Original article

Influence of pump compliance (peristaltic vs. infusion) on urodynamic

measurement during cystometry in conscious rats

Cristina Velasco*, Luciano Guarneri, Amedeo Leonardi, Rodolfo Testa

Pharmaceutical R & D Division-Recordati S.p.A., Via M. Civitali I-20148, Milano, Italy

Received 12 January 2001; accepted 9 June 2001

Abstract

Cystometry, employing natural or pump-induced bladder filling, is the most widely used method for studying bladder reflexes and

micturition in conscious rats. However, discrepancies in basal values of urodynamic parameters are often reported, especially for micturition

pressure. The aim of this study was to establish whether the type of pump used (peristaltic or infusion) might yield different urodynamic

parameters. Differences between natural filling (evaluated in water-loaded animals and considered ‘‘physiological micturition’’) and pump-

evoked cystometrograms, as well as the compliance of these systems, and the effects of pharmacologically diverse drugs (prazosin,

oxybutynin, and naproxen) acting on the bladder voiding were evaluated. Micturition pressure recorded from pump-evoked

cystometrograms showed differences from natural micturition that were related to the total compliance of the system (pump + tube) and

not only to the nature of the pump used. Drug-induced changes of micturition pressure during natural micturition resembled those recorded

during bladder infusion with a peristaltic pump more than those with an infusion pump. Other basal values and drug-induced changes of

bladder capacity were the same during natural and pump-evoked micturition. The present findings indicate that cystometrographic

parameters obtained during pump-evoked micturition with a system at high compliance (peristaltic pump) are equivalent to those observed

during physiological micturition. D 2002 Elsevier Science Inc. All rights reserved.

Keywords: Cystometry in conscious rats; Micturition pressure; Oxybutynin, Prazosin; Naproxen

1. Introduction

Since its first description by Mosso and Pellacani (1892),

cystometry has been employed in humans to measure the

properties of the bladder wall and to evaluate changes in

urodynamic parameters associated with urinary inconti-

nence (Abrams et al., 1988).

Cystometry is also used routinely in vivo to evaluate

bladder volume capacity and micturition pressure (the max-

imal bladder pressure during micturition) in several animal

species e.g., guinea-pig (Peterson et al., 1989), rabbit (Sjog-

ren, 1976), dog (Nishizawa et al., 1989), pig (Blok et al.,

1985), mini-pig (Peterson et al., 1990), cat (Klevmark, 1974),

monkey (Shoukry & Ghoniem, 1992), as well as awake

(Yaksh et al., 1986) and anesthetized (Maggi et al., 1986a,

1986b, 1986c) rats.

In view of the fact that anesthetics may interfere with the

micturition reflex in rats (Yaksh et al., 1986; Matsuura &

Downie, 2000), continuous cystometry in conscious animals

is the preferable model. Urodynamic parameters during

spontaneous voiding are similar to those of pump-evoked

micturition in conscious rats (Yaksh et al., 1986).

Nevertheless, continuous cystometry in conscious rats

has revealed wide between-study discrepancies in basal

values of urodynamic parameters. In particular, values of

micturition pressure ranging from 26 to 122 cm H2O (19 to

90 mmHg) have been reported using different types of

pumps (Durant & Yaksh, 1988; Conte et al., 1988; Guarneri

et al., 1991; Yamamoto et al., 1995; Ishizuka et al., 1997;

Persson et al., 1998; Chai et al., 1999). Cystometric meth-

odology in each of these studies was almost the same except

for slight differences in flow rate and the type of pump used

to fill the bladder (infusion versus peristaltic).

Since it has been demonstrated (Yaksh et al., 1986;

Conte et al., 1988; Guarneri et al., 1991) that different

infusion rates (e.g., between 0.05 and 0.25 ml/min) do not

modify basal micturition parameters, we hypothesized that

the choice of the pump used for filling the bladder during

continuous cystometry (peristaltic versus infusion pump of

1056-8719/02/$ – see front matter D 2002 Elsevier Science Inc. All rights reserved.

