Regional vulnerability of the hippocampus to repeated motor activity deprivation

Spontaneous vertical and horizontal exploratory movements are integral components of rodent behavior. Little is known, however, about the structural and functional consequences of restricted spontaneous exploration. Here, we report two experiments to probe whether restriction in vertical activity (rearing) in rats could induce neuro-hormonal and behavioral disturbances. Rearing movements in rats were deprived for 3 h/day for 30 consecutive days by placing the animal into a circular tunnel task. Rats temporarily deprived of rearing behavior showed elevated plasma corticosterone levels but no detectable psychological distress and/or anxiety-related behavior within an elevated plus maze. However, rats emitted a greater number of 22-kHz ultrasonic vocalizations and spent significantly more time vocalizing than controls when deprived of their rearing behavior. Despite intact spatial performance within wet- and dry-land spatial tasks, rearing-deprived rats also exhibited a significant alteration in search strategies within both spatial tasks along with reduced volume and neuron number in the hippocampal subregion CA2. These data suggest a new approach to test the importance of free exploratory behavior in endocrine and structural manifestations. The results support a central role of the CA2 in spontaneous exploratory behavior and vulnerability to psychological stress. © 2015 Elsevier B.V

The Adverse Effects of Auditory Stress on Mouse Uterus Receptivity and Behaviour

Stress during gestation has harmful effects on pregnancy outcome and can lead to spontaneous abortion. Few studies, however, have addressed the impact of gestational stress, particularly auditory stress, on behavioural performance and pregnancy outcome in mice. This study aimed to examine the effect of two types of gestational stress on uterus receptivity and behavioural performance. Pregnant C57BL/6 mice were randomly assigned to either auditory or physical stress conditions or a control condition from gestational days 12-16. The auditory stress regimen used loud 3000 Hz tone, while the physical stressor consisted of restraint and exposure to an elevated platform. Three behavioural tests were performed in the dams after weaning. Uterine receptivity was investigated by counting the number of sites of implantation and fetal resorption. Also, the offspring survival rates during the early postnatal period were calculated. Auditory stress caused an increase in anxiety-like behaviour, reduced time spent exploring new object/environment, and reduced balance when compared to the physical stress and control groups. Auditory stress also caused higher rates of resorbed embryos and reduction of litter size. Our results suggest that the adverse effect of noise stress is stronger than physical stress for both uterus receptivity and behavioural performance of the dams. © 2017 The Author(s)

Aging, social distancing, and COVID-19 risk: Who is more vulnerable and why?

Perceived social support represents an important predictor of healthy aging. The global COVID-19 pandemic has dramatically changed the face of social relationships and revealed elderly to be particularly vulnerable to the effects of social isolation. Social distancing may represent a double-edged sword for older adults, protecting them against COVID-19 infection while also sacrificing personal interaction and attention at a critical time. Here, we consider the moderating role of social relationships as a potential influence on stress resilience, allostatic load, and vulnerability to infection and adverse health outcomes in the elderly population. Understanding the mechanisms how social support enhances resilience to stress and promotes mental and physical health into old age will enable new preventive strategies. Targeted social interventions may provide effective relief from the impact of COVID-19-related isolation and loneliness. In this regard, a pandemic may also offer a window of opportunity for raising awareness and mobilizing resources for new strategies that help build resilience in our aging population and future generations. Copyright: © 2021 Faraji J et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Infrared Thermography Reveals Sex-Specific Responses to Stress in Mice

Psychogenic hyperthermia is a stress-related condition reported mostly in women. Neuroendocrine responses to stress in females differ from those in males, and these differences cannot be explained solely based on hypothalamic-pituitary-adrenal (HPA) axis activity. Here, we used infrared (IR) thermographic imaging to record changes in cutaneous temperature following two types of stressful experiences in female and male mice. Mice were exposed to either single-session restraint stress or vertical exploration (rearing) deprivation and were monitored for exploratory activity and IR surface thermal changes. Females displayed higher rearing activity than males during the dark phase of the light cycle. Both sexes showed similar plasma corticosterone (CORT) responses after a challenge with restraint and rearing deprivation. However, only females responded to rearing deprivation with increased cutaneous temperature in the head and back, and a reduced thermal response in the tail. Circulating CORT levels were not correlated with the thermal variations. These findings, for the first time, provide evidence for sex-specific cutaneous thermal responses to short-term stress in mice following transient vertical-activity deprivation that may mimic clinical psychogenic hyperthermia. © Copyright © 2020 Faraji and Metz

Use of the parallel beam task for skilled walking in a rat model of cerebral ischemia: A qualitative approach

The parallel beam task (PBT), in which animals walk across two elevated parallel beams, is commonly used to assess motor deficits in laboratory rodents. Performance of the PBT challenges postural balance, inter-limb coordination and skilled walking abilities, and is typically assessed by quantitative measures such as number of foot slips and/or successful traversals. We proposed that including qualitative movement analysis of skilled walking would increase resolution and sensitivity of PBT assessments in rats with cortical ischemic lesion. Pre-trained rats with a unilateral devascularization of the primary motor cortex and controls were recorded from lateral and ventral views as they traversed a PBT made of two parallel metal beams. The new qualitative skilled walking scoring system analyzed four elements of posture, limb placement, and targeting (limb rotation and position, number of placing attempts and foot slips) based on frame-by-frame video analysis. The analysis revealed that motor cortex lesions produced significant deficits in contralateral limb rotation and limb placement in both fore- and hind limbs, compared to ipsilateral limbs and control animals. Fore- and hind limbs showed different patterns in limb placement impairments. The results indicate that forelimb foot slips are a more sensitive measure of lesion-induced deficits than hind limb foot slips. Thus, the PTB is an effective task for the assessment of skilled walking and motor learning strategies especially when combined with qualitative movement analysis in rodent models of stroke. © 2016 Elsevier Inc

