Pain phenotypes classified by machine learning using electroencephalography features.

Pain is a multidimensional experience mediated by distributed neural networks in the brain. To study this phenomenon, EEGs were collected from 20 subjects with chronic lumbar radiculopathy, 20 age and gender matched healthy subjects, and 17 subjects with chronic lumbar pain scheduled to receive an implanted spinal cord stimulator. Analysis of power spectral density, coherence, and phase-amplitude coupling using conventional statistics showed that there were no significant differences between the radiculopathy and control groups after correcting for multiple comparisons. However, analysis of transient spectral events showed that there were differences between these two groups in terms of the number, power, and frequency-span of events in a low gamma band. Finally, we trained a binary support vector machine to classify radiculopathy versus healthy subjects, as well as a 3-way classifier for subjects in the 3 groups. Both classifiers performed significantly better than chance, indicating that EEG features contain relevant information pertaining to sensory states, and may be used to help distinguish between pain states when other clinical signs are inconclusive.

Analysis of continence reflexes by dynamic urethral pressure recordings in a rat stress urinary incontinence model induced by multiple simulated birth traumas.

The present study evaluated real-time changes in urethral pressure during the storage phase using a rat model with stress urinary incontinence (SUI) induced by simulated multiple birth traumas and investigated the relationship between urethral continence function and dynamic parameters associated with the changes in urethral pressure. Sprague-Dawley rats were divided into the following two groups: the sham group, which underwent three catheterizations of the vagina without distension at 2-wk intervals, and the vaginal distension (VD) group, which underwent three VDs at 2-wk intervals. After transection of the T8-T9 spinal cord, simultaneous bladder and urethral pressure recordings were performed during intravesical pressure elevation. Urodynamic parameters such as leak point pressure (LPP), urethral baseline pressure (UBP), maximum urethral pressure (MUP), the MUP-UBP differential (dUP) during intravesical pressure elevation, the bladder pressure when urethral contraction begins (Puc), and the bladder pressure at bladder neck opening (Pno) were then measured and compared. Compared with the sham group, LPP, UBP, dUP, MUP, Puc, and Pno were significantly decreased in the VD group. Pressure differences between LPP and Pno and between LPP and UBP (LPP-UBP) were also significantly different in the two groups. However, difference values of LPP and MUP or Pno and UBP were not altered after VD. Our new methods of simultaneous recordings of dynamic changes in bladder and urethral pressures are useful to fully evaluate the functional alterations in urethral continence function in the SUI model induced by multiple VDs. Moreover, LPP-UBP values, which correspond to the difference between Valsalva LPP and maximum urethral closure pressure in clinical urodynamics, would be useful to evaluate the impaired urethral continence function after simulated birth traumas in animal models.

Role of the serotonergic system in urethral continence reflexes during sneezing in rats.

To clarify the role of serotonin (5-HT) in the prevention of stress urinary incontinence (SUI) during sneezing, we investigated the effect of intraperitoneal application of p-chlorophenylalanine (PCPA; a serotonin synthesis inhibitor) and intravenous application of CP-809101 (a 5-HT2C agonist) or LP44 (a 5-HT7 agonist) using female rats, in which the neurally evoked continence reflex during sneezing was examined. Amplitudes of urethral pressure response during sneezing (A-URS), urethral baseline pressure (UBP) at the middle urethra, and sneeze-induced leak point pressure (S-LPP) were measured in normal female adult rats with or without drug administration. PCPA decreased A-URS by 35.1 cmH2O and UBP by 13.3 cmH2O compared with normal rats. In PCPA-administrated rats, CP-809101 increased A-URS by 24.1 cmH2O and UBP by 15.1 cmH2O, and LP44 also increased A-URS by 20.6 cmH2O and UBP by 11.4 cmH2O compared with rats treated with PCPA alone. SUI was observed with S-LPP of 40.1 cmH2O in PCPA-administrated rats, in which CP-809101 and LP44 increased S-LPP by 28.0 and 15.2 cmH2O, respectively, compared with rats treated with PCPA alone. The effects of CP-809101 and LP44 were antagonized by SB-242084 (a selective 5-HT2C antagonist) and SB-269970 (a selective 5-HT7 antagonist), respectively. These results indicate that activation of 5-HT receptors enhances the active urethral closure reflex during sneezing, at least in part via 5-HT2C and 5-HT7 receptors.

