Atropine Pretreatment Research Articles

Prophylactic Intravenous Aminophylline for Preventing Bradyarrhythmias During Coronary Atherectomy: A 10-Year Single-Center Experience.

Aminophylline, an adenosine antagonist, can be used to prevent adenosine-mediated bradyarrhythmias. Retrospective, observational, descriptive analysis of patients undergoing rotational atherectomy with intravenous (IV) aminophylline pretreatment during a 10-year period (2010-2020). The primary composite outcome was the occurrence of a documented bradyarrhythmia requiring pharmacologic intervention and/or temporary pacemaker (TPM) implantation. A total of 296 patients received IV aminophylline pretreatment. The primary composite outcome occurred in 1.7% (n = 5) of patients. None of the patients required rescue TPM. Bradyarrhythmias were documented in 2.4% (n = 7) of patients. Pharmacologic interventions, typically with IV atropine, were used in 15% (n = 43) of patients. Per-vessel analyses demonstrated that patients undergoing atherectomy to the circumflex and right coronary arteries were more likely than those undergoing atherectomy to other vessels to have bradyarrhythmias requiring pharmacologic intervention (3.4% vs 0%, P = .01). In this 10-year single-center experience using IV aminophylline pretreatment to prevent major bradyarrhythmias in patients undergoing coronary atherectomy, none of the patients required rescue TPM implantation. These data demonstrate that coronary atherectomy can be performed safely without prophylactic TPM, with aminophylline pretreatment and selective use of atropine representing an effective noninvasive approach.

Catecholaminergic and Cholinergic Systems Mediate Beneficial Effect of Vortioxetine on Diabetes-Induced Neuropathic Pain.

The therapeutic potential of vortioxetine on mechanical hyperalgesia/allodynia was investigated in rats with streptozotocin-induced diabetes, and its possible mechanism of action was elucidated in this study. The obtained findings demonstrated that subacute vortioxetine treatment (5 and 10 mg/kg for 2 weeks) increased the reduced paw-withdrawal thresholds of diabetic rats both in the Randall-Selitto and Dynamic plantar tests. Moreover, the falling latencies of animals did not change in the Rota-rod assessments. These results suggest that vortioxetine administration significantly improved diabetes-induced hyperalgesia and allodynia responses in the rats without affecting their motor coordination. The vortioxetine (5 mg/kg)-induced antihyperalgesic and antiallodynic effects were reversed by AMPT, yohimbine, ICI 118,551, sulpiride and atropine pre-treatments, suggesting the involvement of the catecholaminergic system, α2- and β2-adrenoceptors, D2/3 dopaminergic receptors and cholinergic muscarinic receptors in the exhibited pharmacological activity, respectively. Moreover, the data from the immunohistochemical studies indicated that the inhibition of c-Fos overexpression in dorsal horn neurons also mediates the beneficial effect of this drug. Vortioxetine induced no difference in plasma glucose levels in diabetic rats. If clinical studies confirm these findings, the concomitant beneficial effect of vortioxetine on mood disorders and its neutral activity profile on glycemic control may make it an alternative drug for the treatment of neuropathic pain.

Potential use of prophylactic intracoronary atropine in reducing reperfusion vagal reflex-related events in ST-elevation myocardial infarction

In this study, we evaluated the potential use of atropine in reducing reperfusion vagal reflex-related events during emergency percutaneous coronary intervention (PCI) for acute inferior ST-elevation myocardial infarction (STEMI). Retrospectively, we included 142 patients with inferior wall STEMI, who were treated between October 2015 and October 2020, in this study. The patients were divided into an experimental group (n = 70) and a control group (n = 72) depending on whether they received prophylactic intracoronary atropine. The experimental group was then subdivided into a low-dose group (0.5 – 1 mg atropine, n = 40) and a high-dose group (2 mg atropine, n = 30). We compared the incidence of reperfusion vagal reflex-related events and the application of temporary pacemakers between these groups. The results showed that the incidence of bradycardia (24.3% vs. 45.8%, P = 0.007), hypotension (18.6% vs. 40.3%, P = 0.005), ventricular tachycardia (4.3% vs. 19.4%, P = 0.005), and ventricular fibrillation (8.6% vs. 20.8%, P = 0.040) as well as the application of temporary pacemakers (14.3% vs. 29.2%, P = 0.032) were all much lower (all P < 0.05) in the experimental group than in the control group. In addition, the incidence of bradycardia (10% vs. 35%, P = 0.016), hypotension (6.7% vs. 27.5%, P = 0.027), ventricular tachycardia (6.7% vs. 25%, P = 0.044), and ventricular fibrillation (0 vs. 15%, P = 0.034) as well as the application of temporary pacemakers (3.3% vs. 22.5%, P = 0.036) were all much lower (all P < 0.05) in the high-dose group than the low-dose group. Our findings demonstrate that atropine pretreatment could prevent reperfusion vagal reflex-related events and reduce the application of temporary pacemakers during emergency PCI for acute inferior STEMI. These effects can be significantly enhanced by high-dose (2 mg) atropine pretreatment.

