In utero exposure to antiemetic and risk of adult-onset colorectal cancer.

BACKGROUND: Incidence rates of colorectal cancer (CRC) are increasing among adults born in and after the 1960s, implicating pregnancy-related exposures introduced at that time as risk factors. Dicyclomine, an antispasmodic used to treat irritable bowel syndrome, was initially included in Bendectin (comprising doxylamine, pyridoxine, and dicyclomine), an antiemetic prescribed during pregnancy in the 1960s. METHODS: We estimated the association between in utero exposure to Bendectin and risk of CRC in offspring of the Child Health and Development Studies, a multigenerational cohort that enrolled pregnant women in Oakland, CA, between 1959 and 1966 (n = 14 507 mothers and 18 751 liveborn offspring). We reviewed prescribed medications from mothers' medical records to identify those who received Bendectin during pregnancy. Diagnoses of CRC in adult (aged ≥18 years) offspring were ascertained by linkage with the California Cancer Registry. Cox proportional hazards models were used to estimate adjusted hazard ratios, with follow-up accrued from birth through cancer diagnosis, death, or last contact. RESULTS: Approximately 5% of offspring (n = 1014) were exposed in utero to Bendectin. Risk of CRC was higher in offspring exposed in utero (adjusted hazard ratio = 3.38, 95% confidence interval [CI] = 1.69 to 6.77) compared with unexposed offspring. Incidence rates of CRC were 30.8 (95% CI = 15.9 to 53.7) and 10.1 (95% CI = 7.9 to 12.8) per 100 000 in offspring exposed to Bendectin and unexposed, respectively. CONCLUSIONS: Higher risk of CRC in offspring exposed in utero may be driven by dicyclomine contained in the 3-part formulation of Bendectin used during the 1960s. Experimental studies are needed to clarify these findings and identify mechanisms of risk.

Investigations of plausible pharmacodynamics supporting the antispasmodic, bronchodilator, and antidiarrheal activities of Berberis lycium Royle. Via in silico, in vitro, and in vivo studies.

ETHNOPHARMACOLOGICAL RELEVANCE: Berberis lycium Royle, a member of the Berberidaceae family, is a high-value medicinal plant with a documented history of usage in traditional medicine and has demonstrated significant therapeutic results among local populations throughout the globe. It is used traditionally in many parts of Pakistan to treat diarrhea, abdominal spasms, coughs, and chest problems. AIM OF THE STUDY: To investigate the antispasmodic, bronchodilator, and antidiarrheal effects of B. lycium and its possible underlying mechanisms through in silico, in vitro, and in vivo studies. MATERIALS AND METHODS: LC ESI-MS/MS analysis was used to identify bioactive components within the hydromethanolic extract of B. lycium. In silico studies, including network pharmacology and molecular docking, were utilized to investigate the antispasmodic and bronchodilator properties of the extract's bioactive components. In vitro pharmacological studies were conducted using isolated rabbit jejunum, trachea, urinary bladder, and rat ileum preparations. In vivo antidiarrheal activities were conducted in mice, including castor oil-induced diarrhea, intestinal transit, and castor oil-induced enteropooling. RESULTS: The LC ESI-MS/MS analysis of the hydromethanolic extract of B. lycium identified 38 bioactive compounds. Network pharmacology study demonstrated that the mechanism of BLR for the treatment of diarrhea might involve IL1B, TLR4, PIK3R1, TNF, PTPRC, IL2, PIK3CD, and ABCB1, whereas, for respiratory ailments, it may involve PIK3CG, TRPV1, STAT3, ICAM1, ACE, PTGER2, PTGS2, TNF, MMP9, NOS2, IL2, CCR5, HRH1, and VDR. Molecular docking research revealed that chlorogenic acid, epigallocatechin, isorhamnetin, quinic acid, gallic acid, camptothecin, formononetin-7-O-glucoside, velutin, caffeic acid, and (S)-luteanine exhibited a higher docking score than dicyclomine with validated proteins of smooth muscle contractions such as CACB2_HUMAN, ACM3_HUMAN, MYLK_HUMAN, and PLCG1_HUMAN. In vitro investigations demonstrated that Blr.Cr, Blr.EtOAc, and Blr.Aq relaxed spontaneously contracting jejunum preparations; carbachol (1 µM)-induced and K+ (80 mM)-induced jejunum, trachea, and urinary bladder contractions in a concentration-dependent manner, similar to dicyclomine. Moreover, Blr.Cr, Blr.EtOAc, and Blr.Aq exhibited a rightward shift in Ca+2 and carbachol cumulative response curves, similar to dicyclomine, demonstrating the coexistence of antimuscarinic and Ca+2 antagonistic mechanisms due to the presence of alkaloids and flavonoids. In vivo antidiarrheal activities showed that the hydromethanolic extract was significantly effective against castor oil-induced diarrhea and castor oil-induced enteropooling, similar to loperamide, and charcoal meal intestinal transit, similar to atropine, in mice at doses of 50, 100, and 200 mg/kg body weight, which supports its traditional use in diarrhea. CONCLUSION: The dual blocking mechanism of muscarinic receptors and Ca+2 channels behind the smooth muscle relaxing activity reveals the therapeutic relevance of B. lycium in diarrhea, abdominal spasms, coughs, and chest problems.

