Stability of the acetic acid-induced bladder irritation model in alpha chloralose-anesthetized female cats

Alpha-chloralose poisoning in 25 cats: clinical picture and evaluation of treatment with intravenous lipid emulsion

OBJECTIVES

The aims of this study were to describe the clinical picture and progression in cats with alpha-chloralose (AC) intoxication and to determine if treatment with intravenous (IV) lipid emulsion (ILE) influenced either the serum concentration of AC or the clinical signs.

METHODS

Cats with suspected AC poisoning admitted to a university small animal hospital were included. The cats were randomised into two groups: one receiving 20% ILE at a dose of 300 mg/kg as a 2 min bolus, followed by a 1500 mg/kg continuous rate infusion over 30 mins (IL+ group) and the other receiving IV fluid therapy with Ringer's acetate (IL- group). Serum samples were drawn at 0, 2, 12 and 24 h after admission. Samples were tested for AC with a novel validated, quantitative, ultra-high-performance liquid chromatography-tandem mass spectrometry method. Vital and predefined clinical signs were noted at the times of sampling and patients were scored using a previously described intoxication severity score. Telephone interviews were conducted after discharge to assess outcome.

RESULTS

A total of 25 cats were enrolled: 13 cats in the IL+ group and 12 in the IL- group. The most common clinical signs at presentation were tremor (n = 22, 88.0%), cranial nerve deficits (n = 20, 80.0%) and bradycardia (n = 19, 76.0%). No significant difference in AC concentration or change in intoxication score over time was found between the IL+ and IL- groups at any time point (P >0.05). All cats recovered within 72 h.

CONCLUSIONS AND RELEVANCE

ILE did not have any effect on the AC serum concentration or clinical signs in AC-poisoned cats. All cats survived until follow-up. In cats with an acute onset of the described neurological signs, AC intoxication is an important differential diagnosis with an excellent prognosis.

Real-time prediction of bladder urine leakage using fuzzy inference system and dual Kalman filtering in cats

The use of electrical stimulation devices to manage bladder incontinence relies on the application of continuous inhibitory stimulation. However, continuous stimulation can result in tissue fatigue and increased delivered charge. Here, we employ a real-time algorithm to provide a short-time prediction of urine leakage using the high-resolution power spectrum of the bladder pressure during the presence of non-voiding contractions (NVC) in normal and overactive bladder (OAB) cats. The proposed method is threshold-free and does not require pre-training. The analysis revealed that there is a significant difference between voiding contraction (VC) and NVC pressures as well as band powers (0.5-5 Hz) during both normal and OAB conditions. Also, most of the first leakage points occurred after the maximum VC pressure, while all of them were observed subsequent to the maximum VC spectral power. Kalman-Fuzzy method predicted urine leakage on average 2.2 s and 1.6 s before its occurrence and an average of 2.0 s and 1.1 s after the contraction started with success rates of 94.2% and 100% in normal and OAB cats, respectively. This work presents a promising approach for developing a neuroprosthesis device, with on-demand stimulation to control bladder incontinence.

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.

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.

Closed-loop sacral neuromodulation for bladder function using dorsal root ganglia sensory feedback in an anesthetized feline model

Overactive bladder patients suffer from a frequent, uncontrollable urge to urinate, which can lead to a poor quality of life. We aim to improve open-loop sacral neuromodulation therapy by developing a conditional stimulation paradigm using neural recordings from dorsal root ganglia (DRG) as sensory feedback. Experiments were performed in 5 anesthetized felines. We implemented a Kalman filter-based algorithm to estimate the bladder pressure in real-time using sacral-level DRG neural recordings and initiated sacral root electrical stimulation when the algorithm detected an increase in bladder pressure. Closed-loop neuromodulation was performed during continuous cystometry and compared to bladder fills with continuous and no stimulation. Overall, closed-loop stimulation increased bladder capacity by 13.8% over no stimulation (p < 0.001) and reduced stimulation time versus continuous stimulation by 57.7%. High-confidence bladder single units had a reduced sensitivity during stimulation, with lower linear trendline fits and higher pressure thresholds for firing observed during stimulation trials. This study demonstrates the utility of decoding bladder pressure from neural activity for closed-loop control of sacral neuromodulation. An underlying mechanism for sacral neuromodulation may be a reduction in bladder sensory neuron activity during stimulation. Real-time validation during behavioral studies is necessary prior to clinical translation of closed-loop sacral neuromodulation.

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.