Effects of multiple simulated birth traumas on urethral continence function in rats.

Multiple vaginal parities have been reported to be an important risk factor for stress urinary incontinence (SUI). Simulated birth trauma with single vaginal distention (VD) has been used to induce the SUI condition in animals; however, the effect of multiple simulated birth traumas on the urethral continence function has not been well characterized. Therefore, we examined the effects of multiple VDs on urethral functions in vivo and the changes in gene expressions of several molecules in the urethra using female SD rats, which were divided into three groups; sham, VD-1 (single VD), and VD-3 groups (3 times of VDs every 2 wk). Two weeks after the final VD, leak point pressure (LPP) and urethral responses during sneezing were evaluated. Also, changes in mRNA levels of urethral molecules were quantified with RT-PCR.　The VD-1 group did not show any change in LPP with only a tendency of decrease in amplitudes of the urethral responses during sneezing (A-URS); however, the VD-3 group showed a significant decrease in LPP and urethral responses such as baseline urethral pressure and A-URS accompanied with SUI episodes during sneezing. Nicotinic receptor subtypes and transforming growth factor (TGF)-ß1 were significantly increased in both VD-1 and VD-3 groups while TNF receptor (TNFR)-1, IL-6, collagens, and matrix metalloproteinases-9 were significantly increased only in the VD-3 group.　These data indicate that rats with multiple simulated birth traumas exhibit profound impairment of the urethral continence function and that these functional changes are associated with those in cytokines, extracellular matrix molecules, and nicotinic receptor subtypes in the urethra.

IGF-1 as an Important Endogenous Growth Factor for Recovery from Impaired Urethral Continence Function in Rats with Simulated Childbirth Injury.

PURPOSE: We examined the functional role of endogenous IGF-1 (insulin-like growth factor-1) in the recovery phase of stress urinary incontinence induced by simulated childbirth trauma using an IGF-1 receptor inhibitor. MATERIALS AND METHODS: Simulated birth trauma was induced by vaginal distension in female Sprague Dawley® rats. The IGF-1 receptor antagonist JB-1 (10 and 100 µg/kg per day) or vehicle was continuously delivered from 1 day before vaginal distension for 7 days using subcutaneous osmotic pumps. Seven, 14 and 21 days after vaginal distension the effect of JB-1 treatment was examined by functional analyses, including leak point and urethral baseline pressure, and urethral responses during passive increments in intravesical pressure, as well as molecular analyses in urethral tissues, including phosphorylation of Akt, apoptotic changes and peripheral nerve density using Western blot and immunohistochemistry. RESULTS: On functional analyses vehicle treated rats with vaginal distension had significantly decreased leak point and urethral baseline pressure, and urethral responses at 7 days, which recovered to the normal level 14 and 21 days after vaginal distension. In the JB-1 treated vaginal distension group leak point and urethral baseline pressure, and urethral responses were still significantly reduced 21 days after vaginal distension. On molecular analyses JB-1 treatment increased apoptotic cells, induced a significant decrease in phosphorylated Akt and prolonged the decrease of peripheral nerve density in urethral tissues. CONCLUSIONS: Suppression of endogenous IGF-1 activity delayed recovery from stress urinary incontinence induced by simulated childbirth trauma in rats. Thus, IGF-1 is likely to be an important endogenous mediator for functional recovery from childbirth related stress urinary incontinence. This suggests that IGF-1 could be an effective target for treating stress urinary incontinence in women.

Liposome Based Intravesical Therapy Targeting Nerve Growth Factor Ameliorates Bladder Hypersensitivity in Rats with Experimental Colitis.

