Locomotor Activity Levels Research Articles

Behavioral Effects of d‐Methamphetamine and sin vivo microdialysis in rats

The present studies were conducted to examine the relationship between locomotor stimulant effects of d‐methamphetamine (d‐MA) and its ability to increase extracellular concentrations of d‐MA, its active metabolite d‐amphetamine (d‐AMP), dopamine (DA), serotonin (5‐HT), norepinephrine (NE), γ‐aminobutyric acid (GABA), and glutamate (GLU) in dialysate samples obtained from the rat nucleus accumbens (nAcc) shell. First, the effects of cumulatively administered d‐MA (0.3–5.6 mg/kg) on locomotor activity were determined in rats. In other studies, in vivo microdialysis and LC/MS analysis of dialysate samples were used to determine the effects of cumulatively administered d‐MA (0.3–5.6 mg/kg) on extracellular levels of d‐MA, d‐AMP, DA, 5‐HT, NE, GABA, and GLU in the nAcc shell. d‐MA produced dose‐related effects on locomotor activity, characterized by an inverted‐U dose‐response curve; 0.3–3 mg/kg increased activity, whereas 5.6 mg/kg suppressed activity (induced stereotypy). Results from microdialysis studies show that levels of d‐MA (0.3–5.6 mg/kg i.p.) in the nAcc shell increased in a dose‐ and time‐dependent manner with concentrations ranging from 12–319 nM, respectively; peak levels (334 nM) detected 20 min after 5.6 mg/kg slowly declined over the next hour. An increase in d‐AMP was also observed with concentrations ranging from 4.5–130 nM after 0.3–5.6 mg/kg d‐MA; peak levels of d‐AMP were detected 20 min (164 nM) after 5.6 mg/kg d‐MA and remained at this level for more than the next hour 100 min. d‐MA produced dose‐ and time‐dependent increases in DA, 5‐HT, and NE efflux in the nAcc shell to maxima of approximately 642% (17 nM), 582% (1.2 nM), and 422% (0.7 nM) of control values, respectively. In contrast, d‐MA did not produce significant changes in GABA or GLU levels. Time course and dose‐response analysis show that increases in d‐MA levels after 0.3–3.0 mg/kg are concordant with increases in DA, 5‐HT, and NE efflux. However, levels of d‐MA after 5.6 mg/kg appear to reflect increases in DA and 5‐HT but not NE. Correlation analysis revealed an inverse relationship between d‐MA‐induced increases in locomotor activity and in vivo extracellular levels of 5‐HT and d‐AMP. Although not statistically significant, a trend towards an inverse relationship was also observed between d‐MA‐induced increases in locomotor activity and extracellular levels of d‐MA and other neurotransmitters in the nAcc shell. Taken together, the ability to detect and correlate the presence and clearance of in vivo brain levels of d‐MA, and its active metabolite d‐AMP in the nAcc shell of rats to neurochemical and behavioral effects can provide insight into the neuropharmacological effects of d‐MA.

Chronic social defeat stress: Impacts on ethanol-induced stimulation, corticosterone response, and brain monoamine levels.

Chronic exposure to stress may dysregulate the hypothalamic-pituitary-adrenal axis and brain monoamine levels, contributing to the development of ethanol dependence. Exposure to chronic social defeat stress may impact ethanol-related effects, neural, and endocrine functions. This study assessed ethanol-induced locomotor activity, corticosterone responses, and brain monoamine levels in Swiss albino mice 10 days post-exposure to chronic social defeat stress. During a period of 10 days, male Swiss mice were exposed to daily defeat episodes, followed by housing with an aggressive mouse for 24 h. Control mice were housed in pairs and rotated every 24 h. Ten days post-stress, locomotor behavior was recorded after a challenge with ethanol (2.2 g/kg; intraperitoneal) or saline. After the test, blood and brain samples were collected for determination of plasma corticosterone and brain monoamines across different brain areas through high-performance liquid chromatography. Defeated mice failed to show a stimulant locomotor response to ethanol, while controls displayed the expected ethanol-induced stimulation. Ethanol increased plasma corticosterone levels, with lower corticosterone secretion in defeated mice. Brain monoamines were affected by social defeat and ethanol, varying in different brain regions. Social stress reduced levels of dopamine, noradrenaline, and serotonin in the hypothalamus. Defeated mice presented reduced serotonin and dopamine levels in the frontal cortex. In the striatum, ethanol treatment increased dopamine levels in controls, but failed to do so in defeated mice. Our results suggest that chronic exposure to social defeat blunted ethanol-induced locomotor stimulation, and reduced ethanol-induced corticosterone secretion. Social stress promoted differential reductions in brain monoamine levels in the hypothalamus and frontal cortex and blunted ethanol-induced dopamine increases in the striatum.

