its impact on the quality of life is similar to that of hypertension and diabetes and is more serious than that of depression . for these reasons
although oab patients show many variable symptoms , the central symptom of oab is urgency , which is closely related to detrusor overactivity ( do ) during the filling phase in cystometry [ 5 - 7 ] .
it was reported that 83% of patients with do showed urgency , and 64% of patient with urgency showed do .
thus , it is important to observe do objectively in clinical and research studies of oab .
recently , we investigated nonvoiding contractions in awake animal models by simultaneous registrations of intravesical pressure ( ivp ) and intraabdominal pressure ( iap ) .
anticholinergic therapy is the first - line treatment option for patients with oab , owing to the parasympathetic activation of the detrusor contractions .
anticholinergic drugs suppress the involuntary detrusor contractions through competition with acetylcholine for the muscarinic receptors during both the storage and the voiding phase .
however , it is known experimentally that these drugs have no effects on voiding contraction and residual volume , because the amount of acetylcholine released during the voiding phase is much more than those of anticholinergic drugs . however , in clinical studies , some patients complained of straining voiding , increased residual volume , and sometimes acute urinary retention .
this suggests that anticholinergics may have an influence on detrusor contractions during the voiding phase . up to now
, there has been no experimental evaluation of the effect of anticholinergics during the voiding phase in awake rats by simultaneous registrations of ivp and iap .
the objective of this study was therefore to perform simultaneous registrations of ivp and iap to evaluate the effects of propiverine 1 and 3 mg / kg on do during the filling phase and on abdominal straining during the voiding phase in awake rats with intravesical prostaglandin e2(pge2 ) instillation .
a total of 22 sprague - dawley ( sd ) female rats weighing between 200 and 250 g were used in this study .
all procedures were performed in accordance with the guide for the care and use of laboratory animals of the national institutes of health and were approved by the inha - university animal ethics committee .
the rats were maintained under standard laboratory conditions with a 12:12 h light : dark cycle and with free access to food pellets and tap water .
simultaneous ivp and iap were continuously recorded during bladder filing and emptying as described previously . in brief , sd rats were anesthetized with ketamine ( ketamine ; yuhan corp , seoul , korea ; 75 mg / kg intraperitoneally ) and xylazine ( rompun ; bayer korea corp , korea ; 15 mg / kg intraperitoneally ) . through a low abdominal incision , a polyethylene catheter ( pe-50 ; becton dickinson , parsippany , usa ) with a cuff was inserted into the dome of the bladder and was held in place with a purse - string suture . to record iap , an abdominal balloon ( latex ; daewoo medical , incheon , korea ) around the cuff of a catheter tip
was placed 1 cm proximal to the bladder along the catheter to the bladder and was attached with a silk tie to the catheter . a catheter ( pe-10 ; becton dickinson )
these catheters were tunneled subcutaneously and anchored to the skin of the back with a silk ligature .
cystometry was performed 3 days after implantation of the catheters in unanesthetized , unrestrained rats in metabolic cages .
the indwelling catheter to the bladder was connected to a two - way valve that was connected via a t - tube to a pressure transducer ( research grade blood pressure transducer ; harvard apparatus , holliston , usa ) and a microinjection pump ( phd22/2,000 pump ; harvard apparatus ) .
another catheter connected to an air - free abdominal balloon was connected to another pressure transducer to record the iap .
micturition volumes were recorded by means of a fluid collector connected to a force displacement transducer ( research grade isometric transducer ; harvard apparatus ) .
room - temperature saline was infused into the bladder continuously at a rate of 10 ml / h .
ivp , iap , and micturition volumes were recorded continuously with acq knowledge 3.8.1 software and an mp150 data acquisition system ( biopac systems , goleta , usa ) at a sampling rate of 100 hz .
iap was defined as the recorded balloon pressure corrected by subtracting the lowest balloon pressure in each voiding cycle , which is comparable to zeroing in human cystometry .
the ivp rises during the filling phase ( ivprs ) were defined as increments of ivp that exceeded 2 cmh2o from baseline , which was interpreted as abdominal straining if occurring with simultaneous similar changes in iap , or as do if occurring without simultaneous similar changes in iap .
