Comparison of the urethral properties of the female guinea pig and rat

Analysis of adaptive molecular mechanisms in response to low salinity in antennal gland of mud crab, Scylla paramamosain

As an important marine aquaculture species, the mud crab (Scylla paramamosain) is a good candidate for studying the osmoregulatory mechanism of crustaceans. While previous studies have focused on the osmoregulatory function of the gills, this study aims to explore the osmoregulatory function of the antennal glands. By the comparative transcriptomic analysis, we found the pathways of ion regulation including "proximal tubule bicarbonate reclamation" and "mineral absorption" were activated in the antennal glands of the crabs long-term dwelling in low salinity. The enhanced ionic reabsorption was associated with up-regulated ion transport genes such as NKA, CA-c, VPA, and NHE, and with energy metabolism genes such as MDH, SLC25, and PEPCK. The upregulation of NKA and CA-c was also verified by the increased enzyme activity. The lowered osmolality and ion concentration of the hemolymph and the enlarged labyrinth lumen and hemolymph capillary inside the antennal glands indicated the infiltration of external water and the responsively increase of urine excretion, which explained the requirement of enhanced ionic reabsorption. To further confirm these findings, we examined the change of gene expression, enzyme activity, internal ion concentration, and external ion concentration during a 96 h low salinity challenge with seven intervals. The results were basically consistent with the results as shown in the long-term low salinity adaptation. The present study provides valuable information on the osmoregulatory function of the antennal glands of S. paramamosain. The implication of this study in marine aquaculture is that it provides valuable information on the osmoregulatory mechanism of mud crabs, which can be used to improve their culture conditions and enhance their tolerance to salinity stress. The identified genes and pathways involved in osmoregulation can also be potential targets for genetic selection and breeding programs to develop more resilient mud crab strains for aquaculture.

Evaluation of the potentiating effects of antidepressants on the contractile response to noradrenaline in guinea pig urethra smooth muscles

We investigated the potential augmenting effects of 19 clinically available antidepressants on noradrenaline (NA)-induced contractions in guinea pig urethra smooth muscle (USM). Concentration-response curves for NA-induced contractions in guinea pig USM strips were obtained in the absence or presence of selected antidepressants. Desipramine, an active metabolite of imipramine, produced a contraction and potentiated NA-induced contraction at the distal urethra without affecting the proximal urethra. Further, nortriptyline and amoxapine, tricyclic antidepressants, produced a contraction and potentiated NA-induced contraction at the distal urethra. NA-induced contraction was unaffected or reduced by imipramine, clomipramine, trimipramine, and amitriptyline at the proximal and distal urethra. Maprotiline, a tetracyclic antidepressant, potentiated NA-induced contraction at the distal urethra. NA-induced contraction was unaffected by mianserin at the proximal and distal urethra. Paroxetine, a selective serotonin reuptake inhibitor (SSRI), potentiated NA-induced contraction at the distal urethra, while NA-induced contraction was unaffected by fluvoxamine, sertraline, and escitalopram at the proximal and distal urethra. Milnacipran, a serotonin-noradrenaline reuptake inhibitor (SNRI), potentiated NA-induced contraction at the proximal and distal urethra, whereas duloxetine potentiated it at the distal urethra. Mirtazapine slightly inhibited NA-induced contraction at the distal urethra. Aripiprazole and sulpiride did not affect NA-induced contractions at the proximal nor distal urethra. Trazodone inhibited NA-induced contraction at both urethras. Desipramine, nortriptyline, amoxapine, maprotiline, paroxetine, milnacipran, and duloxetine likely induce urinary disturbance by increasing urethral resistance and augmenting NA-induced contraction, which should be carefully considered when delivering guidance for drug administration to patients.

Characterization of mouse neuro-urological dynamics in a novel decerebrate arterially perfused mouse (DAPM) preparation

AIM

To develop the decerebrate arterially perfused mouse (DAPM) preparation, a novel voiding model of the lower urinary tract (LUT) that enables in vitro-like access with in vivo-like neural connectivity.

METHODS

Adult male mice were decerebrated and arterially perfused with a carbogenated, Ringer's solution to establish the DAPM. To allow distinction between central and peripheral actions of interventions, experiments were conducted in both the DAPM and in a "pithed" DAPM which has no brainstem or spinal cord control.