Investigation of the Diuretic Potential of Diosmetin, a Flavonoid from Citrus lemon in Sprague-Dawley Rat Model

Diosmetin is a flavonoid present in citrus fruit like lemon. Interestingly, lemon juice has been reported for its diuretic activity. The present study aimed to investigate diosmetin's diuretic activity in Sprague Dawley (SD) rats after acute and prolonged administration of different doses. The volume of urine, Na+ and K+ levels, and pH had been estimated with the help of urine samples collected after 6 hrs of normal saline-loaded rats. In the acute diuretic study, a potent and significant response (p<0.001) was observed at the dose of 50 mg/kg in comparison to 20 and 40 mg/kg. The values of the diuretic index for the test groups (20, 40, and 50 mg/kg) were observed to be 1.11, 1.15, and 1.56, respectively. The value of Lipschitz showed that, at the dose of 50 mg/kg, the diuretic activity of diosmetin was 57% in comparison with furosemide (100%). In prolonged diuretic study, diosmetin (50 mg/kg) caused significant diuresis and natriuresis. The diuretic action of diosmetin was significantly decreased with atropine pretreatment, indicating the involvement of muscarinic receptors, while no significant change was observed in the response of diosmetin with pretreatment of L-NAME and indomethacin, excluding the involvement of endothelium related mediators (NO and PGI2). Moreover, the hematological analysis indicated that diosmetin at 50 mg/kg exhibited mild changes in blood-related parameters. In addition, histopathological examination indicated no significant pathological changes. However, compared to the control, mild inflammation was observed in diosmetin and furosemide-treated rats. We concluded that diosmetin increased the volume of urine and urine electrolytes (Na+ and K+) concentration in a dose-dependent manner in the acute diuretic study, while a significant response was also observed in the prolonged diuretic model. Therefore, diosmetin may be considered a potential diuretic candidate for further studies.

Vasorelaxant and Antihypertensive Effects of Bergenin on Isolated Rat Aorta and High Salt-Induced Hypertensive Rats.

Bergenin is a phenolic glycoside that has been reported to be present in some medicinal plants which are traditionally used for their antihypertensive actions. So, bergenin was investigated for antihypertensive and vasorelaxant experiments in a rat model. Bergenin produced a significant fall in the mean arterial pressure (MAP) of rats. To explore the involvement of NO and muscarinic receptors, rats were pretreated with L-NAME and atropine in-vivo. The L-NAME did not change significantly the effect of bergenin on MAP excluding the involvement of NO. Unlike the L-NAME, atropine pretreatment reduced the effect of bergenin on MAP, indicating the role of muscarinic receptors. In in-vitro study, the bergenin produced endothelium-dependent (at lower concentrations) and independent (at higher concentrations) vasorelaxation, which was attenuated significantly in the presence of atropine and indomethacin but not with L-NAME. While a partial response was observed against K+-induced contractions. This was further confirmed when bergenin partly shifted the CaCl2-CRCs toward right. Bergenin also suppressed the PE peak formation, indicating the antagonist effect against the release of Ca2+. Moreover, the bergenin-induced vasorelaxant response was not markedly attenuated with TEA, while significantly ablated with 4-AP and BaCl2. In conclusion, the antihypertensive effects of bergenin are due to Ca2+ channel blockade, K+ channels activation, and muscarinic receptor-linked vasodilation.

Investigation into the Antihypertensive Effects of Diosmetin and Its Underlying Vascular Mechanisms Using Rat Model.

