed more variable activity during both the light and dark phases. Adults exhibited relatively stable levels of activity under all experimental conditions, whereas juvenile activity decreased as the light intensity was reduced. The amplitude of Cape mole-rat rhythms was consistently low, but similar across light regimes and between adults and juveniles. Cape mole-rats have functional circadian systems, are primarily nocturnal and respond differentially to light intensity depending on their age. Light intensity does not affect the locomotor activity responses of Cape mole-rats in a predictable manner, and could indicate more complex interactions with light wavelengths. The circadian systems of juveniles appear to be more sensitive than those of adults, although the mechanism of the light response remains unclear.

Repeated dextromethorphan administration in adolescent rats produces long-lasting behavioral alterations

Initiation of non-medical dextromethorphan (DXM) use often occurs in adolescence, yet little is known about the consequences when use begins during this developmental period. The current experiments examined the acute response and the effects of repeated exposure to DXM in adolescence on behavior in adulthood. We examined locomotor activity, locomotor sensitization, and cognitive function, in rats that received repeated administration of DXM. Groups of adolescent (PND 30) and adult (PND 60) male rats were treated with DXM (60 mg/kg) once daily for 10 days. Locomotor activity in response to DXM was assessed following the first injection, on the 10th day of injection (adolescent – PND 39; adult – PND 69), and following 20 days of abstinence (adolescent – PND 59; adult – PND 89). Acute locomotor effects and locomotor sensitization were compared in adolescents and adults; cross-sensitization to ketamine, another dissociative with abuse potential, was also examined. In a separate group of rodents cognitive deficits were assessed following a 20 day abstinence period (adolescent – PND 59; adult – PND 89) in spatial learning and novel object recognition tasks. The locomotor stimulant effect of DXM was much greater in adolescents than adults. Also, only adolescent rats that were repeatedly administered DXM demonstrated locomotor sensitization at the end of 10 days of injection. However, sensitization occurred after the abstinence period in all rats regardless of age. Nonetheless, cross-sensitization to ketamine was only evident in adolescent-treated rats. DXM also led to an increase in perseverative errors in reversal learning only in the adolescent-treated group. We conclude that repeated use of DXM produces long-lasting neuroadaptations that may contribute to addiction. Deficits in cognitive flexibility occur in adolescents, although further work is necessary to confirm these findings. The results extend the understanding of potential long-term consequences of DXM use in adolescents and adults.

MAM-2201 acute administration impairs motor, sensorimotor, prepulse inhibition, and memory functions in mice: a comparison with its analogue AM-2201

Rationale1-[(5-fluoropentyl)-1H-indol-3-yl](4-methyl-1-naphthalenyl) methanone (MAM-2201) is a potent synthetic cannabinoid receptor agonist illegally marketed in “spice” products and as “synthacaine” for its psychoactive effects. It is a naphthoyl-indole derivative which differs from its analogue 1-[(5-Fluoropentyl)-1H-indol-3-yl](1-naphthylenyl) methanone (AM-2201) by the presence of a methyl substituent on carbon 4 (C-4) of the naphthoyl moiety. Multiple cases of intoxication and impaired driving have been linked to AM-2201 and MAM-2201 consumption.ObjectivesThis study aims to investigate the in vitro (murine and human cannabinoid receptors) and in vivo (CD-1 male mice) pharmacodynamic activity of MAM-2201 and compare its effects with those induced by its desmethylated analogue, AM-2201.ResultsIn vitro competition binding studies confirmed that MAM-2201 and AM-2201 possess nanomolar affinity for both CD-1 murine and human CB1 and CB2 receptors, with preference for the CB1 receptor. In agreement with the in vitro binding data, in vivo studies showed that MAM-2201 induces visual, acoustic, and tactile impairments that were fully prevented by pretreatment with CB1 receptor antagonist/partial agonist AM-251, indicating a CB1 receptor mediated mechanism of action. Administration of MAM-2201 also altered locomotor activity and PPI responses of mice, pointing out its detrimental effect on motor and sensory gating functions and confirming its potential use liability. MAM-2201 and AM-2201 also caused deficits in short- and long-term working memory.ConclusionThese findings point to the potential public health burden that these synthetic cannabinoids may pose, with particular emphasis on impaired driving and workplace performance.

Loss of Astrocytic µ Opioid Receptors Exacerbates Aversion Associated with Morphine Withdrawal in Mice: Role of Mitochondrial Respiration.

