Escape Reflex Research Articles

Evaluating the Physiologic Effects of Alfaxalone, Dexmedetomidine, and Midazolam Combinations in Common Blue-Tongued Skinks (Tiliqua scincoides).

Common blue-tongued skinks (Tiliqua scincoides) are popular pet reptiles; however, there has been limited research to investigate sedatives for this species. The purpose of this study was to measure the physiologic effects of four combinations of alfaxalone, dexmedetomidine, and midazolam for minor procedures such as intubation and blood collection. Eleven common blue-tongued skinks (Tiliqua scincoides) were used for this prospective, randomized cross-over study. The subcutaneous combinations were used as follows: 20 mg/kg alfaxalone (A); 10 mg/kg alfaxalone and 1 mg/kg midazolam (AM); 0.1 mg/kg dexmedetomidine and 1 mg/kg midazolam (DM); and 5 mg/kg alfaxalone, 0.05 mg/kg dexmedetomidine, and 0.5 mg/kg midazolam (ADM). Heart rate, respiratory rate, palpebral reflex, righting reflex, escape reflex, toe pinch withdrawal reflex, tongue flicking, and the possibility of intubation were recorded at baseline and every 5 min for 60 min. Venous blood gases were measured at baseline, full sedation, and recovery. Heart and respiratory rates decreased significantly in all groups, but the reductions were most prominent in DM and ADM. Analgesic effects, as measured by the toe pinch withdrawal reflex, were only observed in DM and ADM. Intubation was possible in all four protocols; however, it was not possible in two DM skinks. Based on these trials, ADM and AM are recommended for minor procedures in blue-tongue skinks.

Leeches Predate on Fast-Escaping and Entangling Blackworms by Spiral Entombment.

We investigate how the Helobdella sp. freshwater leeches capture and consume Lumbriculus variegatus blackworms despite the blackworm's ultrafast helical swimming escape reflex and ability to form large tangled "blobs". We describe a spiral "entombment" predation strategy, where Helobdellid leeches latch onto blackworms with their anterior sucker and envelop them in a spiral cocoon. Quantitative analysis shows that larger leeches succeed more often in entombing prey, while longer worms tend to escape. The rate of spiral contraction correlates with entombment outcomes, with slower rates associated with success. These insights highlight the complex interactions between predator and prey in freshwater ecosystems, providing new perspectives on ecological adaptability and predator-prey dynamics.

Enrofloxacin, Effective Treatment of Pseudomonas aeruginosa and Enterococcus faecalis Infection in Oreochromis niloticus.

Enrofloxacin is a broad-spectrum synthetic antimicrobial drug widely used in veterinary medicine. The present study aimed to determine the effective enrofloxacin dose for treating Pseudomonas aeruginosa and Enterococcus faecalis infection in Oreochromis niloticus. P. aeruginosa and E. faecalis isolates were verified using selective differential media and biochemically using the Vitek 2 test. Bacterial isolates were virulent for O. niloticus with LD50 equal to 2.03 × 106 and 2.22 × 107 CFU fish-1 for P. aeruginosa and E. faecalis, respectively. Infected fish suffered from decreased feed intake followed by off-food, tail erosion, darkening of the external body surface, exophthalmia, ascites, and loss of escape reflex. Internally, congested hemorrhagic hepatopancreas with engorged distended gall bladder were dominant. The posterior kidney was congested with enlarged spleen, and empty elementary tract. Pathologically, severe degenerative changes were dominant in the hepatopancreas, posterior kidney, spleen, stomach, and gills of infected fish. Antimicrobial sensitivity test indicated the high susceptibility of P. aeruginosa and E. faecalis to enrofloxacin with MIC estimated at 1 and 0.0625 µg/mL, respectively. Enrofloxacin effectively protected O. niloticus against E. faecalis and P. aeruginosa infection when used with medicated feed at doses of 10 and 20 mg kg-1 body weight.