Objective: Diosmetin is a flavonoid that is found in many important medicinal plants that have antihypertensive therapeutic potential. Diosmetin has been shown to have antiplatelet, anti-inflammatory and antioxidant properties, which suggests that it could be a potential candidate for use in antihypertensive therapy. Methods: In vivo and in vitro methods were used for our investigation into the antihypertensive effects of diosmetin. Results: Diosmetin significantly decreased the mean arterial pressure (MAP). The effects of diosmetin on the MAP and heart rate were more pronounced in hypertensive rats. To explore the involvement of the muscarinic receptors-linked NO pathway, Nω-nitro-L-arginine methyl ester (L-NAME) and atropine were pre-administered in vivo. The pretreatment with L-NAME did not significantly change the effects of diosmetin on the MAP by excluding the involvement of NO. Unlike L-NAME, the atropine pretreatment reduced the effects of diosmetin on the MAP, which demonstrated the role of the muscarinic receptors. In the in vitro study, diosmetin at lower concentrations produced endothelium-dependent and -independent (at higher concentrations) vasorelaxation, which was attenuated significantly by the presence of atropine and indomethacin but not L-NAME. Diosmetin was also tested for high K+-induced contractions. Diosmetin induced significant relaxation (similar to verapamil), which indicated its Ca2+ antagonistic effects. This was further confirmed by diosmetin shifting the CaCl2 CRCs toward the right due to its suppression of the maximum response. Diosmetin also suppressed phenylephrine peak formation, which indicated its antagonist effects on the release of Ca2+. Moreover, BaCl2 significantly inhibited the effects of diosmetin, followed by 4-AP and TEA, which suggested that the K+ channels had a role as well. Conclusions: The obtained data showed the Ca2+ channel antagonism, potassium channel activation and antimuscarinic receptor-linked vasodilatory effects of diosmetin, which demonstrated its antihypertensive potential.

389 Atropine Pretreatment and Adverse Events in Emergency Pediatric Intubation

Atropine may blunt the vagal response to laryngoscopy and endotracheal intubation in children, though its role in emergency pediatric intubation remains unclear. Pediatric Advanced Life Support (PALS) guidelines recommend against the routine use of prophylactic atropine when intubating critically-ill children and infants, but state it “may be reasonable” in specific situations with high risk of bradycardia (eg, when using succinylcholine for paralysis). Our goal was to describe the use of atropine for pediatric intubation in the emergency department (ED) and estimate its association with peri-intubation adverse events (AE). We performed a secondary analysis of prospectively-collected data from the National Emergency Airway Registry (NEAR), a multicenter registry of academic and community EDs in the United States requiring reporting of ≥90% of intubations for participation. Patients ≤15 years of age were included from 2016 through 2018. We report proportions with associated 95% CIs and multivariable logistic regression estimating the association between atropine pretreatment and AEs including bradycardia, hypotension, cardiac arrest, and hypoxia while adjusting for age, pre-intubation blood pressure and oxygen saturation, sedative and paralytic choice, type of laryngoscopy, intubator level of training, number of attempts and clustering within hospitals. 25 EDs provided data for 612 pediatric intubations: 139 <1 year of age; 129 ages 1 year to <3 years; 144 ages 3 years to <8 years; and 200 ages 8 years to ≤15 years. While all intubations were ultimately successful, first pass success rate was 78%. Atropine pretreatment was given in 7% of intubations, of which, 51% were <1 year and 23% received succinylcholine. AEs occurred in 16% of intubation attempts with hypoxia being the most common AE; cardiopulmonary AEs occurred in 4%; bradycardia in 2%. Of the 9 patients who did not receive atropine pretreatment and experienced bradycardia, 6 received rocuronium for paralysis and 3 received succinylcholine. After adjusting for confounding, atropine pretreatment was associated with an increased occurrence of cardiopulmonary AEs (OR 2.60, 95% CI 1.02-6.61). In this multicenter prospective cohort of pediatric intubations, atropine pretreatment was uncommon and associated with increased adverse cardiopulmonary events. This finding challenges the use of atropine to prevent bradycardia in emergency pediatric intubation and further research is required to explore the unexpected association with cardiopulmonary adverse events.

