Glycopyrrolate methobromide: 2. comparison with atropine sulphate in anaesthesia

Normalization of impaired emotion inhibition in bipolar disorder mediated by cholinergic neurotransmission in the cingulate cortex

The muscarinic-cholinergic system is involved in the pathophysiology of bipolar disorder (BD), and contributes to attention and the top-down and bottom-up cognitive and affective mechanisms of emotional processing, functionally altered in BD. Emotion processing can be assessed by the ability to inhibit a response when the content of the image is emotional. Impaired regulatory capacity of cholinergic neurotransmission conferred by reduced M₂-autoreceptor availability is hypothesized to play a role in elevated salience of negative emotional distractors in euthymic BD relative to individuals with no history of mood instability. Thirty-three euthymic BD type-I (DSM-V-TR) and 50 psychiatrically-healthy controls underwent functional magnetic resonance imaging (fMRI) and an emotion-inhibition paradigm before and after intravenous cholinergic challenge using the acetylcholinesterase inhibitor, physostigmine (1 mg), or placebo. Mood, accuracy, and reaction time on either recognizing or inhibiting a response associated with an image involving emotion and regional functional activation were examined for effects of cholinergic challenge physostigmine relative to placebo, prioritizing any interaction with the diagnostic group. Analyses revealed that (1) at baseline, impaired behavioral performance was associated with lower activation in the anterior cingulate cortex in BD relative to controls during emotion processing; (2) physostigmine (vs. placebo) affected behavioral performance during the inhibition of negative emotions, without altering mood, and increased activation in the posterior cingulate cortex in BD (vs. controls); (3) In BD, lower accuracy observed during emotion inhibition of negative emotions was remediated by physostigmine and was associated with cingulate cortex overactivation. Our findings implicate abnormal regulation of cholinergic neurotransmission in the cingulate cortices in BD, which may mediate exaggerated emotional salience processing, a core feature of BD.

Cholinergic enhancement differentially modulates neural response to encoding during face identity and face location working memory tasks

Potentiation of cholinergic transmission influences stimulus processing by enhancing signal detection through suppression and/or filtering out of irrelevant information (bottom-up modulation) and with top-down task-oriented executive mechanisms based on the recruitment of prefrontal and parietal attentional systems. The cholinergic system also plays a critical role in working memory (WM) processes and preferentially modulates WM encoding, likely through stimulus-processing mechanisms. Previous research reported increased brain responses in visual extrastriate cortical regions during cholinergic enhancement in the encoding phase of WM, independently addressing object and spatial encoding. The current study used functional magnetic resonance imaging to determine the effects of cholinergic enhancement on encoding of key visual processing features. Subjects participated in two scanning sessions, one during an intravenous (i.v.) infusion of saline and the other during an infusion of the acetylcholinesterase inhibitor physostigmine. In each scan session, subjects alternated between a face identity recognition and a spatial location WM. Enhanced cholinergic function increased neural activity in the ventral stream during encoding of face identity and in the dorsal stream during encoding of face location. Conversely, a reduction in brain response was found for scrambled sensorimotor control images. The cholinergic effects on neural activity in the ventral stream during encoding of face identity were stronger than those observed in the dorsal stream during encoding of face location, likely as a consequence of the role of acetylcholine in establishing the inherently relevant nature of face identity. Despite the limited sample-size, the results suggest the stimulus-dependent role of cholinergic system in signal detection, as they show that cholinergic potentiation enhances neural activity in regions associated with early perceptual processing in a selective manner depending on the attended stimulus feature.

Cholinergic enhancement reduces functional connectivity and BOLD variability in visual extrastriate cortex during selective attention