PURPOSE: Pelvic organ cross sensitization is considered to contribute to overlapping symptoms in chronic pelvic pain syndrome. Nerve growth factor over expression in the bladder is reportedly involved in the symptom development of bladder pain syndrome/interstitial cystitis. We examined whether a reduction of over expressed nerve growth factor in the bladder by intravesical treatment with liposome and oligonucleotide conjugates would ameliorate bladder hypersensitivity in a rat colitis model. MATERIALS AND METHODS: Adult female rats were divided into 1) a control group, 2) a colitis-oligonucleotide group with intracolonic TNBS (2,4,6-trinitrobenzene sulfonic acid) enema and intravesical liposome-oligonucleotide treatments, 2) a colitis-saline group with intracolonic TNBS and intravesical saline treatments, 4) a sham oligonucleotide group with intravesical liposome-oligonucleotide treatment without colitis and 5) a sham-saline group with intravesical saline treatment without colitis. Liposomes conjugated with nerve growth factor antisense oligonucleotide or saline solution were instilled in the bladder and 24 hours later colitis was induced by TNBS enema. Effects of nerve growth factor antisense treatment were evaluated by pain behavior, cystometry, molecular analyses and immunohistochemistry 10 days after TNBS treatment. RESULTS: In colitis-oligonucleotide rats nerve growth factor antisense treatment ameliorated pain behavior and decreased a reduction in the intercontraction interval in response to acetic acid stimulation as well as nerve growth factor expression in the bladder mucosa. All were enhanced in colitis-saline rats compared to sham rats. CONCLUSIONS: Nerve growth factor over expression in the bladder mucosa and bladder hypersensitivity induced after colitis were decreased by intravesical application of liposome-oligonucleotide targeting nerve growth factor. This suggests that local antinerve growth factor therapy could be effective treatment of bladder symptoms in chronic pelvic pain syndrome.

The effect of ovariectomy on urethral continence mechanisms during sneeze reflex in middle-aged versus young adult rats.

AIMS: Stress urinary incontinence (SUI) is common in post-menopausal women. The present study therefore examined how aging and estrogen deficiency induced by ovariectomy (OVX) affect the urethral continence mechanism that prevents sneeze-induced SUI in rats. METHODS: Young (3 months old) and middle-aged (12 months old) female rats underwent bilateral OVX or sham operation. Urethral activity was measured by the amplitude of urethral responses during sneezing (A-URS) and urethral baseline pressure (UBP). Apoptotic changes in urethral tissue sections were examined by the TUNEL method. RESULTS: In middle-aged rats, UBP, but not A-URS, was significantly decreased compared to young rats. In 3-week OVX rats, A-URS was significantly decreased compared to sham rats in both young and middle-aged groups, and the OVX-induced reduction in A-URS was more pronounced in middle-aged rats. Neither young 3-week OVX nor sham rats leaked during sneezing; however, SUI occurred in 2/8 middle-aged rats with 3-week OVX, and after 6 weeks of OVX, SUI was observed in 5/8 young rats and 6/8 middle-aged rats. In middle-aged rats, TUNEL positive cells were significantly increased in urethral striated muscles whereas, after OVX, the increased number of positive cells was also found in the mucosa. CONCLUSIONS: These results indicate that aging is more likely to impair baseline urethral function than striated muscle-mediated reflex activity although apoptotic changes are found in urethral striated muscle. Estrogen deficiency additionally impairs the striated muscle-mediated continence reflex. Thus, aging and estrogen deficiency differently and additively affect baseline urethral function and neurally-evoked, striated muscle-mediated urethral continence mechanisms to induce SUI.

Characteristics of TRK-130 (Naltalimide), a novel opioid ligand, as a new therapeutic agent for overactive bladder.

We characterized TRK-130 (N-[(5R,6R,14S)-17-(cyclopropylmethyl)-4,5-epoxy-3,14-dihydroxymorphinan-6-yl]phthalimide; naltalimide), an opioid ligand, to clarify the therapeutic potential for overactive bladder (OAB). In radioligand-binding assays with cells expressing human µ-opioid receptors (MORs), δ-opioid receptors (DORs), or κ-opioid receptors (KORs), TRK-130 showed high selectivity for MORs (Ki for MORs, DORs, and KORs = 0.268, 121, and 8.97 nM, respectively). In a functional assay (cAMP accumulation) with cells expressing each human opioid receptor subtype, TRK-130 showed potent but partial agonistic activity for MORs [EC50 (Emax) for MORs, DORs, and KORs = 2.39 nM (66.1%), 26.1 nM (71.0%), and 9.51 nM (62.6%), respectively]. In isovolumetric rhythmic bladder contractions (RBCs) in anesthetized guinea pigs, TRK-130 dose-dependently prolonged the shutdown time (the duration of complete cessation of the bladder contractions) (ED30 = 0.0034 mg/kg i.v.) without affecting amplitude of RBCs. Furthermore, TRK-130 ameliorated formalin-induced frequent urination at doses of higher than 0.01 mg/kg p.o. in guinea pigs under the freely moving condition. Meanwhile, TRK-130 showed only a negligible effect on the gastrointestinal transit at doses of up to 10 mg/kg s.c. in mice. These results indicate that TRK-130 is a potent and selective human MOR partial agonist without undesirable opioid adverse effects such as constipation and enhances the storage function by suppressing the afferent limb of the micturition reflex pathway, suggesting that TRK-130 would be a new therapeutic agent for OAB.