the following conventional urodynamic pressure - volume parameters were investigated : micturition pressure ( mp , maximum bladder pressure during micturition ) , basal pressure ( bp , the lowest bladder pressure during filling ) , threshold pressure ( tp , bladder pressure immediately before micturition ) , bladder capacity ( bc , residual volume at the most recent previous micturition plus the volume of infused saline at micturition ) , micturition volume ( mv , volume of expelled urine ) , residual volume ( rv , bladder capacity minus micturition volume ) , and micturition interval ( mi , time between micturition events ) .
the following do - related parameters during the filling phase were observed : time of filling phase ( interval between the end of a micturition and the point immediately before the next micturition ) , total number of do , frequency of do per minute , and increased amplitude of do as ivp . in all groups , a period of about 30 - 60-min micturition cycles was observed and the values from reproducible micturition cycles were used for evaluation .
stock solutions ( 0.01 m ) of pge2 ( sigma chemical co. , st louis , usa ) were made in absolute ethanol and were then diluted to 50 m in saline just before use .
propiverine 1 or 3 mg / kg was infused into the femoral artery after the baseline cystometry .
the rats were randomly allocated to the following four treatment groups after control cystometries with saline : 1 ) intraarterial propiverine 1 mg / kg only ( n=6 ) , 2 ) intravesical pge2 only ( n=6 ) , 3 ) intravesical pge2 and intraarterial propiverine 1 mg / kg ( n=4 ) , or 4 ) intravesical pge2 and intraarterial propiverine 3 mg / kg ( n=6 ) .
normal distributions were confirmed by use of sigmastat 2.0 ( spss inc , chicago , usa ) .
a total of 22 sprague - dawley ( sd ) female rats weighing between 200 and 250 g were used in this study .
all procedures were performed in accordance with the guide for the care and use of laboratory animals of the national institutes of health and were approved by the inha - university animal ethics committee .
the rats were maintained under standard laboratory conditions with a 12:12 h light : dark cycle and with free access to food pellets and tap water .
simultaneous ivp and iap were continuously recorded during bladder filing and emptying as described previously .
in brief , sd rats were anesthetized with ketamine ( ketamine ; yuhan corp , seoul , korea ; 75 mg / kg intraperitoneally ) and xylazine ( rompun ; bayer korea corp , korea ; 15 mg / kg intraperitoneally ) . through a low abdominal incision ,
a polyethylene catheter ( pe-50 ; becton dickinson , parsippany , usa ) with a cuff was inserted into the dome of the bladder and was held in place with a purse - string suture .
to record iap , an abdominal balloon ( latex ; daewoo medical , incheon , korea ) around the cuff of a catheter tip was placed 1 cm proximal to the bladder along the catheter to the bladder and was attached with a silk tie to the catheter .
these catheters were tunneled subcutaneously and anchored to the skin of the back with a silk ligature .
cystometry was performed 3 days after implantation of the catheters in unanesthetized , unrestrained rats in metabolic cages .
the indwelling catheter to the bladder was connected to a two - way valve that was connected via a t - tube to a pressure transducer ( research grade blood pressure transducer ; harvard apparatus , holliston , usa ) and a microinjection pump ( phd22/2,000 pump ; harvard apparatus ) .
another catheter connected to an air - free abdominal balloon was connected to another pressure transducer to record the iap .
micturition volumes were recorded by means of a fluid collector connected to a force displacement transducer ( research grade isometric transducer ; harvard apparatus ) .
room - temperature saline was infused into the bladder continuously at a rate of 10 ml / h .
ivp , iap , and micturition volumes were recorded continuously with acq knowledge 3.8.1 software and an mp150 data acquisition system ( biopac systems , goleta , usa ) at a sampling rate of 100 hz .
iap was defined as the recorded balloon pressure corrected by subtracting the lowest balloon pressure in each voiding cycle , which is comparable to zeroing in human cystometry .
the ivp rises during the filling phase ( ivprs ) were defined as increments of ivp that exceeded 2 cmh2o from baseline , which was interpreted as abdominal straining if occurring with simultaneous similar changes in iap , or as do if occurring without simultaneous similar changes in iap .