Astrocytes express mu/µ opioid receptors, but the function of these receptors remains poorly understood. We evaluated the effects of astrocyte-restricted knockout of µ opioid receptors on reward- and aversion-associated behaviors in mice chronically exposed to morphine. Specifically, one of the floxed alleles of the Oprm1 gene encoding µ opioid receptor 1 was selectively deleted from brain astrocytes in Oprm1 inducible conditional knockout (icKO) mice. These mice did not exhibit changes in locomotor activity, anxiety, or novel object recognition, or in their responses to the acute analgesic effects of morphine. Oprm1 icKO mice displayed increased locomotor activity in response to acute morphine administration but unaltered locomotor sensitization. Oprm1 icKO mice showed normal morphine-induced conditioned place preference but exhibited stronger conditioned place aversion associated with naloxone-precipitated morphine withdrawal. Notably, elevated conditioned place aversion lasted up to 6 weeks in Oprm1 icKO mice. Astrocytes isolated from the brains of Oprm1 icKO mice had unchanged levels of glycolysis but had elevated oxidative phosphorylation. The basal augmentation of oxidative phosphorylation in Oprm1 icKO mice was further exacerbated by naloxone-precipitated withdrawal from morphine and, similar to that for conditioned place aversion, was still present 6 weeks later. Our findings suggest that µ opioid receptors in astrocytes are linked to oxidative phosphorylation and they contribute to long-term changes associated with opioid withdrawal.

Long-term behavioral alterations following embryonic alcohol exposure in three zebrafish populations

Fetal alcohol exposure may lead to a condition known as fetal alcohol spectrum disorder (FASD), which comprises a set of consequences, including cognitive and behavioral impairments. Although zebrafish has been applied as a reliable model for studying FASD, there is no approach to the disorder’s ontogeny and population differences. Here, we evaluated the behavioral outcomes of AB, Outbred (OB), and Tübingen (TU) zebrafish populations embryonically exposed to alcohol throughout the development to the adult stage. We exposed 24hpf eggs to 0 %, 0.5 %, or 1.0 % alcohol for 2 h. Fish were let grow and locomotor and anxiety-like behaviors were tested in a novel tank at larval - 6dpf, juvenile – 45dpf, and adult- 90dpf stages. At 6dpf, both AB and OB treated with 1.0 % alcohol showed hyperactivity, while 0.5 % and 1.0 % TU fish exhibited hypolocomotion. At 45dpf, AB and TU fish maintained the larval pattern of locomotion. At the adult stage – 90dpf, both AB and TU populations showed increased locomotor activity and anxiogenic responses, while the OB population did not show altered behavior. Our results show for the first time that zebrafish populations exhibit behavioral differences in response to embryonic alcohol exposure and that it varies along animals' ontogeny. AB fish showed the most consistent behavioral pattern through developmental stages, TU fish showed behavioral changes only in adulthood, and OB population showed high interindividual variability. These data reinforce that different populations of zebrafish are better adapted to translational studies, offering reliable results in contrast to domesticated OB populations obtained from farms, which exhibit more variable genomes.

A New Bioassay for the Detection of Paralytic and Amnesic Biotoxins Based on Motor Behavior Impairments of Zebrafish Larvae.

The global concern about the increase of harmful algal bloom events and the possible impacts on food safety and aquatic ecosystems presents the necessity for the development of more accessible techniques for biotoxin detection for screening purposes. Considering the numerous advantages that zebrafish present as a biological model and particularly as a toxicants sentinel, we designed a sensitive and accessible test to determine the activity of paralytic and amnesic biotoxins using zebrafish larvae immersion. The ZebraBioTox bioassay is based on the automated recording of larval locomotor activity using an IR microbeam locomotion detector, and manual assessment of four complementary responses under a simple stereoscope: survival, periocular edema, body balance, and touch response. This 24 h acute static bioassay was set up in 96-well microplates using 5 dpf zebrafish larvae. For paralytic toxins, a significant decrease in locomotor activity and touch response of the larvae was detected, allowing a detection threshold of 0.1-0.2 µg/mL STXeq. In the case of the amnesic toxin the effect was reversed, detecting hyperactivity with a detection threshold of 10 µg/mL domoic acid. We propose that this assay might be used as a complementary tool for environmental safety monitoring.