Enhancing cholinergic function improves performance on various cognitive tasks and alters neural responses in task specific brain regions. We have hypothesized that the changes in neural activity observed during increased cholinergic function reflect an increase in neural efficiency that leads to improved task performance. The current study tested this hypothesis by assessing neural efficiency based on cholinergically-mediated effects on regional brain connectivity and BOLD signal variability. Nine subjects participated in a double-blind, placebo-controlled crossover fMRI study. Following an infusion of physostigmine (1 mg/h) or placebo, echo-planar imaging (EPI) was conducted as participants performed a selective attention task. During the task, two images comprised of superimposed pictures of faces and houses were presented. Subjects were instructed periodically to shift their attention from one stimulus component to the other and to perform a matching task using hand held response buttons. A control condition included phase-scrambled images of superimposed faces and houses that were presented in the same temporal and spatial manner as the attention task; participants were instructed to perform a matching task. Cholinergic enhancement improved performance during the selective attention task, with no change during the control task. Functional connectivity analyses showed that the strength of connectivity between ventral visual processing areas and task-related occipital, parietal and prefrontal regions reduced significantly during cholinergic enhancement, exclusively during the selective attention task. Physostigmine administration also reduced BOLD signal temporal variability relative to placebo throughout temporal and occipital visual processing areas, again during the selective attention task only. Together with the observed behavioral improvement, the decreases in connectivity strength throughout task-relevant regions and BOLD variability within stimulus processing regions support the hypothesis that cholinergic augmentation results in enhanced neural efficiency. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Cholinergic modulation of visual working memory during aging: a parametric PET study

Age-related differences in the regional recruitment of prefrontal cortex (PFC) during cognitive tasks suggests that aging is associated with functional reorganization. Cholinergic enhancement with physostigmine reduces activity in the PFC regions selectively recruited during working memory (WM) and increases activity in visual processing areas, suggesting that augmenting cholinergic function reduces task effort by improving the visual representation of WM stimuli. Here, we investigated how cholinergic enhancement influenced PFC and visual cortical activity in young and older subjects as WM difficulty was altered. Regional cerebral blood flow (rCBF) was measured using H(2)(15)O-PET in 10 young and 10 older volunteers during a parametrically varied face WM task, following an i.v. infusion of saline and physostigmine. Reaction time decreased during physostigmine relative to placebo in both groups. Prefrontal brain regions selectively recruited in each age group that responded differentially to task demands during placebo, had no significant activity during physostigmine. Medial visual processing areas showed task-selective increases in activity during drug in both groups, while lateral regions showed decreased activity in young and increased activity in older participants at longer task delays. These results are consistent with our previous findings, showing that the modulatory role of the cholinergic system persists during aging, and that the effects of cholinergic enhancement are functionally specific rather than anatomically specific. Moreover, the use of the parametric design allowed us to uncover group specific effects in lateral visual processing areas where increasing cholinergic function produced opposite effects on neural activity in the two age groups.

Cholinergic enhancement eliminates modulation of neural activity by task difficulty in the prefrontal cortex during working memory

Previously, we demonstrated that enhancing cholinergic activity during a working memory (WM) task improves performance and reduces blood flow in the right anterior middle/superior frontal cortex, an area known to be important for WM. The purpose of this study was to evaluate the interaction between WM task demands and cholinergic enhancement on neural responses in the prefrontal cortex. Regional cerebral blood flow (rCBF) was measured using H(2)(15)O and positron emission tomography, as 10 young healthy volunteers performed a parametrically varied match-to-sample WM for faces task. For each item, a picture of a face was presented, followed by a delay (1, 6, 11, or 16 sec), then by the presentation of two faces. Subjects were instructed to identify which face they previously had seen. For control items, nonsense pictures were presented in the same spatial and temporal manner. All conditions were performed during an intravenous infusion of saline and physostigmine (1 mg/hr). Subjects were blind to the substance being infused. Reaction time increased significantly with WM delay, and physostigmine decreased reaction time across delay conditions. Significant task-related rCBF increases during saline infusion were seen in superior frontal, middle frontal, and inferior frontal regions, and the response magnitudes in the regions increased systematically with task difficulty. In all of these prefrontal regions, physostigmine administration significantly reduced rCBF during task, particularly at longer task delays, so that no correlation between task delay and rCBF was observed. In the ventral visual cortex, physostigmine increased rCBF at longer task delays in medial regions, and decreased rCBF over delay conditions in lateral cortical areas. These results indicate that, during cholinergic potentiation, brain activity in prefrontal regions is not modulated by increases in WM task demands, and lends further support to the hypothesis that cholinergic modulation enhances visual processing, making the task easier to perform, and thus, compensate for the need to recruit prefrontal cortical regions as task demands increase.

