Acetylcholine receptor agonists effectively attenuated multiple program cell death pathways and improved left ventricular function in trastuzumab-induced cardiotoxicity in rats.

AIMS: Cardiotoxicity is a seriously debilitating complication of trastuzumab (TRZ) therapy in patients with cancer as a consequence of overexpression of the human epidermal growth factor receptor 2. Although most TRZ-induced cardiotoxicity (TIC) cases are reversible, some patients experience chronic cardiac dysfunction, and these irreversible concepts may be associated with cardiomyocyte death. Acetylcholine receptor (AChR) activation has been shown to exert cardioprotection in several heart diseases, but the effects of AChR agonists against TIC have not been investigated. MAIN METHOD: Forty adult male Wistar rats were randomized into 5 groups: (i) CON (0.9 % normal saline), (ii) TRZ (4 mg/kg/day), (iii) TRZ + α7nAChR agonist (PNU-282987: 3 mg/kg/day), (iv) TRZ + mAChR agonists (bethanechol: 12 mg/kg/day), and (v) TRZ + combined treatment (Combined PNU-282987 and bethanechol). KEY FINDINGS: The progression of TIC was driven by mitochondrial dysfunction, autophagic deficiency, and excessive myocyte death including by pyroptosis, ferroptosis, and apoptosis, which were significantly alleviated by α7nAChR and mAChR agonists. Interestingly, necroptosis was not associated with development of TIC. More importantly, the in vitro study validated the cytoprotective effects of AChR activation in TRZ-treated H9c2 cells, while not interfering with the anticancer properties of TRZ. All of these findings indicated that TRZ induced mitochondrial dysfunction, autophagic deficiency, and excessive myocyte death including pyroptosis, ferroptosis, and apoptosis, leading to impaired cardiac function. These pathological alterations were attenuated by α7nAChR and mAChR agonists. SIGNIFICANCE: α7nAChR and mAChR agonists might be used as a future therapeutic target in the mitigation of TIC.

Prevention of salivary gland dysfunction in patients treated with radioiodine for differentiated thyroid cancer: A systematic review of randomized controlled trials.

Introduction: Salivary gland dysfunction (e.g., sialadenitis and xerostomia) is the most common complication of radioactive iodine (RAI) therapy for differentiated thyroid cancer (DTC). Several methods have been used to reduce/prevent this adverse effect. We aimed to systematically review the effectiveness of non-pharmacological and pharmacological interventions in preventing RAI-induced salivary gland dysfunction in patients with DTC. Methods: A systematic review was conducted, according to PRISMA guidelines. The protocol was registered (PROSPERO: CRD42022295229). PubMed, Embase, Scopus, and the Cochrane Library electronic databases were searched from inception to November 2021. Inclusion criteria were randomized controlled trials of DTC patients who were older than 18 years and underwent RAI after thyroidectomy in which at least one studied group received an intervention to prevent salivary gland dysfunction. Results: Twelve studies (a total of 667 participants) were included. Among DTC patients who were treated with RAI, nonpharmacological treatment such as parotid gland massage and aromatherapy ameliorated salivary gland dysfunction. Antioxidants such as vitamin E and selenium demonstrated radioprotective effects on the salivary gland, while other antioxidants did not show radioprotective benefits. Vitamin C showed no significant effects on preventing salivary gland dysfunction. Amifostine had inconsistent outcomes among studies. Among cholinergic agonists, pilocarpine did not demonstrate the radioprotective effect on parotid glands, while bethanechol lowered salivary gland dysfunction. However, the negative results from pilocarpine may be explained by the strong sialorrheic effect of the Cincinnati regimen in both study arms. Conclusion: Among non-pharmacological and pharmacological methods, parotid gland massage, aromatherapy, vitamin E, selenium, amifostine, and bethanechol may have benefits in minimizing RAI-induced salivary gland dysfunction in patients with DTC. The results are limited by a small number of patients and should be confirmed in future larger randomized controlled trials. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=295229, PROSPERO, identifier CRD42022295229.

