Anesthetic modulation of water diffusion: Insights from a diffusion tensor imaging study.

Diffusion tensor imaging (DTI) in animal models are essential for translational neuroscience studies. A critical step in animal studies is the use of anesthetics. Understanding the influence of specific anesthesia regimes on DTI-derived parameters, such as fractional anisotropy (FA) and mean diffusivity (MD), is imperative when comparing results between animal studies using different anesthetics. Here, the quantification of FA and MD under different anesthetic regimes, alpha-chloralose and isoflurane, is discussed. We also used a range of b-values to determine whether the anesthetic effect was b-value dependent. The first group of rats (n = 6) was anesthetized with alpha-chloralose (80 mg/kg), whereas the second group of rats (n = 7) was anesthetized with isoflurane (1.5%). DTI was performed with b-values of 500, 1500, and 1500s/mm2, and the MD and FA were assessed individually. Anesthesia-specific differences in MD were apparent, as manifested by the higher estimated MD under isoflurane anesthesia than that under alpha-chloralose anesthesia (P < 0.001). MD values increased with decreasing b-value in all regions studied, and the degree of increase when rats were anesthetized with isoflurane was more pronounced than that associated with alpha-chloralose (P < 0.05). FA quantitation was also influenced by anesthesia regimens to varying extents, depending on the brain regions and b-values. In conclusion, both scanning parameters and the anesthesia regimens significantly impacted the quantification of DTI indices.

Evidence of a sudden increase in α-chloralose poisoning in dogs and cats in the Netherlands between 2018 and 2021.

BACKGROUND: After changes in European Union biocide legislation, the Dutch Poisons Information Center observed a strong increase in information requests concerning dogs and cats exposed to α-chloralose. To investigate whether α-chloralose-based rodenticides are safe for non-professional use, additional information regarding poisoning scenarios and clinical course was collected. METHODS: Veterinarians reporting α-chloralose exposure over a 2.5-year period were contacted by mail for follow-up information concerning exposure scenario, product formulation, clinical course and treatment, and outcome. In total, information was collected for 96 dogs and 41 cats. RESULTS: Fifty-three of 96 dogs and 17 of 19 cats known to have been exposed to α-chloralose-based rodenticides developed signs of central nervous system (CNS) depression or sensory-induced CNS excitation. Mortality in dogs and cats following exposure was 1% and 18%, respectively. An additional 22 cats presented with clinical signs suggestive of α-chloralose poisoning, with a mortality of 5%. LIMITATIONS: Exposure to α-chloralose was not confirmed by biochemical analyses. CONCLUSION: Dogs and especially cats were at risk of poisoning from α-chloralose. If criteria such as acute toxicity and risk of (secondary) poisoning are applied during the approval of α-chloralose-based rodenticides, similar to anticoagulant-based rodenticides, it can be concluded that α-chloralose is also not safe for non-professional use.

Alpha-chloralose poisoning in cats in three Nordic countries - the importance of secondary poisoning.

BACKGROUND: Alpha-chloralose (AC) is a compound known to be toxic to various animal species and humans. In 2018 and 2019 an increase in suspected cases of AC poisoning in cats related to the use of AC as a rodenticide was reported to national veterinary and chemical authorities in Finland, Norway and Sweden by veterinarians working in clinical practices in respective country. The aims of this study were to prospectively investigate AC poisoning in cats, including possible secondary poisoning by consuming poisoned mice, and to study metabolism and excretion of AC in cats through analysis of feline urine. METHODS: Data on signalment, history and clinical findings were prospectively collected in Finland, Norway and Sweden from July 2020 until March of 2021 using a questionnaire which the attending veterinarian completed and submitted together with a serum sample collected from suspected feline cases of AC-poisoning. The diagnosis was confirmed by quantification of AC in serum samples. Content of AC was studied in four feline urine samples, including screening for AC metabolites by UHPLC-HRMS/MS. Bait intake and amount of AC consumed by mice was observed in wild mice during an extermination of a rodent infestation. RESULTS: In total, 59 of 70 collected questionnaires and accompanying serum samples were included, with 127 to 70 100 ng/mL AC detected in the serum. Several tentative AC-metabolites were detected in the analysed feline urine samples, including dechlorinated and oxidated AC, several sulfate conjugates, and one glucuronic acid conjugate of AC. The calculated amount of AC ingested by each mouse was 33 to 106 mg with a mean of 61 mg. CONCLUSIONS: Clinical recognition of symptoms of AC poisoning in otherwise healthy cats roaming free outdoors and known to be rodent hunters strongly correlated with confirmation of the diagnosis through toxicological analyses of serum samples. The collected feline exposure data regarding AC show together with the calculation of the intake of bait and subsequent AC concentrations in mice that secondary poisoning from ingestion of mice is possible. The results of the screening for AC metabolites in feline urine confirm that cats excrete AC both unchanged and metabolized through dechlorination, oxidation, glucuronidation and sulfatation pathways.