Formosan wood mice (Apodemus semotus) exhibit more exploratory behaviors and central dopaminergic activities than C57BL/6 mice in the open field test.

Three-quarters of the lands in Taiwan are over 1000 m above sea level. Formosan wood mice (Apodemus semotus), also called Taiwanese field mice, are largely found at altitudes of 1400 ~ 3700 m and are the dominant rodents in these areas. Notably, Formosan wood mice show high levels of exploratory behaviors, not only in the wild but also in laboratory situations. Therefore, in this study, we examined the behavioral responses and central dopaminergic activities of male C57BL/6J mice and Formosan wood mice in the open field test. Dopamine and its major metabolite 3,4-dihydroxyphenylacetic acid were used as indices of dopaminergic activities. Formosan wood mice showed higher levels of exploration and locomotor activity than C57BL/6J mice in the open field test. Higher central dopaminergic activities in the nucleus accumbens, striatum, and medial prefrontal cortex were found in Formosan wood mice than in C57BL/6J mice in the open field test. Higher levels of locomotion and central dopaminergic activities in Formosan wood mice were consistent after two exposures to the open field test; however, dramatic decreases in levels of locomotion and central dopaminergic activities in C57BL/6J mice were found after two exposures to the open field test. The present study found that Formosan wood mice exhibited higher levels of locomotor activity and exploration and central dopaminergic activities than C57BL/6J mice after one or two exposures to the open field test.

Intravesical Infusion of Budesonide Foam Improves Symptoms in a Bladder Pain Syndrome/Interstitial Cystitis Rat Model

Purpose: Since intravesically administered steroid therapy may treat bladder pain syndrome/interstitial cystitis (BPS/IC) with fewer side effects than the current treatment of orally administered steroids, we investigated whether the intravesical infusion of budesonide foam can effectively treat BPS/IC symptoms in a rat model of tranilast-induced BPS/IC. Methods: There were 6 rat treatment groups (n = 8 per group): control + single or daily saline infusion, tranilast + single or daily saline infusion, and tranilast + single or daily budesonide infusion. All groups except for the controls were fed a tranilast supplemented diet for 5 weeks. Budesonide and saline were infused intravesically. After the BPS/IC rat model underwent single infusion treatments, we measured the paw pain threshold using the von Frey test and continuous cystometry was taken. After two weeks of daily intravesical infusions, we measured locomotor activity and serum cortisol levels; harvested bladders underwent histological analysis. Results: Both pain threshold and locomotor activity were significantly lower in the saline-infused groups receiving the tranilast diet, but there were no differences between the budesonide-infused groups and the controls. The interval between bladder contractions was significantly shorter in the tranilast group than the control or tranilast + budesonide infusion groups. The serum cortisol levels did not change. Hematoxylin-Eosin stainings of the bladder showed thickening of the bladder muscle layer and mucosal edema in the tranilast group, while the tranilast + budesonide infusion group showed only mild changes. Conclusion: Intravesical infusion of budesonide effectively treated BPS/IC symptoms in a rat model of BPS/IC.

