Automatic analysis of treadmill running to estimate times to fatigue and exhaustion in rodents

Introduction: The determination of fatigue and exhaustion in experimental animals is complicated by the subjective nature of the measurement. Typically, it requires an observer to watch exercising animals, e.g. rats running on the treadmill, and to identify the time of the event. In this study, we hypothesized that automatic analysis of the time-averaged position of a rat on a treadmill could be an objective way for estimating times to fatigue and exhaustion. To test this hypothesis, we compared these times measured by a human observer to the results of an automated video tracking system. Methods: Rats, previously familiarized to running on the treadmill, ran at a fixed speed with zero incline, until exhaustion. The experiments were performed at either room temperature (24 °C) or in a hot environment (32 °C). Each experiment was video recorded. A trained observer estimated the times to fatigue and exhaustion. Then, video tracking software was used to determine the position of the animals on the treadmill belt. The times to fatigue and exhaustion were determined, based on the position on the treadmill using predefined criteria. Results: Manual scores and the average position on the treadmill had significant correlation. Both the observer and the automated video tracking determined that exercise in a hot environment, compared with the exercise at room temperature, results in shorter times to exhaustion and fatigue. Also, estimates of times made by the observer and the automated video tracking were not statistically different from each other. Discussion: A similarity between the estimates of times to fatigue and exhaustion made by the observer and the automated technique suggests that video tracking of rodents running on a treadmill can be used to determine both parameters in experimental studies. Video tracking technique allows for a more objective measure and would allow for an increased performance in experimentation. The Supplemental information to this manuscript contains an Excel file, which includes the code in Virtual Basic with freeware license, to process and visualize running data and automatically estimate the times to fatigue and exhaustion. Instructions for the software are also included

Treadmill running restores MDMA-mediated hyperthermia prevented by inhibition of the dorsomedial hypothalamus

The contribution of exercise to hyperthermia mediated by MDMA is not known. We recently showed that inhibiting the dorsomedial hypothalamus (DMH) attenuated spontaneous locomotion and hyperthermia and prevented deaths in rats given MDMA in a warm environment. The goal of this study was to confirm that restoring locomotion through a treadmill would reverse these effects thereby confirming that locomotion mediated by the DMH contributes to MDMA-mediated hyperthermia. Rats were randomized to receive bilateral microinjections, into the region of the DMH, of muscimol (80pmol/100nl) or artificial CSF followed by a systemic dose of either MDMA (7.5mg/kg, i.v.) or saline. Immediately after the systemic injection, rats were placed on a motorized treadmill maintained at 32°C. Rats were exercised at a fixed speed (10m/min) until their core temperature reached 41°C. Our results showed that a fixed exercise load abolished the decreases in temperature and mortality, seen previously with inhibition of the DMH in freely moving rats. Therefore, locomotion mediated by neurons in the DMH is critical to the development of hyperthermia from MDMA

Qualitative study of healthcare providers’ current practice patterns and barriers to successful rehydration for pediatric diarrheal illnesses in Kenya

Background For children worldwide, diarrhea is the second leading cause of death. These deaths are preventable by fluid resuscitation. Nasogastric tubes (NGs) have been shown to be equivalent to intravenous fluids for rehydration and recommended by the World Health Organization (WHO) for use in severe dehydration. Despite this, NGs are rarely used for rehydration in Kenya. Our objective was to evaluate clinicians’ adherence to rehydration guidelines and to identify barriers to the use of NGs for resuscitating dehydrated children. Methods A case-based structured survey was administered to pediatric care providers in western Kenya to determine their choices for alternative rehydration therapies when oral rehydration and intravenous fluids fail. Providers then participated in a qualitative, semi-structured interview to identify barriers to using nasogastric tubes for rehydration. Analysis included manual, progressive coding of interview transcripts to identify emerging central themes. Results Of 44 participants, only four (9%) followed WHO guidelines that recommend quickly switching to NG for rehydration in their case responses. Participants identified that placing intravenous lines in dehydrated children is a challenge. However, when discussing NG use, many believed NGs are not effective for rehydration. Other participants’ concerns surrounded knowledge and training regarding guidelines as well as not having NGs available. Discussion Healthcare providers in western Kenya do not report using NGs for rehydration in accordance with WHO guidelines for diarrheal illness with severe dehydration. Barriers to the use of NG tubes were lack of knowledge and availability. Education and implementation of guidelines using NG tubes for rehydration may improve outcomes of children suffering from diarrheal illness with severe dehydration

Inhibition of the dorsomedial hypothalamus, but not the medullary raphe pallidus, decreases hyperthermia and mortality from MDMA given in a warm environment.