Insight into the cardiovascular mechanisms of blood pressure lowering effect of gitogenin: a steroidal saponin

ABSTRACT Background/objectives : Steroidal saponins are widely distributed in medicinal plants with potential applications in cardiovascular disorders. Gitogenin, a saponin, has not been explored as antihypertensive; this investigation was aimed to explore its blood pressure lowering potential and underlying mechanisms. Methodology : The effect of gitogenin was evaluated on blood pressure in vivo, using normotensive rat model and the underlying cardiovascular mechanism(s) in vitro, in isolated rat aorta and in atria preparations using PowerLab data acquisition system (ADInstrument, Australia). Results : Intravenous injection of gitogenin decreased mean arterial pressure (MAP) in anesthetized rats. Atropine (1 mg/kg) and L-NAME (100 mg/kg) pretreatment significantly (*p < .05) attenuated effect on MAP to gitogenin. In isolated intact aortic rings, gitogenin induced endothelium-dependent vasodilatation (maximum 65%), which was ablated (maximum 22%) with L-NAME (100 mg/kg) and atropine (1 μM) pretreatment or endothelium removal. Gitogenin was found more potent against angiotensin II precontractions without effect on high K+ and low K+ precontractions. In isolated rat right atria, gitogenin suppressed rate and force of contractions. Atropine (1 μM) pretreatment partially inhibited effect of gitogenin on force and eliminated its effect on rate. Combined atropine (10 μM) and atenolol (0.5 μM) pretreatment was without effect on force of contractions but eliminated effect of gitogenin on rate with 25% increase. Conclusion : These findings indicate that antihypertensive effect of gitogenin is the outcome of vascular and cardiac effects; agonistic effect on vascular M3 and cardiac M2 receptors; and being more selective for M2. Increase in the rate of atrial contraction might be of clinical importance.

Incidence of Bradycardia and the Use of Atropine in Pediatric Rapid Sequence Intubation in the Emergency Department.

Bradycardia during rapid sequence intubation (RSI) is an uncommon but serious adverse effect encountered in pediatric intubations. Atropine has historically been used in the pediatric population as RSI premedication to prevent bradycardia, especially when using succinylcholine as an induction agent. The objective of this analysis was to identify the incidence of bradycardia with or without atropine use. This single-center, retrospective, observational case series reviewed pediatric patients up to 18 years old requiring intubation from January 1, 2015, to December 31, 2018. Bradycardia was determined by analyzing heart rates associated with time during and up to 5 minutes after intubation. A total of 62 patients were included. Three (4.8%) patients experienced a bradycardic event during intubation. A total of 15 (24.2%) patients received atropine for pretreatment of RSI. Incidence of bradycardia was similar between those who received atropine and those who did not. An increasing trend in atropine use was shown throughout the assessment period, yet only 18 (29%) patients met criteria for atropine pretreatment based on the 2015 Pediatric Advanced Life Support guideline recommendations for RSI. Bradycardia incidence was low in pediatric patients undergoing RSI in our emergency department. Use of atropine or succinylcholine did not affect the incidence of bradycardia during pediatric intubation over this study period. Our results show a low incidence of bradycardia and support the 2015 Pediatric Advanced Life Support Guideline recommendation of limiting the use of atropine premedication in pediatric intubations.

Intestinal Electrical Stimulation Enhances Release of Postprandial Incretin Hormones Via Cholinergic Mechanisms.

Intestinal electrical stimulation (IES) has been reported to reduce body weight and improve glucose tolerance in obese and diabetic rats. Our study aimed to investigate possible IES mechanisms involving incretin hormones using intraduodenal glucose infusion in rats. We hypothesized that the enhanced release of postprandial glucagon-like peptide-1 (GLP-1) at early phase by IES was mediated through neuro/paracrine mechanisms involving the vagal nerve and glucose-dependent insulinotropic peptide (GIP). Fifteen normal male Sprague-Dawley rats chronically implanted with duodenal electrodes for IES, and an intra-duodenum catheter for the infusion of glucose were studied in a series of sessions with IES of different parameters with and without atropine and M3 receptor antagonist. Blood samples were collected via the tail vein for the measurement of blood glucose, and plasma GLP-1, and GIP. (1) Compared to sham-IES, IES of 0.3ms reduced blood glucose by 16.5-28.4% between 30 and 120min (all time points p < 0.05), and IES of 3-ms reduced blood glucose at 60 (12.6%) and 90min (11.8%). IES of 0.3ms showed a greater hypoglycemic effect than 3ms (p = 0.024) at 30min. (2) IES elevated plasma GLP-1 with 0.3ms (p = 0.001) and with 3ms p = 0.03). (3) IES substantially elevated plasma GIP with 0.3ms (p = 0.002) and with 3ms (p < 0.001). (4) Pretreatment of atropine and the M3 receptor antagonist 4-DAMP blocked the effects of IES on GLP-1, GIP, and blood glucose. IES reduces postprandial blood glucose by enhancing the release of GLP-1 and GIP mediated via the cholinergic mechanism.