RESULTS

Functional micturition cycles were observed in response to bladder filling. During each void, the bladder showed strong contractions and the external urethral sphincter (EUS) showed bursting activity. Both the frequency and amplitude of non-voiding contractions (NVCs) in DAPM and putative micromotions (pMM) in pithed DAPM increased with bladder filling. Vasopressin (>400 pM) caused dyssynergy of the LUT resulting in retention in DAPM as it increased tonic EUS activity and basal bladder pressure in a dose-dependent manner (basal pressure increase also noted in pithed DAPM). Both neuromuscular blockade (vecuronium) and autonomic ganglion blockade (hexamethonium), initially caused incomplete voiding, and both drugs eventually stopped voiding in DAPM. Intravesical acetic acid (0.2%) decreased the micturition interval. Recordings from the pelvic nerve in the pithed DAPM showed bladder distention-induced activity in the non-noxious range which was associated with pMM.

CONCLUSIONS

This study demonstrates the utility of the DAPM which allows a detailed characterization of LUT function in mice.

A Method for Recording Urethral Pressure Profiles in Female Rats

Aims

Urethral pressure profile (UPP) and leak-point pressure (LPP) measurements as well as external urethral sphincter (EUS) electromyography (EMG) and videourodynamic analyses are the primary methods for evaluating urethral function in humans. However, UPP recording in female rats, a widely used animal model, is challenging due to their small body sizes. This study reports a novel method for recording UPP in female rats.

Materials and Methods

Seventeen anesthetized female rats were studied. LPP data for 14 rats were included. The other 3 rats were excluded because of death or abnormal urogenital organs. UPP curves were recorded using a modified water-perfusion catheter system, with the lateral hole facing the 3-, 6-, 9-, and 12-o’clock positions in a randomized sequence. LPP, functional urethral length (FUL) and maximum urethral closure pressure (MUCP) were analyzed.

Results

The mean LPP was 64.39 ± 20.29 cm H₂O. The mean FUL and MUCP values at the 3-, 6-, 9-, and 12-o’clock positions were 12.90 ± 1.20, 16.70 ± 1.95, 13.90 ± 2.42, and 11.60 ± 0.97 mm, respectively, and 38.70 ± 11.85, 33.90 ± 11.82, 37.40 ± 11.95, and 71.90 ± 23.01 cm H₂O, respectively. The FUL at the 6-o’clock position and MUCP at the 12-o’clock position were significantly greater than those at the other 3 positions. The FUL and MUCP of repeated UPP recordings were not significantly different than those of the first recordings.

Conclusions

UPP recording using a modified method based on a water-perfusion catheter system is feasible and replicable in female rats. It produces UPP curves that sensitively and appreciably reflect detailed pressure changes at different points within the urethra and thus provides opportunity to evaluate urethral structures, especially the urethral sphincter, in detail. These results may enhance the utility of female rat models in research of urinary sphincter mechanisms.

Nitrergic relaxations and phenylephrine contractions are not compromised in isolated urethra in a rat model of diabetes

In vivo experiments in a diabetic rat model revealed compromised nitrergic urethral relaxations and increased sensitivity to adrenergic agonists. This study evaluated contractile and relaxation properties of urethral smooth muscle after streptozotocin (STZ)-induced diabetes, in vitro, with the aim of determining whether in vivo deficiencies are related to smooth muscle dysfunction. Urethral tissue was collected from adult female Sprague-Dawley rats naive, STZ-treated, vehicle-treated and sucrose-fed at 9-12 week post treatment. Strips from proximal, mid, and distal urethra were placed in tissue baths and stimulated using electric field stimulation (EFS) and pharmacological agents. nNOS staining was evaluated using immunohistochemistry. Phenylephrine (PE, 10μM) contracted all urethral strips with the highest amplitude in mid urethra, in all treatment groups. Likewise, EFS-induced relaxation amplitudes were larger and were observed more frequently in mid urethra. Relaxations were inhibited by the NOS inhibitor, L-NAME (1-100μM). Sodium nitroprusside (0.01-1μM), an NO donor, reversed PE-induced contractions. No statistical differences were observed between treatment groups with respect to any parameters. Qualitative immunohistochemistry showed no differences in the urethral nNOS innervation patterns across the treatment groups. In summary, nitrergic relaxations and adrenergic-induced contractions in the isolated diabetic rat urethra display similar properties to controls, suggesting no dysfunction on the nitrergic or alpha1 adrenergic receptor function in the smooth muscle. This further implies that compromised urethral relaxation and increased adrenergic agonist sensitivity observed in vivo in this model may be due to the disruption of neural signaling between the urethra and the spinal cord, or within the CNS.

Aclidinium bromide, a novel long-acting muscarinic antagonist for COPD with improved preclinical renal and urinary safety profile

AIMS

Aclidinium bromide is a novel, long-acting, inhaled muscarinic antagonist currently in registration phase for the treatment of chronic obstructive pulmonary disease. Since urinary difficulty and retention have been reported for anticholinergic agents such as tiotropium and ipratropium, it is important to examine the preclinical urinary and renal safety profile of aclidinium.