Stimulation of the pelvic nerve increases bladder capacity in the PGE2 cat model of overactive bladder

Selective electrical stimulation of the pudendal nerve exhibits promise as a potential therapy for treating overactive bladder (OAB) across species (rats, cats, and humans). More recently, pelvic nerve (PelN) stimulation was demonstrated to improve cystometric bladder capacity in a PGE₂ rat model of OAB. However, PelN stimulation in humans or in an animal model that is more closely related to humans has not been explored. Therefore, our objective was to quantify the effects of PGE₂ and PelN stimulation in the cat. Acute cystometry experiments were conducted in 14 α-chloralose-anesthetized adult, neurologically intact female cats. Intravesical PGE₂ decreased bladder capacity, residual volume, threshold contraction pressure, and mean contraction pressure. PelN stimulation reversed the PGE₂-induced decrease in bladder capacity and increased evoked external urethral sphincter electromyographic activity without influencing voiding efficiency. The increases in bladder capacity generated by PelN stimulation were similar in the rat and cat, but the stimulation parameters to achieve this effect differed (threshold amplitude at 10 Hz in the rat vs. twice threshold amplitude at 1 Hz in the cat). These results highlight the potential of PGE₂ as a model of OAB and provide further evidence that PelN stimulation is a promising approach for the treatment of OAB symptoms.

Real-Time Bladder Pressure Estimation for Closed-Loop Control in a Detrusor Overactivity Model

Overactive bladder (OAB) patients suffer from a frequent urge to urinate, which can lead to a poor quality of life. Current neurostimulation therapy uses open-loop electrical stimulation to alleviate symptoms. Continuous stimulation facilitates habituation of neural pathways and consumes battery power. Sensory feedback-based closed-loop stimulation may offer greater clinical benefit by driving bladder relaxation only when bladder contractions are detected, leading to increased bladder capacity. Effective delivery of such sensory feedback, particularly in real-time, is necessary to accomplish this goal. We implemented a Kalman filter-based model to estimate bladder pressure in real-time using unsorted neural recordings from sacral-level dorsal root ganglia, achieving a 0.88 ± 0.16 correlation coefficient fit across 35 normal and simulated OAB bladder fills in five experiments. We also demonstrated closed-loop neuromodulation using the estimated pressure to trigger pudendal nerve stimulation, which increased bladder capacity by 40% in two trials. An offline analysis indicated that unsorted neural signals had a similar stability over time as compared to sorted single units, which would require a higher computational load. We believe this paper demonstrates the utility of decoding bladder pressure from neural activity for closed-loop control; however, real-time validation during behavioral studies is necessary prior to clinical translation.

Role of neurogenic inflammation in local communication in the visceral mucosa

Intense research has focused on the involvement of the nervous system in regard to cellular mechanisms underlying neurogenic inflammation in the pelvic viscera. Evidence supports the neural release of inflammatory factors, trophic factors, and neuropeptides in the initiation of inflammation. However, more recently, non-neuronal cells including epithelia, endothelial, mast cells, and paraneurons are likely important participants in nervous system functions. For example, the urinary bladder urothelial cells are emerging as key elements in the detection and transmission of both physiological and nociceptive stimuli in the lower urinary tract. There is mounting evidence that these cells are involved in sensory mechanisms and can release mediators. Further, localization of afferent nerves next to the urothelium suggests these cells may be targets for transmitters released from bladder nerves and that chemicals released by urothelial cells may alter afferent excitability. Modifications of this type of communication in a number of pathological conditions can result in altered release of epithelial-derived mediators, which can activate local sensory nerves. Taken together, these and other findings highlighted in this review suggest that neurogenic inflammation involves complex anatomical and physiological interactions among a number of cell types in the bladder wall. The specific factors and pathways that mediate inflammatory responses in both acute and chronic conditions are not well understood and need to be further examined. Elucidation of mechanisms impacting on these pathways may provide insights into the pathology of various types of disorders involving the pelvic viscera.

Inflammation and Tissue Remodeling in the Bladder and Urethra in Feline Interstitial Cystitis

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a debilitating chronic disease of unknown etiology. A naturally occurring disease termed feline interstitial cystitis (FIC) reproduces many features of IC/BPS patients. To gain insights into mechanisms underlying IC/BPS, we investigated pathological changes in the lamina propria (LP) of the bladder and proximal urethra in cats with FIC, using histological and molecular methods. Compared to control cat tissue, we found an increased number of de-granulated mast cells, accumulation of leukocytes, increased cyclooxygenase (COX)-1 expression in the bladder LP, and increased COX-2 expression in the urethra LP from cats with FIC. We also found increased suburothelial proliferation, evidenced by mucosal von Brunn’s nests, neovascularization and alterations in elastin content. Scanning electron microscopy revealed normal appearance of the superficial urethral epithelium, including the neuroendocrine cells (termed paraneurons), in FIC urethrae. Together, these histological findings suggest the presence of chronic inflammation of unknown origin leading to tissue remodeling. Since the mucosa functions as part of a “sensory network” and urothelial cells, nerves and other cells in the LP are influenced by the composition of the underlying tissues including the vasculature, the changes observed in the present study may alter the communication of sensory information between different cellular components. This type of mucosal signaling can also extend to the urethra, where recent evidence has revealed that the urethral epithelium is likely to be part of a signaling system involving paraneurons and sensory nerves. Taken together, our data suggest a more prominent role for chronic inflammation and tissue remodeling than previously thought, which may result in alterations in mucosal signaling within the urinary bladder and proximal urethra that may contribute to altered sensations and pain in cats and humans with this syndrome.