Role of Muscarinic Receptors in Hypoalgesia Induced by Crocin in Neuropathic Pain Rats.

Objective Crocin as an important constituent of saffron has antineuropathic pain properties; however, the exact mechanism of this effect is not known. The aim of this study was whether the hypoalgesic effect of crocin can be exerted through muscarinic receptors. Materials and Methods In the present project, 36 male Wistar rats (200 ± 20 g) were used. Animals randomly divided into six groups (sham, neuropathy, neuropathy + crocin, neuropathy + atropine 0.5 mg/kg, neuropathy + atropine 1 mg/kg, and neuropathy + atropine 1 mg/kg + crocin). Neuropathy was induced by the chronic constriction injury (CCI) method on the sciatic nerve. Crocin and atropine was administered intraperitoneally during 14 days following the 14th day after surgery. Pain response was detected every three days, two hours after each injection and 3 days following last injection. Mechanical allodynia and thermal hyperalgesia were detected using the Von Frey filaments and plantar test device, respectively. Results CCI significantly reduced the paw withdrawal response to mechanical and thermal stimulus (P < 0.01 and P < 0.05, respectively). Crocin therapy significantly reduced mechanical allodynia and thermal hyperalgesia induced by CCI (P < 0.05). Atropine pretreatment significantly blocked the hypoalgesic effect of crocin (P < 0.05 in mechanical allodynia and P < 0.01 in thermal hyperalgesia). Fourteen days administration of atropine alone at a dose of 0.5 mg/kg but not 1 mg/kg significantly reduced CCI-induced mechanical allodynia at day 30 after surgery. Conclusion Crocin significantly decreased CCI-induced neuropathic pain. The hypoalgesic effect of crocin was blocked by atropine pretreatment, which indicates an important role for muscarinic receptors in the effect of crocin.

The Effect of Atropine on Trigeminocardiac Reflex-induced Hemodynamic Changes During Therapeutic Compression of the Trigeminal Ganglion.

Percutaneous compression of the trigeminal ganglion (PCTG) can induce significant hemodynamic perturbations secondary to the trigeminocardiac reflex (TCR). The aim of this study was to investigate the effect of atropine pretreatment on hemodynamic responses during PCTG for trigeminal neuralgia. A total of 120 patients who received PCTG were randomly assigned to control and atropine groups that were pretreated with saline (n=60) and atropine 0.004 mg/kg intravenously (n=60), respectively. Heart rate (HR) and mean arterial pressure (MAP) were measured at 9 timepoints from before induction of anesthesia until the end of the PCTG procedure; the incidence of TCR was also observed. HR was higher in the atropine compared with control group from the time of skin puncture with the PCTG needle until after the procedure was completed (P<0.05). MAP was also higher in the atropine compared with control group, but only at entry of the needle into the foramen ovale until 1 minute after trigeminal ganglion compression (P<0.05). HR was reduced in both groups during entry of the needle into the foramen ovale and during ganglion compression, but less so in the atropine compared with the control group (P<0.05). MAP increased during PCTG compared with baseline in both groups, but with a larger increase in the atropine group (P<0.05). Two and 52 cases in the control group, and 6 and 1 cases in the atropine group, exhibited a TCR during entry of the needle into the foramen ovale and at ganglion compression, respectively (P<0.05). Pretreatment with atropine was effective in most patients at minimizing abrupt reduction in HR during PCTG.

M3 receptor modulates extracellular matrix synthesis via ERK1/2 signaling pathway in human bladder smooth muscle cells