MAIN METHODS

The effect of aclidinium on urine and electrolyte excretion, renal function and voiding cystometry was analysed in conscious water-loaded Wistar rats (10-1000 μg/kg, s.c.), anaesthetised Beagle dogs (1000 μg/kg, i.v.) and anaesthetised guinea pigs (3-100μg/kg, intratracheally), respectively. Aclidinium plasma levels were determined in an independent study. Active comparators were tiotropium (all studies) and ipratropium (cystometry only).

KEY FINDINGS

Aclidinium 1000 μg/kg had no effect on urine excretion in rats, in contrast to tiotropium 100 μg/kg which significantly decreased this parameter (p<0.05). Aclidinium 1000 μg/kg also had no effect on renal function in Beagle dogs. In guinea pigs, aclidinium 3-100 μg/kg had no effect on urinary bladder function, whereas tiotropium and ipratropium 100 μg/kg decreased the peak micturition pressure (p<0.05), increased the volume of urine retained in the bladder (p<0.01) and showed a trend to decrease the volume of urine excreted.

SIGNIFICANCE

Aclidinium had no significant effect on urinary and renal function in the animal models studied. These results, together with the rapid plasma clearance of aclidinium reported previously, suggest a lower propensity to induce urinary retention in humans than tiotropium and ipratropium.

An exploration of the control of micturition using a novel in situ arterially perfused rat preparation

Our goal was to develop and refine a decerebrate arterially perfused rat (DAPR) preparation that allows the complete bladder filling and voiding cycle to be investigated without some of the restrictions inherent with in vivo experimentation [e.g., ease and speed of set up (30 min), control over the extracellular milieu and free of anesthetic agents]. Both spontaneous (naturalistic bladder filling from ureters) and evoked (in response to intravesical infusion) voids were routinely and reproducibly observed which had similar pressure characteristics. The DAPR allows the simultaneous measurement of bladder intra-luminal pressure, external urinary sphincter-electromyogram (EUS-EMG), pelvic afferent nerve activity, pudendal motor activity, and permits excellent visualization of the entire lower urinary tract, during typical rat filling and voiding responses. The voiding responses were modulated or eliminated by interventions at a number of levels including at the afferent terminal fields (intravesical capsaicin sensitization-desensitization), autonomic (ganglion blockade with hexamethonium), and somatic motor (vecuronium block of the EUS) outflow and required intact brainstem/hindbrain-spinal coordination (as demonstrated by sequential hindbrain transections). Both innocuous (e.g., perineal stimulation) and nociceptive (tail/paw pinch) somatic stimuli elicited an increase in EUS-EMG indicating intact sensory feedback loops. Spontaneous non-micturition contractions were observed between fluid infusions at a frequency and amplitude of 1.4 ± 0.9 per minute and 1.4 ± 0.3 mmHg, respectively and their amplitude increased when autonomic control was compromised. In conclusion, the DAPR is a tractable and useful model for the study of neural bladder control showing intact afferent signaling, spinal and hindbrain co-ordination and efferent control over the lower urinary tract end organs and can be extended to study bladder pathologies and trial novel treatments.

Role of p75NTR in female rat urinary bladder with cyclophosphamide-induced cystitis

Previous studies demonstrated changes in urinary bladder neurotrophin content and upregulation of neurotrophin receptors, TrkA and the p75 neurotrophin receptor (p75(NTR)), in micturition reflex pathways after cyclophosphamide (CYP)-induced cystitis. p75(NTR) can bind nerve growth factor (NGF) and modulate NGF-TrkA binding and signaling. We examined p75(NTR) expression and the role of p75(NTR) in the micturition reflex in control and CYP-treated rats. p75(NTR) Immunoreactivity was present throughout the urinary bladder. CYP-induced cystitis (4 h, 48 h, chronic) increased (P < or = 0.05) p75(NTR) expression in whole urinary bladder as shown by Western blotting. The role of p75(NTR) in bladder function in control and CYP-treated rats was determined using conscious cystometry and immunoneutralization or PD90780, a compound known to specifically block NGF binding to p75(NTR). An anti-p75(NTR) monoclonal antibody or PD90780 was infused intravesically and cystometric parameters were evaluated. Both methods of p75(NTR) blockade significantly (P < or = 0.05) decreased the intercontraction interval and void volume in control and CYP-treated rats. Intravesical infusion of PD90780 also significantly (P < or = 0.001) increased intravesical pressure and increased the number of nonvoiding contractions during the filling phase. Control intravesical infusions of isotype-matched IgG and vehicle were without effect. Intravesical instillation of PD90780 significantly (P < or = 0.01) reduced the volume threshold to elicit a micturition contraction in control rats (no inflammation) and CYP-treated in a closed urinary bladder system. These studies demonstrate 1) ubiquitous p75(NTR) expression in urinary bladder and increased expression with CYP-induced cystitis and 2) p75(NTR) blockade at the level of the urinary bladder produces bladder hyperreflexia in control and CYP-treated rats. The overall activity of the urinary bladder reflects the balance of NGF-p75(NTR) and NGF-TrkA signaling.