Maternal immune activation impairs endocannabinoid signaling in the mesolimbic system of adolescent male offspring

Prenatal infections can increase the risk of developing psychiatric disorders such as schizophrenia in the offspring, especially when combined with other postnatal insults. Here, we tested, in a rat model of prenatal immune challenge by the viral mimic polyriboinosinic–polyribocytidilic acid, whether maternal immune activation (MIA) affects the endocannabinoid system and endocannabinoid-mediated modulation of dopamine functions. Experiments were performed during adolescence to assess i) the behavioral endophenotype (locomotor activity, plus maze, prepulse inhibition of startle reflex); ii) the locomotor activity in response to Δ9-Tetrahydrocannabinol (THC) and iii) the properties of ventral tegmental area (VTA) dopamine neurons in vivo and their response to THC; iv) endocannabinoid-mediated synaptic plasticity in VTA dopamine neurons; v) the expression of cannabinoid receptors and enzymes involved in endocannabinoid synthesis and catabolism in mesolimbic structures and vi) MIA-induced neuroinflammatory scenario evaluated by measurements of levels of cytokine and neuroinflammation markers. We revealed that MIA offspring displayed an altered locomotor activity in response to THC, a higher bursting activity of VTA dopamine neurons and a lack of response to cumulative doses of THC. Consistently, MIA adolescence offspring showed an enhanced 2-arachidonoylglycerol-mediated synaptic plasticity and decreased monoacylglycerol lipase activity in mesolimbic structures. Moreover, they displayed a higher expression of cyclooxygenase 2 (COX-2) and ionized calcium-binding adaptor molecule 1 (IBA-1), associated with latent inflammation and persistent microglia activity. In conclusion, we unveiled neurobiological mechanisms whereby inflammation caused by MIA influences the proper development of endocannabinoid signaling that negatively impacts the dopamine system, eventually leading to psychotic-like symptoms in adulthood.

An allosteric potentiator of metabotropic glutamate (mGlu) 2 receptors reduces the cocaine-stimulated ERK1/2 phosphorylation in the mouse striatum

Metabotropic glutamate (mGlu) receptors are involved in the experience-dependent neuroplasticity in the mesolimbic reward circuit. A Gαi/o-coupled mGlu2 subtype is distributed presynaptically in the striatum. These autoreceptors may have a significant influence over striatal neurons in their intracellular signaling pathways in response to a psychostimulant. Here we explored the effect of pharmacological potentiation of mGlu2 receptors on cocaine-stimulated phosphorylation (activation) of extracellular signal-regulated kinases (ERK) in the mouse striatum in vivo. We found that an mGlu2 selective positive allosteric modulator (PAM) LY487379 after a systemic injection did not alter basal phosphorylation of ERK1/2 or c-Jun N-terminal kinases in the striatum. However, pretreatment with LY487379 blocked the ERK1/2 phosphorylation induced by cocaine in the two subdivisions of the striatum, i.e., the caudate putamen and nucleus accumbens. LY487379 also blocked the cocaine-induced phosphorylation of Elk-1, a transcription factor downstream to the ERK pathway. Additionally, LY487379 reduced locomotor behavioral responses to cocaine. These results demonstrate that the mGlu2 PAM LY487379 possesses the ability to attenuate the activation of the ERK1/2 pathway in striatal neurons and reduce locomotor activity in response to cocaine in vivo.

Cognitive and behavioral effects of whole brain conventional or high dose rate (FLASH) proton irradiation in a neonatal Sprague Dawley rat model.

Recent studies suggest that ultra-high dose rates of proton radiation (>40 Gy/s; FLASH) confer less toxicity to exposed healthy tissue and reduce cognitive decline compared with conventional radiation dose rates (~1 Gy/s), but further preclinical data are required to demonstrate this sparing effect. In this study, postnatal day 11 (P11) rats were treated with whole brain irradiation with protons at a total dose of 0, 5, or 8 Gy, comparing a conventional dose rate of 1 Gy/s vs. a FLASH dose rate of 100 Gy/s. Beginning on P64, rats were tested for locomotor activity, acoustic and tactile startle responses (ASR, TSR) with or without prepulses, novel object recognition (NOR; 4-object version), striatal dependent egocentric learning ([configuration A] Cincinnati water maze (CWM-A)), prefrontal dependent working memory (radial water maze (RWM)), hippocampal dependent spatial learning (Morris water maze (MWM)), amygdala dependent conditioned freezing, and the mirror image CWM [configuration B (CWM-B)]. All groups had deficits in the CWM-A procedure. Weight reductions, decreased center ambulation in the open-field, increased latency on day-1 of RWM, and deficits in CWM-B were observed in all irradiated groups, except the 5 Gy FLASH group. ASR and TSR were reduced in the 8 Gy FLASH group and day-2 latencies in the RWM were increased in the FLASH groups compared with controls. There were no effects on prepulse trials of ASR or TSR, NOR, MWM, or conditioned freezing. The results suggest striatal and prefrontal cortex are sensitive regions at P11 to proton irradiation, with reduced toxicity from FLASH at 5 Gy.