Anesthetic modulations dissociate neuroelectric characteristics between sensory-evoked and spontaneous activities across bilateral rat somatosensory cortical laminae.

Spontaneous neural activity has been widely adopted to construct functional connectivity (FC) amongst distant brain regions. Although informative, the functional role and signaling mechanism of the resting state FC are not intuitive as those in stimulus/task-evoked activity. In order to bridge the gap, we investigated anesthetic modulation of both resting-state and sensory-evoked activities. We used two well-studied GABAergic anesthetics of varying dose (isoflurane: 0.5-2.0% and α-chloralose: 30 and 60 mg/kg∙h) and recorded changes in electrophysiology using a pair of laminar electrode arrays that encompass the entire depth of the bilateral somatosensory cortices (S1fl) in rats. Specifically, the study focused to describe how varying anesthesia conditions affect the resting state activities and resultant FC between bilateral hemispheres in comparison to those obtained by evoked responses. As results, isoflurane decreased the amplitude of evoked responses in a dose-dependent manner mostly due to the habituation of repetitive responses. However, α-chloralose rather intensified the amplitude without exhibiting habituation. No such diverging trend was observed for the spontaneous activity, in which both anesthetics increased the signal power. For α-chloralose, overall FC was similar to that obtained with the lowest dose of isoflurane at 0.5% while higher doses of isoflurane displayed increased FC. Interestingly, only α-chloralose elicited relatively much greater increases in the ipsi-stimulus evoked response (i.e., in S1fl ipsilateral to the stimulated forelimb) than those associated with the contra-stimulus response, suggesting enhanced neuronal excitability. Taken together, the findings demonstrate modulation of the FC profiles by anesthesia is highly non-linear, possibly with a distinct underlying mechanism that affects either resting state or evoked activities differently. Further, the current study warrants thorough investigation of the basal neuronal states prior to the interpretation of resting state FC and evoked activities for accurate understanding of neural signal processing and circuitry.

Alpha-chloralose poisoning in cats: clinical findings in 25 confirmed and 78 suspected cases.

OBJECTIVES: The aim of this study was to describe the clinical picture in cats with alpha-chloralose (AC) intoxication and to confirm AC in serum from suspected cases of AC poisoning. METHODS: Suspected cases of AC poisoning were identified in patient records from a small animal university hospital from January 2014 to February 2020. Clinical signs of intoxication described in respective records were compiled, the cats were graded into four intoxication severity scores and hospitalisation time and mortality were recorded. Surplus serum from select cases in late 2019 and early 2020 was analysed to detect AC with a quantitative ultra-high performance liquid chromatography tandem mass spectrometry analysis, and the AC concentration was compared with the respective cat's intoxication severity score. RESULTS: Serum from 25 cats was available for analysis and AC poisoning was confirmed in all. Additionally, 78 cats with a clinical suspicion of AC intoxication were identified in the patient records, most of which presented from September to April. The most common signs of intoxication were ataxia, tremors, cranial nerve deficits and hyperaesthesia. The prevalence of clinical signs and intoxication severity differed from what has previously been reported, with our population presenting with less severe signs and no deaths due to intoxication. The majority had a hospitalisation time <48 h, irrespective of intoxication severity score. CONCLUSIONS AND RELEVANCE: This study describes the clinical signs and prognosis in feline AC intoxication. There were no mortalities in confirmed cases, indicating that AC-poisoned cats have an excellent prognosis when treated in a timely manner. Recognition of AC intoxication as a differential diagnosis for acute onset of the described neurological signs in areas where AC exposure is possible may influence clinical decision-making and help avoid excessive diagnostic procedures. A severe clinical picture upon presentation could be misinterpreted as a grave prognosis and awareness about AC poisoning may avoid unnecessary euthanasia.