Selective effects of cholinergic modulation on task performance during selective attention

The cholinergic neurotransmitter system is critically linked to cognitive functions including attention. The current studies were designed to evaluate the effect of a cholinergic agonist and an antagonist on performance during a selective visual attention task where the inherent salience of attended/unattended stimuli was modulated. Two randomized, placebo-controlled, crossover studies were performed, one (n=9) with the anticholinesterase physostigmine (1.0 mg/h), and the other (n=30) with the anticholinergic scopolamine (0.4 mc/kg). During the task, two double-exposure pictures of faces and houses were presented side by side. Subjects were cued to attend to either the face or the house component of the stimuli, and were instructed to perform a matching task with the two exemplars from the attended category. The cue changed every 4-7 trials to instruct subjects to shift attention from one stimulus component to the other. During placebo in both studies, reaction time (RT) associated with the first trial following a cued shift in attention was longer than RT associated with later trials (p<0.05); RT also was significantly longer when attending to houses than to faces (p<0.05). Physostigmine decreased RT relative to placebo preferentially during trials greater than one (p<0.05), with no change during trial one; and decreased RT preferentially during the attention to houses condition (p<0.05) vs attention to faces. Scopolamine increased RT relative to placebo selectively during trials greater than one (p<0.05), and preferentially increased RT during the attention to faces condition (p<0.05). The results suggest that enhancement or impairment of cholinergic activity preferentially influences the maintenance of selective attention (ie trials greater than 1). Moreover, effects of cholinergic manipulation depend on the selective attention condition (ie faces vs houses), which may suggest that cholinergic activity interacts with stimulus salience. The findings are discussed within the context of the role of acetylcholine both in stimulus processing and stimulus salience, and in establishing attention biases through top-down and bottom-up mechanisms of attention.

Cholinergic stimulation alters performance and task-specific regional cerebral blood flow during working memory

Modulation of the cholinergic neurotransmitter system results in changes in memory performance, including working memory (WM), in animals and in patients with Alzheimer disease. To identify associated changes in the functional brain response, we studied performance measures and regional cerebral blood flow (rCBF) using positron emission tomography (PET) in healthy subjects during performance of a WM task. Eight control subjects received an infusion of saline throughout the study and 13 experimental subjects received a saline infusion for the first 2 scans followed by a continuous infusion of physostigmine, an acetylcholinesterase inhibitor, for the subsequent 8 scans. rCBF was measured using H215O and PET in a sequence of 10 PET scans that alternated between rest and task scans. During task scans, subjects performed the WM task for faces. Physostigmine both improved WM efficiency, as indicated by faster reaction times, and reduced WM task-related activity in anterior and posterior regions of right midfrontal gyrus, a region shown previously to be associated with WM. Furthermore, the magnitudes of physostigmine-induced change in reaction time and right midfrontal rCBF correlated. These results suggest that enhancement of cholinergic function can improve processing efficiency and thus reduce the effort required to perform a WM task, and that activation of right prefrontal cortex is associated with task effort.

Different properties of the bradycardia produced by neostigmine and edrophonium in the cat

PURPOSE

The bradycardia produced by neostigmine and edrophonium was examined according to its relation to cholinesterase inhibition and to its sensitivity to block by muscarinic receptor antagonists. For comparison, the ability of muscarinic antagonists to block the bradycardia produced by electrical stimulation of the vagus nerve was determined.

METHODS

Cats were anaesthetized, vagotomized and propranolol-treated. Heart rate was continuously recorded. Erythrocyte cholinesterase activity of arterial blood was measured using a radiometric technique. The right vagus nerve was isolated for electrical stimulation. The muscarinic antagonists used were atropine, glycopyrrolate, pancuronium, gallamine, and AFDX-116.

RESULTS

Neostigmine produced a dose-dependent decrease in cholinesterase activity which reached a plateau at a cumulative dose of 0.16 mg.kg-1 (ED50 0.009 +/- 0.003 mg.kg-1). Neostigmine produced a dose-dependent decrease in heart rate with the dose-response relationship (ED50 0.1 +/- 0.01 mg.kg-1; P = 0.0006) shifted to the right of that for the inhibition of cholinesterase activity. In contrast to the anticholinesterase effect, the bradycardic effect did not reach a plateau and continued to increase even at doses at which the cholinesterase inhibition was maximal. The maximal decrease in heart rate when the heart was still in sinus rhythm was by 81 +/- 13 bpm (49 +/- 7% of baseline), which was produced by a dose of 0.32 mg.kg-1. Edrophonium produced dose-dependent decreases in cholinesterase activity and heart rate, which were highly correlated (correlation coefficient r = 0.99, P < 0.0001). The ED50 of the reduction in heart rate (0.9 +/- 0.18 mg.kg-1) and cholinesterase activity (0.89 +/- 0.12 mg.kg-1) produced by edrophonium were similar. Moreover, the reduction in heart rate and cholinesterase activity produced by edrophonium reached a plateau at the same dose (6.4 mg.kg-1). At this dose, heart rate decreased by 22 +/- 2 bpm (14.6 +/- 0.9% of baseline). Compared to the bradycardia produced by stimulation of the vagus nerve, that produced by neostigmine was blocked by muscarinic antagonists at significantly lower doses while that produced by edrophonium was blocked at similar doses.