the following conventional urodynamic pressure - volume parameters were investigated : micturition pressure ( mp , maximum bladder pressure during micturition ) , basal pressure ( bp , the lowest bladder pressure during filling ) , threshold pressure ( tp , bladder pressure immediately before micturition ) , bladder capacity ( bc , residual volume at the most recent previous micturition plus the volume of infused saline at micturition ) , micturition volume ( mv , volume of expelled urine ) , residual volume ( rv , bladder capacity minus micturition volume ) , and micturition interval ( mi , time between micturition events ) .
the following do - related parameters during the filling phase were observed : time of filling phase ( interval between the end of a micturition and the point immediately before the next micturition ) , total number of do , frequency of do per minute , and increased amplitude of do as ivp . in all groups , a period of about 30 - 60-min micturition cycles was observed and the values from reproducible micturition cycles were used for evaluation .
stock solutions ( 0.01 m ) of pge2 ( sigma chemical co. , st louis , usa ) were made in absolute ethanol and were then diluted to 50 m in saline just before use .
propiverine 1 or 3 mg / kg was infused into the femoral artery after the baseline cystometry .
the rats were randomly allocated to the following four treatment groups after control cystometries with saline : 1 ) intraarterial propiverine 1 mg / kg only ( n=6 ) , 2 ) intravesical pge2 only ( n=6 ) , 3 ) intravesical pge2 and intraarterial propiverine 1 mg / kg ( n=4 ) , or 4 ) intravesical pge2 and intraarterial propiverine 3 mg / kg ( n=6 ) .
normal distributions were confirmed by use of sigmastat 2.0 ( spss inc , chicago , usa ) .
there were no significance differences in pressure- or volume - related parameters before and after the administration of propiverine 1 mg / kg in normal rats .
thus , we showed that propiverine 1 mg / kg had no effect on pressure - volume parameters in normal rats ( table 1 ) .
the rats showed no changes in iap recorded at the point of bp , tp , or mp after intravesical instillation of pge2 50 m compared with baseline cystometries .
the rats administered intravesical pge2 50 m and simultaneous intraarterial propiverine 1 mg / kg also showed no changes in iap at those three points compared with baseline and pge2-instilled cystometries . the rats administered intravesical pge2
50 m and simultaneous intraarterial propiverine 3 mg / kg showed increased iap at mp ( p<0.05 ) only compared with baseline cystometries ( table 2 ) .
recorded as ivp or dp , oab was successfully induced in rats by intravesical instillation of pge2 , which resulted in increases in bp , tp , and mp compared with baseline cystometries ( p<0.01 , p<0.05 , and p<0.01 , respectively ) .
the rats administered pge2 and propiverine 1 mg / kg showed decreased bp by ivp ( p<0.01 ) , compared with pge2-instilled cystometries , and decreased mp by ivp and dp ( p<0.01 , p<0.01 ) , compared with baseline cystometries .
the rats administered pge2 and propiverine 3 mg / kg showed decreased bp by ivp and dp ( p<0.01 and p<0.01 , respectively ) , compared with pge2-instilled cystometries , and decreased mp by ivp and dp ( p<0.01 and p<0.01 , respectively ) , compared with baseline cystometries ( table 3 ) .
oab was successfully induced in rats by intravesical instillation of pge2 , which resulted in decreases in bc , vv , and mi without changes in rv , compared with baseline cystometries ( p<0.05 , p<0.05 , and p<0.05 , respectively ) .
the rats administered pge2 and propiverine 1 or 3 mg / kg showed no change in volume - related parameters compared with baseline or pge2-instilled cystometries ( table 4 ) .
after intravesical instillations of pge2 , do of 2.00.42 /min was observed ( p<0.01 ) compared with baseline cystometries .
however , do was not significantly decreased after propiverine injection in rats with intravesical pge2 instillation ( table 5 ) .
there were no significance differences in pressure- or volume - related parameters before and after the administration of propiverine 1 mg / kg in normal rats .
thus , we showed that propiverine 1 mg / kg had no effect on pressure - volume parameters in normal rats ( table 1 ) .
the rats showed no changes in iap recorded at the point of bp , tp , or mp after intravesical instillation of pge2 50 m compared with baseline cystometries .