A First Report of HCTZ and Dicyclomine Induced Uncharacteristic Contraction Alkalosis.

Background: Contraction alkalosis is characterized by low serum sodium and chloride and high serum carbon dioxide and bicarbonate levels. Case Report: A 28-year-old Caucasian active-duty male with a history of autosomal dominant polycystic kidney disease and diarrhea-predominant Irritable Bowel Syndrome (D-IBS) presented to his primary care provider (PCP) with elevated blood pressure (136/96 mmHg), was diagnosed with stage-2 hypertension, and started oral HCTZ (25 mg/day). His medications included dicyclomine (10 mg oral three times daily). Subsequently, (Visit 1), his blood pressure was 130/91 mmHg and he was started on telmisartan (20 mg/day). At Visit 2, 4 weeks later, his blood pressure improved (121/73 mmHg); however, blood chemistry revealed elevated serum CO2 (32 mEq/L) and chloride (94 mmol/L). Four days later, the patient presented to the Emergency Department with dyspnea and swallowing difficulty. The patient returned to his PCP 3 days later complaining of cough, congestion, vomiting, and mild dyspnea, blood pressure of 124/84 mmHg. Two months later, sudden onset of projectile vomiting and abdominal pain while running was reported, resolved by rehydration and a single oral dose of prochlorperazine 25 mg. Three months later, (Visit 3), he complained of lightheadedness and cloudy judgment, suggesting contraction alkalosis. HCTZ was discontinued and telmisartan was increased to 20 mg twice daily. A follow-up blood chemistry panel 2 weeks later revealed serum chloride and CO2 levels within normal limits and blood pressure under 130/80 mmHg. Conclusion: This is the first known report of contraction alkalosis driven by drug-drug interaction between dicyclomine and HCTZ.

Formulation and Evaluation of Hydroxypropylmethylcellulose-dicyclomine Microsponges for Colon Targeted Drug Delivery: In Vitro and In Vivo Evaluation.

OBJECTIVE: The objective of the present study was to design novel colon targeted delivery of Dicyclomine Hydrochloride (DCH) microsponges. METHODS: Microsponges (MS1-MS4) based on different ratios of Hydroxypropylmethylcellulose (HPMC) and DCH were prepared by quasi-emulsion solvent diffusion method. Micro-sponges were analyzed by determining percent yield, encapsulation efficiency, drug content, drug-polymer compatibility and thermal stability. Kinetic analysis of thermal stability data was done by Chang method, Friedman method and Broido method. In vitro dissolution study was carried out at pH 1.2, pH 6.8 and pH 7.4 at different time intervals. RESULTS: Results showed that there was no chemical interaction between DCH and HPMC in all microsponge formulations. Production yield, drug content and encapsulation efficiency were enhanced on increasing the drug-polymer ratio. Thermal stability of all the micro-sponges was greater than that of pure drug. In vitro drug release was decreased on increasing the polymer concentration at different pH levels. The newly prepared micro-sponges based on HPMC were confirmed as a promising means of colon-targeted delivery of DCH. An HPLC method was developed and validated for the bioequivalence study of newly designed microsponges. Pharmacokinetics parameters were calculated using the linear trapezoidal method after single oral administration of microsponges in white albino rabbits. Pharmacokinetics results indicate an enhancement in the value of t1/2, tmax, Cmax and AUC0-t of DCH in the microsponges as compared to standard DCH showing enhanced bioavailability of the drug after microsponges formation. CONCLUSION: The current study shows a new approach for colon-specific delivery of DCH based on microsponges.

Investigation of anti-Parkinson activity of dicyclomine.