Comparative Efficiency Analysis of Prophylactic Measures Counteracting Negative Effects of Reduced Physical Activity on Human Physical Performance during a 520-Day Isolation Experiment

Insufficient levels of physical activity is among the leading risk factors of some chronic diseases and premature death. Effects of a reduced level of locomotor activity on human physiology were studied under the conditions of a 520-day isolation experiment simulating a space mission to Mars. A cohort of participants included 6 healthy men from different countries. As a prophylactic against negative effects of reduced locomotor activity, the volunteers performed cyclical exercises on an active treadmill (the moving belt was motorized), a passive treadmill (the belt was moved by the force of human legs), and on a bicycle ergometer. Resistive exercises were performed on the strength training device Multifunctional Dynamometer for Application in Space (MDS), a vibration platform, and with expanders. Three breaks in workouts as the control “pure” isolation periods, when training exercises were suspended, were included into the study program design. The experiment design allowed performing a comparative efficiency analysis of workouts on each of the applied devices in the conditions of reduced locomotor activity. According to the multiparametric assessment, the prophylactic devices were evaluated in terms of efficiency in the following descending order: the passive treadmill, the vibration platform, and the MDS strength training device.

Peripheral blood metabolome predicts mood change-related activity in mouse model of bipolar disorder

Bipolar disorder is a major mental illness characterized by severe swings in mood and activity levels which occur with variable amplitude and frequency. Attempts have been made to identify mood states and biological features associated with mood changes to compensate for current clinical diagnosis, which is mainly based on patients’ subjective reports. Here, we used infradian (a cycle > 24 h) cyclic locomotor activity in a mouse model useful for the study of bipolar disorder as a proxy for mood changes. We show that metabolome patterns in peripheral blood could retrospectively predict the locomotor activity levels. We longitudinally monitored locomotor activity in the home cage, and subsequently collected peripheral blood and performed metabolomic analyses. We then constructed cross-validated linear regression models based on blood metabolome patterns to predict locomotor activity levels of individual mice. Our analysis revealed a significant correlation between actual and predicted activity levels, indicative of successful predictions. Pathway analysis of metabolites used for successful predictions showed enrichment in mitochondria metabolism-related terms, such as “Warburg effect” and “citric acid cycle.” In addition, we found that peripheral blood metabolome patterns predicted expression levels of genes implicated in bipolar disorder in the hippocampus, a brain region responsible for mood regulation, suggesting that the brain–periphery axis is related to mood-change-associated behaviors. Our results may serve as a basis for predicting individual mood states through blood metabolomics in bipolar disorder and other mood disorders and may provide potential insight into systemic metabolic activity in relation to mood changes.

Sigma-1 receptor is a key genetic modulator in amyotrophic lateral sclerosis.

Sigma-1 receptor (S1R) is an endoplasmic reticulum (ER) chaperone that not only regulates mitochondrial respiration but also controls cellular defense against ER and oxidative stress. This makes S1R a potential therapeutic target in amyotrophic lateral sclerosis (ALS). Especially, as a missense mutation E102Q in S1R has been reported in few familial ALS cases. However, the pathogenicity of S1RE102Q and the beneficial impact of S1R in the ALS context remain to be demonstrated in vivo. To address this, we generated transgenic Drosophila that expresses human wild-type S1R or S1RE102Q. Expression of mutant S1R in fly neurons induces abnormal eye morphology and locomotor defects in a dose-dependent manner. This was accompanied by abnormal mitochondrial fragmentation, reduced adenosine triphosphate (ATP) levels and a higher fatigability at the neuromuscular junction during high energy demand. Overexpressing IP3 receptor or glucose transporter mitigates the S1RE102Q-induced eye phenotype, further highlighting the role of calcium and energy metabolism in its toxicity. More importantly, we showed that wild-type S1R rescues locomotor activity and ATP levels of flies expressing the key ALS protein, TDP43. Moreover, overexpressing wild-type S1R enhances resistance of flies to oxidative stress. Therefore, our data provide the first genetic evidence that mutant S1R recapitulates ALS pathology in vivo while increasing S1R confers neuroprotection against TDP43 toxicity.

