Physostigmine reversal of delirium from second generation antipsychotic exposure: a retrospective cohort study from a regional poison center.

INTRODUCTION: Physostigmine is an effective antidote for antimuscarinic delirium. There is little evidence for its use to reverse delirium following second generation antipsychotic exposure. The purpose of this study is to describe the safety and effectiveness of physostigmine in reversing delirium from second generation antipsychotic exposure. METHODS: This is a retrospective cohort study of all patients reported to a single regional poison center treated with physostigmine following a second generation antipsychotic exposure from January 1, 2000 to April 15, 2021. The poison center electronic medical record was queried to identify cases and for data abstraction. The primary outcome was the positive response rate to physostigmine, as determined by two trained abstractors. Secondary outcomes included physostigmine dosing, and adverse events. RESULTS: Of 147 charts reviewed, 138 individual patients were included, and the response to physostigmine was reported in 128 patients. The most common second-generation antipsychotic exposure was quetiapine (97; 70.3 percent). A positive response to physostigmine was noted in 106/128 (82.8 percent) patients [95 percent confidence interval 68.9-83.6 percent]. Median number of physostigmine doses was 1 (interquartile range 1-3; range 1-9). The median total physostigmine dose received was 2 mg (interquartile range 2-6 mg; range 0.15-30 mg). The positive physostigmine response rate for patients with an antimuscarinic co-ingestion was not significantly different compared to patients with a different co-ingestion or no co-ingestion (25/34 versus 81/94; P = 0.09). Adverse events were reported in four (2.9 percent) patients, including one death. DISCUSSION: A positive response to physostigmine to treat antimuscarinic delirium from second generation antipsychotic exposure was reported in 82.8 percent of patients, which is similar to previous physostigmine studies. Adverse events were infrequent, and included diaphoresis (one 0.7 percent), seizure (one; 0.7 percent), and bradycardia (one; 0.7 percent). One (0.7%) patient suffered a cardiac arrest 60 minutes after receiving physostigmine to treat antimuscarinic delirium following having received increasing clozapine doses over the previous month. CONCLUSIONS: In this study, physostigmine appears to be a safe and effective treatment for antimuscarinic delirium from second generation antipsychotic exposure. Further studies are needed to validate the safety and effectiveness of physostigmine for this indication.

Rivastigmine for the management of anticholinergic delirium.

INTRODUCTION: Anticholinergic agents are commonly taken in overdose, often causing delirium. The spectrum of anticholinergic delirium ranges from mild agitation to severe behavioural disturbance. Physostigmine is an effective treatment for anticholinergic delirium, but its availability is limited. As rivastigmine is readily available, it has been used to manage anticholinergic delirium; however, there is limited research investigating its use. METHOD: This was a retrospective review of patients with anticholinergic delirium treated in two toxicology units with rivastigmine (oral capsule or transdermal patch) from January 2019 to June 2023. The primary outcome was the use of further parenteral treatment (sedation or physostigmine) for delirium post rivastigmine administration. RESULTS: Fifty patients were administered rivastigmine for the management of anticholinergic delirium. The median age was 36 years (interquartile range: 25-49 years) and 27 (54 per cent) were females. Features consistent with anticholinergic toxicity included tachycardia in 44 (88 per cent) and urinary retention requiring catheterisation in 40 (80 per cent). Forty-three patients (86 per cent) were treated with physostigmine before rivastigmine administration. Twenty-two were managed with transdermal rivastigmine (most commonly 9.5 mg/24 hour patch), and 28 with oral rivastigmine 6 mg. Further parenteral sedation and/or physostigmine treatment were required more often in patients given transdermal than oral rivastigmine [16/22 (73 per cent) versus 9/28 (32 per cent), P = 0.010)]. No patients had bradycardia or gastrointestinal symptoms following rivastigmine administration. One patient with a history of epilepsy had a seizure, 1.5 hours post physostigmine administration and 7 hours post transdermal rivastigmine. DISCUSSION: Rivastigmine has been increasingly used for the management of patients with anticholinergic delirium, due to the lack of availability of physostigmine. In this case series, rivastigmine transdermal patch appeared to be less effective than oral rivastigmine capsules, likely due to its slow onset of action and/or insufficient dose. CONCLUSION: Rivastigmine can be used to treat anticholinergic delirium. In our case series oral rivastigmine appeared more effective than transdermal rivastigmine.