CONCLUSIONS

The neostigmine-induced bradycardia is poorly correlated with cholinesterase inhibition compared to that produced by edrophonium, and has a higher sensitivity to muscarinic receptor antagonists compared to that produced by edrophonium or vagus nerve stimulation. These results are consistent with the hypothesis that the neostigmine-induced bradycardia is, in part, the result of neostigmine directly activating cholinergic receptors within the cardiac parasympathetic pathway. The bradycardia produced by edrophonium may be accounted for solely by an anticholinesterase action.

Effects of combined treatment with glycopyrrolate and albuterol in acute exacerbation of asthma

STUDY OBJECTIVE

Recent reports suggest that glycopyrrolate is as effective as metaproterenol in the treatment of acute bronchospasm. The purpose of this study was to investigate whether the addition of a single aerosolized dose of glycopyrrolate to an albuterol regimen results in a greater improvement in pulmonary function than treatment with an albuterol regimen alone in patients with acute asthma.

DESIGN

Prospective, randomized, double-blinded, controlled study. All patients received a total of three aerosol treatments and 60 mg solumedrol IV push. Patients were randomized to receive 2 mg aerosolized glycopyrrolate (combination therapy) or aerosolized placebo (control) in addition to their first 2.5 mg albuterol aerosol treatment. Both groups received 2.5 mg aerosolized albuterol alone for the next two treatments.

SETTING

An urban teaching hospital emergency department.

PARTICIPANTS

One hundred twenty-five patients with acute exacerbation of asthma were entered into the study.

MAIN RESULTS

There was no difference in pretreatment forced expiratory volume (one second) (FEV1) between the control group and the glycopyrrolate group. Asthmatic patients receiving combination therapy had less of a change in FEV1 (52%) than did control patients (82%, P < .05).

CONCLUSION

The combination of glycopyrrolate and albuterol does not appear to be beneficial over albuterol alone in treating patients with acute exacerbation of asthma.

Downregulation of cardiac guanosine 5'-triphosphate-binding proteins in right atrium and left ventricle in pacing-induced congestive heart failure

The extent to which congestive heart failure (CHF) is dependent upon increased levels of the cardiac inhibitory GTP-binding protein (Gi), and the impact of CHF on the cardiac stimulatory GTP-binding protein (Gs) and mechanisms by which Gs may change remain unexplored. We have addressed these unsettled issues using pacing-induced CHF in pigs to examine physiological, biochemical, and molecular features of the right atrium (RA) and left ventricle (LV). CHF was associated with an 85 +/- 20% decrease in LV segment shortening (P < 0.001) and a 3.5-fold increase (P = 0.006) in the ED50 for isoproterenol-stimulated heart rate responsiveness. Myocardial beta-adrenergic receptor number was decreased 54% in RA (P = 0.004) and 57% in LV (P < 0.001), and multiple measures of adenylyl cyclase activity were depressed 49 +/- 8% in RA (P < 0.005), and 44 +/- 9% in LV (P < 0.001). Quantitative immunoblotting established that Gi and Gs were decreased in RA (Gi: 59% reduction; P < 0.0001; Gs: 28% reduction; P < 0.007) and LV (Gi: 35% reduction; P < 0.008; Gs: 28% reduction; P < 0.01) after onset of CHF. Reduced levels of Gi and Gs were confirmed by ADP ribosylation studies, and diminished function of Gs was established in reconstitution studies. Steady state levels for Gs alpha mRNA were increased in RA and unchanged in LV, and significantly more GS alpha was found in the supernatant (presumably cytosolic) fraction in RA and LV membrane homogenates after CHF, suggesting that increased Gs degradation, rather than decreased Gs synthesis, is the mechanism by which Gs is downregulated. We conclude that cardiac Gi content poorly predicts adrenergic responsiveness or contractile function, that decreased Gs is caused by increased degradation rather than decreased synthesis, and that alterations in beta-adrenergic receptors, adenylyl cyclase, and GTP-binding proteins are uniform in RA and LV in this model of congestive heart failure.

