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Combined effect of disopyramide and bethanechol: use of bethanechol to prevent anticholinergic side effects of disopyramide without reduction of antiarrhythmic efficacy.

Because bethanechol chloride (B) relieves the anticholinergic side effects of disopyramide (D), we examined the combined effects of D and B on the heart and urinary bladder. B was confirmed to counteract dose dependently the effect of D on the dog bladder. In the ventricular muscle, the combined electrophysiological effects (D + B) were additive, with no reduction in the effect of D. With the control value set as 100%, the decrease in the maximum rate of depolarization with 5 X 10(-6) g/ml D (90 +/- 6%) was not affected by the same dose of B (D + B: 84 +/- 14%). Moreover, the effective refractory period (ERP) was larger with D + B (128 +/- 12%) than with either B (109 +/- 9%, p less than 0.01) or D (115 +/- 11%, p less than 0.05). In contrast, in the atrial muscle and AV and SA nodes, B had marked acetylcholine-like effects. These were completely suppressed by the addition of D except for the atrial ERP with the highest tested concentration of B (5 X 10(-6) g/ml). In the latter case, the prolongation of ERP was minimal (B + D: 105 +/- 14%) as compared with D alone (130 +/- 15%). Since the plasma concentration of B after oral administration of a clinical dose is expected to be on the order of 10(-7) g/ml, no practical effect is anticipated. We conclude that B can be expected to counteract urination disorders caused by D without reducing D's antiarrhythmic efficacy.

Anesthesia

Bladder and urethral function and supersensitivity to subcutaneously administered bethanechol in cats with chronic cauda equina lesions.

The failure of bethanechol chloride to induce voiding in patients with neurogenic bladder, despite a positive bethanechol test, is being reported more frequently. An experimental model was designed in the cat to study the response of the bladder and urethra to subcutaneous and intraarterial bethanechol after complete and partial sacral decentralization. Complete sacral rhizotomy abolished the micturition reflex. Basal urethral perfusion pressure was not affected by complete sacral rhizotomy and a significant part of this basal urethral pressure remained sympathetically mediated. However, the urethral constriction response to bladder filling was lost in half the cats with complete lesions. Bladder and urethral supersensitivity to bethanechol chloride in cats with complete lesions was characterized by a shift to the left of the i.a. dose-response curve, and by the presence of responses to doses of s.c. bethanechol chloride which are subthreshold in normal cats. The urethra also showed exaggerated constriction responses to i.a. and s.c. bethanechol. After complete lesions a part of the bladder and urethral responses to s.c. bethanechol was adrenergically mediated and exerted through the vesicourethral short neuron system. The rest of the response was due to stimulation of urethral muscarinic receptors. Partial sacral lesions were compatible with a micturition reflex and the urethra retained its reflex response to bladder distension. After partial decentralization the bladder and urethra also showed responses to subthreshold doses of s.c. bethanechol. While the bladder response to s.c. bethanechol did not show a significant adrenergic component in cats with partial lesions, most of the urethral response was sympathetically mediated. In conclusion, complete cauda equina lesions result in an areflexic detrusor with frequent loss of the urethral responsiveness to bladder filling. Urethral supersensitivity to s.c. bethanechol might be responsible for a non-voiding outcome after bethanechol injection in patients with complete cauda equina lesions, despite a positive bethanechol test. Because the detrusor reflex is preserved and the urethra is less supersensitive to bethanechol after partial cauda equina lesions, these may represent a better indication for bethanechol therapy than do complete ones.

Animals

Bethanechol-induced responses in mudpuppy parasympathetic neurons.