Safety of Physostigmine for Pediatric Antimuscarinic Poisoning.

INTRODUCTION: Physostigmine fell out of widespread use in the 1980s due to safety concerns; however, more recent research has demonstrated that its safety profile is better than previously thought. These studies have mainly included adults. We theorized that improved safety data may lead to more acceptance. Our objectives, therefore, were to characterize current frequency of use of physostigmine in pediatric patients as well as to study adverse effect rates in a national pediatric patient population. METHODS: The National Poison Data System was queried for cases of patients aged 0-18 years that involved single-substance exposures to antimuscarinic xenobiotics that were reported to a poison center between January 1, 2000, and December 31, 2020. Cases were stratified into groups by therapy received: benzodiazepines alone, benzodiazepines and physostigmine, physostigmine alone, or no physostigmine or benzodiazepines. Patient demographics, clinical effects, and medical outcomes were analyzed. RESULTS: A total of 694,132 cases were reviewed, and 150,075 were included for analysis. Nearly 5% (7562/150,075) of patients received specific pharmacological therapy with benzodiazepines, physostigmine, or both. A benzodiazepine as a single agent was the most frequently used pharmacologic therapy (92% of 7562). Among patients receiving any pharmacological therapy, only 8.3% (n = 627) of patients received physostigmine. Frequency of serious outcomes significantly increased across the study period among patients receiving benzodiazepines alone or with physostigmine. There was no increase in serious outcomes among patients receiving only physostigmine. CONCLUSIONS: Physostigmine frequency of use was low overall, but when used, was associated with less severe outcomes when compared to benzodiazepines.

[Eserine, in Crooked House and Curtain].

Eserine, well-known as physostigmine, is classified as an alkaloid. It is a cholinesterase inhibitor and appears in Agatha Christie's novel entitled, Crooked House and Curtain: Poirot's Last Case. In clinical medicine, eserine was used as an ophthalmic treatment for glaucoma and considered as a treatment for myasthenia gravis, Alzheimer's disease, and hereditary cerebellar ataxias. Currently, it is used as a treatment for anticholinergic poisoning.

Participation of Modulating Rhythms of the Decasecond Range in Intersystem Correlation Interactions in Early Rat Ontogeny.

On newborn non-narcotized 1-day-old (P1) and 16-day-old (P16) rats, a detailed analysis of intersystem somatovisceral interactions (ISI) mediated by decasecond (D1, 5-50 sec) range modulating rhythms was performed. Correlation interactions of the main body systems - cardiovascular, respiratory and somatomotor systems in norm and under conditions of changes in the level of cholinergic regulation were studied. Spectral correlation analysis was used to determine the participation of D1 range modulating rhythms in ISI. It was found that at P1, D1 range rhythms do not play a significant role in integrative processes. In P16 the activation of cholinergic structures, caused by the introduction of the acetylcholinesterase inhibitor physostigmine (eserine) leads to significant disturbances in the degree of correlation in the D1 range. Blockade of muscarinic and nicotinic cholinoreceptors does not alter the degree of correlation of systemic pairs in the slow-wave region (D1-low, 8-50 sec) of the D1 range. Under the influence on the cholinoreactive structures, the most significant changes in the degree of correlation in the ISI affect the somatorespiratory systemic pair. The results obtained indicate that the representation of the slow-wave components of D1 range modulating rhythms involved in the ISI increase during the first weeks of postnatal ontogeny. Changes in the level of cholinergic activation do not directly influence on ISI mediated by D1-low sub-band rhythms.

Chemo- and bio-informatics insight into anti-cholinesterase potentials of berries and leaves of Myrtus communis L., Myrtaceae: an in vitro/in silico study.