Propionic acid induced behavioural effects of relevance to autism spectrum disorder evaluated in the hole board test with rats

Autism spectrum disorders (ASD) are a set of neurodevelopmental disorders characterized by abnormal social interactions, impaired language, and stereotypic and repetitive behaviours. Among genetically susceptible subpopulations, gut and dietary influences may play a role in etiology. Propionic acid (PPA), produced by enteric gut bacteria, crosses both the gut-blood and the blood-brain barrier. Previous research has demonstrated that repeated intracerebroventricular (ICV) infusions of PPA in adult rats produce behavioural and neuropathological changes similar to those seen in ASD patients, including hyperactivity, stereotypy, and repetitive movements. The current study examined dose and time related changes of exploratory and repetitive behaviours with the use of the hole-board task. Adult male Long-Evans rats received ICV infusions twice a day, 4 h apart, of either buffered PPA (low dose 0.052 M or high dose 0.26 M, pH 7.5, 4 μL/infusion) or phosphate buffered saline (PBS, 0.1 M) for 7 consecutive days. Locomotor activity and hole-poke behaviour were recorded daily in an automated open field apparatus (Versamax), equipped with 16 open wells, for 30 min immediately after the second infusion. In a dose dependent manner PPA infused rats displayed significantly more locomotor activity, stereotypic behaviour and nose-pokes than PBS infused rats. Low-dose PPA animals showed locomotor activity levels similar to those of PBS animals at the start of the infusion schedule, but gradually increased to levels comparable to those of high-dose PPA animals by the end of the infusion schedule, demonstrating a dose and time dependent effect of the PPA treatments.

Behavioural consequences of divergent selection on general locomotor activity in chickens

General locomotor activity is a highly variable phenotypic trait of animals. In domestic chickens it is different within and between breeds. The general locomotor activity is a substantially heritable trait and has been shown to be correlated with several other behavioural traits, such as for example feather pecking and anxiety in chickens. However, whether there is a relation between different levels of general locomotor activity and behavioural changes remained unclear. Therefore, a selection line model system has been established, where hens from the same founder population were selected over eight generations for either high or low general locomotor activity. The selection led to significant increases, respectively decreases in general locomotor activity and differences in growth. We here tested 128 hens of the 8th generation in three behavioural tests. We assumed fearfulness to be affected from selection on general locomotor activity, which we tested in a tonic immobility test. Socio-positive and socio-negative behaviours were tested in respective test paradigms. Fearfulness was higher in hens selected for high general locomotor activity. Social behavioural traits and feather pecking were not affected by selection for general locomotor activity. Evolutionary mechanisms that link fear and general locomotor activity are discussed and also why social behaviours and feather pecking seems not to be affected from selection on general locomotor activity. Our results provide interesting new insights on how selection on one trait, general locomotor activity, affects the behavioural phenotype in other dimensions too.

Apelin-13 enhances contextual fear extinction in rats

Fear extinction is considered as a new learning process that is valid to model features of post-traumatic stress disorder (PTSD). The neuropeptide apelin, such as apelin-13, apelin-17 and apelin-36, are endogenous ligands of the G-protein coupled receptor APJ. Apelin and its receptor APJ are widely distributed in the central nervous system. Accumulating evidence suggests the critical role of apelin-13 in modulation of learning and memory, however, its specific role in fear extinction remains unclear. In the present study, we investigated the effect of apelin-13 administration on contextual fear extinction in rats. The behavioral procedure included four sessions: habitation, conditioning, extinction training and extinction recall. Rats received intracerebroventricular infusion of apelin-13 (3 or 6 μg) 0.5 h prior to the extinction training. Percentage of freezing was utilized to assess the conditioned fear response. Results showed that apelin-13, with the dose of 6 but not 3 μg, significantly decreased freezing response during both extinction training and extinction recall test sessions. Furthermore, apelin-13 did not affect the levels of baseline freezing, locomotor activity and anxiety. The results suggest that apelin-13 dose-dependently enhances contextual fear extinction, and may function as a novel target for treatment of PTSD.

Drosophila carboxypeptidase D (SILVER) is a key enzyme in neuropeptide processing required to maintain locomotor activity levels and survival rate.