The effect of bethanechol on membrane potential and excitability was determined in mudpuppy parasympathetic postganglionic neurons. Bethanechol induced a large amplitude hyperpolarization, which was followed by a smaller amplitude depolarization, in 115 out of 135 cells tested. In approximately 20% of these cells, a brief depolarization preceded the hyperpolarization. During the bethanechol-induced hyperpolarization, the membrane input resistance decreased markedly, whereas the input resistance was increased during the subsequent depolarization. The hyperpolarization and depolarization were blocked by atropine and were unaffected by d-tubocurarine, thus, both appeared to be mediated by muscarinic receptors. The bethanechol-induced hyperpolarization was inhibited by the M2 muscarinic receptor antagonist AF-DX 116, whereas the bethanechol-induced depolarization was unaffected. Both a nonselective increase in membrane conductance and a decrease in membrane potassium conductance appeared to be involved in the generation of the bethanechol-induced depolarization. Evidence for the first mechanism was obtained in barium-treated cells in which bethanechol initiated a rapid onset depolarization, which was reversed at membrane potentials near 0 mV. Evidence for the second mechanism was obtained when the hyperpolarization was inhibited by AF-DX 116. In AF-DX 116-treated cells, the membrane input resistance was increased during most of the bethanechol-induced depolarization. Mudpuppy neurons initiate repetitive action potential activity in response to long depolarizing current pulses. Following application of bethanechol, with the hyperpolarization negated electrotonically, the number of action potentials produced by a depolarizing current pulse was greater than that produced prior to application of bethanechol. It is suggested that activation of muscarinic receptors on mudpuppy cardiac neurons influences multiple conductance systems and determines the excitability of these neurons.

Animals

The effects of racemic bethanechol and its (R)- and (S)-enantiomers on pre- and postjunctional muscarine receptors in the guinea-pig ileum.

The effect of racemic bethanechol and its (R)- and (S)-enantiomers on smooth muscle contraction and outflow of [3H]-acetylcholine were studied in the guinea-pig myenteric plexus-longitudinal muscle preparation that had been preincubated with [3H]-choline. (S)-, racemic, and (R)-bethanechol caused concentration-dependent contractions of the longitudinal muscle. The potency ratio of the strong isomer (S) to the weak one (R) was 915. Racemic and (S)-bethanechol concentration-dependently inhibited the evoked outflow of [3H]-acetylcholine. Racemic bethanechol was more potent than (S)-bethanechol. (R)-bethanechol up to a concentration of 1 mM did no affect the evoked outflow of [3H]-acetylcholine. (S)-bethanechol was a substrate, and (R)-bethanechol a weak inhibitor of the tissue cholinesterases. The weak cholinesterase-inhibiting action of the (R)-enantiomer probably reinforces the prejunctional effects of the (S)-enantiomer in the racemic mixture.

Animals

Bethanechol inhibition of chicken intestinal brush border Na/H exchange: role of protein kinase C and other calcium-dependent processes.

Bethanechol, a muscarinic agonist, inhibits the initial rate of amiloride-sensitive Na uptake by intact mucosa of avian small intestine as well as by isolated chicken villus enterocytes, an effect that is maximal at 90 seconds and reverses by 6 minutes. Bethanechol similarly decreases intracellular pH in isolated cells suspended in bicarbonate-free buffer in a time course similar to inhibition of enterocyte Na uptake, suggesting inhibition of Na/H exchange. In brush border membrane vesicles rapidly prepared from cells stimulated with bethanechol, proton-dependent 22Na uptake is transiently inhibited in a time course similar to inhibition of cell Na uptake. Bethanechol also stimulates transient translocation of protein kinase C from the cytosol to the particulate fraction, a portion of this activity translocating to the brush border membrane. To determine the calcium dependence of bethanechol's action, enterocytes were loaded with varying concentrations of the calcium buffering agent quin-2. Inhibition of cell Na uptake by the calcium ionophore ionomycin could be completely reversed by quin-2 buffering in a concentration-dependent manner. In contrast, quin-2 buffering had little or no effect on the inhibition of Na uptake caused by the protein kinase C activators phorbol esters and oleoylacetylglycerol. Bethanechol's inhibitory effects were partially, but not completely reversed by quin-2 buffering. These data suggest that the effects of bethanechol on chicken villus enterocyte brush border Na/H exchange are mediated by calcium-dependent process(es) as well as by protein kinase C.

Animals

Bethanechol-induced water intake in rats: possible mechanisms of induction.