Dog and human bladders have different neurogenic and nicotinic responses in inner versus outer detrusor muscle layers.

The aim of this study was to investigate layer and species variations in detrusor muscle strip responses to myogenic, neurogenic, and nicotinic, and muscarinic receptor stimulations. Strips from bladders of 9 dogs and 6 human organ transplant donors were dissected from inner and outer longitudinal muscle layers, at least 1 cm above urethral orifices. Strips were mounted in muscle baths and maximal responses to neurogenic stimulation using electrical field stimulation (EFS) and myogenic stimulation using potassium chloride (KCl, 120 mM) determined. After washing and re-equilibration was completed, responses to nicotinic receptor agonist epibatidine (10 µM) were determined followed by responses to EFS and muscarinic receptor agonist bethanechol (30 µM) in continued presence of epibatidine. Thereafter, strips and full-thickness bladder sections from four additional dogs and three human donors were examined for axonal density and intramural ganglia. In dog bladders, contractions to KCl, epibatidine, and bethanechol were 1.5- to 2-fold higher in the inner longitudinal muscle layer, whereas contractions to EFS were 1.5-fold higher in the outer (both pre- and post-epibatidine). Human bladders showed 1.2-fold greater contractions to epibatidine in the inner layer and to EFS in the outer, yet no layer differences to KCl or bethanechol were noted. In both species, axonal density was 2- to 2.5-fold greater in the outer layer. Dogs had more intramural ganglia in the adventitia/serosa layer, compared with more internal layers and to humans. These findings indicate several layer-dependent differences in receptor expression or distribution, and neurogenic responses in dog and human detrusor muscles, and myogenic/muscarinic differences between dog versus humans.

Pancreatic acinar cells utilize tyrosine to synthesize L-dihydroxyphenylalanine.

The pancreatic ß cells can synthesize dopamine by taking L-dihydroxyphenylalanine, but whether pancreatic acinar cells synthesize dopamine has not been confirmed. By means of immunofluorescence, the tyrosine hydroxylase -immunoreactivity and aromatic amino acid decarboxylase (AADC)- immunoreactivity were respectively observed in pancreatic acinar cells and islet ß cells. Treatment with L-dihydroxyphenylalanine, not tyrosine, caused the production of dopamine in the incubation of INS-1 cells (rat islet ß cell line) and primary isolated islets, which was blocked by AADC inhibitor NSD-1015. However, only L-dihydroxyphenylalanine, but not dopamine, was detected when AR42J cells (rat pancreatic acinar cell line) were treated with tyrosine, which was blocked by tyrosine hydroxylase inhibitor AMPT. Dopamine was detected in the coculture of INS-1 cells with AR42J cells after treatment with tyrosine. In an in vivo study, pancreatic juice contained high levels of L-dihydroxyphenylalanine and dopamine. Both L-dihydroxyphenylalanine and dopamine accompanied with pancreatic enzymes and insulin in the pancreatic juice were all significantly increased after intraperitoneal injection of bethanechol chloride and their increases were all blocked by atropine. Inhibiting TH with AMPT blocked bethanechol chloride-induced increases in L-dihydroxyphenylalanine and dopamine, while inhibiting AADC with NSD-1015 only blocked the dopamine increase. Bilateral subdiaphragmatic vagotomy of rats leads to significant decreases of L-dihydroxyphenylalanine and dopamine in pancreatic juice. These results suggested that pancreatic acinar cells could utilize tyrosine to synthesize L-dihydroxyphenylalanine, not dopamine. Islet ß cells only used L-dihydroxyphenylalanine, not tyrosine, to synthesize dopamine. Both L-dihydroxyphenylalanine and dopamine were respectively released into the pancreatic duct, which was regulated by the vagal cholinergic pathway. The present study provides important evidences for the source of L-dihydroxyphenylalanine and dopamine in the pancreas.

Airway cholinergic history modifies mucus secretion properties to subsequent cholinergic challenge in diminished chloride and bicarbonate conditions.

