Mahipal Choudhary

Frequency analysis of urinary bladder pre-voiding activity in normal and overactive rat detrusor

To test the hypothesis that voiding in anesthetized rats is preceded by recurrent changes in the pattern of bladder pressure. To explore the use of frequency analysis as an analytical tool for automatically detecting these changes and to provide quantitative data on bladder pre‐voiding activity.

Neurophysiological modeling of bladder afferent activity in the rat overactive bladder model.

The overactive bladder (OAB) is a syndrome-based urinary dysfunction characterized by “urgency, with or without urge incontinence, usually with frequency and nocturia”. Earlier we developed a mathematical model of bladder nerve activity during voiding in anesthetized rats and found that the nerve activity in the relaxation phase of voiding contractions was all afferent. In the present study, we applied this mathematical model to an acetic acid (AA) rat model of bladder overactivity to study the sensitivity of afferent fibers in intact nerves to bladder pressure and volume changes. The afferent activity in the filling phase and the slope, i.e., the sensitivity of the afferent fibers to pressure changes in the post-void relaxation phase, were found to be significantly higher in AA than in saline measurements, while the offset (nerve activity at pressure ~0) and maximum pressure were comparable. We have thus shown, for the first time, that the sensitivity of afferent fibers in the OAB can be studied without cutting nerves or preparation of single fibers. We conclude that bladder overactivity induced by AA in rats is neurogenic in origin and is caused by increased sensitivity of afferent sensors in the bladder wall.

Urethane anesthesia in acute lower urinary tract studies in the male rat

Urethane is a widely used anesthetic in animal lower urinary tract research. Our objective was to investigate the quality of anesthesia and the correlation between bladder (voiding) contractions, micturition pressure, bladder capacity and urethane dosage and body weight. Urethane was given subcutaneously and/or intraperitoneally (1.0–1.2 g/kg). The bladder was filled with saline and the bladder pressure was recorded continuously. Animals in which the subcutaneous/intraperitoneal ratio was higher needed less urethane. Heavier animals needed less extra urethane. In animals, in which no bladder contractions could be evoked, the total amount of urethane given was similar to that in those that did show contractions. In the animals that did void, the bladder never emptied completely and residual volumes remained. There was no relationship between animal weight or total amount of urethane and mean capacity. Anesthesia lasted up till 14 h, during which bladder (voiding) contractions could be recorded. Considering all results, we conclude that urethane is a well suited anesthetic for acute lower urinary tract physiological research in the intact rat.

Effect of tibial nerve stimulation on bladder afferent nerve activity in a rat detrusor overactivity model.

To study the post‐stimulation effect of tibial nerve stimulation on rat bladder afferent activity, and urodynamic parameters in normal and acetic acid‐induced detrusor overactivity conditions.

The frequency spectrum of bladder non-voiding activity as a trigger-event for conditional stimulation: Closed-loop inhibition of bladder contractions in rats

To test the hypothesis that the frequency of bladder non‐voiding contractions (NVCs) can be used as a trigger event for closed‐loop conditional inhibition of detrusor contractions via tibial nerve (TN) or dorsal penile nerve (DPN) stimulation.

Can an algorithm predict a voiding contraction in unconscious rats

Urinary incontinence (UI) is a very common and serious disorder which can be classified in stress and urge incontinence, the latter mainly caused by an overactive bladder (OAB). A definitive treatment for OAB does not exist yet due to its complex nature. Therefore, more attention must be focused on improving the patients quality of life. A device able to alert the patient to development of a voiding contraction would be highly desirable, enabling actions to avoid incontinence. The main hypothesis of this work is that a voiding contraction is preceded by a consistent change in the pattern of intravesical pressure (pves). We developed an algorithm based on frequency analysis of pves recordings of two strains of rats whose bladders were first filled with saline (S fillings) and then with acetic acid (AA fillings); the latter was used as model for OAB in rats. The algorithm was designed to provide an alarm when an increase in the range 0.2-0.6Hz of the amplitude spectrum was detected. The accuracy of the algorithm has been tested and quantified, successful alarms were those taking place within fifty seconds before the start of voiding. Although the results are still very preliminary, due to the low number of tested animals, they seem encouraging since, in five rats, only one showed a percentage of success lower than 50%, with one rat reaching 100%. The accuracy of the algorithm is affected by the choice of the values for the controlling parameters, which have been set the same for all rats; future developments might include individual values for each rat.

A novel single compartment in vitro model: Perflurocarbons for electrophysiological studies of the rat urinary bladder

This study presents a novel single compartment model for in vitro electrophysiological studies of the rat urinary bladder. We tested the functionality and suitability of FC-770 (a Perflurocarbon) for in vitro recording of nerve activity arising from the bladder in a single compartment setup. We have also favorably tested stimulation of the bladder via the bladder nerves in FC-770. The organ viability was monitored by recording spontaneous contractions of the bladder for a certain time. We propose the use of FC-770 as a fluid for nerve recording/stimulation in vitro as well as for maintaining organ viability, over the commonly used two compartmental methods.