THE APOCALYPTIC NATURE OF TODOS OTMACHKA'S PSYCHOWORLD (BASED ON THE PSYCHO-AUTOBIOGRAPHICAL NOVEL «PLAN FOR THE YARD»)

The article elaborates on the apocalyptic nature of the psychoworld of Todos Osmachka based on the material of the psycho–autobiographical novel «The Plan to the Yard». The achievements of psychologists in the field of human emotional existence are analyzed. Affective states are singled out as aspects of the methodology of affect research, which will complement psychologically oriented technologies, aimed at approaching the understanding of mental traits of a creative personality, internal sources of artistry and psychophysiological processes that accompany a creative act. On the basis of Yu. Lesniak's research «Voice and Poetics of Affect», three levels of influence of affects on Todosya Osmachka's work of art «Plan to the Yard» are distinguished. At the first level – the stage of reception – the psycho–autobiographical nature of the plot of the story was traced. At the second stage, which is characterized as a series of complex experiences and emotions, considerable emotional tension of the author was traced during the description of the motives for writing the artistic work. Direct analysis of «Plan to the yard» on the third level – the role and place of the affect itself in the structure of the work of art – contributed to the expression of the worldview and features of the artist's artistic style. The apocalyptic Ukrainian world destroyed by the soviet government and the resulting emotional tension of the heroes of the story are analyzed. It was found that the constant and bright images–details of «Plan to the yard» are: riveting of iron on iron, cemetery, crosses, crows, wasteland, silence. Based on the research, it was found that in the image of Ivan Neradko, Todos Osmachka realizes his own experienced state of affect. Silence as a conscious reaction to fear is artistically transformed in the image of the protagonist of the story "Plans to the Yard". And in «The Rotunda of the Murderers», this state already develops into an escape reflex, which eventually transforms into sharp words and unconditional frankness, which was manifested in the writer's simulation of madness.

A Versatile Semester-Long Course-Based Undergraduate Research Experience using Optogenetics and RNAi to Identify Genes Important for Synapse Function

Compared to traditional teaching laboratory activities, course-based undergraduate research experiences (CUREs) can increase student engagement and confidence, improve scientific literacy, enhance critical thinking, and promote accessibility in STEM. Here we describe a versatile CURE for an upper-level Neurobiology course that incorporates genetic, molecular, cellular, and behavioral experiments into a semester-long investigation to identify genes important for glutamate synapse formation or function in C. elegans. Following introduction to the CURE approach and basic C. elegans techniques, students construct their own low-cost optogenetics rigs, which we describe in detail here, to activate a mechanosensory escape reflex via photostimulation. They then perform a small-scale RNAi screen with this light-activated behavioral readout. Once a gene of interest is identified, students submit a proposal to investigate the role of this gene in nervous system function and spend the rest of the semester carrying out follow-up experiments using mutant strains. We also describe ways in which this CURE can be modified depending on the pedagogical objectives, availability of materials, or research interests of the instructor. Participating in this lab significantly enhanced students’ abilities to see themselves as STEM professionals and prompted students to report substantial gains in skills critical for entry into and success in graduate and medical schools. In addition to the benefits CUREs provide to students, faculty benefit from the generation of preliminary data and training of students for potential independent research projects.

Characterizing the genetic basis of trait evolution in the Mexican cavefish.

Evolution in response to a change in ecology often coincides with various morphological, physiological, and behavioral traits. For most organisms little is known about the genetic and functional relationship between evolutionarily derived traits, representing a critical gap in our understanding of adaptation. The Mexican tetra, Astyanax mexicanus, consists of largely independent populations of fish that inhabit at least 30 caves in Northeast Mexico, and a surface fish population, that inhabit the rivers of Mexico and Southern Texas. The recent application of molecular genetic approaches combined with behavioral phenotyping have established A. mexicanus as a model for studying the evolution of complex traits. Cave populations of A. mexicanus are interfertile with surface populations and have evolved numerous traits including eye degeneration, insomnia, albinism, and enhanced mechanosensory function. The interfertility of different populations from the same species provides a unique opportunity to define the genetic relationship between evolved traits and assess the co-evolution of behavioral and morphological traits with one another. To define the relationships between morphological and behavioral traits, we developed a pipeline to test individual fish for multiple traits. This pipeline confirmed differences in locomotor activity, prey capture, and startle reflex between surface and cavefish populations. To measure the relationship between traits, individual F2 hybrid fish were characterized for locomotor behavior, prey-capture behavior, startle reflex, and morphological attributes. Analysis revealed an association between body length and slower escape reflex, suggesting a trade-off between increased size and predator avoidance in cavefish. Overall, there were few associations between individual behavioral traits, or behavioral and morphological traits, suggesting independent genetic changes underlie the evolution of the measured behavioral and morphological traits. Taken together, this approach provides a novel system to identify genetic underpinnings of naturally occurring variation in morphological and behavioral traits.