BACKGROUND: Myrtus communis L. (MC) has been used in Mesopotamian medicine. Here, the cholinesterase (ChE) inhibitory potential of its methyl alcohol extracts has been investigated and computationally dissected. METHOD: The ChE inhibition has been measured based on usual Ellman's colorimetric method compared to a canonical ChE inhibitor, eserine. Through a deep text mining, the structures of phytocompounds (= ligands) of MC were curated from ChemSpider, PubChem, and ZINC databases and docked into protein targets, AChE (PDB 1EVE) and BChE (PDB 1P0I) after initial in silico preparedness and binding affinity (BA; kcal/mol) reported as an endpoint. The calculation of ADMET (absorption, distribution, metabolism, excretion, and toxicity) features of phytocompounds were retrieved from SwissADME ( http://www.swissadme.ch/ ) and admetSAR software to predict the drug-likeness or lead-likeness fitness. The Toxtree v2.5.1, software platforms ( http://toxtree.sourceforge.net/ ) have been used to predict the class of toxicity of phytocompounds. The STITCH platform ( http://stitch.embl.de ) has been employed to predict ChE-chemicals interactions. RESULTS: The possible inhibitory activities of AChE of extracts of leaves and berries were 37.33 and 70.00%, respectively as compared to that of eserine while inhibitory BChE activities of extracts of leaves and berries of MC were 19.00 and 50.67%, respectively as compared to that of eserine. Phytochemicals of MC had BA towards AChE ranging from -7.1 (carvacrol) to -9.9 (ellagic acid) kcal/mol. In this regard, alpha-bulnesene, (Z)-gamma-Bisabolene, and beta-bourbonene were top-listed low toxic binders of AChE, and (Z)-gamma-bisabolene was a more specific AChE binder. Alpha-cadinol, estragole, humulene epoxide II, (a)esculin, ellagic acid, patuletin, juniper camphor, linalyl anthranilate, and spathulenol were high class (Class III) toxic substances which among others, patuletin and alpha-cadinol were more specific AChE binders. Among intermediate class (Class II) toxic substances, beta-chamigrene was a more specific AChE binder while semimyrtucommulone and myrtucommulone A were more specific BChE binders. CONCLUSION: In sum, the AChE binders derived from MC were categorized mostly as antiinsectants (e.g., patuletin and alpha-cardinal) due to their predicted toxic classes. It seems that structural amendment and stereoselective synthesis like adding sulphonate or sulphamate groups to these phytocompounds may make them more suitable candidates for considering in preclinical investigations of Alzheimer's disease.

Oral and Transdermal Rivastigmine for the Treatment of Anticholinergic Delirium: A Case Report.

BACKGROUND: Anticholinergic toxicity is a common cause of delirium in emergency department patients. The standard antidotal treatment for anticholinergic toxicity is physostigmine. Physostigmine functions as a reversible acetylcholinesterase inhibitor that readily crosses the blood-brain barrier. Rivastigmine is another member of this class currently approved for the treatment of Alzheimer's disease and Parkinson's disease. Rivastigmine also crosses the blood-brain barrier and has been found to be effective in the management of anticholinergic toxicity in limited case reports. CASE REPORT: A 61-year-old women presented to the emergency department via emergency medical services with altered mental status and a Glasgow Coma Scale score of 8 out of 15. She was found down near multiple medication bottles, including diphenhydramine and dicyclomine. Her physical examination was consistent with anticholinergic toxicity with mydriasis, obtundation, and warm flushed skin. In addition to standard resuscitation, she received two doses of rivastigmine 3 mg via nasogastric tube. After the second dose she was alert and oriented. She was admitted to the intensive care unit and had a rivastigmine patch applied. She was deemed back to her baseline 27 h after presentation. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Although the standard antidotal treatment for anticholinergic toxicity is physostigmine, there is a national shortage of this medication. In the absence of this standard antidote, it is reasonable for emergency physicians to use rivastigmine as an alternative treatment. This can be delivered orally or via nasogastric tube with dosing each hour until resolution of symptoms. Alternatively, in consultation with toxicology, it may be reasonable to use transdermal rivastigmine, as it provides consistent drug absorption for 24 h.

Nematostatic activity of isoprenylated guanidine alkaloids from Pterogyne nitens and their interaction with acetylcholinesterase.