BACKGROUND: Parkinson's disease (PD) is a progressive neurodegenerative disorder. The major causative factors that progress the PD are age, genetic abnormalities, environmental factors and degeneration of dopamine neurons in substantia nigra. PD normally exerts a tonic inhibitory effect on striatal cholinergic interneurons. Anticholinergics act by normalizing the disequilibrium between striatal dopamine and acetylcholine-resulted reduction in tremors. OBJECTIVE: This study sought to evaluate the anti-Parkinson potential of dicyclomine in haloperidol (HAL)- and paraquat (PQT)-induced Parkinsonism models in mice. MATERIALS AND METHODS: Sixty albino mice were divided into six groups (n = 10) for each model. Group I: received distilled water 1 mL/kg, Group II: diseased group received HAL (1 mg/kg) for consecutive 21 days and PQT (2 mg/kg) every three days for three weeks, Group III: treated with sinemet (20 mg/kg), Group IV-VI: received 40, 80 and 160 mg/kg dose of dicyclomine, respectively, for consecutive 21 days. The effect of treatments on spontaneous locomotor activity and motor co-ordination was evaluated by using open field, rotarod, actophotometer and light and dark box tests. Cataleptic behavior was estimated by the block method and triple horizontal bar apparatus. Biochemical markers of oxidative stress and levels of neurotransmitters were estimated. RESULTS: Findings from this study showed that dicyclomine at highest dose level of 160 mg/kg prevented HAL- and PQT-induced PD through enhancement of antioxidant defense system. CONCLUSION: The study concluded that dicyclomine could be the potential drug in the management of Parkinsonism.

Misleading meta-analyses of observational studies may generate unjustified alarms: The case of medications for nausea and vomiting in pregnancy.

OBJECTIVES: Because observational studies often use imperfect measurements, results are prone to misclassification errors. We used as a motivating example the possible teratogenic risks of antiemetic agents in pregnancy since a large observational study recently showed that first-trimester exposure to doxylamine-pyridoxine was associated with significantly increased risk of congenital malformations as a whole, as well as central nervous system defects, and previous observational studies did not show such associations. A meta-analysis on this issue was carried out with the aim to illustrate how differential exposure and outcome misclassifications may lead to uncertain conclusions. METHODS: Medline, searched to October 2019 for full text papers in English. Summary Odds Ratios (ORs) with confidence intervals (CIs) were calculated using random-effect models. Probabilistic sensitivity analyses were performed for evaluating the extension of differential misclassification required to account for the exposure-outcome association. RESULTS: Summary ORs were 1.02 (95 % CI, 0.92-1.15), 0.99 (0.82-1.19) and 1.25 (1.08-1.44) for overall congenital, cardiocirculatory, and central nervous system malformations respectively. By assuming exposure and outcome bias factor respectively of 0.95 (i.e., newborns with congenital defects had exposure specificity 5% lower than healthy newborns) and 1.12 (i.e., exposed newborns had outcome sensitivity 12 % higher than unexposed newborns), summary OR of central nervous system defects became 1.13 (95 % CI, 0.99-1.29) and 1.17 (95 % CI, 0.99-1.38). CONCLUSION: Observational investigations and meta-analyses of observational studies need cautious interpretations. Their susceptibility to several, often sneaky, sources of bias should be carefully evaluated.

Protection Versus Progress: The Challenge of Research on Cannabis Use During Pregnancy.

A central tension in pediatric research ethics arises from our desire to protect children from harm while also allowing progress toward discoveries that could improve child health. A prime example of this tension is research on a controversial yet increasingly common practice: the use of cannabis by women to treat nausea and vomiting of pregnancy. Studies of cannabis use in pregnancy face a combination of ethical hurdles because of the inclusion of pregnant women and involvement of a schedule I controlled substance. Given the growing need for research on the safety and efficacy of cannabis for nausea and vomiting of pregnancy, we reflect on the multiple historical contexts that have contributed to the challenge of studying cannabis use during pregnancy and make a case for the ethical rationale for such research.

M1 muscarinic receptor is a key target of neuroprotection, neuroregeneration and memory recovery by i-Extract from Withania somnifera.

