Afferent Measurement (SAA technique)
The picture below shows the experimental setup of the SAA (Single Afferent Activity) technique used in our laboratory to measure the afferent signals of the lower urinary tract. The use of this animal model enables you to measure the activity (potentials) of single-unit primary afferent fibers coming from the bladder or the urethra. Different interventions (drugs, bladder filling, pelvic nerve stimulation, etc) and the resulting afferent response of the lower urinary tract can be determined.
In order to measure the afferent potentials, a laminectomy is done in the rat at the lumbar level of the spinal cord. With the use of a recording electrode, afferent potentials (L6 dorsal root level) are measured. Recorded nerve activity is pre-amplified and filtered. With final amplification, the activity is displayed on an oscilloscope (TDS-310, Tektronix, Inc., Beaverton, OR). Analysis of the data is done with the Spike program (CED, Cambridge, UK).
The picture below illustrates the cystometry setup, which enables to measure changes in bladder pressure during repeated voiding cycles in rats. A catheter is inserted through the bladder dome (= suprapubic catheter) and connected with a NE-1000 syringe pump (New Era Pump Systems, Farmingdale, New York) and pressure transducer (Emka technologies) via a 3-way stopcock. Bladder pressure, after signal amplification (Emka Technologies), is monitored with time using WINDAQ® DI-710 data acquisition.
Our laboratory developed a model to investigate the interaction between the bladder and colon. Bladder activity, measured by cystometry, can be evaluated during a colorectal distension. A custom-made latex balloon catheter (little finger of a size 6 Triflex® surgical glove) is inserted into the rectum and connected to a pressure controlled distention device (2PK+ pipette pressure/vacuum generator, ALA Scientific Intstruments, Farmingdale, New York) to enable colorectal distension at constant pressure.
The organ bath setup is used to measure autonomous bladder activity, with or without drug and/or electrical stimulation. An isolated rat bladder is inserted into the inner chamber of the bath (filled with Krebs solution) and filled through a transurethral catheter. Bladder pressure is transduced (Emka technologies), amplified (Emka technologies) and monitored with time (WINDAQ® DI-710 data acquisition).
Extra: The organ bath is also used for tension measurement on bladder strips.
With the Agilent Arbitrary Waveform generator 33220A, we are able to design our own waveform types with few restrictions of pulse duration and frequency. The stimulator has a voltage output, while for the bladder or urethra stimulation procedure we need a constant current output.
To convert the voltage output to a constant output, a direct stimulus isolator is needed. The Stimulus Isolator ISO-STIM 01DPI is attached to a simple switch which in its turn is connected with on one side to cathode and on the other side to anode.
The combination of these devices allows us to generate waveforms with different pulse shapes (exponential rise or decline, biphasic, sine wave, etc.) and durations, and with an amplitude ranging from 0.01μA to 10mA.
The metabolic cage (Techniplast, Italy) is a convenient way to obtain accurate data on the amount and frequency of excreta produced by the rat. The cage provides a perfect separation of faeces and urine. This will result in reliable samples for accurate metabolic monitoring.
The use of this universal stereomicroscope (Zeiss Stemi 2000, Zeiss, Germany) with a magnification range of 6.5x to 50x allows you to accurate visualize structures. This microscope is used in different setups, like catheterization of the bladder and the surgical preparations of the SAA technique.