Although new nematicides have appeared, the demand for new products less toxic and more efficient for the control of plant-parasitic nematodes are still high. Consequently, studies on natural secondary metabolites from plants, to develop new nematicides, have increased. In this work, nineteen extracts from eleven Brazilian plant species were screened for activity against Meloidogyne incognita. Among them, the extracts of Piterogyne nitens showed a potent nematostatic activity. The alkaloid fraction obtained from the ethanol extract of leaves of P. nitens was more active than the coming extract. Due to the promising activity from the alkaloid fraction, three isoprenylated guanidine alkaloids isolated from this fraction, galegine (1), pterogynidine (2), and pterogynine (3) were tested, showing similar activity to the alkaloid fraction, which was comparable to that of the positive control Temik at 250 µg/mL. At lower concentrations (125-50 µg/mL), compound 2 showed to be the most active one. As several nematicides act through inhibition of acetylcholinesterase (AChE), the guanidine alkaloids were also employed in two in vitro AChE assays. In both cases, compound 2 was more active than compounds 1 and 3. Its activity was considered moderated compared to the control (physostigmine). Compound 2 was selected for an in silico study with the electric eel (Electrophorus electricus) AChE, showing to bind mostly to the same site of physostigmine in the AChEs, pointing out that this could be the mechanism of action for this compound. These results suggested that the guanidine alkaloids 1,2 and 3 from P. nitens are promising for the development of new products to control M. incognita, especially guanidine 2, and encourage new investigations to confirm the mechanism of action, as well as to determine the structure-activity relationship of the guanidine alkaloids.

In vitro deacetylation of N-acetylserotonin by arylacetamide deacetylase.

Arylacetamide deacetylase (AADAC) is a deacetylation enzyme present in the mammalian liver, gastrointestinal tract, and brain. During our search for mammalian enzymes capable of metabolizing N-acetylserotonin (NAS), AADAC was identified as having the ability to convert NAS to serotonin. Both human and rodent recombinant AADAC proteins can deacetylate NAS in vitro, although the human AADAC shows markedly higher activity compared with rodent enzyme. The AADAC-mediated deacetylation reaction can be potently inhibited by eserine in vitro. In addition to NAS, recombinant hAADAC can deacetylate melatonin (to form 5-methoxytryptamine) and N-acetyltryptamine (NAT) (to form tryptamine). In addition to the in vitro deacetylation of NAS by the recombinant AADAC proteins, liver (mouse and human) and brain (human) extracts were able to deacetylate NAS; these activities were sensitive to eserine. Taken together, these results demonstrate a new role for AADAC and suggest a novel pathway for the AADAC-mediated metabolism of pineal indoles in mammals.

Dose-Dependent Heart Rhythm Disturbance Occurring in Response to the Activation of Choline-Reactive Structures in Early Rat Ontogeny.

The effect of dose-dependent activation of cholinoreactive structures on the severity of sinus bradycardia occurring in some intact newborn rats during the first weeks after birth was analyzed in non-narcotized one-day-old (P1) and 16-day-old (P16) rats. The parameters of low-amplitude bradycardic oscillations of heart rhythm in norm and after administration of the acetylcholinesterase inhibitor physostigmine (eserine) in different doses (1/100, 1/10, and 3/4LD50) to rats were studied. The maximum increase in the power of low-amplitude brady-cardic oscillations was achieved during moderate activation of cholinoreactive structures after injection of eserine in a dose of 1/10LD50. Further increase in acetylcholine level led to disappearance of the sinus rhythm and development of pathological bradycardia. The data obtained indicate the immaturity of the mechanisms of heart rhythm regulation in rats immediately after birth. During activation of cholinoreactive structures, the severity of bradycardia oscillations increases exponentially at P1 and has an inverse exponential character at P16, which indicates a high risk of cardiac rhythmogenesis disorders and dysrhythmia development in newborn rats under conditions of excessive enhancement of cholinergic activation.

Ventral Tegmental Area M5 Muscarinic Receptors Mediate Effort-Choice Responding and Nucleus Accumbens Dopamine in a Sex-Specific Manner .