the rats administered intravesical pge2 50 m and simultaneous intraarterial propiverine 1 mg / kg also showed no changes in iap at those three points compared with baseline and pge2-instilled cystometries . the rats administered intravesical pge2
50 m and simultaneous intraarterial propiverine 3 mg / kg showed increased iap at mp ( p<0.05 ) only compared with baseline cystometries ( table 2 ) .
recorded as ivp or dp , oab was successfully induced in rats by intravesical instillation of pge2 , which resulted in increases in bp , tp , and mp compared with baseline cystometries ( p<0.01 , p<0.05 , and p<0.01 , respectively ) .
the rats administered pge2 and propiverine 1 mg / kg showed decreased bp by ivp ( p<0.01 ) , compared with pge2-instilled cystometries , and decreased mp by ivp and dp ( p<0.01 , p<0.01 ) , compared with baseline cystometries .
the rats administered pge2 and propiverine 3 mg / kg showed decreased bp by ivp and dp ( p<0.01 and p<0.01 , respectively ) , compared with pge2-instilled cystometries , and decreased mp by ivp and dp ( p<0.01 and p<0.01 , respectively ) , compared with baseline cystometries ( table 3 ) .
oab was successfully induced in rats by intravesical instillation of pge2 , which resulted in decreases in bc , vv , and mi without changes in rv , compared with baseline cystometries ( p<0.05 , p<0.05 , and p<0.05 , respectively ) .
the rats administered pge2 and propiverine 1 or 3 mg / kg showed no change in volume - related parameters compared with baseline or pge2-instilled cystometries ( table 4 ) .
after intravesical instillations of pge2 , do of 2.00.42 /min was observed ( p<0.01 ) compared with baseline cystometries .
however , do was not significantly decreased after propiverine injection in rats with intravesical pge2 instillation ( table 5 ) .
oab is known to include various different pathophysiologic mechanisms . recently , among those mechanisms , special attention has been given to the sensory and afferent mechanisms .
research on the new generation of oab drugs is focused on the inhibition of afferent firing before the generation of a detrusor contraction during the filling phase , whereas the present anticholinergic drugs suppress the afferent firing after the generation of do .
the intravesical pge2 instillation method , one of the oab models , induces do by the indirect activation of afferent nerves in the bladder as well as the direct activation of detrusor muscle .
when the bladder is injured or stimulated , the prostanoids activate capsaicin - sensitive afferents .
then , tachykinins are released from the afferents , which lower the threshold for afferent firing , and , finally , stimulate the detrusor to induce overactivity [ 15 - 17 ] .
experimentally , the tachykinins initiate a micturition reflex by stimulating nk1,nk2 receptors , and intravesical prostanoids can induce do in cystometry in vivo . in our study ,
the cystometric features of oab patients were successfully generated by intravesical prostanoids in rats , which showed increased bp , tp , and mp and decreased bc , mv , and mi . the detrusor contraction is mainly caused by stimulating muscarinic receptors , and the m3 subtype in particular is believed to have the most major action for detrusor contraction . in general , anticholinergic drugs inhibit involuntary detrusor contraction during the storage phase , but they do not significantly affect contractions during the voiding phase , because the quantity of acetylcholine is several dozen times higher than that during the storage phase . in the present study , propiverine significantly decreased bp only , the basal tension of the bladder , in the intravesical pge2 group and showed no effect on mp , bc , vv , or mi .
this might be partly related to the accumulation of continuously infused intravesical prostanoids in this rat model .
however , we know that there were some effects of the propiverine , because this group showed no differences in pressure or volume parameters compared with the control group , unlike the intravesical pge2 only instillation group .
if we look at the effects by different concentrations of propiverine on the pge2-instilled state of rat bladder , propiverine 3 mg / kg decreased bp by dp but not by ivp , whereas propiverine 1 mg / kg showed no decrease in bp by either ivp or dp .
this suggests that the higher dose of propiverine decreased the basal tension of the detrusor .
this is not in accordance with previously reported studies , in which the investigators did not observe any difference in bp , but only in mp .
our study is the first observation of propiverine effects in the animal model of prostanoid - induced oab .