NEW FINDINGS: What is the central question of this study? What is the impact of airway cholinergic history on the properties of airway mucus secretion in a cystic fibrosis-like environment? What is the main finding and its importance? Prior cholinergic challenge slightly modifies the characteristics of mucus secretion in response to a second cholinergic challenge in a diminished bicarbonate and chloride transport environment. Such modifications might lead to retention of mucus on the airway surface, thereby potentiating exacerbations of airway disease. ABSTRACT: Viral infections precipitate exacerbations in many airway diseases, including asthma and cystic fibrosis. Although viral infections increase cholinergic transmission, few studies have examined how cholinergic history modifies subsequent cholinergic responses in the airway. In our previous work, we found that airway resistance in response to a second cholinergic challenge was increased in young pigs with a history of airway cholinergic stimulation. Given that mucus secretion is regulated by the cholinergic nervous system and that abnormal airway mucus contributes to exacerbations of airway disease, we hypothesized that prior cholinergic challenge would also modify subsequent mucus responses to a secondary cholinergic challenge. Using our established cholinergic challenge-rechallenge model in pigs, we atomized the cholinergic agonist bethanechol or saline control to pig airways. Forty-eight hours later, we removed tracheas and measured mucus secretion properties in response to a second cholinergic stimulation. The second cholinergic stimulation was conducted in conditions of diminished chloride and bicarbonate transport to mimic a cystic fibrosis-like environment. In pigs previously challenged with bethanechol, a second cholinergic stimulation produced a mild increase in sheet-like mucus films; these films were scarcely observed in animals originally challenged with saline control. The subtle increase in mucus films was not associated with changes in mucociliary transport. These data suggest that prior cholinergic history might modify mucus secretion characteristics with subsequent stimulation in certain environmental conditions or disease states. Such modifications and/or more repetitive stimulation might lead to retention of mucus on the airway surface, thereby potentiating exacerbations of airway disease.

The beneficial effects of a muscarinic agonist on pancreatic ß-cells.

The brain and nervous system play an important role in pancreatic ß-cell function. This study investigated the role of muscarinic agonists or acetylcholine, which is the major neurotransmitter in the vagal nerve, in regulating pancreatic ß-cell mass and glucose homeostasis. Administration of the muscarinic agonist bethanechol increased insulin secretion and improved glucose tolerance in insulin-receptor substrate 2 (IRS2)-knockout (IRS-2-/-) mice and diet-induced obesity mice. Oral administration of bethanechol increased ß-cell mass and proliferation in wild-type mice, but not IRS-2-/- mice. The muscarinic agonist also increased the incorporation of 5-bromo-2'-deoxyuridine (BrdU) into islets isolated from wild-type mice and pancreatic ß-cell line MIN6. The phosphorylation of protein kinase B (Akt) induced by oral administration of bethanechol was observed in wild-type mice, but not IRS-2-/- mice. The secretion of glucagon-like peptide-1 (GLP-1) was also stimulated by bethanechol in wild-type mice, and a GLP-1 antagonist partially inhibited the bethanechol-induced increase in ß-cell mass. These results suggest that the muscarinic agonist exerted direct and indirect effects on ß-cell proliferation that were dependent on the IRS-2/Akt pathway. The bethanechol-stimulated release of GLP-1 may be indirectly associated with ß-cell proliferation.

MALT Lymphoma, Stress Ulcer and Cholinergic Nerves from the Viewpoint of Bilateral and Unilateral Truncal Vagotomy and Substance P.