Extracellular matrix (ECM) accumulation plays a key role in the progression of bladder outlet obstruction (BOO). Muscarinic receptors have been widely reported to serve as pivotal regulators in lung tissue remodeling. However, the influence of them on human bladder smooth muscle cells (HBSMCs) and the underlying molecular mechanisms have not yet been evaluated. The purposes of the present study are to investigate the effect of muscarinic receptors on the synthesis of ECM in HBSMCs and the involvement of intracellular signal transducers. The results indicated that M1 -M5 muscarinic receptors were all encoded in HBSMCs. The expression rank order was M2 > M1 > M5 > M3 > M4 . The gene and protein expression of collagen I (COL1), TIMP-1, and TIMP-2 was carbachol (CCH) concentration-dependently enhanced. The synthesis of COL1 in the supernatant of cell culture medium was significantly elevated by exposure to CCH. The CCH-induced protein expression of COL1, TIMP-1, and TIMP-2, however, was obviously reduced by the pretreatment of muscarinic receptor antagonists, atropine, and M3 -preferring antagonist (1,1-dimethyl-4-diphenyl-acetoxypiperidinium iodide [4-DAMP]). Furthermore, ERK1/2 was activated by 100 µM CCH when compared with the control group and the pretreatment of ERK1/2 inhibitor significantly suppressed the synthesis of COL1 induced by 100 µM CCH. Besides, CCH-induced phosphorylation of ERK1/2 was remarkably restrained by the pretreatment of 4-DAMP. All in all, these findings demonstrated that M3 receptor can modulate extracellular matrix synthesis via the ERK1/2 signaling pathway, which may provide potential novel therapeutic targets for BOO.

Aberrant sinus node firing during β-adrenergic stimulation leads to cardiac arrhythmias in diabetic mice.

Cardiovascular complications, including cardiac arrhythmias, result in high morbidity and mortality in patients with type-2 diabetes mellitus (T2DM). Clinical and experimental data suggest electrophysiological impairment of the natural pacemaker of the diabetic heart. The present study examined sinoatrial node (SAN) arrhythmias in a mouse model of T2DM and physiologically probed their underlying cause. Electrocardiogramswere obtained from conscious diabetic db/db and lean control db/+ mice. In vivo SAN function was probed through pharmacological autonomic modulation with isoprenaline, atropine and carbachol. Blood pressure stability and heart rate variability (HRV) were evaluated. Intrinsic SAN function was evaluated through ex vivo imaging of spontaneous Ca2+ transients in isolated SAN preparations. While lean control mice showed constant RR intervals during isoprenaline challenge, the diabetic mice experienced SAN arrhythmias with large RR fluctuations in a dose-dependent manner. These arrhythmias were completely abolished by atropine pre-treatment, while carbachol pretreatment significantly increased SAN arrhythmia frequency in the diabetic mice. Blood pressure and HRV were comparable in db/db and db/+ mice, suggesting that neither augmented baroreceptor feedback nor autonomic neuropathy is a likely arrhythmia mechanism. Cycle length response to isoprenaline was comparable in isolated SAN preparations from db/db and db/+ mice; however, Ca2+ spark frequency was significantly increased in db/db mice compared to db/+ at baseline and after isoprenaline. Our results demonstrate a dysfunction of cardiac pacemaking in an animal model of T2DM upon challenge with a β-adrenergic agonist. Ex vivo, higher Ca2+ spark frequency is present in diabetic mice, which may be directly linked to in vivo arrhythmias.

A robust diving response in the laboratory mouse.

The diving response is a coordinated physiological response to submersion under water and has been documented amongst all mammals tested to date. The physiological response consists of three primary reflexes: an immediate bradycardia, apnea, and selective constriction of peripheral blood vessels. We hypothesized that mice would exhibit a diving response upon voluntary submersion into water typically seen in other mammals. In this study, telemeters that measure arterial pressure were implanted into male and female C57Bl/6J mice. These mice were trained to voluntarily dive underwater for a distance of 40cm over a 4-6s period. Just before the dive, the interbeat interval (IBI) was 87 ± 6ms (mean ± SD) and diastolic pressure was 99 ± 14mmHg. Underwater submersion caused (1) a dramatic bradycardia immediately at the onset of each dive, as IBI increased to 458 ± 104ms, and (2) a large drop in diastolic pressure, to 56 ± 16mmHg despite the elevation in peripheral resistance. Mice experienced a short bout (~ 2s) of hypertension (diastolic pressure rose to 131 ± 17mmHg) upon emergence. The bradycardia and hypotension appeared to be vagally mediated, since both these responses were blocked with atropine pre-treatment. These data demonstrate that the mouse exhibits a robust diving response upon voluntary submersion into water.