Therapeutic effects of IGF-1 on stress urinary incontinence in rats with simulated childbirth trauma.

PURPOSE: We examined the effect of IGF-1 in a rat model of stress urinary incontinence induced by simulated childbirth trauma. MATERIALS AND METHODS: Simulated birth trauma was induced by vaginal distension in female Sprague Dawley® rats. Four, 7, 14 and 28 days after distension we performed functional assessment by measuring leak point pressure, urethral baseline pressure and the urethral response during a passive increment in intravesical pressure. The expression of IGF-1 and IGF1R mRNA and protein in damaged tissues was examined by real-time reverse transcriptase-polymerase chain reaction and immunohistochemistry. Thereafter hrIGF-1 (50 and 150 µg/kg per day) was continuously delivered from 1 day before distension using subcutaneous osmotic pumps. Four and 7 days after distension the effect of hrIGF-1 treatment was examined by functional analysis of leak point pressure, urethral baseline pressure and the urethral response as well as Western blot and histological analysis. RESULTS: After 4 and 7 days rats with vaginal distension had significantly decreased leak point pressure, urethral baseline pressure and urethral responses. IGF-1 and IGF1R mRNA and protein levels were significantly increased in urethral and pudendal nerves 4 and 7 days after distension. IGF-1 treated groups showed significant improvement in leak point pressure, urethral baseline pressure and urethral responses 4 and 7 days after distension. Moreover, IGF-1 treatment increased Akt phosphorylation and induced cellular proliferation and antiapoptotic effects in the urethra. CONCLUSIONS: IGF-1 treatment accelerated recovery from stress urinary incontinence induced by simulated childbirth trauma in association with activation of the Akt signal transduction pathway in rats. This suggests that IGF-1 has therapeutic potential for stress urinary incontinence in women.

Central nervous targets for the treatment of bladder dysfunction.

BACKGROUND: The functions of the lower urinary tract, to store and periodically release urine, are dependent on the activity of smooth and striated muscles in the urinary bladder, urethra, and external urethral sphincter. This activity is in turn controlled by neural circuits in the brain, spinal cord, and peripheral ganglia. AIMS: This paper will review recent advances in our understanding of the pathophysiology of voiding disorders, especially focusing on the central nervous system. METHODS: Various neurotransmitters, including acetylcholine, norepinephrine, dopamine, serotonin, excitatory and inhibitory amino acids, adenosine triphosphate, nitric oxide, and neuropeptides, have been implicated in the neural regulation of the lower urinary tract. RESULTS: Injuries or diseases of the nervous system, as well as drugs and disorders of the peripheral organs, can produce voiding dysfunctions such as urinary frequency, urgency, or incontinence. CONCLUSION: We discuss the potential targets in the central nervous system and new modalities for the treatment of voiding dysfunction.

Inhibitory role of the spinal cholinergic system in the control of urethral continence reflex during sneezing in rats.