BACKGROUND: Vagal nerve plays an important role in the stomach function. The cholinergic nerves are the most abundantly distributed nerves in the gastric tissue. It has recently been reported that the vagal nerve is significantly related to both gastric cancer development and progression. However, its relation to the mesenchymal tumor, including MALT lymphoma, is not known. In this study, we investigated the effect of unilateral truncal vagotomy on gastric MALT lymphoma development by using Helicobacter heilmannii-infected mouse model as well as that of bilateral truncal vagotomy on stress-induced ulcer formation. METHODS: In the first part of this study, the distribution of the cholinergic nerves in the rat gastric mucosa and the effect of bilateral truncal vagotomy, as well as various kinds of agents acting on autonomic nerves in rats, were investigated by the histochemical and macroscopic method. In the second part, we employed MALT lymphoma formation in C57BL/6NCrl mice that were infected with Helicobacter heilmannii. A total of 38 infected mice underwent unilateral vagotomy under microscopy. The mice were randomized into 4 groups from which samples were collected; 2, 3, 4 and 6 months after infection. Both the anterior and posterior sides of the stomachs were sampled from each mouse for pathological and immunohistochemical analyses. RESULTS: The bilateral truncal vagotomy significantly suppressed the restraint-induced gastric ulcer formation in rats, while bethanechol, and 6-hydroxydopamine led to an increase of the gastric ulcer formation. In the unilateral truncal vagotomy study using MALT lymphoma, the thickness of the gastric mucosa was reduced in the vagotomized side compared to the non-vagotomized side. Furthermore, the gastric MALT lymphoma was more prominently found in the vagotomized anterior side of stomach compared with that in the non-vagotomized posterior side of stomach. Substance P-immunoreactive nerves markedly increased surrounding the MALT lymphoma and the neurokinin-1 receptor immunoreactive lymphocytes increased within the MALT lymphoma in the vagotomized side. In conclusion, vagotomy enhanced gastric MALT lymphoma development possibly through the substance P-neurokinin-1 receptor pathway.

Changes of Bladder M1,3 Muscarinic Receptor Expression in Rats Fed with Short-Term/Long-Term High-Fat Diets.

OBJECTIVES: To investigate the effect of high-fat diet (HFD) on bladder M1,3 muscarinic receptor expression and contractile function in the rat. METHODS: Eight-week-old male rats were divided into two groups including one with HFD for 8 weeks (short-term) and the other for 24 weeks (long-term). Each group was compared to age-matched rats fed with normal chow as controls. The body weight, food intake amount and blood biochemistry were monitored. Bladder muscle contractile responses to acetylcholine (0.1-10 µM), bethanechol (10 µM) and KCl (50 mM) were studied in an organ bath set-up. Bladder M1 and M3 muscarinic receptor protein expressions were measured by Western blotting analysis. RESULTS: Increase in body weight as well as blood triglyceride, cholesterol and sugar levels compared to controls were noted in both 8- and 24-week HFD rats. Eating appetite change with increased food and water intakes was noted in the HFD rats. Significantly decreased bladder contractile responses to acetylcholine and bethanechol were shown in both HFD groups. On the other hand, decreased bladder contractile response to KCl was demonstrated in the 24-week group but not the 8-week group. The expressions of bladder M1 and M3 muscarinic receptor proteins were significantly and progressively decreased by HFD feeding from 8 to 24 weeks. CONCLUSIONS: High-fat diet induces obesity and polyphagia in rats. Short-term and long-term HFD feeding decrease rat bladder M1 and M3 receptor expressions as well as contractile responses to the agonistic stimulation. In addition, bladder muscle dysfunction develops after long-term HFD feeding.

Identification of Drug Candidates to Suppress Cigarette Smoke-induced Inflammation via Connectivity Map Analyses.

Cigarette smoking is the main risk factor for chronic obstructive pulmonary disease, and to date, existing pharmacologic interventions have been ineffective at controlling inflammatory processes associated with the disease. To address this issue, we used the Connectivity Map (cMap) database to identify drug candidates with the potential to attenuate cigarette smoke-induced inflammation. We queried cMap using three independent in-house cohorts of healthy nonsmokers and smokers. Potential drug candidates were validated against four publicly available human datasets, as well as six independent datasets from cigarette smoke-exposed mice. Overall, these analyses yielded two potential drug candidates: kaempferol and bethanechol. Subsequently, the efficacy of each drug was validated in vivo in a model of cigarette smoke-induced inflammation. BALB/c mice were exposed to room air or cigarette smoke and treated with each of the two candidate drugs either prophylactically or therapeutically. We found that kaempferol, but not bethanechol, was able to reduce cigarette smoke-induced neutrophilia, both when administered prophylactically and when administered therapeutically. Mechanistically, kaempferol decreased expression of IL-1α and CXCL5 concentrations in the lung. Our data suggest that cMap analyses may serve as a useful tool to identify novel drug candidates against cigarette smoke-induced inflammation.