Barrington's nucleus in the guinea pig (Cavia porcellus): location in relation to noradrenergic cell groups and connections to the lumbosacral spinal cord

Micturition is largely controlled by Barrington's nucleus in the dorsolateral tegmentum of the pons. This nucleus coordinates simultaneous bladder contraction and external urethral sphincter relaxation, by means of a specific pattern of projections to the lumbosacral spinal cord. The most widely used small animal model in neurourological research is the rat. However, urodynamic studies suggest that, in sharp comparison to rat, guinea pig micturition is very similar to human micturition. Therefore, the present study, using retrograde and anterograde tracing and double immunofluorescence, was designed to investigate the location of Barrington's nucleus in the guinea pig, to identify Barrington's nucleus projections to the spinal cord and to clarify the relationship of Barrington's nucleus to pontine noradrenergic cell groups. Results show that Barrington's nucleus is located in the dorsolateral pons, projects to the intermediolateral and intermediomedial cell groups of the lumbosacral spinal cord and is clearly distinct from the pontine noradrenergic cell groups. These results show that the neuroanatomical circuitry in the spinal cord and brainstem that controls micturition in the guinea pig is similar to that in rat. This means that the differences between rat and guinea pig micturition on a behavioral level are not the result of different neuroanatomical connections in these parts of the central nervous system. These results provide a neuroanatomical basis for further neurourological studies in guinea pig.

Pudendal nerve stimulation of a preparation of isolated guinea-pig urethra

OBJECTIVE

To assess the functional response of the urethral striated muscle to activation of its nerves, using a novel isolated organ-bath preparation.

MATERIALS AND METHODS

The urethra of the female guinea-pig was chosen as a suitable model for investigation, as it is functionally and structurally similar to the human urethra. Female Dunkin-Hartley guinea-pigs (400-500 g) were used; for the histochemical and immunohistochemical experiments, unfixed urethras were cryo-sectioned (14 microm thick) and were stained using established methods. For in vitro experiments, whole urethras were suspended vertically, with pudendal nerves intact, for isometric tension and intraluminal pressure recording in a 40-mL organ bath. Drugs were applied directly to the bathing solution.

RESULTS

In the striated muscle layer of the urethra there was positive beta-NADPH-diaphorase activity. In organ-bath studies the pudendal nerve-evoked contractions (0.2 ms pulses, 5 s trains, 70 V and 1-100 Hz) were abolished in the presence of tubocurarine (10(-6)m), and unaffected by guanethidine and atropine (both 10(-6)m). Pre-incubation with sodium nitroprusside and SIN-1 chloride significantly reduced the initial peak pressure responses (P < 0.05, anova for paired data) evoked by electrical field stimulation of the pudendal nerves at stimulus parameters of 0.2 ms pulses, 5 s trains, 70 V and 25 Hz.

CONCLUSION

Electrically induced contractions were abolished by tubocurarine, confirming that the pudendal nerve innervates the striated muscle of the guinea-pig external urethral sphincter via nicotinic receptors. beta-NADPH-diaphorase histochemistry gave positive staining around guinea-pig striated muscle cells and possibly identified neuromuscular junction sites staining positively for the nitric oxide synthase marker. Together with the results of the organ-bath experiments, the results suggest that the striated muscle cells of the guinea-pig urethra have the machinery to respond to nitric oxide.

Neurons in the guinea pig (Cavia porcellus) lateral lumbosacral spinal cord project to the central part of the lateral periaqueductal gray matter

In order to micturate successfully, information from the bladder has to be conveyed to the brainstem. In most experimental animals, this information is relayed, via the lumbosacral spinal cord, to the periaqueductal gray matter (PAG). Although the rat is the most used experimental animal in neurourological research, urodynamic studies show that guinea pig may be a better small experimental animal because its urodynamic profile is, in contrast to that of a rat, similar to that of humans. Therefore, the present study, using anterograde and retrograde tracing, was performed to determine whether the lumbosacral spinal cord projects to the PAG in guinea pig. Results show that neurons in the lateral part of the lumbosacral spinal cord project to the central parts of the PAG. This pathway may convey information about the level of bladder filling to the PAG.