The activation of the TRPM8 channel, a member of the large class of TRP ion channels, has been reported to be involved in overactive bladder and painful bladder syndrome, although an endogenous activator has not been identified. In this study, N-(3-aminopropyl)-2-{[(3-methylphenyl) methyl]oxy}-N-(2-thienylmethyl)benzamide hydrochloride salt (AMTB) was evaluated as a TRPM8 channel blocker and used as a tool to evaluate the effects of this class of ion channel blocker on volume-induced bladder contraction and nociceptive reflex responses to noxious bladder distension in the rat. AMTB inhibits icilin-induced TRPM8 channel activation as measured in a Ca(2+) influx assay, with a pIC(50) of 6.23. In the anesthetized rat, intravenous administration of AMTB (3 mg/kg) decreased the frequency of volume-induced bladder contractions, without reducing the amplitude of contraction. The nociceptive response was measured by analyzing both visceromotor reflex (VMR) and cardiovascular (pressor) responses to urinary bladder distension (UBD) under 1% isoflurane. AMTB (10 mg/kg) significantly attenuated reflex responses to noxious UBD to 5.42 and 56.51% of the maximal VMR response and pressor response, respectively. The ID50 value on VMR response was 2.42 +/- 0.46 mg/kg. These results demonstrate that TRPM8 channel blocker can act on the bladder afferent pathway to attenuate the bladder micturition reflex and nociceptive reflex responses in the rat. Targeting TRPM8 channel may provide a new therapeutic opportunity for overactive bladder and painful bladder syndrome.
Prostaglandin EP3 receptors in the central nervous system (CNS) may exert an excitatory effect on urinary bladder function via modulation of bladder afferent pathways. We have studied this action, using two EP3 antagonists, (2E)-3-{1-[(2,4-dichlorophenyl)methyl]-5-fluoro-3-methyl-1H-indol-7-yl}-N-[(4,5-dichloro-2-thienyl)sulfonyl]-2-propenamide (DG041) and (2E)-N-{[5-bromo-2-(methyloxy)phenyl] sulfonyl}-3-[2-(2-naphthalenylmethyl)phenyl]-2-propenamide (CM9). DG041 and CM9 were proven to be selective EP3 antagonists with radioligand binding and functional fluorescent imaging plate reader (FLIPR) assays. Their effects on volume-induced rhythmic bladder contraction and the visceromotor reflex (VMR) response to urinary bladder distension (UBD) were evaluated in female rats after intrathecal or intracerebroventricular administration. Both DG041 and CM9 showed a high affinity for EP3 receptors at subnanomolar concentrations without significant selectivity for any splice variants. At the human EP3C receptor, both inhibited calcium influx produced by the nonselective agonist PGE2. After intrathecal or intracerebroventricular administration both CM9 and DG041 dose-dependently reduced the frequency, but not the amplitude, of the bladder rhythmic contraction. With intrathecal administration DG041 and CM9 produced a long-lasting and robust inhibition on the VMR response to UBD, whereas with intracerebroventricular injection both compounds elicited only a transient reduction of the VMR response to bladder distension. These data support the concept that EP3 receptors are involved in bladder micturition at supraspinal and spinal centers and in bladder nociception at the spinal cord. A centrally acting EP3 receptor antagonist may be useful in the control of detrusor overactivity and/or pain associated with bladder disorders.