Octodon degus, a new model to study the agonist and plexus-induced response in the urinary bladder

Urinary bladder function consists in the storage and controlled voiding of urine. Translational studies require animal models that match human characteristics, such as Octodon degus, a diurnal rodent. This study aims to characterize the contractility of the detrusor muscle and the morphology and code of the vesical plexus from O. degus. Body temperature was measured by an intra-abdominal sensor, the contractility of detrusor strips was evaluated by isometric tension recording, and the vesical plexus was studied by electrical field stimulation (EFS) and immunofluorescence. The animals showed a diurnal chronotype as judged from core temperature. The myogenic contractile response of the detrusor muscle to increasing doses of KCl reached its maximum (31.04 mN/mm2) at 60 mM. In the case of cumulative dose-response of bethanecol, the maximum response (37.42 mN/mm2) was reached at 3.2 × 10-4 M. The response to ATP was clearly smaller (3.8 mN/mm2). The pharmacological dissection of the EFS-induced contraction identified ACh and sensory fibers as the main contributors to this response. The neurons of the vesical plexus were located mainly in the trigone area, grouped in big and small ganglia. Out of them, 48.1 % of the neurons were nitrergic and 62.7 % cholinergic. Our results show functional and morphological similarities between the urinary bladder of O. degus and that of humans (AU)

No disponible

Octodon degus, a new model to study the agonist and plexus-induced response in the urinary bladder.

Urinary bladder function consists in the storage and controlled voiding of urine. Translational studies require animal models that match human characteristics, such as Octodon degus, a diurnal rodent. This study aims to characterize the contractility of the detrusor muscle and the morphology and code of the vesical plexus from O. degus. Body temperature was measured by an intra-abdominal sensor, the contractility of detrusor strips was evaluated by isometric tension recording, and the vesical plexus was studied by electrical field stimulation (EFS) and immunofluorescence. The animals showed a diurnal chronotype as judged from core temperature. The myogenic contractile response of the detrusor muscle to increasing doses of KCl reached its maximum (31.04 mN/mm2) at 60 mM. In the case of cumulative dose-response of bethanecol, the maximum response (37.42 mN/mm2) was reached at 3.2 × 10-4 M. The response to ATP was clearly smaller (3.8 mN/mm2). The pharmacological dissection of the EFS-induced contraction identified ACh and sensory fibers as the main contributors to this response. The neurons of the vesical plexus were located mainly in the trigone area, grouped in big and small ganglia. Out of them, 48.1 % of the neurons were nitrergic and 62.7 % cholinergic. Our results show functional and morphological similarities between the urinary bladder of O. degus and that of humans.

Influence of bethanechol on salivary parameters in irradiated patients.

BACKGROUND: Some studies have shown evidence that the prophylactic use of bethanechol chloride (BC) may be useful in preventing the incidence and/or severity of xerostomia (XT). However, the indication of BC in irradiated patients with XT needs to be better characterized. The study aimed to evaluate the influence of BC on XT, salivary flow rate, and salivary composition in patients previously submitted to head and neck radiotherapy. MATERIAL AND METHODS: Forty five irradiated patients complaining of XT used 50 mg/day of BC for 3 months, and the salivary parameters were evaluated in 4 Phases (Before BC therapy, after one month of BC, 2 months of BC, and 3 months of BC). Biochemical analysis included buffering capacity; pH; total protein concentration (TP); amylase concentration (AM); catalase (CAT) and peroxidase (PX) activities. In addition, unstimulated and stimulated salivary flow rates were determined and XT was classified. RESULTS: According to the XT grading system used, patients showed improvement in XT between Phase 1, and Phases 2, 3 and 4. In addition, some changes were observed in TP concentration (decreased); AM concentration (increased); and PX and CAT activities (decreased and increased, respectively) after Phase 2, for stimulated saliva collection (p<0.05). CONCLUSIONS: Our results suggested that when BC was used to treat salivary gland dysfunction induced by head and neck radiotherapy, improvement in XT symptoms, and some changes in saliva composition were shown.