Suspected malignant hyperthermia after halothane anesthesia in a cat

A 6 month old domestic shorthaired cat died of suspected malignant hyperthermia. Anesthesia was induced and maintained with halothane vaporized in oxygen and nitrous oxide, after acepromazine premedication. Before an incision was made, the cat's heart rate dropped from 140 to 90 beats/min concomitant with a drop in blood pressure. Glycopyrrolate administration resulted in severe ventricular tachycardia (340 beats/min). Halothane and nitrous oxide were discontinued and the surgery was abandoned. Lidocaine administration resulted in a normal sinus rhythm. In recovery, the cat was tachypneic and struggling, with a rectal temperature of 40.1 degrees C that quickly increased to 41.4 degrees C. While the cat was being cooled, cardiac dysrhythmias progressed to ventricular fibrillation that was not responsive to cardiorespiratory resuscitation. Blood specimens obtained while the cat was being cooled showed hyperkalemia (10.0 mEq/L) and increased serum creatine kinase activity (780 IU/L). There was extreme extensor rigidity (rigor mortis) within 5 min of cardiac arrest. Results of microscopic and electron microscopic examination of muscle showed occasional perivascular infiltrates of lymphocytes with infrequent perimysial and epimysial neutrophils and a few sarcomeres with streaming of Z-bands (suggesting a contracted state). Histochemical evaluation of skeletal muscle showed no significant difference between type I and type II fibers.

Effect of halogenated anaesthetics on heart rate changes during reversal of neuromuscular block with glycopyrrolate and neostigmine

The effect of halothane and enflurane on changes in heart rate during reversal of neuromuscular blockade was compared in 48 patients. Premedication and anaesthetic technique was standardized. Either halothane or enflurane was used as the primary anaesthetic. Neuromuscular block was reversed by injection of glycopyrrolate and neostigmine, given either separately or simultaneously. Heart rate changes were significantly different between the halothane and enflurane subgroups. Patients anaesthetized with enflurane showed less fluctuations in heart rate. Simultaneous injection of glycopyrrolate and neostigmine minimized the tachycardia in the halothane subgroups only.

Glycopyrrolate: pharmacology and clinical use

This is a review of glycopyrrolate whose function in clinical practice is compared with that of atropine.

A comparison of atropine and glycopyrrolate in anaesthetic practice

The two anticholinergics, atropine and glycopyrrolate, were used for premedication and as an adjunct to reversal of residual neuromuscular block in a double-blind study. Glycopyrrolate, being about twice as potent as atropine in the clinical situation, was used in half the dosage of atropine. When used for premedication, no difference was found between the drugs concerning patients complaining of dry mouth, but more patients in the glycopyrrolate group had a gastric juice pH greater than 2.5 compared to the atropine group (not statistically different). The reversal mixture consisted of necostigmine 2.5 mg with either atropine 1 mg or glycopyrrolate 0.5 mg. The heart rate response between 2 and 10 min after injecting the reversal mixture was statistically significant (P ranged from 0.0001 to 0.05), the atropine group showing the most marked decrease: 18% in the atropine group had sinus bradycardia compared to 5% in the glycopyrrolate group: 34% in the atropine group exhibited arrhythmias compared to 10% in the glycopyrrolate group, the most common form being a nodal rhythm in both groups. More patients in the atropine group had "excessive" oropharyngeal secretions (more than 2 ml) when extubated (P less than 0.05). The postoperative assessment showed little difference in the two groups, apart from a lower incidence of nausea and vomiting in the atropine group (not statistically different). The study shows that the use of glycopyrrolate was associated with a more stable cardiovascular system, fewer arrhythmias and superior control of oropharyngeal secretions at the time of reversal.

Atropine and glycopyrrolate: changes in cardiac rate and rhythm in conscious and anaesthetised children

Heart rate and rhythm were studied in conscious children and children under nitrous oxide and halothane anaesthesia following intravenous administration of atropine or glycopyrrolate. Both drugs produced a similar increase in heart rate when the potency of glycopyrrolate is considered twice that of atropine. There is no difference in the response of anaesthetised and awake children. Junctional rhythm is the main dysrhythmia observed which appears to occur more frequently in anaesthetised children. The administration of both drugs is safe in paediatric patients.