Juglone as antihypertensive agent acts through multiple vascular mechanisms

ABSTRACTBackground: Juglone, a natural phenolic compound obtained from the walnut tree, is known for its wide range of biological activities. However, it has yet to be tested for its effects on hypertension and vascular tone. This investigation was aimed to explore the antihypertensive effect and the nature of vascular reactivity of juglone in rat models.Methods: Juglone was tested in in vivo and in vitro experiments in rats. The responses were analyzed and recorded through a PowerLab data acquisition system.Results: Intravenous injection of juglone significantly decreased the mean arterial blood pressure (MAP) in normotensive and hypertensive rats (Max. fall, 43.50 ± 2.96 vs 49.66 ± 3.28 mmHg). In rats pretreated with Nω-Nitro l-arginine methyl ester (L-NAME), the effect of juglone on MAP was reduced as compared to the control. However, in rats pretreated with atropine the fall in MAP by juglone was not altered. Juglone induced relaxation in the phenylephrine, K+ (80 mM), and angiotensin II pretreated isolated rat aortic rings. This vasorelaxant effect was reduced with L-NAME pretreatment. Atropine pretreatment did not modify the vasorelaxant effect of juglone. Pre-incubation with juglone attenuated the intracellular Ca2+ release by suppressing phenylephrine peak formation and also shifted CaCl2 concentration–response curves (CRCs) to the right. Of note, combined treatment with 4-aminopyridine and barium chloride also reduced juglone-mediated vasorelaxation suggesting a role of K+-channels as well.Conclusion: In conclusion, juglone exerts its antihypertensive effect through vasorelaxation, which is mediated by nitric oxide, inhibition of intracellular calcium release and opening of K+-channels.

Atropine or Ephedrine Pretreatment for Preventing Bradycardia in Elderly Patients

Atropine or Ephedrine Pretreatment for Preventing Bradycardia in Elderly Patients

Muscarinic M1 and M2 receptor subtypes play opposite roles in LPS-induced septic shock

BackgroundTo compare pharmacologic effects of pirenzepine and AF-DX116, a selective competitive antagonist for M1 and M2 subtype muscarinic cholinergic receptors (mAChRs), respectively, with atropine, a non-selective competitive antagonist for mAChRs, on Lipopolysaccharide (LPS).MethodsMale C57BL/6 mice were used to establish models of LPS-induced experimental endotoxemia. Mice were intraperitoneally injected 10 min prior to LPS injection with control (saline), atropine, pirenzepine and AF-DX116, respectively. Overall survival time was estimated using Kaplan-Meier plots. Inflammatory cytokine tumor necrosis factor-α (TNF-α) was monitored at various intervals after LPS injection and individual reagent administration. Pathological alternations in lungs and liver were analyzed.ResultsPirenzepine and atropine pretreatment improved survival rate of LPS-induced septic shock; in contrast, AF-DX116 accelerated death from sepsis. Moreover, TNF-α plasma level was decreased in response to pirenzepine or atropine, whereas increased in response to AF-DX116. Pirenzepine and atropine relieved whereas AF-DX116 accelerated LPS-induced pulmonary and hepatic injury. Pirenzepine reduced proportion of M1 subtype of macrophages, while AF-DX116 promoted polarization of macrophages to M1 subtype. Pirenzepine pretreatment reduced while AF-DX116 enhanced expression of SOCS3 at mRNA level.ConclusionsThe administration of pirenzepine and atropine may have beneficial effects on septic shock.