Distinct Aging-Vulnerable and -Resilient Trajectories of Specific Motor Circuit Functions in Oxidation- and Temperature-Stressed Drosophila.

In Drosophila, molecular pathways affecting longevity have been extensively studied. However, corresponding neurophysiological changes underlying aging-related functional and behavioral deteriorations remain to be fully explored. We examined different motor circuits in Drosophila across the life span and uncovered distinctive age-resilient and age-vulnerable trajectories in their established functional properties. In the giant fiber (GF) and downstream circuit elements responsible for the jump-and-flight escape reflex, we observed relatively mild deterioration toward the end of the life span. In contrast, more substantial age-dependent modifications were seen in the plasticity of GF afferent processing, specifically in use dependence and habituation properties. In addition, there were profound changes in different afferent circuits that drive flight motoneuron activities, including flight pattern generation and seizure spike discharges evoked by electroconvulsive stimulation. Importantly, in high-temperature (HT)-reared flies (29°C), the general trends in these age-dependent trajectories were largely maintained, albeit over a compressed time scale, lending support for the common practice of HT rearing for expediting Drosophila aging studies. We discovered that shortened life spans in Cu/Zn superoxide dismutase (Sod) mutant flies were accompanied by altered aging trajectories in motor circuit properties distinct from those in HT-reared flies, highlighting differential effects of oxidative versus temperature stressors. This work helps to identify several age-vulnerable neurophysiological parameters that may serve as quantitative indicators for assessing genetic and environmental influences on aging progression in Drosophila.

Characteristics of the toxic effect of imidacloprid on the state of Eisenia fetida (Annelida, Clitellata, Lumbricidae)

Imidacloprid became the most sold neonicotinoid insecticide in the world in the 21st century. Due to their constant use, neonicotinoids are stored in soils, bottom deposits, and surface waters. It is known that neonicotinoids reveal toxicity for non-target species: annelid worms, insects, fish, birds, and mammals. Neonicotinoids exhibit reproductive toxicity, neuro-, hepato-, and genotoxicity for mammals. Earthworms are useful modeling organisms that are proposed to carry out toxicity tests. Eisenia fetida is considered a convenient and adequate species in toxicological studies. Analysis of available data shows that even low concentrations of imidacloprid caused protrusion of a belt, blackening, leakage of a cellar fluid, narrowing areas of the body with edema in segments, and dark body pigmentation in E. fetida. There are also biochemical changes. Low concentrations of imidacloprid (<0.2 mg/L) suppress the activity of cellulase. Imidacloprid also causes damage to DNA, production of reactive oxygen species, and alterations in antioxidant enzymes activity in E. fetida: inhibition of catalase, but activation of superoxide dismutase and glutathione-S-transferase. Imidacloprid reduces reproductive success in E. fetida, causing significant deformation of sperm, reducing the average number and size of cocoons and the success of birth. At concentrations ≥10 mg/kg of imidacloprid, the high mortality of worms makes it impossible for vermiculture. At 5 mg/kg of imidacloprid in plants remains for vermicomposting in seven weeks, the mortality rate of 25% of E. fetida individuals is fixed. The stereotypical escape reflex behavior in the worms was observed in relation to imidacloprid at a concentration of 1.32 mg/kg. At the same time, molecular and cellular mechanisms of toxic effects of imidacloprid on E. fetida are almost not studied and needed special attention with further research.