PII: S1056 -8719 (01 )00151 -4

* Corresponding author. Fax: +39-2-48-70-9017.

Journal of Pharmacological and Toxicological Methods 45 (2001) 215–221

varying volume) is the main source of baseline urody-

namic variation.

To compare the two different bladder filling systems,

experiments have been performed to evaluate: a) the diffe-

rences between natural and pump-evoked cystometrograms,

b) the compliance of the systems, c) the effects of drugs

acting on the bladder voiding cycle via different mechanisms.

The anticholinergic drug oxybutynin, the a1-adrenoceptor

antagonist prazosin, and the COX inhibitor naproxen

were selected.

2. Materials and methods

2.1. Animals

Male Sprague-Dawley rats [Crl: CD� (SD) BR] of 300–350 g b.w. from Charles River Italia were used. Animals

were housed with free access to food and water and

maintained on forced light-dark cycle at 22–24�C. The

animals were handled according to internationally accepted

principles for care of laboratory animals (E.E.C. Council

Directive 86/609, O.J. No L358, 18/12/86).

2.2. Surgical procedure

Rats were anesthetised with 3 ml/kg Equitensin (com-

position for 125 ml of aqueous solution: 1.2 g of pentobar-

bital, 5.3 g of chloral hydrate, 2.7 g of MgSO4, 49.5 ml of

propylene glycol, 12.5 ml of ethanol) and placed in a

supine position. An approximately 10 mm incision was

made in the shaved and cleaned abdominal wall. The

urinary bladder was gently freed from adhering tissues and

a polyethylene tube (Portex, ID 0.58 mm, OD 0.96 mm),

heated to create a collar, was passed through a small incision

at the apex of the bladder dome. A suture was tightened

around the collar of the catheter and, to prevent urine

leakage, the external tip of the catheter was closed by heat.

For intravenous (iv) injection, another polyethylene catheter

(Portex, ID 0.58 mm, OD 0.96 mm) filled with physiological

heparinized saline (40 UI/ml) was inserted into the jugular

vein. A trocar was passed through the abdominal muscles at

1 cm from the upper end of the incision and tunneled

subcutaneously to emerge through the skin in the back of

the neck. The catheters were then passed through the trocar,

where a 1 cm-long piece of Silastic tubing (ID 0.30 mm;

OD 0.65 mm) was inserted around the external part of the

bladder catheter to prevent its slipping back under the skin of

the animal. The rats were allowed to recover from the

anesthesia, and the experiments were carried out 1 day after

catheter implantation.

2.3. Evaluation of urodynamic parameters

On the day of the experiment, the rats were placed in

modified Bollman’s cages that were large enough to

permit them to adopt a normal crouched posture but

narrow enough to prevent turning around. These cages

also enabled measurements of micturition volumes by

means of a fluid collector connected to a force isometric

transducer (Basile 7003 DY1).

The following schemes of experiments were performed

(see Fig. 1 for details):

1. After a stabilization period of 20 min, the free tip

of the bladder catheter was connected by a T-shaped tube

to a transducer (Statham P 23 XL or Marb type P82).

The physiological micturition was evaluated on water-

loaded rats (15 ml/rat by oral gavage) by recording three

to five cystometrograms.

2. On the same rats, cystometrograms were also obtained,

opening the other side of the T-shaped tube connected with

switched-off pumps.

3. In another group of water-loaded rats, after record-

ing the physiological micturition, pump-evoked cystomet-

rograms were obtained by connecting the T-shaped tube

alternatively to two different pumps to perform a con-

tinuous infusion into the bladder, at a constant rate of

0.1 ml/min.

Two different kinds of pumps were utilized: a peristaltic

pump (Gilson minipuls II), equipped with polyvinylchlo-

ride tube 0.38 mm ID, or an infusion pump (Harvard

model 22), equipped with plastic syringes of different

volumes (2.5–10–20–50 ml).