Hormonal Responses to Cholinergic Input Are Different in Humans with and without Type 2 Diabetes Mellitus.

UNLABELLED: Peripheral muscarinic acetylcholine receptors regulate insulin and glucagon release in rodents but their importance for similar roles in humans is unclear. Bethanechol, an acetylcholine analogue that does not cross the blood-brain barrier, was used to examine the role of peripheral muscarinic signaling on glucose homeostasis in humans with normal glucose tolerance (NGT; n = 10), impaired glucose tolerance (IGT; n = 11), and type 2 diabetes mellitus (T2DM; n = 9). Subjects received four liquid meal tolerance tests, each with a different dose of oral bethanechol (0, 50, 100, or 150 mg) given 60 min before a meal containing acetaminophen. Plasma pancreatic polypeptide (PP), glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), glucose, glucagon, C-peptide, and acetaminophen concentrations were measured. Insulin secretion rates (ISRs) were calculated from C-peptide levels. Acetaminophen and PP concentrations were surrogate markers for gastric emptying and cholinergic input to islets. The 150 mg dose of bethanechol increased the PP response 2-fold only in the IGT group, amplified GLP-1 release in the IGT and T2DM groups, and augmented the GIP response only in the NGT group. However, bethanechol did not alter ISRs or plasma glucose, glucagon, or acetaminophen concentrations in any group. Prior studies showed infusion of xenin-25, an intestinal peptide, delays gastric emptying and reduces GLP-1 release but not ISRs when normalized to plasma glucose levels. Analysis of archived plasma samples from this study showed xenin-25 amplified postprandial PP responses ~4-fold in subjects with NGT, IGT, and T2DM. Thus, increasing postprandial cholinergic input to islets augments insulin secretion in mice but not humans. TRIAL REGISTRATION: ClinicalTrials.gov NCT01434901.

Activation of M1/4 receptors phase advances the hamster circadian clock during the day.

The mammalian circadian clock in the suprachiasmatic nucleus (SCN) can be reset by the cholinergic agonist carbachol. In hamsters, intraSCN carbachol produces phase advances during the day. This phenomenon has previously been attributed to the muscarinic receptors, as carbachol-induced phase shifts are blocked by pretreatment with the muscarinic antagonist atropine. The SCN contains all five muscarinic receptors, leaving open the question as to which muscarinic receptors mediate these shifts. Here we test two selective muscarinic agonists, the M1/4 agonist McN-A-343 and the M2/3 agonist bethanechol, in addition to the non-selective cholinergic agonist carbachol. Consistent with previous reports, carbachol produced significant phase advances when injected to the SCN during the mid-subjective day. At the doses used here, McN-A-343, but not bethanechol, also produced significant phase shifts when injected to the SCN during the mid-subjective day. Phase shifts to McN-A-343 were as large as those produced by carbachol, suggesting that activation of the M1/4 receptors alone can fully account for the daytime phase advances produced by cholinergic agonists. Given acetylcholine's role in arousal, and the similarity between phase advances to carbachol/McN-A-343 and to exercise and arousal manipulations, it is possible that acetylcholine may contribute to non-photic resetting of the circadian clock.

The molecular basis of the genesis of basal tone in internal anal sphincter.

