A Comparison of Brain-State Dynamics across Common Anesthetic Agents in Male Sprague-Dawley Rats.

Anesthesia is a powerful tool in neuroscientific research, especially in sleep research where it has the experimental advantage of allowing surgical interventions that are ethically problematic in natural sleep. Yet, while it is well documented that different anesthetic agents produce a variety of brain states, and consequently have differential effects on a multitude of neurophysiological factors, these outcomes vary based on dosages, the animal species used, and the pharmacological mechanisms specific to each anesthetic agent. Thus, our aim was to conduct a controlled comparison of spontaneous electrophysiological dynamics at a surgical plane of anesthesia under six common research anesthetics using a ubiquitous animal model, the Sprague-Dawley rat. From this direct comparison, we also evaluated which anesthetic agents may serve as pharmacological proxies for the electrophysiological features and dynamics of unconscious states such as sleep and coma. We found that at a surgical plane, pentobarbital, isoflurane and propofol all produced a continuous pattern of burst-suppression activity, which is a neurophysiological state characteristically observed during coma. In contrast, ketamine-xylazine produced synchronized, slow-oscillatory activity, similar to that observed during slow-wave sleep. Notably, both urethane and chloral hydrate produced the spontaneous, cyclical alternations between forebrain activation (REM-like) and deactivation (non-REM-like) that are similar to those observed during natural sleep. Thus, choice of anesthesia, in conjunction with continuous brain state monitoring, are critical considerations in order to avoid brain-state confounds when conducting neurophysiological experiments.

Mass food challenges in a vacant COVID-19 stepdown facility: Exceptional opportunity provides a model for the future.

BACKGROUND: Internationally, the COVID-19 pandemic severely curtailed access to hospital facilities for those awaiting elective/semi-elective procedures. For allergic children in Ireland, already waiting up to 4 years for an elective oral food challenge (OFC), the restrictions signified indefinite delay. At the time of the initiative, there were approx 900 children on the Children's Health Ireland (CHI) waiting list. In July 2020, a project was facilitated by short-term (6 weeks) access to an empty COVID stepdown facility built, in a hotel conference centre, commandeered by the Health Service Executive (HSE), Ireland. The aim of this study was to achieve the rapid roll-out of an offsite OFC service, delivering high throughput of long waiting patients, while aligning with existing hospital policies and quality standards, international allergy guidelines and national social distancing standards. METHODS: The working group engaged key stakeholders to rapidly develop an offsite OFC facility. Consultant paediatric allergists, consultant paediatricians, trainees and allergy clinical nurse specialists were seconded from other duties. The facility was already equipped with hospital beds, bedside monitors (BP, pulse and oxygen saturation) and bedside oxygen. All medication and supplies had to be brought from the base hospital. Daily onsite consultant anaesthetic cover was resourced and a resuscitation room equipped. Standardized food challenge protocols were created. Access to the onsite hotel chef facilitated food preparation. A risk register was established. RESULTS: After 6 weeks of planning, the remote centre became operational on 7/9/2020, with the capacity of 27 OFC/day. 474 challenges were commenced: 465 (98%) were completed and 9 (2%) were inconclusive. 135 (29%) OFCs were positive, with 25 (5%) causing anaphylaxis. No child required advanced airway intervention. 8 children were transferred to the base hospital. The CHI allergy waiting list was reduced by almost 60% in only 24 days. CONCLUSIONS: Oral food challenges remain a vital tool in the care of allergic children, with their cost saving and quality-of-life benefits negatively affected by a delay in their delivery. This project has shown it is possible to have huge impacts on a waiting list efficiently, effectively and safely with good planning and staff buy-in-even in a pandemic. Adoption of new, flexible and efficient models of service delivery will be important for healthcare delivery in the post-COVID-19 era.

ANI inactivation: unconditioned anxiolytic effects of anisomycin in the ventral hippocampus.

Although hippocampal function is typically described in terms of memory, recent evidence suggests a differentiation along its dorsal/ventral axis, with dorsal regions serving memory and ventral regions serving emotion. While long-term memory is thought to be dependent on de novo protein synthesis because it is blocked by translational inhibitors such as anisomycin (ANI), online (moment-to-moment) functions of the hippocampus (such as unconditioned emotional responding) should not be sensitive to such manipulations since they are unlikely to involve neuroplasticity. However, ANI has recently been shown to suppress neural activity which suggests (1) that protein synthesis is critical for neural function and (2) that paradigms using ANI are confounded by its inactivating effects. We tested this idea using a neurobehavioral assay which compared the influence of intrahippocampal infusions of ANI at dorsal and ventral sites on unconditioned emotional behavior of rats. We show that ANI infusions in ventral, but not dorsal, hippocampus produced a suppression of anxiety-related responses in two well-established rodent tests: the elevated plus maze and shock-probe burying tests. These results are similar to those previously observed when ventral hippocampal activity is directly suppressed (e.g., by using sodium channel blockers). The present study offers compelling behavioral evidence for the proposal that ANI adversely affects ongoing neural function and therefore its influence is not simply limited to impairing the consolidation of long-term memories

Intravenous chloral hydrate anesthesia provides appropriate analgesia for surgical interventions in male Sprague-Dawley rats.