AIMS: The urethral continence reflex during stress conditions such as sneezing or coughing is an important mechanism preventing stress urinary incontinence (SUI). Although the spinal noradrenergic and serotonergic pathways are known to modulate this reflex activity, the role of spinal cholinergic pathways in the control of urethral continence reflex has not been elucidated. We therefore investigated the effect of intrathecal administration of an acetylcholine esterase (AChE) inhibitor, which increases ACh in synaptic terminals, and anti-cholinergic agents on the sneeze-induced urethral reflex in rats. METHODS: Female SD rats were anesthetized with urethane. Urethral function was evaluated during sneezing induced by insertion of the rat whisker into the nostril. Effects of an AChE inhibitor, neostigmine, and muscarinic or nicotinic receptor antagonists administered at the level of L6-S1 spinal cord were examined. RESULTS: Neostigmine dose-dependently and significantly decreased the amplitude of urethral responses during sneezing (A-URS) with an approximately 70% reduction at 3 nmol, without changing urethral baseline pressure. The neostigmine-induced decrease in A-URS was significantly reversed by pretreatment with atropine (nonselective muscarinic receptor antagonist), methoctramine (M2 receptor antagonist) or 4-DAMP (M3 receptor antagonist), but not with pirenzepine (M1 receptor antagonist), tropicamide (M4 receptor antagonist), or mecamylamine (nicotinic receptor antagonist). CONCLUSIONS: These results indicate that an increase in endogenous ACh in the lumbosacral spinal cord inhibits the sneeze-induced urethral continence reflex via activation of M2 and/or M3-muscarinic receptors, implying the inhibitory role of spinal cholinergic pathways in the control of urethral continence reflex under stress conditions such as sneezing.

Bladder afferent hyperexcitability in bladder pain syndrome/interstitial cystitis.

Bladder pain syndrome/interstitial cystitis is a disease with lower urinary tract symptoms, such as bladder pain and urinary frequency, which results in seriously impaired quality of life of patients. The extreme pain and urinary frequency are often difficult to treat. Although the etiology of bladder pain syndrome/interstitial cystitis is still not known, there is increasing evidence showing that afferent hyperexcitability as a result of neurogenic bladder inflammation and urothelial dysfunction is important to the pathophysiological basis of symptom development. Further investigation of the pathophysiology will lead to the effective treatment of patients with bladder pain syndrome/interstitial cystitis.

Discovery of potent transient receptor potential vanilloid 1 antagonists: design and synthesis of phenoxyacetamide derivatives.

We aimed to discover a novel type of transient receptor potential vanilloid 1 (TRPV1) antagonist because such antagonists are possible drug candidates for treating various disorders. We modified the structure of hit compound 7 (human TRPV1 IC50=411 nM) and converted its pyrrolidino group to a (hydroxyethyl)methylamino group, which substantially improved inhibitory activity (15d; human TRPV1 IC50=33 nM). In addition, 15d ameliorated bladder overactivity in rats in vivo.

[Pharmacological effects of nalfurafine hydrochloride, a kappa-opioid receptor agonist].

Nalfurafine hydrochloride, a kappa-opioid receptor agonist, was approved in January 2009 and released to the market on March 2009 for the indication of "Improvement of pruritus in hemodialysis patients (only for cases resistant to conventional treatments)" in Japan (Brand Name: REMITCH CAPSULES 2.5 microg, Marketing Authorization Holder: Toray Industries, Inc., Distributed by Torii Pharmaceutical Co., Ltd., Co-developed by Japan Tobacco Inc.). In addition to antipruritic effect, nalfurafine hydrochloride showed ameliorating effects on pain, neuropathic pain, drug dependence, schizophrenia and dyskinesia in non-clinical studies. Therefore, nalfurafine hydrochloride may become a useful therapeutic agent for their diseases.

Peripheral tetrahydrobiopterin is involved in the pathogenesis of mechanical hypersensitivity in a rodent postsurgical pain model.

Because treatment for postsurgical pain (PSP) remains a major unmet medical need, the emergence of safe and innovative nonopioid drugs has been strongly coveted. Tetrahydrobiopterin (BH4) is an interesting molecule for gaining a better understanding the pathological mechanism of neuropathic pain. However, whether BH4 and its pathway are involved in the pathogenesis of PSP remains unclear. In this study, we found that early in a rat paw incision model, the gene expression of GTP cyclohydrolase 1 (GTPCH) and sepiapterin reductase (SPR), BH4-producing enzymes in the de novo pathway, were significantly increased in incised compared with naive paw skin. Although a significant increase in GTPCH protein levels was observed in incised paw skin until only 1 day after incision, a significant increase in BH4 levels was observed until 7 days after incision. In vivo, Spr-knockout mice showed an antinociceptive phenotype in the hind paw incision compared with the wild-type and Spr heterozygote groups. Furthermore, QM385, the SPR inhibitor, showed a significant dose-dependent, antinociceptive effect, which was supported by a reduction in BH4 levels in incised skin tissues, with no apparent adverse effects. Immunohistochemical analysis demonstrated that macrophages expressing GTPCH protein were increased around the injury site in the rat paw incision model. These results indicate that BH4 is involved in the pathogenesis of PSP, and that inhibition of the BH4 pathway could provide a new strategy for the treatment of acute PSP.