the volume parameters were significantly decreased after pge2 instillation and increased to the levels of control rats after propiverine injection .
this suggests that propiverine inhibits the effects of pge2 , regardless of concentrations of propiverine .
also , do was not seen in control rats , but was shown in pge2-instilled animals .
the propiverine showed no effects on the frequency or pressure of do , which is in contrast with the conventional concept for anticholinergic drugs .
we conclude that the propiverine did not have any effect on the do in animal models of prostanoid - induced oab .
this is supported by the fact that some anticholinergic drugs for oab show no effects in some patients .
the side effects of anticholinergic drugs are well known and described through clinical and basic research . however , straining voiding , which is a complaint from some people taking anticholinergic medication , has not been well investigated in previous reports .
this symptom is a straining of the abdomen to void because of feeling difficulty in voiding or a sense of residual urine and could be related to urinary retention . in the present study , we checked the grade of straining during the voiding phase by using our models .
there were no differences in abdominal straining on mp between the control rats and the pge2-induced oab model .
straining was not increased after infusion of propiverine 1 mg / kg but was significantly increased after infusion of propiverine 3 mg / kg .
this suggests that in the oab model , taking a higher dose of anticholinergic drugs showed more straining during voiding .
this finding may be associated with acute urinary retention and dysuria , which are among the complications of anticholinergic drugs .
according to the study by elisa et al , which was based on patient information collected by general practitioners in the united kingdom , increased risk of voiding difficulty and acute urinary retention were observed in patients administered anticholinergic drugs , and these patients should be closely monitored during the first 30 days of treatment for signs or symptoms of urinary retention .
therefore , the presence and significance of these symptoms need to be taken into consideration when elucidating the side effects of anticholinergic drugs in future research .
propiverine improved pressure and volume - related parameters in an oab model induced by intravesical pge2 , showing that propiverine can inhibit the activation of bladder contractions and possibly providing experimental evidence for decreased urgency symptoms after administration of propiverine in patients . furthermore , propiverine also decreased the do frequency .
however , a higher concentration of propiverine induced straining voiding , suggesting the need for clinical studies of the side effects of anticholinergic drugs , which are still unknown .
 purposewe investigated the effect of propiverine on cystometric parameters based on intraabdominal pressure ( iap ) in awake rats in an overactive bladder ( oab ) model induced by intravesical instillation of prostaglandin e2 ( pge2).materials and methodstwenty - two female sprague - dawley rats were used . 
 polyethylene catheters were implanted into the bladder to record the intravesical pressure ( ivp ) and into the femoral artery to administer medication . 
 a balloon - fitted catheter was positioned in the abdominal cavity to record the iap . 
 awake cystometries were performed before and after intraarterial administration of propiverine 1 mg / kg ( n=6 ) , intravesical administration of 50 m pge2 only ( n=6 ) , or intravesical pge2 plus 1 mg / kg ( n=4 ) or 3 mg / kg ( n=6 ) of intraarterial propiverine . 
 cystometric pressure and volume parameters and variables related to detrusor overactivity ( do ) were investigated.resultsrats administered intravesical pge2 showed increased pressure parameters and decreased volume parameters comparable to the do model , which was effectively prevented by propiverine ( 1 or 3 mg / kg ) . 
 typical do shown during the filling phase was decreased by intraarterial propiverine ( 3 mg / kg ) injection . 
 after propiverine ( 3 mg / kg ) injection , iap was increased at the time of micturition pressure with or without threshold pressure ( p<0.05 , p<0.01 ) depending on the dose administered.conclusionspropiverine improved pressure- and volume - related parameters in an oab model . 
 furthermore , it also decreased the frequency of do . 
 however , higher concentrations of propiverine induced straining voiding . 
INTRODUCTION
MATERIALS AND METHODS
1. Animals
2. Bladder, intraabdominal, and intraarterial catheter implantation
3. Cystometric investigations
4. Administration of drug
5. Statistical analysis
RESULTS
1. Effects of propiverine 1 mg/kg on normal rats
2. Effects of PGE
3. Effects of PGE
4. Effects of PGE
5. Effects of PGE
DISCUSSION
CONCLUSIONS