Pumps, pressure transducers, and bladder catheters were

connected to each other by polyethylene tube (Portex, ID

0.58 mm, OD 0.96 mm) of the same length filled with

saline, as exemplified in Fig. 1.

The urodynamic parameters evaluated from cystome-

trograms recorded on the polygraph (ALFOS WK-480R

with BM 614/2 preamplifier from Biomedia Mangoni)

were: micturition pressure (MP), micturition time (MT),

and micturition volume (MV). Bladder volume capacity

(BVC) was evaluated with pump-evoked cystometro-

grams. MP (in mmHg) is defined as the maximal

intravesical pressure induced by contraction of the

detrusor during micturition. MV (in milliliters) is defined

as the urinated volume expelled in a single micturition.

MT (in second) is defined as the time elapsed between

the threshold pressure point and the return to basal

pressure after voiding. BVC (in milliliters) is defined

as the volume of saline infused into the bladder between

two micturitions.

2.4. Evaluation of the compliance of the systems

The total compliance (catheter + pump) of the system

was evaluated after clamping off flow on the animal

catheter and connecting alternatively the two (switched-

on) different pumps to the pressure transducer via the

T-shaped tube by using the pump catheter. Compliance

was determined for pressure increase between 0 and

100 mmHg.

C. Velasco et al. / Journal of Pharmacological and Toxicological Methods 45 (2001) 215–221216

2.5. Evaluation of mechanistically different drugs on the

bladder voiding cycle

To verify whether the system used in awake animals

might interfere with the effects of drugs, groups of rats were

treated iv with 0.3 mg/kg of prazosin or oxybutynin, as well

as with 3.0 mg/kg of naproxen. Matched vehicle-treated rats

were also evaluated. Cystometrograms were obtained by

infusing saline into the bladder at the constant rate of

0.1 ml/min by an infusion pump equipped with 50ml syringe

or a peristaltic pump using 0.38 mm (ID) tubing. Basal

BVC and MP values were evaluated as mean of two

complete and reproducible cystometrograms. Basal MV

was the mean of volumes collected in the same cystometro-

grams. At this point, drugs or vehicles were administered

intravenously by bolus injection, with concomitant continu-

ous infusion of the bladder. Changes in urodynamic param-

eters were evaluated as average of the second and third

cystometrogram after treatment. The same protocol was

applied to groups of rats in which natural fill was studied.

2.6. Drugs and chemicals

Oxybutynin HCl and prazosin HCl were purchased from

Sigma-Aldrich (Milano, Italy). Naproxen was from Record-

ati S.p.A., Milano. All the other substances were from

commercial sources.

2.7. Statistical analysis

Statistical significance of the differences in urodynamic

parameter values in conscious rats before and after drug

treatments was evaluated by Student’s t test for paired data.

Two-way ANOVA and Dunnett’s test was used to evaluate

the differences of cystometrographic parameters recorded

during physiological micturition and during pump-evoked

cystometry. To improve the degree of confidence, 1% level

of probability was always retained to distinguish two

different means.

3. Results

3.1. Comparison between natural and pump-evoked

cystometrograms

Urodynamic parameters (MP, MV, & MT) were eval-

uated in a group of rats after an oral water load to facilitate

natural micturition without bladder infusion. Cystometro-

grams were initially obtained without any connection to the

Fig. 1. Scheme showing equipment utilized to perform cystometry in unanesthetized rats. Saline was alternately delivered into the bladder through chronically

implanted catheter by two different pumps: a peristaltic pump or an infusion pump equipped with syringes of different volumes. Animals were relatively

restrained and located over a stainless steel funnel that emptied into a strain gauge-mounted cup. Bladder pressure was monitored by a transducer connected

with the rats and with one of the pumps via T-shaped connection tube. Outputs of transducer and strain gauge were simultaneously monitored on a polygraph.