Optimization of effort-related choices is impaired in depressive disorders. Acetylcholine (ACh) and dopamine (DA) are linked to depressive disorders, and modulation of ACh tone in the ventral tegmental area (VTA) affects mood-related behavioral responses in rats. However, it is unknown if VTA ACh mediates effort-choice behaviors. Using a task of effort-choice, rats can choose to lever press on a fixed-ratio 5 (FR5) schedule for a more-preferred food or consume freely available, less-preferred food. VTA administration of physostigmine (1 µg and 2 µg/side), a cholinesterase inhibitor, reduced FR5 responding for the more-preferred food while leaving consumption of the less-preferred food intact. VTA infusion of the M5 muscarinic receptor negative allosteric modulator VU6000181 (3 µM, 10 µM, 30 µM/side) did not affect lever pressing or chow consumption. However, VU6000181 (30 µM/side) coadministration with physostigmine (2 µg/side) attenuated physostigmine-induced decrease in lever pressing in female and male rats and significantly elevated lever pressing above vehicle baseline levels in male rats. In in vivo voltammetry experiments, VTA infusion of combined physostigmine and VU6000181 did not significantly alter evoked phasic DA release in the nucleus accumbens core (NAc) in female rats. In male rats, combined VTA infusion of physostigmine and VU6000181 increased phasic evoked DA release in the NAc compared with vehicle, physostigmine, or VU6000181 infusion alone. These data indicate a critical role and potential sex differences of VTA M5 receptors in mediating VTA cholinergic effects on effort choice behavior and regulation of DA release. SIGNIFICANCE STATEMENT: Effort-choice impairments are observed in depressive disorders, which are often treatment resistant to currently available thymoleptics. The role of ventral tegmental area (VTA) acetylcholine muscarinic M5 receptors, in a preclinical model of effort-choice behavior, is examined. Using the selective negative allosteric modulator of the M5 receptor VU6000181, we show the role of VTA M5 receptors on effort-choice and regulation of dopamine release in the nucleus accumbens core. This study supports M5 receptors as therapeutic targets for depression.

Pretreatment of rhesus monkeys with transdermal patches containing physostigmine and procyclidine: implications of the delivery system for the potential application against VX nerve agent intoxication in humans.

Physostigmine (Phs) is a reversible inhibitor of acetylcholinesterase (AChE) that penetrates the blood-brain barrier (BBB) and could be used to protect the central nervous system (CNS) against the effects of nerve agents. For prophylactic effectiveness, long, steady, and adequate inhibition of AChE activity by Phs is needed to broadly protect against the CNS effects of nerve agents. Here, we evaluated the efficacy of transdermal patches containing Phs and procyclidine (PC) as prophylactic agents. Patches (25 cm2) containing 4.4 mg Phs and 17.8 mg PC had a protective ratio of approximately 78.6-fold in rhesus monkeys challenged with VX nerve agent and given an antidote. Physiologically based pharmacokinetic model in conjunction with an indirect pharmacodynamic (PBPK/PD) was developed for Phs and scaled to rhesus monkeys. The model was able to reproduce the concentration profile and inhibitory effect on AChE of Phs in monkeys, as evidenced by correlation coefficients of 0.994 and 0.992 for 25 cm2 and 49 cm2 patches, respectively (i.e., kinetic data), and 0.989 and 0.968 for 25 cm2 and 49 cm2 patches, respectively (i.e., dynamic data). By extending the monkey PBPK/ PD model to humans, the effective human dose was predicted to be five applications of a 25 cm2 patch (i.e., 22 mg Phs), and two applications of a 49 cm2 patch (i.e., 17.4 mg Phs). Therefore, given that patch application of Phs in rhesus monkeys has a prolonged effect (namely, AChE inhibition of 19.6% for the 25 cm2 patch and 23.0% for the 49 cm2 patch) for up to 216 h, patch formulation of Phs may provide similar protection against nerve agent intoxication in humans.

Cholinergic system adaptations are associated with cognitive function in people recently abstinent from smoking: a (-)-[18F]flubatine PET study.

The cholinergic system is a critical mediator of cognition in animals. People who smoke cigarettes exhibit cognitive deficits, especially during quit attempts. Few studies jointly examine the cholinergic system and cognition in people while trying to quit smoking. We used positron emission tomography (PET) brain imaging with the ß2-subunit containing nicotinic acetylcholine receptor (ß2*-nAChR) partial agonist radioligand (-)-[18F]flubatine and the acetylcholinesterase inhibitor physostigmine to jointly examine the cholinergic system, smoking status, and cognition. (-)-[18F]Flubatine scans and cognitive data were acquired from twenty people who recently stopped smoking cigarettes (aged 38 ± 11 years; 6 female, 14 male; abstinent 7 ± 1 days) and 27 people who never smoked cigarettes (aged 29 ± 8 years; 11 female, 16 male). A subset of fifteen recently abstinent smokers and 21 never smokers received a mid-scan physostigmine challenge to increase acetylcholine levels. Regional volume of distribution (VT) was estimated with equilibrium analysis at "baseline" and post-physostigmine. Participants completed a cognitive battery prior to (-)-[18F]flubatine injection and physostigmine administration assessing executive function (Groton Maze Learning test), verbal learning (International Shopping List test), and working memory (One Back test). Physostigmine significantly decreased cortical (-)-[18F]flubatine VT, consistent with increased cortical acetylcholine levels reducing the number of ß2*-nAChR sites available for (-)-[18F]flubatine binding, at comparable magnitudes across groups (p values < 0.05). A larger magnitude of physostigmine-induced decrease in (-)-[18F]flubatine VT was significantly associated with worse executive function in people who recently stopped smoking (p values < 0.05). These findings underscore the role of the cholinergic system in early smoking cessation and highlight the importance of neuroscience-informed treatment strategies.