Smooth muscle sphincters exhibit basal tone and control passage of contents through organs such as the gastrointestinal tract; loss of this tone leads to disorders such as faecal incontinence. However, the molecular mechanisms underlying this tone remain unknown. Here, we show that deletion of myosin light-chain kinases (MLCK) in the smooth muscle cells from internal anal sphincter (IAS-SMCs) abolishes basal tone, impairing defecation. Pharmacological regulation of ryanodine receptors (RyRs), L-type voltage-dependent Ca(2+) channels (VDCCs) or TMEM16A Ca(2+)-activated Cl(-) channels significantly changes global cytosolic Ca(2+) concentration ([Ca(2+)]i) and the tone. TMEM16A deletion in IAS-SMCs abolishes the effects of modulators for TMEM16A or VDCCs on a RyR-mediated rise in global [Ca(2+)]i and impairs the tone and defecation. Hence, MLCK activation in IAS-SMCs caused by a global rise in [Ca(2+)]i via a RyR-TMEM16A-VDCC signalling module sets the basal tone. Targeting this module may lead to new treatments for diseases like faecal incontinence.

Haustral boundary contractions in the proximal 3-taeniated rabbit colon.

The rabbit proximal colon is similar in structure to the human colon. Our objective was to study interactions of different rhythmic motor patterns focusing on haustral boundary contractions, which create the haustra, using spatiotemporal mapping of video recordings. Haustral boundary contractions were seen as highly rhythmic circumferential ring contractions that propagated slowly across the proximal colon, preferentially but not exclusively in the anal direction, at ∼0.5 cycles per minute; they were abolished by nerve conduction blockers. When multiple haustral boundary contractions propagated in the opposite direction, they annihilated each other upon encounter. Ripples, myogenic propagating ring contractions at ∼9 cycles per min, induced folding and unfolding of haustral muscle folds, creating an anarchic appearance of contractile activity, with different patterns in the three intertaenial regions. Two features of ripple activity were prominent: frequent changes in propagation direction and the occurrence of dislocations showing a frequency gradient with the highest intrinsic frequency in the distal colon. The haustral boundary contractions showed an on/off/on/off pattern at the ripple frequency, and the contraction amplitude at any point of the colon showed waxing and waning. The haustral boundary contractions are therefore shaped by interaction of two pacemaker activities hypothesized to occur through phase-amplitude coupling of pacemaker activities from interstitial cells of Cajal of the myenteric plexus and of the submuscular plexus. Video evidence shows the unique role haustral folds play in shaping contractile activity within the haustra. Muscarinic agents not only enhance the force of contraction, they can eliminate one and at the same time induce another neurally dependent motor pattern.

Conscious voiding during bladder obstruction in guinea pigs correlates with contractile activity of isolated bladders.

PURPOSE: There are many hypotheses accounting for detrusor overactivity; however, the exact mechanisms are still incompletely understood. We used a model of bladder outlet obstruction in male guinea pigs as a way to produce detrusor overactivity. The objective was to determine whether changes in voiding of obstructed guinea pigs correlates with specific changes in contractile activity of their isolated bladders in vitro. MATERIAL AND METHODS: Conscious voiding activity of sham-operated and obstructed animals was measured in metabolic cages. Contractile activity (spontaneous or evoked by distension, electrical field stimulation or cholinergic agonists) was recorded via a pressure transducer in the isolated bladders in vitro. RESULTS: The frequency of conscious voiding increased (while voiding volume decreased) in the obstructed group, compared with the sham-operated group, 4 weeks after surgical intervention. In comparison to the sham-operated animals, the bladders from the obstructed guinea pigs were enlarged and inflamed, their frequency of spontaneous contractions was higher, while the amplitudes of electrical field stimulation (EFS)-induced contractions and bladder compliance were lower. Changes in conscious voiding during obstruction were significantly associated with alterations in structural parameters (bladder weight, thickness and histological damage score) and functional contractile parameters (frequency of spontaneous contractions, amplitude of EFS-induced contractions and bladder compliance) of their isolated bladders. CONCLUSIONS: Our findings revealed significant association between conscious voiding and structural and contractile activity changes of the isolated bladders in obstruction. The data suggest that change in contractile activity of the bladder itself is a major contributor to obstruction-induced bladder overactivity.