The present study investigated whether 3-adrenoceptor activation acts on the bladder afferent pathway by examination of the visceromotor reflex (VMR) and pressor responses to urinary bladder distension (UBD) and whether 3-adrenoceptor activation produces urinary bladder relaxation in hyperactive spontaneously hypertensive rats (SHRs) in comparison with their normotensive control rats [Wistar-Kyoto (WKY)]. Using the VMR responses to noxious UBD as a measure of bladder afferent signal transmission, SHRs did not present a sensitized bladder phenotype. However, reduced bladder compliance accompanied by a reduced void threshold was detected in the SHR detrusor. Furthermore, the selective 3-adrenoceptor agonist) failed to attenuate VMR or pressor responses to UBD in either SHRs or WKY rats, but it dose-dependently inhibited rhythmic contraction (RC) in SHRs. The minimal effective dose was 0.001 mg/kg. Using the same model in WKY rats, CL-316243 did not elicit significant inhibition of contractions in the bladder RC assay. These results suggest that SHRs represent abnormal efferent/ detrusor function (detrusor overactivity) without mechanosensory afferent hypersensitivity. The 3-adrenoceptor agonist CL-316243 acts on the detrusor muscle to increase urine storage in SHRs.The overactive bladder (OAB) is defined by the symptom of urgency (Abrams et al., 2002), which is the complaint of a sudden compelling desire to pass urine. The evaluation of urgency as a sensation is not easy in humans; however, several scales are available to measure the intensity of urgency. In animals, "urgency" cannot be used as a measurement, and only a few parameters of physiological endpoints, which are unique to humans as a consequence of urgency, can be measured by urodynamic studies. For example, spontaneously hypertensive rats (SHRs) exhibit such an animal model that mimics the pathophysiology of OAB patients with increased voiding frequency and lower bladder capacity (Persson et al., 1998;Spitsbergen et al., 1998). The mechanism behind the detrusor overactivity (DO) in SHRs and how the model simulates urgency in humans is not known. The alternations of both the afferent pathway and the efferent pathway in SHRs compared with their normotensive controls [Wistar-Kyoto (WKY)] have been proposed. The evidence for an enhanced afferent limb of the micturition reflex pathway in SHRs was based on an increased production of nerve growth factor by bladder smooth muscle Clemow et al., 1999). The consequence of an increased nerve growth factor level includes enlargement of bladder sensory neuron size (Clemow et al., 1997) and sensitization of the bladder afferent nerve activity (Dmitrieva and McMahon, 1996). However, direct evidence of enhanced afferent activity in SHRs is still lacking.The function of adrenoceptors (ARs) in the efferent limb (efferent outflow/bladder function) may also underlie the DO in SHRs. Blockade of spinal ␣1-AR removed the abnormal bladder contractions, and activation of peripherally postjuncArticle, publication date...
Current results using the rat urinary bladder distension model are consistent with previous research demonstrating a role of the analgesics (morphine, U50,488, and mexiletine) in the inhibition of visceral nociceptive transmission. The utility of the reflex responses to urinary bladder distension may provide a method useful to examine mechanisms which target the bladder sensory pathway.
The excitatory roles of EP3 receptors at the peripheral afferent nerve innervating the rat urinary bladder have been evaluated by using the selective EP3 antagonist (2E)-3-{1-[(2,4-dichlorophenyl)methyl]-5-fluoro-3-methyl-1H-indol-7-yl}-N-[(4,5-dichloro-2-thienyl)sulfonyl]-2-propenamide (DG-041). The bladder rhythmic contraction model and a bladder pain model measuring the visceromotor reflex (VMR) to urinary bladder distension (UBD) have been used to evaluate DG-041 in female rats. In addition, male rats [spontaneously hypertensive rat (SHR), WistarKyoto (WKY), and Sprague-Dawley (SD)] were anesthetized with pentobarbital sodium, and primary afferent fibers in the L 6 dorsal root were isolated for recording the inhibitory response to UBD following intravenous injection of DG-041. Intravenous injection of DG-041 (10 mg/kg), a peripherally restricted EP 3 receptor antagonist, significantly reduced the frequency of bladder rhythmic contraction and inhibited the VMR response to bladder distension. The magnitude of reduction of the VMR response was not different in the different strains of rats (SD, SHR, and WKY). Furthermore, quantitative characterization of the mechanosensitive properties of bladder afferent nerves in SHR, WKY, and SD rats did not show the SHR to be supersensitive to bladder distension. DG-041 selectively attenuated responses of mechanosensitive afferent nerves to UBD, with strong suppression on the slow-conducting, high-threshold afferent fibers, with equivalent activity in the three strains. We conclude that sensitization of afferent nerve activity was not one of the mechanisms of bladder hypersensitivity in SHR. EP 3 receptors are involved in the regulation of bladder micturition and bladder nociception at the peripheral level.EP3; viscermotor reflex; bladder rhythmic contraction; bladder distension; afferent nerve SENSATION ASSOCIATED WITH the urinary bladder is conveyed primarily by pelvic and hypogastric nerves, by which the signal is relayed to the central nervous system (CNS). Most afferent fibers innervating the musculature of the bladder body pass through the pelvic nerve, whereas the majority of afferent endings in the bladder submucosa are derived from the hypogastric nerve (41), suggesting that the afferent fibers in the pelvic and hypogastric nerves have different roles, signaling mechanical stimulation (e.g., bladder distension) and chemical stimulation (e.g., inflammation), respectively (20,22,30,34). Bladder distension is a natural mechanical stimulus to evoke sensations such as fullness, urgency, and pain while the literature suggests a complex regulatory role of prostaglandins (PGs) in multiple aspects of urinary bladder physiology/pathophysiology. PGE 2 , one of the principal PGs, is synthesized in urothelium and detrusor smooth muscle (19,24,25,27) as well as in neurons and glial cells (18,23) and is released in response to various physiological (e.g., bladder distension) and pathological (e.g., mediators of inflammation) stimulation. PGE 2 interacts with four EP receptor subt...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.