Neuropeptides are processed from larger preproproteins by a dedicated set of enzymes. The molecular and biochemical mechanisms underlying preproprotein processing and the functional importance of processing enzymes are well-characterised in mammals, but little studied outside this group. In contrast to mammals, Drosophila melanogaster lacks a gene for carboxypeptidase E (CPE), a key enzyme for mammalian peptide processing. By combining peptidomics and neurogenetics, we addressed the role of carboxypeptidase D (dCPD) in global neuropeptide processing and selected peptide-regulated behaviours in Drosophila. We found that a deficiency in dCPD results in C-terminally extended peptides across the peptidome, suggesting that dCPD took over CPE function in the fruit fly. dCPD is widely expressed throughout the nervous system, including peptidergic neurons in the mushroom body and neuroendocrine cells expressing adipokinetic hormone. Conditional hypomorphic mutation in the dCPD-encoding gene silver in the larva causes lethality, and leads to deficits in starvation-induced hyperactivity and appetitive gustatory preference, as well as to reduced viability and activity levels in adults. A phylogenomic analysis suggests that loss of CPE is not common to insects, but only occurred in Hymenoptera and Diptera. Our results show that dCPD is a key enzyme for neuropeptide processing and peptide-regulated behaviour in Drosophila. dCPD thus appears as a suitable target to genetically shut down total neuropeptide production in peptidergic neurons. The persistent occurrence of CPD in insect genomes may point to important further CPD functions beyond neuropeptide processing which cannot be fulfilled by CPE.

Testosterone does not mediate variation in basal metabolic rate and activity in relation to reproductive condition and photoperiod in white-footed mice (Peromyscus leucopus).

The photoperiodic response of many temperate zone rodents, including white-footed mice (Peromyscus leucopus), is a heritable life-history trait with underlying physiological variation. Previous studies of intact male P. leucopus utilized two wild-derived bidirectional selection lines, a short photoperiod responsive (R) line selected for reproductive suppression in short-day conditions (SD) and a nonresponsive (NR) line selected for reproductive maturity in SD. NR mice in SD had greater food intake, but also higher levels of locomotor activity, and basal metabolic rate (BMR) than R mice. We hypothesized that testosterone may be a key mediator of this metabolic difference, as it is likely to be significantly reduced in R SD mice. Male P. leucopus from either line in SD were castrated and given either an implant containing testosterone (T) or a sham control (C). They were then tested for variation in metabolic rate and activity in SD, thermoneutral conditions. T mice had significantly higher levels of food intake, testosterone, and seminal vesicle dry weight than C mice. Seminal vesicle dry weight was significantly and positively correlated with average testosterone level, indicating an effect of the T implants. There was no statistically significant difference among treatment groups in BMR and average daily metabolic rate, suggesting that differences in testosterone alone are not the cause of differences in metabolic rate between selection lines.

Empathy in stroke rats is modulated by social settings

Rodents display “empathy” defined as perceived physical pain or psychological stress by cagemates when co-experiencing socially distinct traumatic events. The present study tested the hypothesis that empathy occurs in adult rats subjected to an experimental neurological disorder, by allowing co-experience of stroke with cagemates. Psychological stress was measured by general locomotor activity, Rat Grimace Scale (RGS), and plasma corticosterone. Physiological correlates were measured by Western blot analysis of advanced glycation endproducts (AGE)-related proteins in the thymus. General locomotor activity was impaired in stroke animals and in non-stroke rats housed with stroke rats suggesting transfer of behavioral manifestation of psychological stress from an injured animal to a non-injured animal leading to social inhibition. RGS was higher in stroke rats regardless of social settings. Plasma corticosterone levels at day 3 after stroke were significantly higher in stroke animals housed with stroke rats, but not with non-stroke rats, indicating that empathy upregulated physiological stress level. The expression of five proteins related to AGE in the thymus reflected the observed pattern of general locomotor activity, RGS, and plasma corticosterone levels. These results indicate that stroke-induced psychological stress manifested on both the behavioral and physiological levels and appeared to be affected by empathy-associated social settings.