Partial agonistic effects of pilocarpine on Ca(2+) responses and salivary secretion in the submandibular glands of live animals.

NEW FINDINGS: What is the central question of this study? Pilocarpine stimulates salivary secretion via muscarinic ACh receptors (mAChRs), although the Ca(2+) -mobilizing effect of pilocarpine in salivary gland cells is extremely small. Therefore, we examined the effect of pilocarpine on Ca(2+) responses in submandibular gland cells and on secretion in vitro and in vivo. What is the main finding and its importance? Pilocarpine induces small Ca(2+) responses and reduces the effects of other mAChR agonists on Ca(2+) responses via its partial agonistic effects. These effects of pilocarpine on Ca(2+) responses in the submandibular gland were further established in vivo with a novel Ca(2+) imaging system and a genetically encoded Ca(2+) indicator. Pilocarpine stimulates salivary secretion via muscarinic ACh receptors (mAChRs), although the effect of pilocarpine on Ca(2+) responses in dispersed salivary gland cells is extremely small. Here, we demonstrate the effect of pilocarpine on Ca(2+) responses and salivary secretion in the rat submandibular gland (SMG). In fura-2-loaded SMG cells, the maximal effect of pilocarpine on [Ca(2+) ]i elevation was 16% of that of carbachol, and pilocarpine attenuated carbachol- and bethanechol (Bet)-induced [Ca(2+) ]i increases, indicating that pilocarpine acts as a partial agonist for mAChR-mediated Ca(2+) responses. The partial agonistic effect of pilocarpine on Ca(2+) dynamics in the SMG was also confirmed in live animals using the genetically encoded Ca(2+) indicator, YC-Nano50. Administration of pilocarpine (3 mg kg(-1) , i.p.) elicited a small increase in [Ca(2+) ]i in the SMG. Quantitative analyses demonstrated that resting [Ca(2+) ]i was ∼37 nm, which was increased by pilocarpine (3 mg kg(-1) ) and Bet (10 mg kg(-1) ) to 44 and 69 nm, respectively. The inhibitory effects of pilocarpine on Bet-induced Ca(2+) responses were also elucidated in vivo. We further examined real-time changes in pilocarpine-induced SMG salivary secretion and showed that pilocarpine induced an extremely weak secretory response and reduced Bet-induced secretion. Unlike Ca(2+) responses, pilocarpine failed to reduce the effect of Bet on SMG blood flow. Our results demonstrate that pilocarpine acts as a partial agonist of mAChRs to induce weak salivary secretion that is correlated with small increases in [Ca(2+) ]i . Furthermore, pilocarpine exhibits an antagonistic effect on mAChR-induced Ca(2+) responses and salivary secretion.

Effects of bethanechol chloride and distigmine bromide on postvoiding residual volume in patients with underactive bladder.

AIM: The efficacy of cholinergic drugs for reduction of post-voiding residual volume (PVR) in patients with underactive bladder is still controversial. This study was performed to examine whether cholinergic drugs have such an effect on PVR. METHODS: Patients with underactive bladder treated for more than two months with cholinergic drugs, which were later discontinued, were extracted retrospectively based on their charts. The changes in PVR, cholinesterase activity (ChE), renal function, and voiding function before and after discontinuation of cholinergic drugs were reviewed and analyzed. RESULTS: Twenty-nine patients were included in this study. In multiple linear regression analysis, the discontinuation of distigmine bromide (DB) was indicated as a significant covariate for PVR increase and ChE increase, while bethanechol chloride (BC) was not a significant covariate. The increase in ChE was significantly correlated with both PVR and voided volume after discontinuation of cholinergic drugs. CONCLUSION: DB could reduce PVR via a decrease in ChE. However, BC at doses up to 60 mg did not reduce PVR. DB may be recommended for the reduction of PVR in patients with underactive bladder.