Anesthesia with intramuscular administration of alfaxalone in Spanish ribbed newt (Pleurodeles waltl)

The objective of this investigation was to assess the usefulness of three different doses of alfaxalone administered intramuscularly in amphibian species. Thirty-two healthy, adult (5–9 years old) captive Spanish ribbed newts (Pleurodeles waltl) were used. Alfaxalone at a dose of 15, 20, and 30 mg/kg was administered into the muscles of the front legs of each newt, with a 4-week washout period between trials. Heart rate and depth of sedation were assessed for each animal prior to the administration of anesthetic (T0), and at 2-minute intervals over the initial 20 minutes, then at 5-minute intervals over 60 minutes, and at 15-minute intervals until a full duration of 120 minutes for each trial. The average induction time was reduced with increasing doses. The recovery period was prolonged with increasing doses. Intramuscular administration of alfaxalone proved a feasible method for immobilization and sedation in Spanish ribbed newts and resulted in loss of both the escape reflex and righting reflex.

The effect of foodborne sertraline on rainbow trout (Oncorhynchus mykiss)

The worldwide consumption of antidepressants is raising as well as their concentrations in the aquatic environment. This increases the risk of food chain contamination and bioaccumulation in aquatic biota. The aim of this study was to describe a potential risk of sertraline as a pollutant from water environment, wherein rainbow trout (Oncorhynchus mykiss) has been chosen as the test organism, because predatory fish are on the top of the food chain in the aquatic environment. The effects of foodborne sertraline were tested on rainbow trout during a 28-day toxicity test according to OECD 215 method. Sertraline was incorporated in commercial feed at a dose of 4.4 µg/kg (environmental concentration), 42 µg/kg and 400 µg/kg. The results confirmed that sertraline has a significant effect on fish behaviour, resulting in suppression of the escape reflex and increased resistance to stress. Moreover, increased Fultońs condition factor was found in fish fed with the highest concentration of sertraline. Haematological analysis revealed a statistically significant increase in the number of neutrophilic bands and neutrophil/lymphocyte ratio, and decreased number of lymphocytes. The results of biochemical examination showed a statistically significant decrease in ammonia and lactate concentrations and histological examination revealed changes in gills and caudal kidney. Although sertraline reduces stress in fish, the decline in nonspecific immunity is a risk to fish population stability.

Change from baseline as an outcome illustrates escape behaviour of rats in hot plate method

Background: The Hot Plate test is a thermal hyperalgesia model to assess the analgesic activity of many compounds. Traditional analysis compares reaction times with controls, reports only analgesic activity without considering escape reflex. Escape reflex to pain sensation also provides an indirect measure of analgesic activity. However, it requires repeated exposure of rats to hot plate. We explored the learning activities and escape behaviour of rats by calculating the change from baseline of reaction times.Methods: Male Wister strain albino rats, weighing between 150-200mg were used for assessment of hot-plate induced hyperalgesia. Author analysed the analgesic activity of aspirin (100mg/Kg) and compared with animals receiving saline. Aspirin and saline were administered 1hr orally before the commencement of the experiment. The reaction time was recorded at every 30 min up to 6hrs.Results: With traditional analysis, we can observe that the onset of action, peak action and duration of analgesic activity of aspirin was at 0.5, 2.0 and 5.0 hours respectively. Peak inhibition of reaction time was seen at 2 hours with a magnitude of 474%. When we applied a statistical procedure, absolute change from baseline statistics, we found that animals treated with aspirin also exhibited escape reflex after fading of drug response and animals treated with saline demonstrated early (0.5hr) escape behaviour from the hot plate and continued throughout the rest of the experiment.Conclusions: Change from baseline as an outcome illustrates escape behaviour of rats in hot plate method and it should be employed along with percentage inhibition during assessment of analgesic activity.

Methods and Tips for Intravenous Administration of Adeno-associated Virus to Rats and Evaluation of Central Nervous System Transduction.