Effects of bisphenol S, a major substitute of bisphenol A, on neurobehavioral responses and cerebral monocarboxylate transporters expression in mice

Bisphenol A has been restricted in a large variety of products. Bisphenol S (BPS) is its major substitute. Yet, the impacts of BPS on the central nervous system are unknown, especially in vulnerable populations like children. The aim of this study was to investigate the effects of BPS on behavioral performances and the expression of cerebral monocarboxylate transporters (MCTs). Male Swiss mice were exposed to BPS at 100 μg/kg in drinking water for 10 weeks. The protocol started after the lactation period, which is a sensitive period of early social-emotional development. Elevated T-maze and open field tests were used to measure respectively, anxiety-related and activity-related behaviors. Molecular expressions of MCTs isoforms (MCT1, MCT2, MCT4) were determined in the frontal cortex. Data showed that BPS does not affect mRNA expression of MCTs. However, BPS decreases the number of entries into the open arms and the time spent on them for BPS-treated mice. These data reveal an anxiogenic effect of BPS. For locomotor activity and exploratory behavior levels, differences did not reach a statistically significant level in the BPS-exposed group. The effect of BPS on behavioral performances unravels a putative risk for psychopathology development in early childhood and calls for more attention.

P2‐164: NEUROPROTECTIVE MECHANISM OF SPERMIDINE ALONE AND IN COMBINATION WITH NITRIC OXIDE PATHWAY MODULATORS AGAINST 3‐NP‐INDUCED BEHAVIORAL, BIOCHEMICAL AND NEUROTRANSMITTER ALTERATIONS IN RAT STRIATUM

Huntington's disease (HD) is fatal, hyperkinetic and characterized by motor and non-motor symptoms for there is no clinically available drug. Emerging strides have implicated the role of neurotransmitters alteration, excitotoxicity, oxidative stress, mitochondrial dysfunction, neuroinflammation in HD pathophysiology. Polyamines (Spermidine) are documented to regulate mitochondria Ca2+ transport, nitric oxide synthase, neuroinflammation and oxidative stress. 3-NP induces a spectrum of HD-like neuropathology in rat striatum and widely used as experimental tool to study HD. Rats were administered with 3-NP (10 mg/kg/day, i.p.) for 3 weeks. Spermidine (5 and 10 mg/kg/day, p.o.) was given once a day, 1 hour prior to 3-NP treatment for 3 weeks. Either, L-NAME (10 mg/kg; i.p.), a nitric oxide synthase inhibitor and L-arginine (50 mg/kg; i.p.), a nitric oxide synthase precursor were administered with spermidine in respective groups. In the end of study, animals were sacrificed and striatum was isolated for various biochemical, neuroinflammation and neurotransmitters analysis. 3-NP treatment significantly changed body weight, locomotor activity, motor coordination, oxidative defense, pro-inflammatory mediators and striatal neurotransmitters level. Pre-treatment with spermidine (5 and 10 mg/kg; p.o.) alone for 21 days significantly prevented the 3-NP induced alterations. In addition, concurrent treatment of Spermidine (5 mg/kg; p.o.) with L-NAME (10 mg/kg; i.p.) significantly enhanced observed protective effect of Spermidine (5 mg/kg; p.o.) whereas concurrent treatment of Spermidine (10 mg/kg; p.o.) with L-Arg (50 mg/kg; i.p.) significantly reduced observed protective effect of Spermidine (10 mg/kg; p.o.). The observed neuroprotective efficacy of Spermidine is attributed to its anti-oxidant and anti-inflammatory properties and prevention of neurotransmitters level in striatum.

Effects of Elevated Grids on Growing Male Chickens Differing in Growth Performance