Development and Validation of a Quantitative UHPLC-MS-MS Method for the Determination of Alpha-Chloralose in Feline Blood and Application on Blood Samples Collected from Cats with Symptoms of Alpha-Chloralose Poisoning.

Alpha-chloralose (AC) is used as a rodenticide as well as an anesthetic agent in laboratory animals. It was previously also used as an avicide. Detection of AC in blood samples or in body tissues collected postmortem is key for the diagnosis of clinical cases and a requirement for surveillance of secondary toxicosis, including potential cases in wild animals. Reports on poisoning of humans and non-laboratory animals confirmed by the detection of AC or its metabolites are available, however poisoning of domestic animals are rarely available. Furthermore, reports on clinical cases in domestic animals rarely report quantifications of AC in blood or body tissues. The present study describes the validation of a quantitative ultra high performance liquid chromatography--tandem mass spectrometry (UHPLC--MS-MS) method that can be used in cases of suspected AC poisoning in cats. The validation study showed the method to be fit for purpose. In serum, the limit of quantification was 100 ng/mL and the limit of detection was 30 ng/mL. The new analytical method was applied on blood samples collected from 20 individual cats with a preliminary clinical diagnosis of acute AC poisoning. AC was confirmed in all 20 feline blood samples, and the concentration range of AC was 538-17,500 ng/mL. The quantitative method developed in this study was found to be a fast and selective method for confirmation of AC poisoning using blood samples from cats.

Caffeine enhances BOLD responses to electrical whisker pad stimulation in rats during alpha-chloralose anaesthesia.

By reducing the cerebral blood flow and thereby increasing the resting deoxyhaemoglobin concentration, many human studies have shown that caffeine has a beneficial effect on enhancing the magnitude of blood-oxygenation-level-dependent (BOLD) responses. However, the effect of caffeine on BOLD responses in animals under anaesthesia has not been demonstrated. In this study, we aimed to determine the effect of systemic caffeine administration on BOLD responses in rats under alpha-chloralose. By applying electric whisker pad stimulation to male Sprague-Dawley rats, we performed fMRI measurements before and after the caffeine injection (40 mg/kg, n = 7) or an equivalent volume of saline (n = 6) at 7T. To understand the potential perturbation of animal physiology during stimulation, arterial blood pressure was measured in a separate group of animals (n = 3) outside the scanner. Caffeine significantly decreased baseline BOLD signals (p = .05) due to the increased deoxyhaemoglobin level. Both BOLD responses and t-values in the primary somatosensory cortex were significantly increased (both p < .05). The blood pressure changed insignificantly (p > .05). No significant differences in BOLD responses and t-values were observed in the control condition of saline injection (both p > .05). These findings suggested that, although the cerebral activity was lower under alpha-chloralose anaesthesia, the higher level of deoxygemoglobin at the baseline under the caffeinated condition can benefit the magnitude of BOLD responses in rats. These findings suggest that animal models might serve as potential platforms for further caffeine-related fMRI research studies.

Anesthetic agents affect urodynamic parameters and anesthetic depth at doses necessary to facilitate preclinical testing in felines.

Urodynamic studies, used to understand bladder function, diagnose bladder disease, and develop treatments for dysfunctions, are ideally performed with awake subjects. However, in small and medium-sized animal models, anesthesia is often required for these procedures and can be a research confounder. This study compared the effects of select survival agents (dexmedetomidine, alfaxalone, and propofol) on urodynamic (Δpressure, bladder capacity, bladder compliance, non-voiding contractions, bladder pressure slopes) and anesthetic (change in heart rate [∆HR], average heart rate [HR], reflexes, induction/recovery times) parameters in repeated cystometrograms across five adult male cats. The urodynamic parameters under isoflurane and α-chloralose were also examined in terminal procedures for four cats. Δpressure was greatest with propofol, bladder capacity was highest with α-chloralose, non-voiding contractions were greatest with α-chloralose. Propofol and dexmedetomidine had the highest bladder pressure slopes during the initial and final portions of the cystometrograms respectively. Cats progressed to a deeper plane of anesthesia (lower HR, smaller ΔHR, decreased reflexes) under dexmedetomidine, compared to propofol and alfaxalone. Time to induction was shortest with propofol, and time to recovery was shortest with dexmedetomidine. These agent-specific differences in urodynamic and anesthetic parameters in cats will facilitate appropriate study-specific anesthetic choices.