The following schemes of experiments were performed: (a) physiological micturition was evaluated on water-loaded rats choking the catheter connecting

pumps. On the same rats, natural cystometrograms were also obtained connecting the T-shaped tube with switched-off pumps. Pump-evoked cystometrograms

were obtained connecting the T-shaped tube alternatively with the different pumps; (b) total compliance (catheter + pump) of the system was evaluated after

choke of flow on the animal catheter and connecting alternatively the two different pumps to the pressure transducer via the T-shaped tube by using the pump

catheter. Compliance was determined for pressure increase between 0 and 100 mmHg; (c) the effects of the different drugs tested were evaluated on pump-

evoked micturition filling the bladder alternatively with the peristaltic pump or the syringe pump connected with the T-shaped tube by the pump catheter.

C. Velasco et al. / Journal of Pharmacological and Toxicological Methods 45 (2001) 215–221 217

pumps (see Fig. 1), and the recorded values are summarized in

the Table 1 as physiological micturition (Table 1). On the

same animals, other cystometrograms were later recorded

after the connection of the switched-off pumps. In the case of

the infusion pump, different volume syringeswere also tested.

No statistically significant differences in MV and MT

were observed between physiological micturition (with no

pumps connected) to that obtained when the different pumps

(switched off) were connected into the system. In contrast,

MP was significantly reduced after connection with infusion

pump equipped with 50 ml and 20 ml syringes. MP values

recorded connecting the peristaltic pump were the same as

those recorded during physiological micturition.

In another group of orally water-loaded rats, physio-

logical micturition (no pumps connected, then followed by

bladder infusion using two different pumps) yielded no

significant differences in MV and MT (Table 1). MP values

recorded with the infusion pump equipped with 50 and 20 ml

volume syringes were not significantly different from those

during physiological micturition. In contrast, significantly

higher MP values were observed with syringes of 10 and

20 ml and also with the use of a peristaltic pump (Table 1).

3.2. Measurement of total (catheter + pump) compliance

The peristaltic pump fitted with 0.38 mm (ID) tube or

the infusion pump (fitted with different volume syringes)

were connected alternatively to the pressure transducer via

the T-shaped tube by using the same catheter and setting the

flow to 0.1 ml/min (1.67 ml/s). Initially the T-tube allowed

free outflow through the animal catheter (Fig. 1). A

pressure ramp was obtained by clamping off flow on the

animal catheter, and compliance was determined for pres-

sure increases between 0 and 100 mmHg. Under these

experimental conditions, the pressure increased as a linear

function of time according to the following equation (Ask

et al., 1977; Ask & Hok, 1990): P = F�t / C, where F is

the infusion flow, C is the compliance of the system and t

is the time. The slope of the pressure versus time plot i.e.,

the pressure rise rate represents therefore the ratio F/C.

The compliance values obtained with the infusion pump

varied from 1.7089 ml/mmHg with the 50 ml syringe to

0.0830 ml/mmHg with the 2.5 ml syringe. These values

correspond to pressure rise rates of about 1 mmHg/s by

using the 50 ml syringe to 20 mmHg/s with the 2.5 ml

syringe. The compliance of the system using the peristaltic

pump was 0.0123 ml/mmHg, corresponding to pressure rise

rate of about 136 mmHg/s. These data indicate that the

compliance of the system utilizing the infusion pump

equipped with a 50 ml volume syringe is typically about

100-fold lower than that utilizing the peristaltic pump

equipped with 0.38 mm (ID) tube.

On the other hand, when the peristaltic pump was

equipped with a 2.28 mm (ID) tube the compliance

evaluated as described above was 0.1412 ml/mmHg, cor-

responding to a pressure rise rate of about 11.8 mmHg/s.

This is similar to the value obtained with the infusion

pump equipped with 10 ml syringe (compliance = 0.1315 ml/mmHg and pressure rise = 12.7 mmHg/s).

As shown in Fig. 2, the different compliance values

obtained might explain the results of Table 1. In both the

experimental situations (switched-off or switched-on

pumps) the differences in MP values recorded during

physiological micturition and after the connection with the

pumps were linearly related to compliance values.