An Electroencephalography Bioassay for Preclinical Testing of Analgesic Efficacy.

We present a multimodal method combining quantitative electroencephalography (EEG), behavior and pharmacology for pre-clinical screening of analgesic efficacy in vivo. The method consists of an objective and non-invasive approach for realtime assessment of spontaneous nociceptive states based on EEG recordings of theta power over primary somatosensory cortex in awake rats. Three drugs were chosen: (1) pregabalin, a CNS-acting calcium channel inhibitor; (2) EMA 401, a PNS-acting angiotensin II type 2 receptor inhibitor; and (3) minocycline, a CNS-acting glial inhibitor. Optimal doses were determined based on pharmacokinetic studies and/or published data. The effects of these drugs at single or multiple doses were tested on the attenuation of theta power and paw withdrawal latency (PWL) in a rat model of neuropathic pain. We report mostly parallel trends in the reversal of theta power and PWL in response to administration of pregabalin and EMA 401, but not minocycline. We also note divergent trends at non-optimal doses and following prolonged drug administration, suggesting that EEG theta power can be used to detect false positive and false negative outcomes of the withdrawal reflex behavior, and yielding novel insights into the analgesic effects of these drugs on spontaneous nociceptive states in rats.

Decreased Monoamine Oxidase A Expression and Activity in the Bladders of Rats With Partial Outlet Obstruction.

OBJECTIVE: To investigate changes in expression and activity of monoamine oxidase A (MAO-A) in rats with partial bladder outlet obstruction (pBOO). Previous studies suggested that monoamines, such as serotonin (5-hydroxytryptamine [5-HT]) and noradrenaline, are involved in bladder hyperactivity secondary to pBOO. However, little is known about the role of MAO-A, an enzyme oxidizing 5-hydroxytryptamine and noradrenalin, in the pathogenesis. MATERIALS AND METHODS: Female Sprague Dawley rats were subjected to sham or pBOO operations for 7 days, then their bladders were isolated. MAO-A protein levels in the bladder were examined by Western blotting. MAO-A activity was measured by the commercially available MAO-Glo Assay kit. In addition, MAO-A distribution in the bladder was examined by immunohistochemistry. RESULTS: Weights of the bladders from rats with pBOO were increased about 3.5-fold, compared with those from sham rats. Significant decreases in MAO-A protein and activity levels were observed in whole bladder of rats with pBOO compared with those of sham rats. By immunohistochemistry, it was firstly demonstrated that MAO-A was predominantly expressed in the detrusor layer of the sham rat bladders. The intensity of staining was decreased after pBOO operation. CONCLUSION: We demonstrated, for the first time, the distribution of MAO-A in the bladder and the pathologic changes in MAO-A protein and activity levels in rats with pBOO. This marked decrease in MAO-A potentially resulting in increased monoamine levels, especially in the detrusor of rat bladder, might be a key factor explaining the mechanism of bladder overactivity associated with pBOO.

Mechanisms of inhibitory action of TRK-130 (Naltalimide), a µ-opioid receptor partial agonist, on the micturition reflex.

PURPOSE: To clarify the mechanism of inhibitory action of TRK-130 (Naltalimide), a unique µ-opioid receptor partial agonist, on the micturition reflex. METHODS: The effect of TRK-130 on isovolumetric rhythmic bladder contractions (RBCs) was examined in guinea pigs, the effect of which was clarified by co-treatment with naloxone or in spinal cord transection. The effect of TRK-130 on urodynamic parameters was also observed in guinea pigs. In addition, the effect of TRK-130 on bladder contraction induced by peripheral stimulation of the pelvic nerve was investigated in rats. RESULTS: TRK-130 (0.001-0.01 mg/kg, iv) dose-dependently inhibited RBCs, which was dose-dependently antagonized by naloxone; however, the antagonism susceptibility was different from morphine (1 mg/kg, iv). The minimum effective dose (0.003 mg/kg) of TRK-130 remained similar in spinal cord-transected animals. TRK-130 (0.0025 mg/kg, iv) increased bladder capacity without changing the voiding efficiency, maximum flow rate, and intravesical pressure at the maximum flow rate, whereas oxybutynin (1 mg/kg, iv) increased the bladder capacity but affected the other parameters. TRK-130 (0.005 mg/kg, iv) did not produce significant changes on the bladder contractions induced by peripheral stimulation of the pelvic nerve, while oxybutynin (1 mg/kg, iv) significantly suppressed the bladder contractions. CONCLUSIONS: These results suggest that TRK-130 enhances the bladder storage function by modulating the afferent limb of the micturition reflex through µ-opioid receptors in the spinal cord. TRK-130 could be a more effective and safer therapeutic agent with a different fashion from antimuscarinics and conventional opioids for overactive bladder.