Suspected seizure-survival of a lethal dose of the rodenticide alpha-chloralose.

A 58-year-old female was admitted due to a suspected seizure. A blue colored pharyngeal fluid was visualized during intubation, which is indicative of poisoning. Clinical research revealed an ingestion of 2.4 g of alpha-chloralose, a rodenticide with a lethal dose of 1 g. Immediate detoxification by gastroscopy, gastric lavage and hemodialysis led to full recovery. Substance detection was carried out by gas chromatography-mass spectometry of a urine sample. There are only a few cases reporting poisoning by this substance. Coma and bilateral myoclonus have been reported but blue gastric fluid as the "red flag" in this case has never been described.

[Impact of different anesthetic states on acupuncture-mediated modulation of autonomic nervous system in animal studies].

Acupuncture therapy has a positive role in the prevention and treatment of some related diseases by regulating autonomic nervous function. But it has been found in experimental researches that the modulatory effects of acupuncture on autonomic nervous system are not always consistent with each other. Because in the animal studies on the mechanism of acupuncture intervention, the anesthetic agent has to be used and definitely affects the activities of the autonomic nervous system while playing its pharmacological effects. Hence, it is very significant to explore the rational application of anesthetic agents and minimize their unfavorable impacts on the research outcomes. In the present paper, we make a retrospective analysis on (1) the effect of acupuncture intervention on activities of the autonomic nerve in animal models of myocardial ischemia, gastrointestinal mobility, and urinary system; (2) the effect of anesthetics as isoflurane, urethane, pentobarbital sodium, ketamine, α-chloralose, propofolum, etc. on activities of the autonomic nerve system. In terms of different anesthetic modes and various depths of anesthesia by using isoflurane inhalation, mixed solution of urethane and chloralose, etc., some approaches for assessing the state of anesthesia in accordance with the pupillary reflex, righting reflex, footboard reflex, swallowing reflex, heart rate, blood pressure, body temperature, respiration frequency, ventilation volume, oxygen saturation, partial pressure of carbon dioxide, neuromuscular blo-ckade, etc. in combination with the indexes directly and indirectly reflecting functions of the sympathetic and vagus nerves are proposed to analyze the impact of different anesthetic states on the therapeutic effect of acupuncture in various models of dysfunction of the autonomic nerve system. Under the circumstances, it is possible to provide a reference for rational use of anesthetic agents and dosages in the acupuncture research of autonomic nerve regulation.

Development of a decerebrate model for investigating mechanisms mediating viscero-sympathetic reflexes in the spinalized rat.

Autonomic dysreflexia (AD) often occurs in individuals living with spinal cord injury (SCI) and is characterized by uncontrolled hypertension in response to otherwise innocuous stimuli originating below the level of the spinal lesion. Visceral stimulation is a predominant cause of AD in humans and effectively replicates the phenotype in rodent models of SCI. Direct assessment of sympathetic responses to viscerosensory stimulation in spinalized animals is challenging and requires invasive surgical procedures necessitating the use of anesthesia. However, administration of anesthesia markedly affects viscerosensory reactivity, and the effects are exacerbated following spinal cord injury (SCI). Therefore, the major goal of the present study was to develop a decerebrate rodent preparation to facilitate quantification of sympathetic responses to visceral stimulation in the spinalized rat. Such a preparation enables the confounding effect of anesthesia to be eliminated. Sprague-Dawley rats were subjected to SCI at the fourth thoracic segment. Four weeks later, renal sympathetic nerve activity (RSNA) responses to visceral stimuli were quantified in urethane/chloralose-anesthetized and decerebrate preparations. Visceral stimulation was elicited via colorectal distension (CRD) for 1 min. In the decerebrate preparation, CRD produced dose-dependent increases in mean arterial pressure (MAP) and RSNA and dose-dependent decreases in heart rate (HR). These responses were significantly greater in magnitude among decerebrate animals when compared with urethane/chloralose-anesthetized controls and were markedly attenuated by the administration of urethane/chloralose anesthesia after decerebration. We conclude that the decerebrate preparation enables high-fidelity quantification of neuronal reactivity to visceral stimulation in spinalized rats. NEW & NOTEWORTHY In animal models commonly used to study spinal cord injury, quantification of sympathetic responses is particularly challenging due to the increased susceptibility of spinal reflex circuits to the anesthetic agents generally required for experimentation. This constitutes a major limitation to understanding the mechanisms mediating regionally specific neuronal responses to visceral activation in chronically spinalized animals. In the present study, we describe a spinalized, decerebrate rodent preparation that facilitates quantification of sympathetic reactivity in response to visceral stimuli following spinal cord injury. This preparation enables reliable and reproducible quantification of viscero-sympathetic reflex responses resembling those elicited in conscious animals and may provide added utility for preclinical evaluation of neuropharmacological agents for the management of autonomic dysreflexia.