In a further experiment, cystometrographic recordings

performed on rats with bladder infused with the peristaltic

pump equipped with a tube of 2.28 mm (ID) gave a mean MP

value of 57.2 mmHg. This value was very similar to that

obtained during infusion with 10 ml syringe, having similar

compliance, confirming that the different MP values

recorded during pump-evoked micturition are related to the

compliance of the system and not only to the pump utilized.

3.3. Comparison of the effects of different drugs on BVC

and MP values obtained during physiological or

pump-evoked micturition

As far as the BVC is concerned, basal values recorded in

the different groups of animals were in the range from 0.4 to

0.8 ml, and no difference in these values was observed with

the different pumps or during physiological micturition

(Table 2). MV values were always similar to the BVC

values (data not shown).

Table 1

Comparison of micturition parameters measured in conscious rats

Infusion pump

Physiological micturition 50 ml 20 ml 10 ml 2.5 ml Peristaltic pump

A (n = 6) MP (mmHg) 21 ± 1.0 12 ± 1.1* 16 ± 1.6* 19 ± 2.0 18 ± 1.1 22 ± 1.5

MV (ml) 0.44 ± 0.08 0.42 ± 0.07 0.48 ± 0.14 0.46 ± 0.10 0.46 ± 0.09 0.41 ± 0.07

MT (s) 14 ± 1.8 14 ± 2.3 15 ± 2.3 13 ± 1.7 13 ± 1.8 13 ± 3.1

B (n = 9) MP (mmHg) 24 ± 4.2 19 ± 1.1 27 ± 2.4 51 ± 3.4* 66 ± 4.3* 87 ± 7.5*

MV (ml) 0.45 ± 0.08 0.46 ± 0.05 0.42 ± 0.09 0.46 ± 0.09 0.45 ± 0.07 0.37 ± 0.04

MT (s) 12 ± 1.3 13 ± 1.4 12 ± 1.2 12 ± 0.9 11 ± 0.7 11 ± 0.5

Parameters were measured on cystometrograms obtained from the same animals: (a) without connection to infusion pumps (physiological micturition), (b) after

connection to the pumps but with the pumps switched off (A), or (c) during pump-evoked cystometrograms (B). Data represent the mean values ± S.E.

* P < .01 versus physiological micturition values (two-way ANOVA and Dunnett’s t test).

C. Velasco et al. / Journal of Pharmacological and Toxicological Methods 45 (2001) 215–221218

In the vehicle-treated rats, no significant changes of BVC

were observed, either during natural micturition or when the

bladder was infused with the peristaltic or the infusion

pump. Prazosin and oxybutynin induced non-statistically

significant changes of BVC that were roughly of the same

magnitude in all kind of cystometrograms. Naproxen

induced a BVC increase of about 40% in water-loaded

animals and during pump-evoked micturition.

As expected, basal MP values were markedly different

when the two different pumps were utilized. Cystometro-

grams recorded with the infusion pump equipped with 50 ml

syringe gave basal MP values in the range 20–30 mmHg as

observed in the water-loaded groups of rats, whereas with

the peristaltic pump these values ranged 65–100 mmHg.

When the infusion pump was utilized, only oxybutynin

treatment induced a significant (but no more than 14%)

decrease of MP. When the peristaltic pump was used,

prazosin treatment did not changed MP, naproxen induced

a nonsignificant decrease of the parameter (about 20%),

and the effect of oxybutynin was much higher, reaching

55% decrease of MP. The drug-induced changes of MP

recorded on cystometrograms of water-loaded rats were

close to those observed in the groups infused with the

peristaltic pump.