BACKGROUND: The use of chloral hydrate as a sole maintenance anesthetic agent in rodent research has been controversial due to statements made in reference literature conflicting with results of primary research studies regarding its analgesic efficacy, and because of its associated tissue damage when administered intraperitoneally. OBJECTIVE: Our aim was to assess the analgesic efficacy of chloral hydrate using an intravenous (i.v.) route of administration, in order to prevent the local tissue irritation or ileus that has been previously reported using intraperitoneal (i.p.) routes. METHODS: We measured tail withdrawal latencies to a nociceptive thermal stimulus (infrared beam) in Sprague-Dawley rats-first when awake (unanesthetized), and then subsequently during i.v. chloral hydrate anesthesia. During anesthesia we also measured ongoing heart and respiration rates. RESULTS: Withdrawal latencies during chloral hydrate anesthesia were significantly higher, and often maximal, indicating a robust analgesic effect. Importantly, both respiration and heart rate remained unchanged following exposure to the nociceptive stimulus, and were comparable to values observed under other anesthetics and during natural sleep. CONCLUSIONS: Together with previous studies, these results demonstrate that i.v. chloral hydrate provides excellent anesthetic depth and analgesic efficacy for surgical manipulations in rats.

Long-term stability of physiological signals within fluctuations of brain state under urethane anesthesia.

Urethane, an acute laboratory anesthetic, produces distinct neurophysiological and physiological effects creating an effective model of the dynamics of natural sleep. As a model of both sleep-like neurophysiological activity and the downstream peripheral function urethane is used to model a variety of physiological and pathophysiological processes. As urethane is typically administered as a single-bolus dose, it is unclear the stability of peripheral physiological functions both within and between brain-states under urethane anesthesia. In this present study, we recorded respiration rate and heart rate concurrently with local field potentials from the neocortex and hippocampus to determine the stability of peripheral physiological functions within and between brain-states under urethane anesthesia. Our data shows electroencephalographic characteristics and breathing rate are remarkable stable over long-term recordings within minor reductions in heart rate on the same time scale. Our findings indicate that the use of urethane to model peripheral physiological functions associated with changing brain states are stable during long duration experiments.

Prenatal fruit juice exposure enhances memory consolidation in male post-weanling Sprague-Dawley rats.

OBJECTIVES: Nutritional intake during gestation is known to impact health outcomes for progeny. Correlational evidence in humans suggests that increased fruit consumption of pregnant mothers enhances infant cognitive development. Moreover, wild-type Drosophila supplemented with a combination of orange and tomato juice showed robust enhancements in performance on an associative olfactory memory task. The current study aimed to experimentally test the effects of prenatal fruit juice exposure in a non-human, mammalian model of learning and memory. METHODS: Across three separate birth cohorts, pregnant rats were given access to diluted tomato and orange juice (N = 2 per cohort), with control rats (N = 2 per cohort) receiving only water, in addition to standard rodent chow, throughout the duration of gestation, ending at parturition. Following weaning, male offspring were tested for learning and memory in a spatial version of the circular water maze and an auditory-cued fear-conditioning task. RESULTS: All pregnant rats increased fluid and food intake over the gestational period. Fruit juice-fed pregnant rats had increased fluid intake compared to control pregnant rats. When testing progeny, there were no effects of prenatal fruit juice on spatial learning, while it appeared to impair learning in fear conditioning relative to controls. However, we measured significant enhancements in both spatial memory and conditioned fear memory in the prenatal fruit-juice group compared to controls. Measures of vigilance, in response to the conditioned cue, were increased in prenatal fruit rats compared to controls, suggesting less generalized, and more adaptive, anxiety behaviours. DISCUSSION: Our results corroborate the human and Drosophila findings of prenatal fruit effects on behaviour, specifically that prenatal fruit juice exposure may be beneficial for early-life memory consolidation in rats.

Review of morphometric measurements used in anuran species descriptions and recommendations for a standardized approach.

Standardization and repeatability is at the heart of all scientific research, yet very little literature exists to standardize morphometric measurements within vertebrate groups. This is particularly true for amphibians. Our study attempts to rectify this lack of methodological standardization for the measurement of morphological characters in anurans through an extensive literature survey of 136 species descriptions representing 45 currently recognized families of frogs. The survey revealed 42 morphological measurements represented in five percent or more of the literature reviewed. All measurements are listed by most commonly used name, acronym, and most precise definition, and we provide statistics summarizing the variation in measurement use and description from the surveyed literature. Of these 42 measurements, a subset of 16 were found in the top 75% of all surveyed descriptions and identified as a focal set of recommended measurements in an effort to standardize the morphometric measurements that describe anuran species diversity. Illustrations of these 16 measurements are provided as a visual reference for standardizing their measurement.

Additions to Philippine Slender Skinks of the Brachymeles bonitae Complex (Reptilia: Squamata: Scincidae) I: a new species from Lubang Island.

A new species of slender skink is described from the Philippines. The species is endemic to Lubang Island, and is assigned to the Brachymeles bonitae Complex based on phenotypic and genetic data. Specimens were collected from Lubang Island between 1991 and 2012, and were examined based on morphological data (qualitative traits, meristic counts, and mensural measurements). Published genetic sequence data from phylogenetic studies of the genus reveal the new species to be highly divergent from congeners. Brachymeles ligtas sp. nov. is differentiated from other members of the genus based on a number of distinct morphological features, including small body size (SVL 60.7-79.6 mm), bidactyl fore-limbs, digitless hind limbs, high number of presacral vertebrae (50), and the absence of auricular openings. Additionally, the new species has diagnostic, distinct dorsal head scale patterns. This new species becomes the only member of the genus known to occur on the deep-ocean island of Lubang.