Acute administration of the parasympathomimetic agent, bethanechol, at 2, 4, 8 and 12 mg/kg body wt, IP, induced drinking and increased urine output of rats in a dose-dependent fashion. The first significant increases in both water intake and urine output above that of controls occurred when 4 mg/kg was administered. The drinking and increased urine output in response to administration of 8 mg bethanechol/kg was inhibited by atropine sulfate (3 and 6 mg/kg, IP). In addition, the beta-adrenergic antagonist, propranolol (6 mg/kg, IP, administered 30 min prior to treatment with bethanechol), inhibited bethanechol (8 mg/kg, IP)-induced drinking. Urine output, however, was unaffected by propranolol. Further, the angiotensin I converting enzyme inhibitor, captopril, inhibited significantly the drinking response, but not the increased urine output, accompanying administration of bethanechol (8 mg/kg). The effect of bethanechol and the beta-adrenergic agonist, isoproterenol (25 micrograms/kg) separately and in combination, on water intake was also studied. Both compounds increased water intake but they exerted no interactive effect when administered simultaneously. Administration of bethanechol (8 mg/kg) to conscious rats was also accompanied by a significant reduction in both mean blood pressure and heart rate that reached minimal levels within 10 min after treatment. Both responses had returned to control level by one hr after treatment. These results suggest that bethanechol induces drinking in rats by way of the renin-angiotensin system.

Animals

Bethanechol increases the diagnostic yield in patients with esophageal chest pain.

The diagnostic yield of routine esophageal manometrics in evaluating noncardiac chest pain is low. To determine if bethanechol stimulation would increase the diagnostic yield, we examined 87 patients with chest pain but no gastroesophageal reflux, 47 patients with gastroesophageal reflux but no chest pain, and 20 normal subjects. All subjects underwent standard esophageal manometrics before and after two doses of 50 micrograms/kg body wt bethanechol administered subcutaneously 15 min apart. Mean amplitude and duration of contractions and percentage of abnormal contractions were measured in the distal 7 cm of the esophageal body. Pathologic manometric parameters were defined as mean +/- 2 SD of values obtained in normal patients. Patients with chest pain had pathological responses for amplitude of contraction, duration of contraction, and percentage of abnormal contractions of 31%, 14%, and 22%, respectively, in the basal period. This increased to 43%, 66%, and 40%, respectively, after the first dose of bethanechol and to 53%, 85%, and 82% after the second dose of bethanechol. Chest pain was reproduced with new manometric abnormalities in 46% of patients after the first dose of bethanechol and in 77% after the second dose. Our conclusions are that: sequential bethanechol administration significantly increases the diagnostic yield of standard esophageal manometrics in the evaluation of noncardiac chest pain and duration of contraction after pharmacologic provocation with bethanechol is the best parameter to segregate patients with chest pain from normal subjects and gastroesophageal reflux patients.

Adult

Central actions of bethanechol on the urinary bladder in dogs.

Bethanechol has been used to promote bladder emptying although the clinical efficacy of bethanechol remains uncertain. Both laboratory and clinical observations suggest that the pharmacologic actions of bethanechol are dependent to some extent on intact reflex mechanisms of the bladder. The objective of this study was to determine the effects of central nervous system administration of bethanechol on reflex detrusor contractions. Twelve isolated cross perfusion studies of the central nervous system in dogs were done to determine the cystometric response to central bethanechol administration. Central bethanechol resulted in reflex bladder contractions, decreased cystometric volume, increased maximum intravesical pressure, and increased periurethral EMG activity. This study demonstrated a central nervous system site of pharmacologic activity of bethanechol.

Animals

Prospective evaluation of high-dose bethanechol in investigation of esophageal chest pain.