Adeno-associated virus (AAV) vectors are a key reagent in the neurosciences for clustered regularly interspaced short palindromic repeats (CRISPR), optogenetics, cre-lox targeting, etc. The purpose of this manuscript is to aid the investigator attempting expansive central nervous system (CNS) gene transfer in the rat via tail vein injection of AAV. Wide-scale expression is relevant for conditions with widespread pathology, and a rat model is significant due to its greater size and physiologic similarities to humans compared to mice. In this example application, a wide-scale neuronal transduction is used to mimic a neurodegenerative disease that affects the entire spinal cord, amyotrophic lateral sclerosis (ALS). The efficient wide-scale CNS transduction can also be used to deliver therapeutic protein factors in pre-clinical studies. After a post-injection expression interval of several weeks, the effects of the transduction are evaluated. For a green fluorescent protein (GFP) control vector, the amount of GFP in the cerebellum is estimated quickly and reliably by a basic imaging program. For motor disease phenotypes that are induced by the ALS related protein transactive response DNA-binding protein of 43 kDa (TDP-43), the deficits are scored by escape reflex and rotarod. Beyond disease modeling and gene therapy, there are diverse potential applications for the wide-scale gene targeting described here. The expanded use of this method will aid in expediting hypothesis testing in the neurosciences and neurogenetics.

Influence of aluminum chloride exposure on embryonic development of zebrafish and neurobehavior of juvenile fish

Objective: To investigate the influence of aluminum chloride (AlCl(3)) solution on the embryon-ic development of zebrafish and neurobehavior of juvenile fish. Methods: The embryos of zebrafishat 6 hours after fertilization were exposed to AlCl(3) solution at a concentration of 0, 55.0, 60.5, 66.6, 73.5, 80.5, or 100.0 mg/L, and embryonic hatching rates at 48 and 72 hours after fertilization were calculated. The embryos of zebrafishat 6 hours after fertilization were exposed to AlCl(3) solution at a concentration of 0, 60.0, 72.0, 86.4, 103.7, or 124.4 mg/L, and the embryonic mortality rates at 12, 24, 48, 72, and 96 hours after fertilization were calculat-ed. The embryos of zebrafish at 6 hours after fertilization were exposed to AlCl(3) solution at a concentration of 0, 50, 100, 200, 400, or 800 μg/L, and the changes in the neurobehavior of juvenile fish were observed after hatching, including touch-escape reaction at 72 hours after fertilization and autonomic movement and panic es-cape reflex at 7 days after fertilization. Results: Compared with the 0 mg/L group, the≥66.6 mg/L group had a sig-nificant reduction in embryonic hatching rate at 48 and 72 hours after fertilization, and the ≥72.0 mg/L group had a significant increase in embryonic mortality rate at 96 hours after fertilization (P<0.05) . Compared with the 0 μg/L group, the≥100 μg/L group had a significant reduction in the number of times of touch-escape reaction (P<0.05) .Compared with the 0 and 50 μg/L groups, the 100-800 μg/L groups had significant reductions in total movement distance and average speed (P<0.05) . Compared with the dark period before illumination, all groups had a significant increase in movement speed during the light period of the panic escape reflex test (i.e., the third minute) (P<0.05) ; within 2 minutes after the light was turned off, there was no significant change in movement speed in the 0-200 μg/L groups (P>0.05) ; the 400 and 800 μg/L groups had a significant increase in movement speed (P<0.05) . Conclusion: AlCl(3) exposure may cause embryonic developmental disorder in zebrafish and ab-normal neurobehavior in juvenile fish.

Anti-Cytokine Activity of Curcumin and Its Binding to a Fragment of AβPP

Since it has been shown that Alzheimer’s disease is accompanied by higher peripheral concentrations of cytokines, we focused on the correction of chronic inflammation causing Aβ excess and aggregation what should have a positive impact. Proinflammatory cytokines action is realized by NF-κB intracellular signals. Curcumin can inhibit activation of the proinflammatory transcription factor NF-κB and is able to be mounted in the amyloid-β fibrils and encourage their disaggregation. To study the influence of anti-inflammatory effect of curcumin and its ability to model complexes with a fragment of AβPP. Investigation was carried out on rats with model of Alzheimer’s disease using nasal therapy with curcumin Concentration of cytokines in cerebral cortex, hippocampus and blood serum, and indicators of conditioned active escape reflex were determined in this study. Methods of molecular dynamics and docking were used to examine the interactions of curcumin with fragment of AβPP. Аβ42_Human in the hippocampus of rats provoked chronic neuroinflammation specifically and primarily at the injection site. Curcumin performance revealed specific depressing effect on cytokines in the cerebral cortex and in the hippocampus it appeared similar to the above, but of lower level. Anti-inflammatory activity of curcumin led to the recovery of memory parameters. Analysis of restriction sites of AβPP has shown that position of curcumin in Site II is energetically more favorable for binding. Our suggestion that curcumin is an effective anti-cytokine factor was confirmed by experimental results obtained in vivo and explain the mechanism describing its effect on NF-κB Curcumin doesn’t block the excision Aβ but binding with its hydrophobic region.