Memory loss is one of the most tragic symptoms of Alzheimer's disease. Our laboratory has recently demonstrated that 'i-Extract' of Ashwagandha (Withania somnifera) restores memory loss in scopolamine (SC)-induced mice. The prime target of i-Extract is obscure. We hypothesize that i-Extract may primarily target muscarinic subtype acetylcholine receptors that regulate memory processes. The present study elucidates key target(s) of i-Extract via cellular, biochemical, and molecular techniques in a relevant amnesia mouse model and primary hippocampal neuronal cultures. Wild type Swiss albino mice were fed i-Extract, and hippocampal cells from naïve mice were treated with i-Extract, followed by muscarinic antagonist (dicyclomine) and agonist (pilocarpine) treatments. We measured dendritic formation and growth by immunocytochemistry, kallikrein 8 (KLK8) mRNA by reverse transcription polymerase chain reaction (RT-PCR), and levels of KLK8 and microtubule-associated protein 2, c isoform (MAP2c) proteins by western blotting. We performed muscarinic receptor radioligand binding. i-Extract stimulated an increase in dendrite growth markers, KLK8 and MAP2. Scopolamine-mediated reduction was significantly reversed by i-Extract in mouse cerebral cortex and hippocampus. Our study identified muscarinic receptor as a key target of i-Extract, providing mechanistic evidence for its clinical application in neurodegenerative cognitive disorders.

Nausea and vomiting of pregnancy and hyperemesis gravidarum.

Nausea and vomiting of pregnancy (NVP) is a common condition that affects as many as 70% of pregnant women. Although no consensus definition is available for hyperemesis gravidarum (HG), it is typically viewed as the severe form of NVP and has been reported to occur in 0.3-10.8% of pregnant women. HG can be associated with poor maternal, fetal and child outcomes. The majority of women with NVP can be managed with dietary and lifestyle changes, but more than one-third of patients experience clinically relevant symptoms that may require fluid and vitamin supplementation and/or antiemetic therapy such as, for example, combined doxylamine/pyridoxine, which is not teratogenic and may be effective in treating NVP. Ondansetron is commonly used to treat HG, but studies are urgently needed to determine whether it is safer and more effective than using first-line antiemetics. Thiamine (vitamin B1) should be introduced following protocols to prevent refeeding syndrome and Wernicke encephalopathy. Recent advances in the genetic study of NVP and HG suggest a placental component to the aetiology by implicating common variants in genes encoding placental proteins (namely GDF15 and IGFBP7) and hormone receptors (namely GFRAL and PGR). New studies on aetiology, diagnosis, management and treatment are under way. In the next decade, progress in these areas may improve maternal quality of life and limit the adverse outcomes associated with HG.

New evidence for concern over the risk of birth defects from medications for nausea and vomitting of pregnancy.

OBJECTIVES: The aim of the study was to quantify the risk of major congenital malformations (MCM) associated with first-trimester exposure to antiemetics. STUDY DESIGN AND SETTING: Using the Quebec Pregnancy Cohort (1998-2015), first-trimester doxylamine-pyridoxine, metoclopramide, and ondansetron exposures were assessed for their association with MCM. Generalized estimating equations were used to estimate odds ratios (OR), adjusting for potential confounders (aOR). RESULTS: Within 17 years of follow-up, the prevalence of antiemetic use during pregnancy increased by 76%. Within our cohort, 45,623 pregnancies were exposed to doxylamine-pyridoxine, 958 to metoclopramide, and 31 to ondansetron. Doxylamine-pyridoxine and metoclopramide use were associated with an increased risk of overall MCM (aOR 1.07, 95% confidence interval [CI]: 1.03-1.11; 3,945 exposed cases) and (aOR 1.27, 95% CI: 1.03-1.57; 105 exposed cases), respectively. Doxylamine-pyridoxine exposure was associated with increased risks of spina bifida (aOR 1.87, 95% CI: 1.11-3.14; 23 exposed cases), nervous system (aOR 1.25, 95% CI: 1.06-1.47; 225 exposed cases), and musculoskeletal system defects (aOR 1.08, 95% CI: 1.02-1.14; 1,735 exposed cases). Metoclopramide exposure was associated with an increased risk of genital organ defects (aOR 2.26, 95% CI: 1.14-4.48; 10 exposed cases). No statistically significant association was found between ondansetron exposure and the risk of overall MCM. CONCLUSION: First-trimester doxylamine-pyridoxine and metoclopramide exposure was associated with a significantly increased risk of overall and specific MCM.

Chemical cross-linking: A feasible approach to prolong doxylamine/pyridoxine release from spray-dried chitosan microspheres.