We compared the value of bethanechol 80 micrograms/kg subcutaneously, acid infusion with a 0.1 normal hydrochloric acid, and edrophonium 80 micrograms/kg intravenously as provocative agents to reproduce chest pain and manometric alterations in 72 patients with noncardiac chest pain. No patient developed typical chest pain and manometric alteration with acid infusion, while five (6.9%) patients developed these changes with edrophonium and four (5.6%) with bethanechol. Only one patient developed diagnostic changes exclusively with bethanechol. All patients tested with bethanechol developed some degree of local pain or significant cholinergic symptoms, with two patients requiring atropine for relief. Side effects from edrophonium were infrequent (28% of patients tested) and did not require atropine administration. We conclude that, using the parameters of typical chest pain and the development of manometric alterations as proof of the esophageal origin of chest pain, bethanechol at 80 micrograms/kg adds little information beyond that obtainable with edrophonium. Further, the high incidence of bethanechol-related side effects at 80 micrograms/kg suggests that this dose should not be generally recommended.

Bethanechol

Galanin and bethanechol appear to activate the same inwardly rectifying potassium current in mudpuppy parasympathetic neurons.

Galanin- and bethanechol-activated whole cell currents were studied in dissociated mudpuppy parasympathetic neurons kept in 12.5 mM KCl. The bethanechol-induced current was reduced when generated during a galanin-induced current. The galanin and bethanechol currents reversed at -45 mV and exhibited inward rectification at more negative potentials. Both the galanin- and bethanechol-induced current relaxations recorded during negative voltage steps were fitted best by two exponentials with the averaged time constant values not significantly different for the galanin and bethanechol currents. We conclude that galanin and bethanechol activate a similar membrane potassium conductance which is different from the background potassium conductance.

Animals

Early effects of bethanechol on the esophageal motor function of infants with gastroesophageal reflux.

Lower esophageal sphincter (LES) pressure, as well as esophageal peristaltic amplitude, duration, and velocity were measured in 16 infants with gastroesophageal reflux before administration of subcutaneous bethanechol, and at 10, 20, and 30 min after. Seven infants received 0.1 mg/kg, and 9 received 0.2 mg/kg. Significant increases in LES pressure occurred at both doses and lasted for 20 min. The amplitude and duration of peristaltic contractions were increased only after the larger bethanechol dose, and the increases were of greater magnitude in the distal esophagus than in the middle esophagus. The velocity of peristalsis decreased significantly in both the lower and middle esophagus, but only after the larger dose of bethanechol. Bethanechol had no effect on any motor function of the upper third of the esophagus. The changes in esophageal peristalsis produced by bethanechol may improve the efficiency of distal esophageal acid clearance and thus may be responsible in part for the therapeutic effect of bethanechol in infants with gastroesophageal reflux.

Bethanechol

Effects of bethanechol on the pancreas in antrectomized and normal rats.

The effect of chronic administration of bethanechol and pentagastrin on the pancreas was examined. Rats were either antrectomized or subjected to a sham operation. Three weeks after surgery, rats received a daily intraperitoneal injection of either bethanechol (12 mg/kg) or pentagastrin (250 micrograms/kg) for 14 days. The fasting serum gastrin after bethanechol treatment increased to 1.89 times that of controls treated with saline. Although antrectomy decreased fasting serum gastrin to approximately 40% of controls, serum gastrin increased by 2.17 times that of the antrectomized rats and 1.37 times that of controls in the bethanechol group. After 14 days of bethanechol treatment, weight and amylase in the pancreas increased significantly compared with control; DNA and protein also increased 1.3 and 1.5 times that of control. The increase in DNA and pancreatic weight indicated that hyperplasia was the predominant mechanism. The pancreas showed atrophy in antrectomized rats but this was reversed by both bethanechol and pentagastrin. The results indicate that either endogenous gastric or extragastric gastrin release by cholinergic stimuli may have an important role in the regulation of pancreatic growth.

Animals

Effects of bethanechol and the octapeptide of cholecystokinin on colonic smooth muscle in the cat.