The effect of caffeine on cerebral metabolism during alpha-chloralose anesthesia differs from isoflurane anesthesia in the rat brain.

RATIONALE: Caffeine is a widely studied psychostimulant, even though its exact effect on brain activity remains to be elucidated. Positron emission tomography (PET) allows studying mechanisms underlying cerebral metabolic responses to caffeine in caffeine-naïve rats. Rodent studies are typically performed under anesthesia. However, the anesthesia may affect neurotransmitter systems targeted by tested drugs. OBJECTIVES: The scope of the present study was to address the impairing or enhancing effect of two common anesthetics, alpha-chloralose and isoflurane, on the kinetics of caffeine. METHODS: The first group of rats (n = 15) were anesthetized under 1.5% isoflurane anesthesia. The second group of rats (n = 15) were anesthetized under alpha-chloralose (80 mg/kg). These rats received an intravenous injection of saline (n = 5) or of 2.5 mg/kg (n = 5) or 40 mg/kg (n = 5) caffeine for both groups. RESULTS: With 2.5 mg/kg or 40 mg/kg caffeine, whole-brain cerebral metabolism was significantly reduced by 17.2% and 17% (both P < 0.01), respectively, under alpha-chloralose anesthesia. However, the lower dose of caffeine (2.5 mg/kg) had a limited effect on brain metabolism, whereas its higher dose (40 mg/kg) produced enhancements in brain metabolism in the striatum, hippocampus, and thalamus (all P < 0.05) under isoflurane anesthesia. CONCLUSION: These findings demonstrate significant differences in brain responses to caffeine on the basic of the anesthesia regimen used, which highlights the importance of attention to the anesthetic used when interpreting findings from animal pharmacological studies because of possible interactions between the anesthetic and the drug under study.

Gradient-echo and spin-echo blood oxygenation level-dependent functional MRI at ultrahigh fields of 9.4 and 15.2 Tesla.

PURPOSE: Sensitivity and specificity of blood oxygenation level-dependent (BOLD) functional MRI (fMRI) is sensitive to magnetic field strength and acquisition methods. We have investigated gradient-echo (GE)- and spin-echo (SE)-BOLD fMRI at ultrahigh fields of 9.4 and 15.2  Tesla. METHODS: BOLD fMRI experiments responding to forepaw stimulation were performed with 3 echo times (TE) at each echo type and B0 in α-chloralose-anesthetized rats. The contralateral forelimb somatosensory region was selected for quantitative analyses. RESULTS: At 9.4 T and 15.2 T, average baseline T2* (n = 9) was 26.6 and 17.1 msec, whereas baseline T2 value (n = 9) was 35.7 and 24.5 msec, respectively. Averaged stimulation-induced ΔR2* was -1.72 s-1 at 9.4 T and -3.09 s-1 at 15.2 T, whereas ΔR2 was -1.19 s-1 at 9.4 T and -1.97 s-1 at 15.2 T. At the optimal TE of tissue T2* or T2 , BOLD percent changes were slightly higher at 15.2 T than at 9.4 T (GE: 7.4% versus 6.4% and SE: 5.7% versus 5.4%). The ΔR2* and ΔR2 ratio of 15.2 T to 9.4 T was 1.8 and 1.66, respectively. The ratio of the macrovessel-containing superficial to microvessel-dominant parenchymal BOLD signal was 1.73 to 1.76 for GE-BOLD versus 1.13 to 1.19 for SE-BOLD, indicating that the SE-BOLD contrast is less sensitive to macrovessels than GE-BOLD. CONCLUSION: SE-BOLD fMRI improves spatial specificity to microvessels compared to GE-BOLD at both fields. BOLD sensitivity is similar at the both fields and can be improved at ultrahigh fields only for thermal-noise-dominant ultrahigh-resolution fMRI.

Functional connectivity under six anesthesia protocols and the awake condition in rat brain.