Spray-dried chitosan microparticles have been widely exploited as vehicles for mucosal drug delivery. Despite their advantages as pharmaceutical formulations, one of the major challenges is achieving sustained drug release, which would diminish toxicity and dosage frequency. The aim of this study was to formulate mucoadhesive glutaraldehyde cross-linked chitosan microparticles loaded with doxylamine succinate and pyridoxine hydrochloride as potential nasal drug delivery systems with sustained release. Microparticle models were formulated via spray-drying technique, using glutaraldehyde in different concentrations (0.1-1.0 mg/mL) as a cross-linking agent for chitosan. The obtained particles were with spherical shape, smooth surface and median diameter of 4 µm. The drug entrapment efficiency was high (80.47%-94.25%), indicating a tendency to decrease at higher glutaraldehyde concentrations. FTIR data demonstrated that there were no chemical interactions between glutaraldehyde and the drugs. The in vitro studies showed that the cross-linking process substantially limited particles swelling. The cross-linked particles exhibited sustained drug release characteristics at pH 6.8 over a period of 5 h with an initial burst-effect in the first 30 min. Drug release followed Korsmeyer-Peppas kinetics. Although a decrease of the particles mucoadhesive properties was observed after modification, all cross-linked formulations demonstrated high in vitro adsorption of mucin. The proposed models of mucoadhesive microsphere with sustained drug release are a perspective ground for further development of a novel delivery system for nasal administration of doxylamine and pyridoxine.

The human muscarinic acetylcholine receptor antagonist, Dicyclomine targets signal transduction genes and inhibits the virulence factors in the human pathogen, Candida albicans.

Dicyclomine is a human muscarinic acetylcholine receptor antagonist used for the treatment of abdominal cramps. We are reporting here that dicyclomine can inhibit the in vitro growth and virulence factors of the human pathogen Candida albicans very effectively. Dicyclomine inhibited adhesion, early biofilm, mature biofilm, and planktonic growth. Yeast to hyphal form transition of C. albicans in various inducer media such as serum, proline, glucose, and N-acetylglucosamine was inhibited. Dicyclomine also could kill C. albicans cells within 15 min of exposure. Dicyclomine appears to inhibit the yeast to hyphal conversion by affecting signal transduction pathway. The expression of selected genes associated with yeast to hyphal form transition in serum in presence of dicyclomine was studied using real-time polymerase chain reaction (RtPCR). The RtPCR analysis showed that dicyclomine targets both cAMP pathway as well as MAPK cascade. Eight genes were upregulated. Out of these, three major upregulated genes were Bcy1, Tup1, and Mig1. Dicyclomine downregulated Ume6, Ece1, and Pde2 genes which are involved in cAMP signaling pathway and also downregulated the DNA binding protein gene, Rfg1. Dicyclomine significantly upregulated the master negative regulator of hyphal formation, Tup1. Based on this study we suggest that the muscarinic acetylcholine receptor antagonist, dicyclomine could be repositioned as a potential anti-Candida albicans as well as anti-virulence agent.

Inhibitory action of dicyclomine on lipase activity, kinetics and molecular study.

Lipase is one of the most important groups of enzymes for industry and medicine. It breaks down triacylglycerol to glycerol and fatty acids. Some bacteria use lipase to degrade the extracellular matrix of the host cells to penetrate into the tissues. Dicyclomine is a muscarinic antagonist receptor that relieves the smooth muscle spasm of the gastrointestinal tract and affects the cardiovascular system. In this research, the effect of a dicyclomine on the lipase activity of Pseudomonas aeruginosa was studied. Hanes-Woolf plot showed that the drug inhibited the enzyme by competitive inhibition. The IC50 value (60uM) and Ki (30uM) of the drug revealed that the drug bound to enzyme with high affinity. Determination of enzyme activity in various temperature showed that the maximum activity of lipase was at 60°C both in the presence and absence of the drug. Arrhenius plot determined that the activation energy of the enzyme reaction was increased in the presence of the drug. The model of binding demonstrated that the drug entered a pocket containing 10 amino acids and interacted by hydrogen bond and hydrophobic interaction and the conformational change of the enzyme after binding of the drug was confirmed by fluorescence measurement.

A pharmacological evidence for the presence of antihistaminic and anticholinergic activities in Equisetum debile Roxb.

