Protocol for Anesthesia Animal Model in Biomedical Study

Recognition of pain depends upon intact pathways from pain receptors to thethalamus and cerebral cortex, as well as functional cerebral cortex and subcorticalstructures. Thus any means that renders the cerebral cortex nonfunctional, suchas hypoxia or drug depression, prevents pain. When this happens, stimuli thatevoke motor nerve reflexes that may be painful to the conscious animal are notpainful in the unconscious animal. Equally painful stimuli administered toanimals chemically paralyzed by curare or succinylcholine will not evoke a motorreflex simply because of paralysis, but will cause pain because of the consciousstate. Hence, it is possible that unconscious animals may feel no pain but respondto certain stimuli, and paralyzed animals may feel pain but cannot respond.

Protocol for Anesthesia Animal Model in Biomedical Study

Recognition of pain depends upon intact pathways from pain receptors to thethalamus and cerebral cortex, as well as functional cerebral cortex and subcorticalstructures. Thus any means that renders the cerebral cortex nonfunctional, suchas hypoxia or drug depression, prevents pain. When this happens, stimuli thatevoke motor nerve reflexes that may be painful to the conscious animal are notpainful in the unconscious animal. Equally painful stimuli administered toanimals chemically paralyzed by curare or succinylcholine will not evoke a motorreflex simply because of paralysis, but will cause pain because of the consciousstate. Hence, it is possible that unconscious animals may feel no pain but respondto certain stimuli, and paralyzed animals may feel pain but cannot respond.

Full-Mouth Intraoral Radiographic Survey in Rabbits

Dental pathologies are highly prevalent in pet rabbit populations, making oral radiography an essential tool in the evaluation of lagomorph dentitions. The unique anatomy of the rabbit’s mouth limits the examination of the conscious animal to the rostral portion of it's mouth. In addition, the oral examination of an aradicular hypsodont tooth is restricted to the short coronal fraction of its crown. Erstwhile images obtained by the extraoral technique were once considered the most practical and informative tool in rabbit dentistry; however, limited visualization of the key structures of individual teeth became the major drawback of this technique. As new imaging technologies are becoming widely available and affordable for veterinarians, intraoral radiography offers the ability to prevent, diagnose, and treat oral pathologies in lagomorphs. This article describes a step-by-step procedure to obtain a full-mouth radiographic survey in rabbits. For this technique, a standard dental X-ray generator and intraoral storage phosphor plates are used while applying the bisecting angle technique. Among the advantages of this technique are detailed visualization of internal and external dental structures, identification of early lesions, and detection of occult pathologies. Furthermore, intraoral images offer superior resolution and higher diagnostic quality with minimal radiation exposure, making this method safer for the veterinarian, staff members, and their patients.

Neurophysiological assessment of animal welfare

Livestock industries such as the pork industry are striving to continuously improve the welfare of animals. Inherent to the success of this is the ability to rigorously assess the welfare of animals in the field. While much progress has been made towards the development of methodology to assess the welfare of animals, there have been major challenges to establishing practical and definitive procedures to assess the welfare of animals. These include, but are not limited to, establishing a universally accepted definition of animal welfare and the choice of measures that are taken from the animal to assess its welfare. Measures of biological functioning and affective (emotional) state of the animal have been common, but there have been many limitations in terms of practical application. Some of the reasons for this include the choice of physiological measures, which are often restrictive in providing information about welfare, affective measures being restricted to specific behavioural measures and the biological-functioning and affective-states approaches being undertaken in isolation. Biological and affective functioning are integrated and controlled by the brain. Many of the regions of the brain involved in the regulation of biological and emotional functioning have been identified. Furthermore, there is considerable knowledge about the roles and interactions among the neurophysiological systems in these brain regions. We propose a strategy to use this knowledge to develop procedures to assess animal welfare. The initial phase is to identify the neural pathways that regulate the physiological and emotional processes that allow animals to adapt and cope. The next phase is to determine the activity of these pathways in conscious animals in the field. This requires the identification of biomarkers of specific neuronal activity that can be measured in the conscious animal in the field. Emerging technologies are offering promise in the identification of such biomarkers and some of these are already applicable to the pig. There is now the opportunity to apply this strategy within the pork industry to assess the welfare of pigs throughout the value chain.

Multiscale entropy analysis of heart rate variability in heart failure, hypertensive, and sinoaortic-denervated rats: classical and refined approaches

The analysis of heart rate variability (HRV) by nonlinear methods has been gaining increasing interest due to their ability to quantify the complexity of cardiovascular regulation. In this study, multiscale entropy (MSE) and refined MSE (RMSE) were applied to track the complexity of HRV as a function of time scale in three pathological conscious animal models: rats with heart failure (HF), spontaneously hypertensive rats (SHR), and rats with sinoaortic denervation (SAD). Results showed that HF did not change HRV complexity, although there was a tendency to decrease the entropy in HF animals. On the other hand, SHR group was characterized by reduced complexity at long time scales, whereas SAD animals exhibited a smaller short- and long-term irregularity. We propose that short time scales (1 to 4), accounting for fast oscillations, are more related to vagal and respiratory control, whereas long time scales (5 to 20), accounting for slow oscillations, are more related to sympathetic control. The increased sympathetic modulation is probably the main reason for the lower entropy observed at high scales for both SHR and SAD groups, acting as a negative factor for the cardiovascular complexity. This study highlights the contribution of the multiscale complexity analysis of HRV for understanding the physiological mechanisms involved in cardiovascular regulation.

Baroreflex mechanisms regulating mean level of SNA differ from those regulating the timing and entrainment of the sympathetic discharges in rabbits

The arterial baroreflex pathway provides the fundamental basis for the short-term control of blood pressure via the rapid regulation of the mean level of sympathetic nerve activity (SNA) in response to changes in blood pressure. A central tenet in the generation and regulation of bursts of SNA is that input from the arterial baroreceptors also regulates the timing of the bursts of sympathetic activity. With the use of an implantable telemetry-based amplifier, renal SNA was recorded in intact and arterial baroreceptor-denervated (SAD) conscious rabbits. Data were collected continuously while animals were in their home cage. Mean levels of SNA were not different between SAD and baroreceptor-intact animals. Whereas SNA was unresponsive to changes in blood pressure in SAD rabbits, the timing of the bursts of SNA relative to the arterial pulse wave was maintained (time between the diastolic pressure and the next maximum SNA voltage averaged 107 ± 12 ms SAD vs. 105 ± 7 ms intact). Transfer function analysis between blood pressure and SNA indicates the average gain at the heart rate frequency was not altered by SAD, indicating strong coupling between the cardiac cycle and SNA bursts in SAD animals. Further experiments in anesthetized rabbits showed that this entrainment is lost immediately after performing baroreceptor denervation surgery and remained absent while the animal was under anesthesia but returned within 20 min of turning off the anesthesia. We propose that this finding indicates the regulation of the mean level of SNA requires the majority of input from baroreceptors to be functional; however, the regulation of the timing of the bursts in the conscious animal requires only minimal input, such as a sensitive trigger mechanism. This observation has important implications for understanding the origin and regulation of SNA.