Pullets, i. e., chickens of layer lines are often raised in housings equipped with perches. In contrast, broiler chickens most often are raised in a barren environment that lacks any three-dimensional structures, even though broilers also are motivated to use elevated structures. In addition, environmental enrichment may improve welfare problems in broiler chickens, such as skeletal disorders or contact dermatitis. Due to ethical reasons, currently there are attempts to fatten the male chickens of layer strains or to use dual purpose strains. However, there is only limited knowledge on the behavior of these chickens until now. The aim of this study was to test the use of elevated grids and their effect on animal-based indicators (e.g., physical condition). In two successive trials, we kept a total of 1,217 male chickens from three strains (Lohmann Dual, Lohmann Brown Plus, Ross 308) that show differences in growth performance in 24 pens (two trials × three strains × eight pens). In half of the pens, grids were offered at three different heights (enriched groups); in the other half of the pens, no elevated structures were installed (control groups). We recorded the number of birds using the grids at the different heights as well as locomotor activity, walking ability, plumage cleanliness, and the footpad health of chickens. Chickens with low and medium growth performance preferred the highest grids during both the light and dark periods. In contrast, fast-growing chickens used the lowest grid more frequently. Fast-growing chickens kept in the enriched pens tended to have a higher level of locomotor activity and reduced chest cleanliness. Chickens from the medium growth performance strain showed better walking ability when kept in the enriched pens. Enrichment did not affect any of the welfare measures in the slow-growing chickens. These findings suggest that elevated structures may improve chicken welfare, particularly for medium growing chickens. For fast-growing chickens we found evidence for an improvement of animal-based indicators although they used the elevated structures less. However, regardless of growth performance, elevated grids offer the birds an opportunity to rest in a species-specific manner.

Environmental Cycles, Melatonin, and Circadian Control of Stress Response in Fish.

Fish have evolved a biological clock to cope with environmental cycles, so they display circadian rhythms in most physiological functions including stress response. Photoperiodic information is transduced by the pineal organ into a rhythmic secretion of melatonin, which is released into the blood circulation with high concentrations at night and low during the day. The melatonin rhythmic profile is under the control of circadian clocks in most fish (except salmonids), and it is considered as an important output of the circadian system, thus modulating most daily behavioral and physiological rhythms. Lighting conditions (intensity and spectrum) change in the underwater environment and affect fish embryo and larvae development: constant light/darkness or red lights can lead to increased malformations and mortality, whereas blue light usually results in best hatching rates and growth performance in marine fish. Many factors display daily rhythms along the hypothalamus-pituitary-interrenal (HPI) axis that controls stress response in fish, including corticotropin-releasing hormone (Crh) and its binding protein (Crhbp), proopiomelanocortin A and B (Pomca and Pomcb), and plasma cortisol, glucose, and lactate. Many of these circadian rhythms are under the control of endogenous molecular clocks, which consist of self-sustained transcriptional-translational feedback loops involving the cyclic expression of circadian clock genes (clock, bmal, per, and cry) which persists under constant light or darkness. Exposing fish to a stressor can result in altered rhythms of most stress indicators, such as cortisol, glucose, and lactate among others, as well as daily rhythms of most behavioral and physiological functions. In addition, crh and pomca expression profiles can be affected by other factors such as light spectrum, which strongly influence the expression profile of growth-related (igf1a, igf2a) genes. Additionally, the daily cycle of water temperature (warmer at day and cooler at night) is another factor that has to be considered. The response to any acute stressor is not only species dependent, but also depends on the time of the day when the stress occurs: nocturnal species show higher responses when stressed during day time, whereas diurnal fish respond stronger at night. Melatonin administration in fish has sedative effects with a reduction in locomotor activity and cortisol levels, as well as reduced liver glycogen and dopaminergic and serotonergic activities within the hypothalamus. In this paper, we are reviewing the role of environmental cycles and biological clocks on the entrainment of daily rhythms in the HPI axis and stress responses in fish.

1940-P: Disruption of the Exocyst Trafficking Complex Results in Impaired Glucose Uptake in Skeletal Muscle