Environmental determinants of behavioural responses to short-term stress in rats: Evidence for inhibitory effect of ambient landmarks

Behavioural responses to stress occur in an environment-dependent manner. Complex environments require flexible behavioural coping strategies and chronic stress usually generates psychomotor inhibition. Here, we examine if short-term stress also exerts an inhibitory effect on novelty-seeking, exploratory behaviours. Rats underwent acute restraint stress or were left undisturbed, and their neuroendocrine and behavioural responses were assessed at short- and long-term time points. Animals were individually tested in the open field task (OFT) and the corridor field task (CFT) with and without a central object for free exploration and novelty seeking behaviour. Stress-related psychomotor alterations were measured by path speed, path length, number of stops and thigmotaxis in both tasks. Short-term stress activated the hypothalamic-pituitary-adrenal axis causing elevated plasma corticosterone levels. Stress also impacted psychomotor functions in terms of motivational changes (higher speed and longer path) only in the central-object variations of the OFT and CFT. Moreover, stress-induced emotional alterations were manifested by a higher number of stops and thigmotactic behaviour only in the central-object condition. These findings suggest that environmental landmarks determine the type and direction of exploratory behaviour under transient stress. © 2019 Elsevier B.V

The syntactic organization of pasta-eating and the structure of reach movements in the head-fixed mouse

Mice are adept in the use of their hands for activities such as feeding, which has led to their use in investigations of the neural basis of skilled-movements. We describe the syntactic organization of pasta-eating and the structure of hand movements used for pasta manipulation by the head-fixed mouse. An ethogram of mice consuming pieces of spaghetti reveals that they eat in bite/chew bouts. A bout begins with pasta lifted to the mouth and then manipulated with hand movements into a preferred orientation for biting. Manipulation involves many hand release-reach movements, each with a similar structure. A hand is advanced from a digit closed and flexed (collect) position to a digit extended and open position (overgrasp) and then to a digit closed and flexed (grasp) position. Reach distance, hand shaping, and grasp patterns featuring precision grasps or whole hand grasps are related. To bite, mice display hand preference and asymmetric grasps; one hand (guide grasp) directs food into the mouth and the other stabilizes the pasta for biting. When chewing after biting, the hands hold the pasta in a symmetric resting position. Pasta-eating is organized and features structured hand movements and so lends itself to the neural investigation of skilled-movements. © 2017 The Author(s)

A mouse's spontaneous eating repertoire aids performance on laboratory skilled reaching tasks: A motoric example of instinctual drift with an ethological description of the withdraw movements in freely-moving and head-fixed mice

Rodents display a spontaneous “order-common” pattern of food eating: they pick up food using the mouth, sit on their haunches, and transfer the food to the hands for handling/chewing. The present study examines how this pattern of behaviour influences performance on “skilled-reaching” tasks, in which mice purchase food with a single hand. Here five types of withdraw movement, the retraction of the hand, in three reaching tasks: freely-moving single-pellet, head-fixed single-pellet, and head-fixed pasta-eating is described. The withdraw movement varied depending upon whether a reach was anticipatory, no food present, or was unsuccessful or successful with food present. Ease of withdraw is dependent upon the extent to which animals used order-common movements. For freely-moving mice, a hand-to-mouth movement was assisted by a mouth-to-hand movement and food transfer to the mouth depended upon a sitting posture and using the other hand to assist food holding, both order-common movements. In the head-fixed single-pellet task, with postural and head movements prevented, withdraw was made with difficulty and tongue protrude movements assisted food transfer to the mouth once the hand reached the mouth. Only when a head-fixed mouse made a bilateral hand-to-mouth movement, a component of order-common eating, was the withdraw movement made with ease. The results are discussed with respect to the use of order-common movements in skilled-reaching tasks and with respect to the optimal design of tasks used to assess rodent skilled hand movement. © 201

Stress inhibits psychomotor performance differently in simple and complex open field environments

Stress affects psychomotor profiles and exploratory behavior in response to environmental features. Here we investigated psychomotor and exploratory patterns induced by stress in a simple open-field arena and a complex, multi-featured environment. Groups of rats underwent seven days of restraint stress or no-stress conditions and were individually tested in three versions of the ziggurat task (ZT) that varied according to environmental complexity. The hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis due to stress procedure was evaluated by the pre- and post-stress levels of circulating corticosterone (CORT). Horizontal activity, exploration, and motivation were measured by the number of fields entered, the time spent in the central fields, path length and speed, and stop duration. In addition, vertical exploratory behavior was measured by the times rats climbed onto ziggurats. Stress-induced psychomotor changes were indicated by reduced path length and path speed and increased duration of stops only within the complex arena of the ZT. Rats in stress groups also showed a significant decline in the vertical movements as measured by the number of climbing onto ziggurats. No stress-induced changes were revealed by the simple open-field arena. The exploratory patterns of stressed animals suggest psychomotor inhibition and reduced novelty-seeking behaviors in an environment-dependent manner. Thus, multi-featured arenas that require complex behavioral strategies are ideally suited to reveal the inhibitory effects of stress on psychomotor capabilities in rodents. © 2013 Elsevier Inc