Resting-state functional magnetic resonance imaging (rsfMRI) is a translational imaging method with great potential in several neurobiologic applications. Most preclinical rsfMRI studies are performed in anesthetized animals, but the confounding effects of anesthesia on the measured functional connectivity (FC) are poorly understood. Therefore, we measured FC under six commonly used anesthesia protocols and compared the findings with data obtained from awake rats. The results demonstrated that each anesthesia protocol uniquely modulated FC. Connectivity patterns obtained under propofol and urethane anesthesia were most similar to that observed in awake rats. FC patterns in the α-chloralose and isoflurane-medetomidine combination groups had moderate to good correspondence with that in the awake group. The FC patterns in the isoflurane and medetomidine groups differed most from that in the awake rats. These results can be directly exploited in rsfMRI study designs to improve the data quality, comparability, and interpretation.

Environmental stress and vestibular inputs modulate cardiovascular responses to orthostasis in hypertensive rats.

The frequent accompaniment of hypertension by orthostatic circulatory disorders prompted us to investigate the effect of repeated and sustained head-up and head-down tilt positions on cardiovascular responses in spontaneously hypertensive rats vs. Wistar rats using radiotelemetric implants. Repeated orthostasis caused a transient elevation in blood pressure (7.3±1.7 mmHg) and heart rate (39.7±10.5 BPM), while repeated antiorthostasis led only to reversible tachycardia (85.6±11.7-54.3±16.8 BPM) in spontaneously hypertensive rats. In contrast to the Wistar rats, sustained tilt failed to affect the blood pressure or heart rate in spontaneously hypertensive rats because the environmental stress of being placed in horizontal tilt cages prior to the sustained tilt test induced marked changes in cardiovascular parameters. Non-specific stress responses were eliminated both by the anxiolytic diazepam and a sub-anesthetic dose of chloralose. Unlike diazepam, chloralose amplified the orthostatic pressor responses in the Wistar rats. In contrast to diazepam preventing the pressor response and associated tachycardia in spontaneously hypertensive rats, chloralose elicited this effect during both sustained orthostasis (36.0±7.3 mmHg, 63.7±21.8 BPM) and antiorthostasis (42.9±10.9 mmHg, 82.8±25.4 BPM), with a reduced baroreflex sensitivity. However, during sustained orthostasis, removal of the vestibular input led to a depressor response with bradycardia (12.5±3.2 mmHg, 59.3±17.3 BPM), whereas antiorthostasis only reduced blood pressure (20.5±7.1 mmHg) in the spontaneously hypertensive rats. We conclude that repeated tilts induce a transient pressor response and/or tachycardia in spontaneously hypertensive rats. Cardiovascular parameters are suppressed by diazepam, whereas chloralose evokes both blood pressure and heart rate responses during sustained tilts, which are primarily elicited by baroreflex suppression in hypertension. Vestibular inputs support cardiovascular tolerance to sustained postural changes in a rat model of human 'essential' hypertension.

Caregiver-Fabricated Illness in a Child: A Case Report of Three Siblings.

Caregiver-fabricated illness in a child is a form of child maltreatment caused by a caregiver inducing a child's illness, leading to unnecessary and potentially harmful medical procedures and treatments. This condition can result in significant morbidity and mortality. We present the case of three siblings in Tunisia who were poisoned with chloralose by their own mother. The symptoms that the children presented with led to misdiagnoses, which resulted in the death of two of the children. Characteristics of the clinical presentation are articulated, followed by a discussion of the legal measures that apply to the offender and the role of physicians, nurses, and medicolegal experts involved in such a complex medical situation.

Hysteretic behavior of bladder afferent neurons in response to changes in bladder pressure.

BACKGROUND: Mechanosensitive afferents innervating the bladder increase their firing rate as the bladder fills and pressure rises. However, the relationship between afferent firing rates and intravesical pressure is not a simple linear one. Firing rate responses to pressure can differ depending on prior activity, demonstrating hysteresis in the system. Though this hysteresis has been commented on in published literature, it has not been quantified. RESULTS: Sixty-six bladder afferents recorded from sacral dorsal root ganglia in five alpha-chloralose anesthetized felines were identified based on their characteristic responses to pressure (correlation coefficient ≥ 0.2) during saline infusion (2 ml/min). For saline infusion trials, we calculated a maximum hysteresis ratio between the firing rate difference at each pressure and the overall firing rate range (or Hmax) of 0.86 ± 0.09 (mean ± standard deviation) and mean hysteresis ratio (or Hmean) of 0.52 ± 0.13 (n = 46 afferents). For isovolumetric trials in two experiments (n = 33 afferents) Hmax was 0.72 ± 0.14 and Hmean was 0.40 ± 0.14. CONCLUSIONS: A comprehensive state model that integrates these hysteresis parameters to determine the bladder state may improve upon existing neuroprostheses for bladder control.