Prophylactic potential of memantine against soman poisoning in rats

BackgroundCarbamates physostigmine and pyridostigmine have been used as a pretreatment against poisoning with nerve agents in order to reversibly inhibit and thus protect from irreversible inhibition a portion of acetylcholinesterase (AChE) in brain and respiratory muscles that is crucial for survival. Memantine, an adamantine derivative, has emerged as a promising alternative to carbamates, since it prevented the fasciculations and skeletal muscle necrosis induced by carbamates and organophosphates, including nerve agents. AimThis experimental study was undertaken in order to investigate and compare the protective and behavioural effects of memantine and standard carbamates physostigmine and pyridostigmine in rats poisoned with soman and treated with atropine, oxime HI-6 and diazepam. Another goal was to elucidate the mechanisms of the antidotal effect of memantine and its potential synergism with standard antidotes against nerve agents. Materials and methodsMale Wistar rats were used throughout the experiments. In dose-finding experiments memantine was administered at dose interval 0–72 mg/kg sc 60 min before sc injection of soman. In time-finding experiments memantine was injected 18 mg/kg sc 0–1440 min before soman. Standard treatment antidotes - atropine 10 mg/kg, HI-6 50 mg/kg and diazepam 2.5 mg/kg – were administered im within 15 s post-exposure. Soman 0.75 LD50 was used to study its inhibitions of neuromuscular transmission on the phrenic nerve-diaphragm preparation in situ and of tissue AChE activity. Behavioural effects of the prophylactic antidotes were investigated by means of the rotarod test. Based on these data therapeutic index and therapeutic width was calculated for all three prophylactic agents. ResultsMemantine pretreatment (18 mg/kg sc) produced in rats poisoned with soman significantly better protective ratios (PRs) than the two carbamates – 1.25 when administered alone and 2.3 when combined with atropine pretreatment and 6.33 and 7.23 with atropine/HI-6 and atropine/HI-6/diazepam post-exposure therapy, respectively. The highest PR of 10.11 obtained in Atr/HI-6-treated rats was achieved after pretreatment with memantine 36 mg/kg. This additional protection lasted for 8 h. All three prophylactic regimens antagonised the soman-induced neuromuscular blockade, but the effect of memantine was fastest. Pretreatment with memantine assured higher AChE activity in brain and diaphragm than in unpretreated rats (46% vs 28% and 68% vs. 38%, respectively). All three prophylactic regimens affected the rotarod performance in rats, but the effect of memantine was relatively strongest. Memantine and pyridostigmine had lowest and highest therapeutic index and therapeutic width, respectively. ConclusionsAlthough memantine assures better and longer-lasting protection against soman poisoning in rats than the two carbamates, its small therapeutic index and narrow therapeutic width seriously limit its potential as a pretreatment agent. Despite its behavioural effects, memantine seems to be beneficial antidote when administered after soman, along with atropine/HI-6/diazepam therapy. Mechanism of the antidotal effect of memantine against soman poisoning appears to be a combination of AChE-protecting and NMDA receptor-blocking action.

Antihypertensive effect of the methanolic extract from Eruca sativa Mill., (Brassicaceae) in rats: Muscarinic receptor-linked vasorelaxant and cardiotonic effects

Ethnopharmacological relevanceEruca sativa Mill., (Brassicaceae) is a popular remedy for the treatment of hypertension in Pakistan. However, direct effect of the extract and its fractions on blood pressure and vascular tone are unknown. Aim of the studyThis investigation was aimed to explore the pharmacological base for the traditional use of E. sativa in hypertension. Materials and methodsIn-vivo blood pressure study was carried out using normotensive and high salt-induced hypertensive rats under anaesthesia. The cardiovascular mechanisms were explored using rat aorta and atria in-vitro. Preliminary phytochemical analysis, spectrophotometric detection of total phenols, flavonoids and HPLC analysis of crude extract were performed using quercetin and erucin as marker compounds. ResultsIntravenous injection of crude extract induced a fall in mean arterial pressure (MAP) in both normotensive (max fall: 41.79 ± 1.55% mmHg) and hypertensive (max fall: 58.25 ± 0.91% mmHg) rats. Atropine (1 mg/kg) pretreatment attenuated this effect significantly (p < 0.001), suggesting the involvement of muscarinic receptor in its antihypertensive effect. Fractions also induced atropine-sensitive antihypertensive effect. Similarly, oral administration of crude and aqueous extracts resulted a fall in MAP in the hypertensive rats. In isolated rat aortic rings from normotensive rats, crude extract and fractions induced an endothelium-dependent relaxation. This relaxation was partially inhibited with L-NAME and atropine pretreatment and with denudation of aortic rings, indicating involvement of muscarinic receptor-linked nitric oxide (NO). In aorta from the hypertensive rats, crude extract and fractions induced endothelium-independent relaxation. This relaxation was not affected by pretreatment with L-NAME or atropine. Crude extract and fractions also suppressed phenylephrine contractions in Ca+2 free/EGTA medium. In isolated rat atrial preparations, crude extract and fractions induced negative inotropic and chronotropic effects with a positive inotropic effect by the n-hexane fraction, which were not affected with atropine pretreatment. Phytochemical screening and spectrophotometric analysis indicated the presence of phenols and flavonoids, whereas HPLC analysis of crude extract revealed the presence of quercetin (flavonoid) and erucin (isothiocyanate). ConclusionThe results suggest that E. sativa is an antihypertensive remedy which is mainly due to its vasodilatory and partly cardiac effects. Muscarinic receptors-linked NO release and dual inhibitory effect on Ca+2 influx and release underlie the vasodilation. This finding provides pharmacological base to the traditional use of E. sativa in hypertension. The presence of quercetin and erucin further support this finding.