The aim of this study is to compare the action of the cholinergic agonist, bethanechol, with the action of the octapeptide of cholecystokinin (CCK-OP) on feline circular colonic smooth muscle membrane potential and isometric tension, using the double sucrose gap. Depolarization of the membrane greater than 10 mV by K+ or bethanechol increased tension and spontaneous spike activity. CCK-OP (10(-9) M) depolarized the membrane (6.1 +/- 1.3 mV) without an increase in tension or spike activity. Depolarization of the membrane by increasing [K+]o was associated with a decrease in the membrane resistance. The slow-wave duration (2.3 +/- 0.2 s) was unchanged by administration of K+ or bethanechol but was prolonged after increasing concentrations of CCK-OP. The maximum effect occurred at a 10(-10) M concentration of CCK-OP (4.5 +/- 0.4 s, P less than 0.01). At higher concentrations of CCK-OP (greater than 10(-10) M), the slow-wave pattern became disorganized. Addition of increasing concentrations of [K+]o or bethanechol, but not CCK-OP, stimulated a concentration-dependent increase in the maximum rate of rise (dV/dtmax) of an evoked spike potential. These studies suggest 1) bethanechol decreased the membrane potential without altering the slow-wave activity, whereas CCK-OP has a minimal effect on the membrane potential but distorted the slow-wave shape; 2) an increased amplitude of the spike and dV/dtmax of the spike were associated with an increase in phasic contractions after bethanechol or increased [K+]o; 3) the lack of an increase in the spike amplitude and the dV/dtmax to CCK-OP was associated with no increase in phasic contraction.

Animals

Effects of atropine on pancreatic response to bethanechol, cholecystokinin, and food intake in rats.

Atropine was used to examine the role of cholinergic mechanisms in the pancreatic secretory response to food intake. Unanesthetized rats with gastric, jugular vein, bile-pancreatic, and duodenal cannulas were used; bile-pancreatic juice was recirculated. The maximal response to bethanechol (4 mg.kg-1.h-1) was similar to cholecystokinin (CCK)-8-induced maximal secretion. Atropine (25-200 micrograms.kg-1.h-1) markedly inhibited basal amylase output and caused dose-related inhibition of the incremental response to a maximal dose of bethanechol. Atropine (50 micrograms.kg-1.h-1) shifted the dose-response curve to bethanechol (1-32 mg.kg-1.h-1) to the right but did not alter maximal amylase output. L 364718 (0.5 mg/kg), a CCK receptor antagonist, had no effect on bethanechol-stimulated pancreatic secretion. Atropine (50 micrograms.kg-1.h-1) did not affect the incremental responses to low doses of CCK-8; the maximal response occurred at a higher CCK-8 dose because atropine decreased basal secretion. Atropine (50 or 200 micrograms.kg-1.h-1) did not decrease the amylase response to ingestion of a liquid meal. We conclude that 1) bethanechol is a full agonist for stimulation of pancreatic enzyme secretion and its effects are not mediated by CCK release; 2) atropine is a competitive antagonist of bethanechol-induced pancreatic secretion in vivo but does not directly affect responses to CCK-8; 3) cholinergic mechanisms do not mediate the pancreatic enzyme response to a liquid meal in rats.

Animals

Bethanechol induced contraction in mouse spleen.

Bethanechol was shown to induce contraction in mouse spleen. The possibility of initiating such response by stimulating solely muscarinic receptors was tested in isolated spleens from mice. The present data showed that bethanechol was able to further increase the maximum splenic contraction induced by phenylephrine, suggesting that the bethanechol induced contraction was possibly unrelated to stimulating adrenergic receptors. Moreover, clonidine which was able to suppress the phenylephrine induced splenic contraction, was unable to suppress the splenic contraction induced by bethanechol, and this result supported the above notion. These data suggest that the bethanechol induced splenic contraction could be the result of a direct stimulation of muscarinic receptors in mouse spleens, and an indirect effect mediated through the stimulation by bethanechol of sympathetic neurotransmitter release from sympathetic varicosities seems unlikely.

Animals

Pirenzepine and propantheline effects on esophageal pressure responses to bethanechol.