Comparing the Effects of Isoflurane and Alpha Chloralose upon Mouse Physiology.

Functional magnetic resonance imaging of mice requires that the physiology of the mouse (body temperature, respiration and heart rates, blood pH level) be maintained in order to prevent changes affecting the outcomes of functional scanning, namely blood oxygenation level dependent (BOLD) measures and cerebral blood flow (CBF). The anesthetic used to sedate mice for scanning can have major effects on physiology. While alpha chloralose has been commonly used for functional imaging of rats, its effects on physiology are not well characterized in the literature for any species. In this study, we anesthetized or sedated mice with isoflurane or alpha chloralose for up to two hours, and monitored physiological parameters and arterial blood gasses. We found that, when normal body temperature is maintained, breathing rates for both drugs decrease over the course of two hours. In addition, alpha chloralose causes a substantial drop in heart rate and blood pH with severe hypercapnia (elevated blood CO2) that is not seen in isoflurane-treated animals. We suggest that alpha chloralose does not maintain normal mouse physiology adequately for functional brain imaging outcome measures.

Determination of Anticoagulant Rodenticides and α-Chloralose in Human Hair. Application to a Real Case.

Anticoagulant rodenticides are the largest group of poisons used to kill harmful rodents. Their fundamental mode of action consists in the inhibition of the vitamin K epoxide reductase, which causes blood-clotting alteration, ultimately leading to hemorrhagic events as the cause of death. In this study, we developed an UHPLC-MS-MS for the simultaneous determination of 10 anticoagulant hydroxycoumarine rodenticides, plus α-chloralose in human hair, with the scope of detecting potential trace of chronological poison exposure in clinical and forensic cases. The method was fully validated and applied to a case of intentional poisoning perpetrated by administration of difenacoum and α-chloralose to a 97-year-old woman, who was hospitalized because of severe symptoms, including drowsiness, convulsions, pallor and hematoma. Hair sample from the victim was segmentally analyzed. Difenacoum was detected in the proximal 3-cm hair segment at the concentration of 2.9 pg/mg. To our knowledge, this is the first study to report that exposure to difenacoum is detectable in real hair samples. The other target analyte found in the hair sample was α-chloralose, which was detected in the 0-3 cm segment at the concentration of 85 pg/mg. The two subsequent and consecutive segments (3-6 cm and 6-9 cm) showed only traces of difenacoum (below LOQ) and low but quantifiable concentrations of α-chloralose (29 and 6 pg/mg, respectively). Therefore, hair segmental analysis allowed us to conclude that the victim was repeatedly exposed to two poisons in the period corresponding to the first segment of hair.

Layer-specific interhemispheric functional connectivity in the somatosensory cortex of rats: resting state electrophysiology and fMRI studies.

The spontaneous cerebral hemodynamic fluctuations observed during the resting state have been frequently visualized using functional magnetic resonance imaging (rsfMRI). However, the neuronal populations and neuroelectric characteristics underlying the functional connectivity of cerebrohemodynamic activities are poorly understood. We investigated the characteristics of bi-hemispheric functional connectivity via electrophysiology and rsfMRI in the primary sensory cortex of rats anesthetized by α-chloralose. Unlike the evoked responses, the spontaneous electrophysiological activity was concentrated in the infragranular layers and could be classified into subtypes with distinctive current sources and sinks. Both neuroelectric and rsfMRI signals were interhemispherically correlated in a layer-specific manner, suggesting that there are independent neural inputs to infragranular and granular/supragranular layers. The majority of spontaneous electrophysiological activities were bilaterally paired with delays of up to ~50 ms between each pair. The variable interhemispheric delay implies the involvement of indirect, multi-neural pathways. Our findings demonstrated the diverse activity patterns of layer-specific electrophysiological substrates and suggest the recruitment of multiple, non-specific brain regions in construction of interhemispheric functional connectivity.