Characterization of Aeromonas sobria Isolated from Fish Rohu (Labeo rohita) Collected from Polluted Pond

One of the major threats to fish aquaculture sector is the infection by Aeromonas Spp. The current study assesses the phenotypic characteristics and biochemical characterization of the A. sobria strains from the fish cases with septicaemia in order to understand the frequency and occurrence of this infection in the state of Jammu and Kashmir. Clinically the infected fish Rohu (Labeo rohita), one of the Indian Major carps (IMC), was observed for symptoms like loss of escape reflex and skin darkness associated with skin haemorrhages. We isolated 30 colonies of A. sobria strain from 10 cultured Labeo rohita collected from a controlled fish pond in District Poonch of the state. The pond was affected by mismanagement practices, elevated pollution levels and anthropogenic activities. Microscopic examination revealed that the strain was rod-shaped and gram negative. The revealed percent probability identification of A. sobria from the biochemical characterization in Vitek system was 93% with GN card. This study could give us clues for understanding A. sobria harbouring in fish species and shall help in better understanding of the threat prevalent to the fish species of the region by this infection.

Athletic humpbacked conches leap to safety

When a predatory cone snail launches an attack, it is hardly a high-speed encounter. Lumbering towards an unsuspecting humpbacked conch, the cone snail looks likely to outpace its quarry; but then events take an unexpected turn. As soon as the conch gets a whiff of the approaching predator, it leaps out of reach. And Sjannie Lefevre from the University of Oslo, Norway, explains that the athletic conches can continue flipping for as long as 5 min to get clear of danger. Intrigued by the humble mollusc's remarkable escape reflex, Lefevre and her colleagues, Sue-Ann Watson and Philip Munday from James Cook University, Australia, and Göran Nilsson from the University of Oslo, wondered how the animals powered their gymnastics. Lefevre explains that the oxygen consumption of fish rockets when they exert themselves, but she was less sure that the conches – with their relatively simple hearts and circulatory systems – could rise to the challenge in quite the same way.Collecting conches buried in the sand in the Lizard Island lagoon, the team headed back to the lab to measure the animals’ oxygen consumption rate while resting and leaping. However, before Lefevre could entice the conches to exert themselves, she had to collect some of the terrifying odour from the water bathing the predatory snails: ‘[The humpback conches] react very quickly; almost as soon as you inject the odour into the respirometer, they start jumping’, she says. And Lefevre was amazed to see the oxygen levels in the respirometer plummet as soon as the conches began jumping to evade the smell. ‘We had some conches increase their oxygen consumption six times’, she says, adding that this is similar to the metabolic boost measured in escaping fish. So, despite their unsophisticated circulatory systems, the conches were able to increase their oxygen consumption dramatically as their metabolism soared during an escape bid.But then the team wondered how well the molluscs will cope as climate change takes hold and the planet's oceans become more acidic. Lefevre explains that the additional physical burden of increased temperature and acidity limits the performance of many ectotherms as they divert energy to cope with the physiological challenges. To test how well the conches may cope in the future, Lefevre turned up the thermometer – first to 33°C and then to 38°C – and measured their oxygen consumption while resting and leaping. However, the conches didn't miss a beat, successfully sustaining their athletic leaps at the highest temperature when other species would have diverted energy from their exertions to combat the heat. And when Lefevre turned up the pressure and increased the CO2 level of the water from about 450 μatm to nearly 1000 μatm – to simulate conditions in 2100 – she was amazed to see that the conches barely suffered any ill effects and continued leaping. ‘These snails have aerobic capacity in excess of current and future needs’, she says.However, this does not mean that the future will be all plain sailing for the athletic conches. Lefevre explains that increased levels of CO2 in the water affect the ability of many aquatic species to react to predators, making them more vulnerable to predation. She suspects that the nimble conches may suffer the same fate, as she and her colleagues have found that the molluscs are reluctant to jump in high-CO2 water. But, she is optimistic that enough of them will retain the ability to sniff-out a foe and take evasive action to keep the conches leaping into the future.

