Novel technique for monitoring micturition and sexual function in male rats using telemetry

Abstract

We developed a novel technique to simultaneously monitor micturitions and erections in rats by using pressure monitoring within the corpus spongiosum of the penis (CSP). We present data validating this technique and report pressure waveform characteristics of micturition and erectile events during four different behavioral contexts in 10 awake, freely-moving male rats. Telemetric pressure transducers were implanted in the bulb of the CSP. CSP pressure was monitored while the animals were simultaneously recorded on video for determination of presence and volume (n = 7) of micturitions and while the animals underwent behavioral tests for determination of erections. Observed micturitions and CSP pressure waveforms characteristic of micturitions occurred simultaneously (r = 0.98) at a frequency of 32 +/- 4 micturitions per 24 h and with a volume of 0.95 +/- 0.12 ml/urination. Micturition duration recorded by CSP pressure and volume determined by urine weight were highly correlated (r = 0.82). We found that 100% of visually confirmed erectile events occurred simultaneously with CSP pressure waveforms characteristic of erections during ex copula reflex erection tests. During noncontact erection and mating tests more erections were identified by telemetry than by observation alone. Erections during mating tests had a different appearance than those seen in other contexts; they were shorter in duration (P < 0.05) and typically were characterized by a single suprasystolic CSP pressure peak, highlighting the context-specificity of erections. Quality of recordings remained stable in three of four rats we followed for 8 wk. We demonstrate that telemetric recording of CSP pressure provides a quantitative and qualitative assessment of penile erections and micturition in freely behaving rats.

Autonomic Consequences of Spinal Cord Injury

“…Videofluoroscopy is a clinical relevant technique in which the bladder is filled with radio-opaque medium and the volume is detected by X-ray (354,355). Penis corpus spongiosum pressure is traditionally monitored by an implanted telemeter to evaluate sexual function that has been validated for evaluating LUT function in spinal cord injured rats (264,265). Additionally, transabdominal ultrasound can be used to detect the volume of urine in spinal cord injured rats (164).…”

Methods for behavioral testing of spinal cord injured rats

“…In the ex copula reflex erection test, the preputial sheath of a conscious animal is retracted to elicit a reflex erection and maintained in this position for 20 min by placing the glans of the penis through a hole in a small piece of tape fastened to the abdomen. Events are visually scored from 1 (weak glans engorgement) to 5 (intense flaring or cup of the distal glans together with dorsiflexion or flip of the penile body greater than 901 with respect to the body of the rat) (Holmes et al, 1988;Schmidt et al, 1995;Nout et al, 2007). In the non-contact erection test, a male rat is put into one half of a cage, separated from the other half by a sheet of wire mesh, and left for 5 min to adjust to his new environment.…”

“…After that, an estrous female rat, whose rut is ensured by the administration of estradiol and progesterone and a preliminary approximation to a healthy male rat, is placed into the second half of the cage and events are observed for 30 min. They are scored using a 3 point scale (1-visible erections, 2-grooming of the body parts, 3-grooming of the genital area) (Sachs et al, 1994;Nout et al, 2007). The mating test has a similar arrangement as the one above, except the male and female rats are put together and the scale is 6-pointed.…”

“…The mating test has a similar arrangement as the one above, except the male and female rats are put together and the scale is 6-pointed. The first 3 points of the scale are the same and the other 3 points describe the following mating behaviors: 4-mounts, 5-intromissions, 6-ejaculations (Nout et al, 2007).…”

“…To simultaneously evaluate micturition parameters and describe erectile events in rats with SCI, a new method of telemetric monitoring of corpus spongiosum penis pressure has been recently developed (Nout et al, 2005(Nout et al, , 2007. The development of this technique was based on previous experiments by Schmidt et al (1995).…”