Functional role of prostacyclin receptor in rat dorsal root ganglion neurons.

Recent studies on prostanoids showed that some of prostanoid receptors are expressed in rat dorsal root ganglion (DRG) neurons. These facts suggest that prostanoid receptors might be involved in the excitation mechanism of DRG neurons. In the present study, PCR experiments revealed that one of prostanoid receptor, prostacyclin receptor (IP receptor) was expressed in L6 and S1 rat DRG neurons and that the expression of IP receptor was not changed in DRG neurons obtained from the cyclophosphamide (CYP)-induced cystitis rat. We examined the functional role of IP receptor agonist and other prostanoids by measuring cyclic AMP (cAMP) accumulation and substance P (SP) release in primary cultured DRG neurons. The pretreatment of DRG neurons with prostanoid agonists such as iloprost (IP), butaprost (EP(2)), misoprostol (EP(2-4)), PGE(2) (EP(1-4)) or PGD(2) (DP and CRTH2) sensitized the DRG neurons and hence potentiated the lys-bradykinin-induced SP release. The increase of SP release by lys-BK plus prostanoid agonists was proportion to cAMP accumulation. Iloprost was the most potent agonist to induce cAMP accumulation and SP release among prostanoid agonists evaluated in this study and its effect is mediated by IP receptor. Moreover, capsaicin-, ATP- and KCl-induced SP release was also enhanced by iloprost although iloprost did not change intracellular Ca(2+) and membrane depolarization induced by these chemical stimuli. These results strongly indicate that IP receptor play an important role in the sensitization of rat sensory neuron.

TRK-380, a novel selective human ß3-adrenoceptor agonist, ameliorates formalin-induced pollakiuria in rats and carbachol-induced bladder contraction in dogs.

OBJECTIVE: To investigate the effects of TRK-380, a selective ß3-adrenoceptor (ß3-AR) agonist, on voiding behavior in rats with pollakiuria and on carbachol (CCh)-induced bladder contraction in dogs. METHODS: The voiding behavior of female Sprague Dawley rats was recorded continuously with a balance. Rats were intravesically pretreated with 2.5% formalin under isoflurane anesthesia. The next day, the effect of TRK-380 (7.5-30 mg/kg, orally) or tolterodine, an antimuscarinic drug (3.75-15 mg/kg, orally), on the voiding frequency was evaluated. In another experiment, male beagle dogs were anesthetized with pentobarbital, CCh (3 µg/kg, intravenously) was administered to them, and the effect of TRK-380 (0.1 or 0.3 µg/kg/minute, intravenously infusion) on CCh-induced bladder contraction was evaluated. RESULTS: Rats treated with formalin showed a significant increase in the voiding frequency compared with the sham group, and the increase in it was significantly and dose-dependently suppressed by TRK-380 at doses of ≥15 mg/kg. In contrast, tolterodine did not lead to a significant change in the voiding frequency even at the highest dose. In dogs, CCh-induced bladder contraction was dose-dependently suppressed by TRK-380; the plasma concentration required for 30% suppression of the CCh-induced bladder contraction (30% relaxation) was 4.90 ng/mL. CONCLUSION: This study indicated that TRK-380 ameliorated pollakiuria, which was resistant to an antimuscarinic drug, and that it also suppressed the bladder contraction induced by cholinergic stimulation in dogs, whose bladder relaxation is known to be predominantly mediated by ß3-ARs, as in humans. These data strengthen the therapeutic potential of ß3-AR for the treatment of overactive bladder.