Sex difference in the contribution of GABAB receptors to tibial neuromodulation of bladder overactivity in cats

This study investigated the role of γ-aminobutyric acid subtype B (GABA_B) receptors in tibial and pudendal neuromodulation of bladder overactivity induced by intravesical administration of dilute (0.5%) acetic acid (AA) in α-chloralose-anesthetized cats. To inhibit bladder overactivity, tibial or pudendal nerve stimulation (TNS or PNS) was applied at 5 Hz and two or four times threshold (T) intensity for inducing toe or anal sphincter twitch. TNS at 2T or 4T intensity significantly (P < 0.05) increased the bladder capacity to 173.8 ± 16.2 or 198.5 ± 24.1%, respectively, of control capacity. Meanwhile, PNS at 2T or 4T intensity significantly (P < 0.05) increased the bladder capacity to 217 ± 18.8 and 221.3 ± 22.3% of control capacity, respectively. CGP52432 (a GABA_B receptor antagonist) at intravenous dosages of 0.1-1 mg/kg completely removed the TNS inhibition in female cats but had no effect in male cats. CGP52432 administered intravenously also had no effect on control bladder capacity or the pudendal inhibition of bladder overactivity. These results reveal a sex difference in the role of GABA_B receptors in tibial neuromodulation of bladder overactivity in cats and that GABA_B receptors are not involved in either pudendal neuromodulation or irritation-induced bladder overactivity.

Lumbosacral spinal segmental contributions to tibial and pudendal neuromodulation of bladder overactivity in cats

AIMS

To determine the spinal segmental afferent contributions to tibial and pudendal inhibition of bladder overactivity.

METHODS

Intravesical infusion of 0.5% acetic acid was used to irritate the bladder and induce bladder overactivity in anesthetized cats. Tibial or pudendal nerve stimulation was used to suppress the bladder overactivity and increase bladder capacity during cystometry. L5-S3 dorsal roots ipsilateral to the stimulation were exposed by a laminectomy and transected sequentially during the experiments to determine the role of individual dorsal roots in tibial or pudendal neuromodulation.

RESULTS

Transection of L5 dorsal root had no effect. Transection of L6 dorsal root in four cats produced an average 18% reduction in tibial inhibition, which is not a significant change when averaged in the group of 10 cats. Transection of L7 dorsal root completely removed the tibial inhibition without changing reflex bladder activity or pudendal inhibition. Transection of S1 dorsal root reduced the pudendal inhibition, after which transection of S2 dorsal root completely removed the pudendal inhibition. Transection of S3 dorsal root had no effect. The control bladder capacity was increased only by transection of S2 dorsal root.

CONCLUSIONS

This study in cats revealed that tibial and pudendal neuromodulation of reflex bladder overactivity depends on activation of primary afferent pathways that project into different spinal segments. This difference may be related to the recent observation in cats that the two types of neuromodulation have different mechanisms of action.

Neurotransmitter Mechanisms Underlying Sacral Neuromodulation of Bladder Overactivity in Cats

OBJECTIVE

To determine the role of opioid, β-adrenergic, and metabotropic glutamate 5 receptors in sacral neuromodulation of bladder overactivity.

MATERIAL AND METHODS

In α-chloralose anesthetized cats, intravesical infusion of 0.5% acetic acid (AA) irritated the bladder and induced bladder overactivity. Electric stimulation (5 Hz, 0.2 ms, 0.16-0.7V) of S1 or S2 sacral dorsal roots inhibited the bladder overactivity. Naloxone, propranolol, or MTEP were given intravenously (i.v.) to determine different neurotransmitter mechanisms.

RESULTS

AA significantly (p < 0.05) reduced bladder capacity to 7.7 ± 3.3 mL from 12.0 ± 5.0 mL measured during saline infusion. S1 or S2 stimulation at motor threshold intensity significantly (p < 0.05) increased bladder capacity to 179.4 ± 20.0% or 219.1 ± 23.0% of AA control, respectively. Naloxone (1 mg/kg) significantly (p < 0.001) reduced the control capacity to 38.3 ± 7.3% and the bladder capacity measured during S1 stimulation to 106.2 ± 20.8% of AA control, but did not significantly change the bladder capacity measured during S2 stimulation. Propranolol (3 mg/kg) significantly (p < 0.01) reduced bladder capacity from 251.8 ± 32.2% to 210.9 ± 33.3% during S2 stimulation, but had no effect during S1 stimulation. A similar propranolol effect also was observed in naloxone-pretreated cats. In propranolol-pretreated cats during S1 or S2 stimulation, MTEP (3 mg/kg) significantly (p < 0.05) reduced bladder capacity and naloxone (1 mg/kg) following MTEP treatment further reduced bladder capacity. However, a significant inhibition could still be induced by S1 or S2 stimulation after all three drugs were administered.

CONCLUSIONS

Neurotransmitter mechanisms in addition to those activating opioid, β-adrenergic, and metabotropic glutamate 5 receptors also are involved in sacral neuromodulation.