The central mechanisms through which MDMA mediates life-threatening hyperthermia when taken in a warm environment are not well described. It is assumed that MDMA alters normal thermoregulatory circuits resulting in increased heat production through interscapular brown adipose tissue (iBAT) and decreased heat dissipation through cutaneous vasoconstriction. We studied the role of the dorsomedial hypothalamus (DMH) and medullary raphe pallidus (mRPa) in mediating iBAT, tail blood flow, and locomotor effects produced by MDMA. Rats were instrumented with guide cannulas targeting either the DMH or the mRPa-brain regions involved in regulating iBAT and cutaneous vascular beds. In all animals, core temperature and locomotion were recorded with surgically implanted telemetric transmitters; and additionally either iBAT temperature (via telemetric transmitter) or tail artery blood flow (via tail artery Doppler cuff) were also recorded. Animals were placed in an environmental chamber at 32°C and microinjected with either control or the GABA agonist muscimol (80pmol) followed by an intravenous injection of saline or MDMA (7.5 mg kg-1). To prevent undue suffering, a core temperature of 41°C was chosen as the surrogate marker of mortality. Inhibition of the DMH, but not the mRPa, prevented mortality and attenuated hyperthermia and locomotion. Inhibition of either the DMH or the mRPa did not affect iBAT temperature increases or tail blood flow decreases. While MDMA increases iBAT thermogenesis and decreases heat dissipation through cutaneous vasoconstriction, thermoregulatory brain regions known to mediate these effects are not involved. Rather, the finding that inhibiting the DMH decreases both locomotion and body temperature suggests that locomotion may be a key central contributor to MDMA-evoked hyperthermia

Yohimbine is a 5-HT1A agonist in rats in doses exceeding 1 mg/kg.

Yohimbine is a prototypical alpha2-adrenergic receptor antagonist. Due to its relatively high selectivity, yohimbine is often used in experiments whose purpose is to examine the role of these receptors. For example, yohimbine has been employed at doses of 1–5 mg/kg to reinstate drug-seeking behavior after extinction or to antagonize general anesthesia, an effects presumably being a consequence of blocking alpha2-adrenergic receptors. In this report we characterized dose-dependent autonomic and behavioral effects of yohimbine and its interaction with an antagonist of 5-HT1A receptors, WAY 100635. In low doses (0.5 – 2 mg/kg i.p.) yohimbine induced locomotor activation which was accompanied by a tachycardia and mild hypertension. Increasing the dose to 3–4.5 mg/kg reversed the hypertension and locomotor activation and induced profound hypothermia. The hypothermia as well as the suppression of the locomotion and the hypertension could be reversed by the blockade of 5-HT1A receptors with WAY 100635. Our data confirm that yohimbine possesses 5-HT1A properties, and demonstrated that in doses above 1 mg/kg significantly activate these receptors