Pirenzepine is an antisecretory anticholinergic type drug that has recently been shown to be relatively free of usual anticholinergic side effects on esophageal smooth muscle. It has also been suggested that this drug might release some of the inhibitory control of the esophagus and allow increased muscle contractions. To test this hypothesis, we compared the response of the lower esophageal sphincter (LES) and esophageal peristaltic contractions to bethanechol in 12 healthy controls after background oral doses of placebo, pirenzepine (50 mg), and propantheline (30 mg). After baseline placebo, bethanechol (40 micrograms/kg subcutaneously) produced the expected significant increases in LES pressure and amplitude of peristaltic contractions. Maximal increases were 51.9 +/- 14.9 and 29.5 +/- 7.0%, respectively. Also as expected, propantheline inhibited the cholinergic stimulation from bethanechol, allowing only a 10.1 +/- 13.6% increase in LES pressure and a decrease in peristaltic contraction amplitudes (-44.1 +/- 5.0%) after bethanechol. After background pirenzepine, the responses to bethanechol were intermediate between the other two drugs. A significant increase (44.2 +/- 16.4%) in LES pressure occurred after bethanechol while no significant changes (6.9 +/- 5.8%) were noted in peristaltic amplitudes with this drug. Typical side effects of dry mouth were noted in six of the 12 subjects with propantheline and in only three subjects after pirenzepine. These studies once again confirm the absence of usual anticholinergic side effects with oral pirenzepine compared to oral propantheline in the doses studied. We could find no evidence for a release of cholinergic inhibition after pirenzepine administration.

Adult

Adrenergic influence on pentagastrin and bethanechol stimulated gastric acid secretion in dogs with gastric fistula.

The purpose of this study was to elucidate the effect of alpha-, beta- and dopaminergic receptor stimulation and blockade on pentagastrin and bethanechol stimulated gastric acid secretion in conscious dogs with gastric fistula. Gastric acid secretion was found to be subject to a dose related inhibition by isoprenaline. The dose of isoprenaline producing approximately 50% inhibition was higher in the bethanechol--than the pentagastrin experiments (0.10 vs. 0.03 micrograms/kg/min.) and slightly lower after parietal cell vagotomy. The antisecretory effect was mediated via the beta 1-receptors alone. The inhibitory effect of isoprenaline on pentagastrin stimulated acid secretion showed the characteristics of competitive type and on bethanechol stimulated acid secretion of non competitive type. An increasing and dose-dependent stimulation of bethanechol stimulated gastric acid secretion was found for dopamine 1, 5 and 10 micrograms/kg/min. Dopamine (40 micrograms/kg/min.) exerted an inhibitory effect on pentagastrin and bethanechol stimulated gastric acid secretion mediated, via the beta 1-receptors. The stimulatory effect of low doses of dopamine during bethanechol stimulation could not be defined as an effect via beta-receptors. This dual response, the weak inhibitory effects and the potent decreasing effect on antral gastric motility indicate that dopamine has no physiologic relevant effect on gastric acid secretion. One may conclude that beta 1- and beta 2-receptors may exert an influence on gastric acid secretion in dogs. The main effect of dopamine seems to be on gastric motility, while the effect on gastric acid secretion is of minor importance.

Adrenergic beta-Agonists

Bethanechol for pediatric gastroesophageal reflux: a prospective, blind, controlled study.

To investigate the effect of bethanechol on postprandial gastroesophageal reflux in children, and the relationship between its effect on the lower esophageal sphincter pressure and its effect on reflux, we studied 31 consecutive children with pathologic reflux, using manometry and pH probe, both before and after administration of bethanechol. The initial sphincter pressure was subnormal in only 35% of the patients. The bethanechol-treated sphincter pressure was increased in 97% of the patients (from 13.4 +/- 1.3 to 34.1 +/- 2.6 mm Hg) and was normal in 97% of the patients, yet bethanechol did not improve any measure of postprandial reflux in the patient group as a whole. Furthermore, the 20 patients with normal sphincter pressures had significant worsening of their percent of postprandial time with reflux (from 21.8 +/- 5.3 to 33.8 +/- 6.0%, p = 0.009). Thus, this study demonstrates a failure of the acute administration of bethanechol to improve postprandial gastroesophageal reflux and raises the issue of whether the widespread use of bethanechol to treat reflux in children is appropriate.

Bethanechol Compounds