Habituation of the C-Start Response in Larval Zebrafish Exhibits Several Distinct Phases and Sensitivity to NMDA Receptor Blockade

The zebrafish larva has been a valuable model system for genetic and molecular studies of development. More recently, biologists have begun to exploit the surprisingly rich behavioral repertoire of zebrafish larvae to investigate behavior. One prominent behavior exhibited by zebrafish early in development is a rapid escape reflex (the C-start). This reflex is mediated by a relatively simple neural circuit, and is therefore an attractive model behavior for neurobiological investigations of simple forms of learning and memory. Here, we describe two forms of short-lived habituation of the C-start in response to brief pulses of auditory stimuli. A rapid form, persisting for ≥1 min but <15 min, was induced by 120 pulses delivered at 0.5–2.0 Hz. A more extended form (termed “short-term habituation” here), which persisted for ≥25 min but <1 h, was induced by spaced training. The spaced training consisted of 10 blocks of auditory pulses delivered at 1 Hz (5 min interblock interval, 900 pulses per block). We found that these two temporally distinguishable forms of habituation are mediated by different cellular mechanisms. The short-term form depends on activation of N-methyl-d-aspartate receptors (NMDARs), whereas the rapid form does not.

Evaluating the Effects of Forestry Herbicides on Fish Development Using Rapid Phenotypic Screens

AbstractHerbicides are used to control invasive or noxious plants on public lands throughout the western United States. These chemicals are often applied in the upper reaches of watersheds that provide spawning and rearing habitat for anadromous species of Pacific salmon Oncorhynchus spp., steelhead O. mykiss, and bull trout Salvelinus confluentus. As a consequence, natural resource managers must often weigh the ecological benefits of using herbicides to control nonnative plants against the potential for unintended toxicological impacts on salmonids, particularly during early life stages. However, the effects of chemical control agents on fish development have not been widely investigated. Their use in the vicinity of aquatic habitats, including areas that support threatened and endangered species, is therefore a concern. To address this uncertainty, we used the zebrafish Danio rerio as a model experimental system for investigating developmental toxicity, which involved conducting rapid and sensitive phenotypic screens for potential developmental defects resulting from exposure to six herbicides (picloram, clopyralid, imazapic, glyphosate, imazapyr, and triclopyr) and several technical formulations (Tordon K, Transline, Habitat, Plateau, Garlon 3A, and Renovate). Zebrafish embryos were exposed continuously through 5 d of development at nominal concentrations ranging from 3 μg/L to 10 mg/L. Detailed screens were used to examine aspects of ontogeny from early development (gastrulation and segmentation) through organogenesis, hatching, and morphology as free‐swimming larvae. Growth was measured at the end of each exposure interval. To detect defects in neural development (sensorimotor integration), the escape reflex of larvae was monitored at 3, 4, and 5 d after fertilization. No developmental toxicity was observed in response to the six individual herbicides or the different technical formulations. The absence of toxicity at relatively high exposure concentrations suggests that noxious weed control activities are not likely to pose a direct threat to the health of salmonids at early life stages.

Mauthner cells

Mauthner cells

Relationship between the types of behavioral reaction in a conditioned shake-off reflex and neocortical lateralization

The nature of the spike activity and interhemisphere interactions of neurons in the parietal cortex (somatosensory representation of the ear) during the intersignal period before active shake-off and passive (freezing) reactions to stimuli was studied in rabbits after acquisition of a conditioned defensive escape reflex. Before passive reactions, in contrast to the situation before active shake-off, there were increases in right-sided influences on cells in the left hemisphere with delays of up to 100 msec, leading to asymmetry in interhemisphere interactions with right-sided dominance. Passive reactions were preceded by increases in the extent of frequencies in the delta range in the spike activity of individual neurons and in interactions between pairs of cells. These data provide evidence that the existence and nature of interhemisphere asymmetry before stimulation is one of the factors determining the passive or active type of behavioral reaction and reflecting the level of activation of the cortex.