Premedication with atropine or glycopyrrolate in children. Effects on heart rate and rhythm during induction and maintenance of anesthesia

Atropine 15 micrograms/kg and glycopyrrolate 5 or 10 microgram/kg were studied as anticholinergic premedicants in groups of 20 children each. A control group of 20 children did not receive anticholinergic premedication. Both atropine and the higher dose of glycopyrrolate produced significant increases in heart rate prior to induction of anaesthesia. The subsequent increase during the process of induction was less than in those who had not received an anticholinergic drug or glycopyrrolate 5 micrograms/kg. Dysrhythmias during induction of anaesthesia occurred slightly less frequently in the patients given atropine or the higher dose of glycopyrrolate. Although the incidence was similar in these two groups, ventricular ectopic beats occurred less frequently following the use of glycopyrrolate. The control of secretions was also superior with this anticholinergic premedicant.

Effects of intravenous administration of glycopyrrolate and atropine in anaesthetised patients

The effects of glycopyrrolate in doses of 5, 10 and 15 microgram/kg and atropine 10, 20 and 30 microgram/kg on heat rate and rhythm was studied in anesthetised patients. Both drugs produced a dose-related increase in heart rate. Glycopyrrolate was approximately twice as potent as atropine in increasing heart rate. The average time taken to achieve peak effect was 2-6 and 3-7 minutes for atropine and glycopyrrolate respectively, and this was significantly different. The smallest doses of both drugs were generally associated with supraventricular dysrhythmias, whereas these were mainly ventricular following the highest dose of both drugs.

Modification of chronotropic response to anticholinergics by halogenated anaesthetics in children

Cardiac rate and rhythm changes were studied in 40 children after intravenous injection of atropine or glycopyrrolate following induction of anaesthesia with halothane and enflurane. Premedication was standardized in all groups and ventilation controlled to achieve normal end tidal carbon dioxide. Heart rate increased in all cases following anticholinergic medication and the increase in heart rate was significantly higher in children receiving halothane anaesthesia as compared to those given enflurane. There was no significant difference between atropine and glycopyrrolate groups. There was no difference in frequency of occurrence of junctional tachycardia, which was the only arrhythmia observed, in the four groups studied. Our findings suggest that, in clinical situations where development of marked tachycardia is a concern, the combination of enflurane and anticholinergic drugs offers an advantage over the combination of halothane and anticholinergic drugs in paediatric patients.

Atropine versus glycopyrrolate. A study of intraocular pressure and pupil size in man

Following control observations of intraocular pressure and pupil size, in doses suitable for pre-anaesthetic medication, glycopyrrolate (0.004 mg/kg) and atropine (0.01 mg/kg) were given intramuscularly to healthy volunteers in a randomised, cross-over fashion. No significant change in either intraocular pressure or pupil size was noted 45 min after drug administration.

Effects on muscarinic receptors of various agents in reversal of neuro-muscular blockade: a study evaluating atropine, glycopyrron, neostigmine and pyridostigmine

The effects were studied of various drug combinations, recommended for use in reversal of neuromuscular blockade, on heart rate and salivary secretions in 80 healthy patients anaesthetized with nitrous oxide-oxygen-halothane and relaxed with d-tubocurarine. The drug combinations were mixtures of atropine 1 mg--neostigmine 2.5 mg, atropine 1 mg--pyridostigmine 15 mg, glycopyrron 0.5 mg--neostigmine 2.5 mg, and glycopyrron 0.5 mg--pyridostigmine 15 mg, respectively. It was found that administration of the atropine-containing mixtures induced more pronounced initial increases and delayed decreases in heart rate than the mixtures containing glycopyrron. Pyridostigmine-containing mixtures elicited a somewhat more pronounced initial increase in heart rate than neostigmine-containing mixtures, but a less pronounced and delayed decrease in heart rate. Supraventricular arrhythmias occurred less frequently in the pyridostigmine groups than in the neostigmine groups. No such difference was found between the atropine and glycopyrron groups. Glycopyrron caused a more intense dryness of the mouth than atropine. A differential attitude towards the use of drugs for reversal of neuromuscular blockade, based on the cardiovascular state of the particular patient, might be recommendable.