Assessment of Inhibitory Effects of Hypnotics on Acetylcholine-Induced Contractions in Isolated Rat Urinary Bladder Smooth Muscle

Abstract

The present study aimed to investigate the potential inhibitory effects of 21 clinically available hypnotics on acetylcholine (ACh)-induced contractions in rat urinary bladder smooth muscle (UBSM) in order to predict whether these hypnotics could induce voiding impairment. ACh-induced contraction in rat UBSM was inhibited only by diphenhydramine (a histamine H 1 receptor antagonist) at a concentration that was clinically relevant. ACh-induced contraction was also significantly inhibited by flurazepam (a benzodiazepine hypnotic) and suvorexant (an orexin receptor antagonist), albeit at concentrations that substantially exceeded clinically achievable blood levels. These three drugs (at 10 5 M) also inhibited high-KCl (80 mM) Locke-Ringer solution-induced contractions. In contrast to the effects of the abovementioned hypnotics, ACh-induced contractions were not significantly affected by triazolam, etizolam, brotizolam, lormetazepam, estazolam, flunitrazepam, nitrazepam (benzodiazepine hypnotics), thiopental, thiamylal, pentobarbital, amobarbital, secobarbital, phenobarbital (barbiturate hypnotics), zolpidem (an imidazopyridine hypnotic), zopiclone (a cyclopyrrolone hypnotic), ramelteon (a melatonin receptor agonist), bromovalerylurea, and chloral hydrate. These findings suggest that most clinically used hypnotics are not likely to result in anticholinergicinduced dysuria within their clinically achievable blood concentration ranges. Diphenhydramine may, however, induce voiding impairment, an action attributable to diminished UBSM contractility within its clinical dose range.

Inhibitory Effects of Antipsychotics on the Contractile Response to Acetylcholine in Rat Urinary Bladder Smooth Muscles

“…The effects of antipsychotics on UBSM contraction were assessed as previously described. 21,22) Briefly, isolated rat UBSM strips were equilibrated under a 0.5 g resting tone for 20 min in a 20 mL organ bath containing Locke-Ringer solution equilibrated with 95% O 2 and 5% CO 2 at 32 ± 1°C; the solution was comprised of the following (mM): NaCl, 154; KCl, 5.6; CaCl 2 , 2.2; MgCl 2 , 2.1; NaHCO 3 , 5.9; and glucose, 2.8. The UBSM preparation was contracted using 10 −4 M ACh at least three times at 20 min intervals (preliminary procedures).…”

“…Data Analysis and Statistics CRCs for ACh-induced contractions and Schild plot analysis of anxiolytics versus ACh concentrations were performed using GraphPad Prism (GraphPad Software Inc., San Diego, CA, U.S.A.), as previously described. 21,22) All values are presented as mean ± standard error of the mean (S.E.M.) or mean with 95% confidence intervals (CIs) for different numbers (n) of preparations.…”

Pharmacological Characteristics of Anxiolytics on Acetylcholine-Induced Contractions in Rat Detrusor Smooth Muscle

“…Assessment of anxiolytic effects on DSM contraction was performed as previously described [5]. Briefly, isolated rat DSM strips (approximately 2 mm in width × 25 mm in length) equilibrated under 0.5 g resting tone for 20 min in a 20 mL organ bath containing Locke-Ringer solution equilibrated with 95% O 2 and 5% CO 2 at 32 ± 1 ° C of the following composition (mmol/L): NaCl, 154; KCl, 5.6; CaCl 2 , 2.2; MgCl 2 , 2.1; NaHCO 3 , 5.9, and glucose, 2.8.…”

“…Concentration-response curves for ACh-induced contractions and Schild plot analysis of anxiolytics versus ACh concentrations were performed using GraphPad Prism TM (GraphPad Software Inc., San Diego, CA, USA) as previously described [5]. Binding data were subjected to nonlinear regression analyses using Graph-Pad Prism TM as previously described [6].…”

“…Clotiazepam, diazepam, paroxetine, escitalopram, and hydroxyzine significantly inhibited ACh-induced contractions. These anxiolytics may inhibit these contractions via inhibiting voltage-dependent L-type Ca 2+ channels since the maximum response of the concentration-response curve for ACh was suppressed to 43.6 ± 7.2% by pretreatment with an inhibitor of this type of channel, verapamil (10 -5 mol/L) [5]. Therefore, we investigated the effects of these anxiolytics on depolarizing contraction induced by 80 mmol/L high KCl solution.…”