Effect of distigmine on the contractile response of guinea pig urinary bladder to electrical field stimulation

Pharmacological study on the enhancing effects of U46619 on guinea pig urinary bladder smooth muscle contraction induced by acetylcholine and α,β-methylene ATP and the possible involvement of protein kinase C

We examined whether U46619 (a prostanoid TP receptor agonist) could enhance the contractions of guinea pig urinary bladder smooth muscle (UBSM) in response to acetylcholine (ACh) and an ATP analog (α,β-methylene ATP (αβ-MeATP)) through stimulation of the UBSM TP receptor and whether protein kinase C (PKC) is involved. U46619 (10-7 M) markedly enhanced UBSM contractions induced by electrical field stimulation and ACh/αβ-MeATP (3 × 10-6 M each), the potentiation of which was completely suppressed by SQ 29,548 (a TP receptor antagonist, 6 × 10-7 M). PKC inhibitors did not attenuate the ACh-induced contractions enhanced by U46619 although they partly suppressed the U46619-enhanced, αβ-MeATP-induced contractions. While phorbol 12-myristate 13-acetate (PMA, a PKC activator, 10-6 M) did not enhance ACh-induced contractions, it enhanced αβ-MeATP-induced contractions, an effect that was completely suppressed by PKC inhibitors. αβ-MeATP-induced contractions, both with and without U46619 enhancement, were strongly inhibited by diltiazem. U46619/PMA enhanced 50 mM KCl-induced contractions, the potentiation of which was partly/completely attenuated by PKC inhibitors. These findings suggest that U46619 potentiates parasympathetic nerve-associated UBSM contractions by stimulating UBSM TP receptors. PKC-increased Ca2+ influx through voltage-dependent Ca2+ channels may partially play a role in purinergic receptor-mediated UBSM contractions enhanced by TP receptor stimulation.

Platelet-activating factor (PAF) strongly enhances contractile mechanical activities in guinea pig and mouse urinary bladder

In this study, we investigated the effects of platelet-activating factor (PAF) on the basal tone and spontaneous contractile activities of guinea pig (GP) and mouse urinary bladder (UB) smooth muscle (UBSM) tissues to determine whether PAF could induce UBSM tissue contraction. In addition, we examined the mRNA expression of the PAF receptor, PAF-synthesizing enzyme (lysophosphatidylcholine acyltransferase, LPCAT), and PAF-degrading enzyme (PAF acetylhydrolase, PAF-AH) in GP and mouse UB tissues using RT-qPCR. PAF (10^-9-10^-6 M) strongly enhanced the basal tone and spontaneous contractile activities (amplitude and frequency) of GP and mouse UBSM tissues in a concentration-dependent manner. The enhancing effects of PAF (10^-6 M) on both GP and mouse UBSM contractile activities were strongly suppressed by pretreatment with apafant (a PAF receptor antagonist, GP: 10^-5 M; mouse: 3 × 10^-5 M). The PAF receptor (Ptafr), LPCAT (Lpcat1, Lpcat2), and PAF-AH (Pafah1b3, Pafah2) mRNAs were detected in GP and mouse UB tissues. These findings reveal that PAF strongly enhances the contractile mechanical activities of UBSM tissues through its receptor and suggest that the PAF-synthesizing and -degrading system exists in UBSM tissues. PAF may serve as both an endogenous UBSM constrictor and an endogenous mediator leading to detrusor overactivity.

[Mechanism of the Long-lasting Potentiating Effect of Distigmine on Urinary Bladder Motility]

Distigmine bromide (distigmine) is a carbamate cholinesterase (ChE) inhibitor, which is mainly used for the treatment of myasthenia gravis. Distigmine is also used in Japan for the treatment for underactive bladder and glaucoma. The effectiveness of distigmine for underactive bladder treatment has been confirmed by many clinical reports, and this effect is thought to be caused by potentiating urinary bladder smooth muscle contraction due to inhibition of acetylcholine degradation during micturition. However, the pharmacological effects of distigmine on urinary bladder smooth muscle have not been well studied. The most distinctive pharmacological feature of distigmine is that it shows long-lasting effects than other ChE inhibitors; however, few studies have investigated the persistence of the enhancing effect of distigmine on the contractile function of urinary bladder smooth muscle. Moreover, this mechanism remains unclear. In this review, we present our findings on the mechanism of the potentiating effect of distigmine on isolated guinea pig urinary bladder smooth muscle contraction. We also discuss the long-lasting potentiating effect of distigmine on urinary bladder motility and the mechanism of these effects using guinea pig urinary bladder smooth muscle in vivo and in vitro. In addition, we present our investigations on the long-lasting mechanism of distigmine using recombinant human acetylcholinesterase.

Effects of Distigmine on the Mechanical Activity of Urinary Bladder Smooth Muscle

Distigmine bromide (distigmine) is a reversible carbamate cholinesterase (ChE) inhibitor. Its principle clinical application is in the treatment of myasthenia gravis. Distigmine is also used as a remedy for dysuria and glaucoma. Its effectiveness in the management of dysuria has been demonstrated in several clinical reports. Distigmine may improve (enhance) urinary bladder smooth muscle (UBSM) contraction during micturition by inhibiting acetylcholine (ACh) decomposition. However, the pharmacological effects of distigmine on UBSM have not been adequately studied so far. In this review article, we summarize the reported effects of distigmine on the contractile responses elicited by exogenous and endogenous ACh in isolated UBSM preparations. We also discuss the effects of distigmine on the UBSM basal tone and the contractile response of UBSM to ATP, which is co-released with ACh from parasympathetic nerve terminals.