OBJECTIVE: The study was designed to evaluate possible antihistaminic and anticholinergic activities of Equisetum debile. MATERIALS AND METHODS: Effects of crude ethanolic (Ed.Eth) and effects of crude aqueous (Ed.Aq) extracts of E. debile were studied using isolated guinea pig ileum, rabbit jejunum, and rabbit trachea. Tissue responses were recorded using isotonic and isometric transducers, connected with PowerLab data acquisition system. RESULTS: A dose-dependent (0.1-0.3 mg/ml) rightward shift was demonstrated in histamine concentration-response curves. Whereas a complete relaxation of carbachol (1 µM)-induced contractions in isolated rabbit jejunum (3 mg/ml) and tracheal (10 mg/ml) preparations was observed, similar to dicyclomine at 1 and 3 µM, respectively. However, no significant difference between the effects of Ed.Eth and Ed.Aq was observed. CONCLUSION: Study provides pharmacological evidence for the presence of antihistaminic and anticholinergic activities in crude extracts of E. debile and also highlight its medicinal significance in the management of airway and gastrointestinal disorders.

8-Way Randomized Controlled Trial of Doxylamine, Pyridoxine and Dicyclomine for Nausea and Vomiting during Pregnancy: Restoration of Unpublished Information.

OBJECTIVES: We report information about an unpublished 1970s study ("8-way" Bendectin Study) that aimed to evaluate the relative therapeutic efficacy of doxylamine, pyridoxine, and dicyclomine in the management of nausea and vomiting during pregnancy. We are publishing the trial's findings according to the restoring invisible and abandoned trials (RIAT) initiative because the trial was never published. DESIGN: Double blinded, multi-centred, randomized placebo-controlled study. SETTING: 14 clinics in the United States. PARTICIPANTS: 2308 patients in the first 12 weeks of pregnancy with complaints of nausea or vomiting were enrolled. INTERVENTIONS: Each patient was randomized to one of eight arms: placebo, doxylamine/pyridoxine/dicylcomine, doxylamine/pyridoxine, dicylomine/pyridoxine, doxylamine, dicyclomine/pyridoxine, pyridoxine and dicyclomine. Each patient was instructed to take 2 tablets at bedtime and 1 additional tablet in the afternoon or morning if needed, for 7 nights. OUTCOMES: Reported outcomes included the number of hours of nausea reported by patients, the frequency of vomiting reported by patients and the overall efficacy of medication as judged by physicians. RESULTS: Data from 1599 (69% of those randomized) participants were analyzed. Based on the available summary data of physician evaluation of symptoms and ignoring missing data and data integrity issues, the proportion of participants who were "evaluated moderate or excellent" was greater in each of the seven active treatment groups when compared with placebo (57%): doxylamine/pyridoxine/dicylcomine (14% absolute difference versus placebo; 95% CI: 4 to 24), doxylamine/pyridoxine (21; 95% CI 11 to 30), dicylomine/pyridoxine (21; 95% CI 11 to 30), doxylamine (20; 95% CI 10 to 29), dicyclomine/pyridoxine (4; 95% CI -6 to 14), pyridoxine (9; 95% CI -1 to 19) and dicyclomine (4; 95% CI -6 to 14). Based on incomplete information, the most common adverse events were apparently drowsiness and fatigue. There is a high risk of bias in these previously unpublished results given the high attrition rate in a 7 day trial, the lack of prespecified outcomes or analyses, and the exclusion of some data because of questionable data integrity. CONCLUSION: The available information about this "8-way Bendectin" trial indicates it should not be used to support the efficacy of doxylamine, pyridoxine or dicyclomine for the treatment of nausea and vomiting during pregnancy because of a high risk of bias. TRIAL REGISTRATION: Not registered.

M1 muscarinic receptors are necessary for retrieval of remote context fear memory.

Several studies have investigated the transition of consolidation of recent memory to remote memory in aversively motivated tasks, such as contextual fear conditioning (CFC) and inhibitory avoidance (IA). However, the mechanisms that serve the retrieval of remote memories, has not yet been fully understood. Some evidences suggest that the central cholinergic system appears be involved in the modulation of these processes. Therefore, the present study aimed to investigate the effects of a pre-test administration of dicyclomine, a high-affinity M1 muscarinic receptor antagonist, on the retrieval of remote memories in fear conditioning and IA tasks. Male Wistar rats were trained, and after 1 or 28days, the rats received dicyclomine (16 or 32mg/kg, intraperitoneally, i.p.) and were tested in CFC, tone fear conditioning (TFC) and IA tasks. At both time intervals, 32mg/kg dicyclomine induced impairment of CFC. In TFC task only the performance of the rats 28days after training was impaired. The IA task was not affected in any of the studied intervals. These findings suggest a differential contribution of muscarinic receptors on recent and remote memories retrieval revealing a more generalized role in remote memory.