Table 2

Effect of iv administration of prazosin, oxybutynin, and naproxen on bladder volume capacity (BVC) and micturition pressure (MP) during physiological

micturition (water-loaded animals) and pump-evoked cystometry parameters in conscious rats

BVC or MV (ml) MP (mmHg)

Treatments (mg/kg iv) No. rats Before After % change Before After % change

Physiological micturition Vehicle 5 0.60 ± 0.12 0.66 ± 0.14 10.0 23 ± 2.3 22 ± 2.2 � 4.3

Prazosin (0.3) 5 0.76 ± 0.08 0.84 ± 0.12 10.5 23 ± 2.5 21 ± 1.3 � 8.7

Oxybutynin (0.3) 5 0.72 ± 0.13 0.70 ± 0.11 � 2.8 18 ± 3.1 11 ± 2.8* � 38.9

Naproxen (3.0) 7 0.66 ± 0.10 0.91 ± 0.18* 37.9 25 ± 3.3 25 ± 3.3 0

Infusion pump Vehicle 9 0.44 ± 0.03 0.43 ± 0.05 � 2.3 22 ± 0.8 23 ± 1.0 4.5

Prazosin (0.3) 9 0.70 ± 0.11 0.76 ± 0.21 8.6 25 ± 1.8 21 ± 1.8 � 16.0

Oxybutynin (0.3) 8 0.51 ± 0.08 0.40 ± 0.04 � 21.6 21 ± 1.9 18 ± 1.9* � 14.3

Naproxen (3.0) 9 0.51 ± 0.07 0.71 ± 0.10* 39.2 23 ± 1.4 22 ± 1.5 � 4.3

Peristaltic pump Vehicle 5 0.54 ± 0.12 0.55 ± 0.15 1.9 91 ± 12.5 85 ± 10.4 � 6.6

Prazosin (0.3) 8 0.71 ± 0.19 0.73 ± 0.16 2.8 79 ± 9.2 80 ± 9.4 1.3

Oxybutynin (0.3) 10 0.51 ± 0.07 0.48 ± 0.09 � 5.9 100 ± 10.3 45 ± 4.9* � 55.0

Naproxen (3.0) 6 0.54 ± 0.11 0.71 ± 0.11* 31.5 110 ± 11.1 89 ± 8.5 � 19.1

Bladder infusion was performed with the infusion pump equipped with a 50 ml syringe or with the peristaltic pump equipped with 0.38 mm (ID) tube. Data

represent the mean values ± S.E. of BVC and MP and the % changes versus basal values.

* P < .01 versus basal values (Student’s t test for paired data).

Fig. 2. (a) Correlation between the differences of MP values (4 mmHg) recorded during physiological micturition minus the values in the same animals

recorded after connection with switched-off pumps (data from Table 1A), and the compliance of the pump + catheter systems. Correlation coefficient = .9737;

P < .01. (b) Correlation between compliance of the pump + catheter systems and the difference between the observed MP values recorded after connection with

the switched-on pumps and the MP values recorded during ‘‘physiological micturition’’ (data from Table 1B). Correlation coefficient = .9763; P < .01.

C. Velasco et al. / Journal of Pharmacological and Toxicological Methods 45 (2001) 215–221 219

4. Discussion

Cystometry is a widely used in vivo method for quant-

itative studies on physiopharmacology of micturition in

several animal species (Peterson et al., 1989, 1990; Sjogren,

1976; Nishizawa et al., 1989; Blok et al., 1985; Klevmark,

1974; Shoukry & Ghonicm, 1992; Yaksh et al., 1986;

Maggi et al., 1986a, 1986b, 1986c), as well as to evaluate

changes in urodynamic parameters associated with urinary

incontinence in humans (Abrams et al., 1988).

During cystometry in animals, continuous filling of

bladder is obtained by an intravesical catheter connected

to a delivery system, which pumps saline into the bladder at

constant rate. Usually, a peristaltic or an infusion pump is

used, simultaneously filling the bladder of four to eight

animals with saline continuously delivered to the bladder

also during the micturition.

A literature review of urodynamic parameters, especially

regarding micturition pressure, revealed remarkable diffe-

rences (Durant & Yaksh, 1988; Conte et al., 1988; Guarneri

et al., 1991; Yamamoto et al., 1995; Ishizuka et al., 1997;

Persson et al., 1998; Chai et al., 1999). Even under similar

experimental conditions micturition pressures between

about 40 and 90 cm H2O have been reported (Persson

et al., 1998; Ishizuka et al., 1997; Igawa et al., 1993).