On-site treatment of exertional heat stroke

Background: Exertional heat stroke is a devastating condition that can cause significant morbidity and mortality. Rapid cooling is the most effective means of treating heat stroke, but little is published on the safety and logistics of cooling patients on site at a major sporting event. Purpose: To describe an on-site exertional heat stroke treatment protocol and to compare the outcomes of patients treated on site to those transferred to hospitals. Study Design: Descriptive epidemiological study. Methods: Using race-day medical records and ambulance run sheets, patients who developed exertional heat stroke at the Indianapolis half-marathon from 2005 to 2012 were identified. Exertional heat stroke was defined as runners with a core temperature measured with a rectal thermometer greater than 102°F and altered mental status. Clinical information and patient outcomes were abstracted from the race medical tent and hospital charts by 3 separate trained reviewers using structured methods and a data collection form. Two reviewers, using a RedCAP database and dual-data entry, abstracted records for each patient. A third arbitrated all discrepancies between reviewers. Clinical signs, treatments, and outcomes were calculated using descriptive statistics, and data were grouped and compared for patients treated on site or transferred to local hospitals for treatment. Results: Over 235,000 athletes participated in the event over the 8-year period, with 696 seeking medical care. A total of 32 heat stroke victims were identified during the study period; of these, 22 were treated on site. Of these, 68% were treated with cold-water immersion and 59% were discharged home from the race. Ten exertional heat stroke patients were transported from the race course to local hospitals. None of them underwent cold-water immersion, and 40% of them were subsequently discharged home. No patients in the study died. Conclusion: On-site treatment of athletes who develop exertional heat stroke appears to be both safe and effective. On-site treatment may decrease the local burden of critically ill patients to emergency departments during large athletic events

Independent of 5-HT1A receptors, neurons in the paraventricular hypothalamus mediate ACTH responses from MDMA

Acute and chronic complications from the substituted amphetamine 3,4-methylenedioxymethamphetamine (MDMA) are linked to activation of the hypothalamic-pituitary-adrenal (HPA) axis. How MDMA activates the HPA axis is not known. HPA responses to stress are known to be mediated through the paraventricular (PVH) hypothalamus and to involve serotonin-1a (5-HT1A) receptors. We sought to determine if the PVH and 5-HT1A receptors were also involved in mediating HPA responses to MDMA. Rats were pretreated with either saline or a 5-HT1A antagonist, WAY-100635 (WAY), followed by a systemic dose of MDMA (7.5mg/kg i.v.). Animals pretreated with WAY had significantly lower plasma ACTH concentrations after MDMA. To determine if neurons in the PVH were involved, and if their involvement was mediated by 5-HT1A receptors, rats implanted with guide cannulas targeting the PVH were microinjected with the GABAA receptor agonist muscimol, aCSF, or WAY followed by MDMA. Compared to aCSF, microinjections of muscimol significantly attenuated the MDMA-induced rise in plasma ACTH (126 vs. 588pg/ml, P=<0.01). WAY had no effect. Our data demonstrates that neurons in the PVH, independent of 5-HT1A receptors, mediate ACTH responses to MDMA

Disinhibiting neurons in the dorsomedial hypothalamus delays the onset of exertional fatigue and exhaustion in rats exercising in a warm environment

Stimulants cause hyperthermia, in part, by increasing heat generation through exercise. Stimulants also delay the onset of fatigue and exhaustion allowing animals to exercise longer. If used in a warm environment, this combination (increased exercise and decreased fatigue) can cause heat stroke. The dorsomedial hypothalamus (DMH) is involved in mediating locomotion from stimulants. Furthermore, inhibiting the DMH decreases locomotion and prevents hyperthermia in rats given stimulants in a warm environment. Whether the DMH is involved in mediating exercise-induced fatigue and exhaustion is not known. We hypothesized that disinhibiting neurons in the dorsomedial hypothalamus (DMH) would delay the onset of fatigue and exhaustion in animals exercising in a warm environment. To test this hypothesis, we used automated video tracking software to measure fatigue and exhaustion. In rats, using wearable mini-pumps, we demonstrated that disinhibiting the DMH, via bicuculline perfusion (5 µM), increased the duration of exercise in a warm environment as compared to control animals (25 ± 3 min vs 15 ± 2 min). Bicuculline-perfused animals also had higher temperatures at exhaustion (41.4 ± 0.2 °C vs 40.0 ± 0.4 °C). Disinhibiting neurons in the DMH also increased the time to fatigue. Our data show that the same region of the hypothalamus that is involved in mediating locomotion to stimulants, is also involved in controlling exhaustion and fatigue. These findings have implications for understanding the cause and treatment of stimulant-induced-hyperthermia