Objectives: Skeletal muscle cells are responsible for 80-90% of the insulin-induced glucose uptake in the body. Insulin signaling in skeletal muscle results in the targeted trafficking of glucose transporter type 4 (GLUT4) onto the cell membrane, enabling glucose uptake. Insulin resistant cells show defects in insulin-induced GLUT4 exocytosis. The eight-protein exocyst complex has an essential role in the insulin-induced exocytosis of GLUT4 vesicles in cultured adipocytes but it is not known if the exocyst-mediated molecular mechanism is conserved in other, insulin-responsive tissues, such as the skeletal muscle. We hypothesized that the exocyst complex is essential for the insulin-induced exocytosis of GLUT4-containing vesicles in skeletal muscle as well and that the exocyst is a master regulator of glucose homeostasis in insulin-responsive tissues. Methods/Results: We have generated a tamoxifen-inducible skeletal muscle-specific knockout mouse strain of exocyst central subunit Exoc5 (Exoc5-SMKO) to assess the exocyst’s role in glucose homeostasis in vivo. Exoc5 knockout does not affect grip strength, motor coordination or locomotor activity levels in these animals. Both male and female Exoc5-SMKO mice present with elevated fasting glucose levels, as compared to control littermates. Glucose tolerance testing revealed an impaired glucose clearance in Exoc5-SMKO mice, while insulin tolerance, fasting insulin levels, and A1C levels were similar between knockouts and controls. Conclusion: Our findings suggest that Exoc5 and the exocyst are necessary for insulin-stimulated glucose uptake in skeletal muscle. Ongoing work will further investigate the molecular mechanism of exocyst-mediated GLUT4 trafficking in skeletal muscle. Disclosure B. Fujimoto: None. L.T. Carter: None. A.M. Wong: None. M.W. Pitts: None. R.K. Villiger: None. M. Young: None. B. Fogelgren: None. N. Polgar: None. Funding National Institute of General Medical Sciences (5P20GM113134)

A Drosophila melanogaster mitotype may have an adaptive meaning

Several different mitochondrial clades have been found in natural populations of Drosophila melanogaster. Most often, the difference is in single nucleotide substitutions, some of which are conservative. Some clades are rare, and others dominate. It has been reported that clade III dominates over clades V and VI in seven populations of D. melanogaster. We compared D. melanogaster strains with different mitotypes by locomotor activity (using TriKinetics Drosophila Activity Monitor), energy expenditure (by indirect calorimetry, based on measuring oxygen consumption) and life span (under extreme conditions at 29 °C). The nuclear genomes of these strains were aligned for several generations by backcrosses. According to our data, individuals with the mitotype from clade III had a higher level of locomotor activity and longer life span. In terms of energy expenditure, the strains studied did not differ. However, the same level of energy expenditure may be differently distributed between the state of activity and the state of rest or sleep. If the energy expenditure during the sleep in flies with different locomotor activity is the same, then an individual with the same overall energy expenditure can move a greater distance or be active longer. This can be interpreted as an advantage of the strain with the mitotype from clade III compared to the other two mitotypes studied. If individuals have different energy expenditure values at rest, the strains with lower energy expenditure at rest spend less energy during forced inactivity. In this case, the mitotype from clade III should also be advantageous. What nucleotide substitutions in the mitotype from clade III can provide an adaptive advantage is not clear yet. We assume that individuals with widespread clade М(III) may have adaptive advantages compared to other mitotypes due to their greater locomotor activity even with the same energy expenditure. Further studies are required, for mitotypes are polymorphic for single nucleotide polymorphism not only between but also within the clades.

Assessing the Architecture of Drosophila mojavensis Locomotor Evolution with Bulk Segregant Analysis.

Behavior is frequently predicted to be especially important for evolution in novel environments. If these predictions are accurate, there might be particular patterns of genetic architecture associated with recently diverged behaviors. Specifically, it has been predicted that behaviors linked to population divergence should be underpinned by a few genes of relatively large effect, compared to architectures of intrapopulation behavioral variation, which is considered to be highly polygenic. More mapping studies of behavioral variation between recently diverged populations are needed to continue assessing the generality of these predictions. Here, we used a bulk segregant mapping approach to dissect the genetic architecture of a locomotor trait that has evolved between two populations of the cactophilic fly Drosophila mojavensis. We created an F8 mapping population of 1,500 individuals from advanced intercross lines and sequenced the 10% of individuals with the highest and lowest levels of locomotor activity. Using three alternative statistical approaches, we found strong evidence for two relatively large-effect QTL that is localized in a region homologous to a region of densely packed behavior loci in Drosophila melanogaster, suggesting that clustering of behavior genes may display relatively deep evolutionary conservation. Broadly, our data are most consistent with a polygenic architecture, though with several loci explaining a high proportion of variation in comparison to similar behavioral traits. We further note the presence of several antagonistic QTL linked to locomotion and discuss these results in light of theories regarding behavioral evolution and the effect size and direction of QTL for diverging traits in general.