We have examined, therefore, in the same conscious

animals, urodynamic parameters, from cystometrograms

obtained during spontaneous voiding after an oral water

load, and pump-evoked micturition, using two different kind

of pumps.

No significant differences were seen in MV and MT

recorded during natural voiding cycle after connection with

switched-off pump or during pump-evoked micturition.

In contrast, MP recorded when the switched-off infusion

pump, equipped with 50 and 20 ml syringes, was utilized was

significantly lower than that recorded during physiological

micturition. The hydrostatic pressure exerted by the bladder

duringcontractionmaybeconsideredconstant.Whenthe50ml

syringe is connected, the pressure rise speed of the system is

about 1 mmHg/s. Taking into account that micturition lasted

13–14 s, nomore than 13–14mmHgcould be recorded by the

system.After connection of the 20ml syringe, the rise speed of

pressure is about 4 mmHg/s. This could allow the system to

reach the same pressure as during physiological micturition.

The lower values of MP reached with both of these syringes

might due to the larger area (syringe diameter) on which the

stiffness of the bladder is exerted during contraction.

During pump-evoked cystometrograms, MP showed

increasing values, moving from the 50 ml infusion pump to

infusion pumps with lower volumes (up to a 3-fold increase

with 2.5 ml volume syringe) and to the peristaltic pump (up to

a 4-fold increase). When the bladder pressure reaches a

threshold pressure, the urethral sphincter opens and, theoret-

ically, detrusor pressure could remain at the level of threshold

pressure during micturition. However, the continuous deliv-

ery of fluid to the bladder by the infusion pumps alters bladder

pressure. The degree of pressure detected by the transducer

could be again related to the surface of the system (syringes or

tube diameter) and speed in recording the pressure rise.

Therefore, the similarity between MP values recorded during

pump-evoked cystometrograms using the infusion pump

equipped with 50 and 20 ml volume syringes and those

recorded during physiological micturition (Table 1), as well

as the higher values recorded with low volume syringes and

peristaltic pump, were all influenced by system artefacts.

Finally the differences in the MP values recorded after

connection with the different pumps and the values during

physiological micturition were found to be a function of the

different compliance of the systems, and not dependent

upon the pump.

The effects of prazosin, oxybutynin, and naproxen on

BVC evaluated by performing cystometry with peristaltic

and infusion pump, as well as in water-loaded animals, were

almost the same. Prazosin and oxybutynin did not signifi-

cantly change BVC, and naproxen was found to increase

BVC (about 40% in all the experimental situations).

Using the infusion pump equipped with 50 ml volume

syringe, oxybutynin reduced slightly (about 15%) but

significantly bladder contractility, whereas naproxen was

inactive. On the contrary, when higher MP values are

reached by infusing the bladder with the peristaltic pump,

the effect of oxybutynin is highlighted and naproxen also

affected, although not significantly, the parameter, whereas

prazosin remained inactive.

It is noteworthy that although obtained in an experimental

condition in which the recorded MP values can be considered

an artefact, the results obtained with peristaltic pump are in

agreement with those obtained during physiological micturi-

tion in water-loaded animals. Water-loaded animals, how-

ever, cannot be considered a good screening model to

evaluate the effects of compounds on micturition. After water

load, a series of voiding cycles sufficiently close to allow the

evaluation of basal values and the effect of a treatment can be

obtained only considering the protocol utilized in the present

paper (IV treatment and evaluation of the effect considering

the second and third cystometrogram after treatment). Owing

to the fact that after less than 1 h diuresis become normal, a

time course of the effects after an iv administration or after

oral administration of a compound is not feasible.

In conclusion, the present findings indicate that only the

effects on cystometrographic parameters (expressed as per-

cent changes) obtained during pump-evoked micturition

with a high compliance system (peristaltic pump) can be

considered equivalent to those observed during physio-

logical micturition.

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