Case series profile of olanzapine post-injection delirium/sedation syndrome.

Olanzapine pamoate is an intramuscular depot injection for the treatment of schizophrenia. Approximately 1.4% of patients develop a serious adverse event called post-injection delirium/sedation syndrome (PDSS), characterised by drowsiness, anticholinergic and extrapyramidal symptoms. The objective is to investigate olanzapine PDSS presentations including clinical features and treatment approach. This is a retrospective review of olanzapine PDSS patients from three toxicology units and the NSW Poisons Information Centre between 2017 and 2022. Adult patients were included if they had intramuscular olanzapine then developed PDSS criteria. Clinical symptoms, treatment, timing and length of symptoms were extracted into a preformatted Excel database. There were 18 patients included in the series, with a median age of 49 years (interquartile range [IQR]: 38-58) and male predominance (89%). Median onset time post injection was 30 min (IQR: 11-38). PDSS symptoms predominate with drowsiness, confusion and dysarthria. Median length of symptoms was 24 h (IQR: 20-54). Most common treatment included supportive care without any pharmacological intervention (n = 10), benzodiazepine (n = 4) and benztropine (n = 3). In one case, bromocriptine and physostigmine followed by oral rivastigmine were given to manage antidopaminergic and anticholinergic symptoms respectively. This proposed treatment combination could potentially alleviate some of the symptoms but needs further studies to validate the findings. In conclusion, this case series supports the characterisation of PDSS symptomology predominantly being anticholinergic with similar onset (<1 h) and duration (<72 h). Bromocriptine is proposed to manage PDSS if patients develop severe dopamine blockade and physostigmine followed by rivastigmine for anticholinergic delirium.

Diphenhydramine-Induced Antimuscarinic Delirium Treated with Physostigmine and Transdermal Rivastigmine.

INTRODUCTION: Recurrent physostigmine shortages present a challenge to healthcare providers treating antimuscarinic delirium. Other centrally acting acetylcholinesterase inhibitors such as rivastigmine may represent a therapeutic alternative or adjunct during physostigmine shortage; however, previous reports of use have not documented serum antimuscarinic toxin concentrations, limiting evaluation of effectiveness. Combination therapy with physostigmine and rivastigmine has not been described. In this report, the authors present a case of diphenhydramine-induced antimuscarinic delirium with elevated diphenhydramine serum concentrations treated with physostigmine and transdermal rivastigmine without observed adverse effect. CASE REPORT: A 48-year-old female presented to an emergency department after ingesting 3.75 g (41.2 mg/kg) of diphenhydramine. She had antimuscarinic delirium with a presenting serum diphenhydramine concentration of 1500 ng/mL (therapeutic range, 25-112 ng/mL) and required two doses of physostigmine to avert intubation prior to intensive care unit (ICU) admission. At hospital hour 22, in the ICU, antimuscarinic delirium persisted but no further physostigmine was available due to hospital shortage. Therefore, a 9.5-mg transdermal rivastigmine patch was applied. By hospital hour 24, her delirium had resolved. A serum diphenhydramine concentration at hospital hour 25 was elevated at 760 ng/mL. Transdermal rivastigmine was discontinued at hospital hour 48 without recurrent delirium. Despite persistent normal mental status after rivastigmine discontinuation, the patient had a dry mouth, difficulty urinating, and mydriasis until hospital day 5. She never developed muscarinic toxicity. DISCUSSION: Transdermal rivastigmine may be a useful treatment alternative or adjunct during physostigmine shortage for antimuscarinic delirium and has a long duration of action without aspiration risk. Muscarinic toxicity was not observed.

Differential pharmacological and sex-specific effects of antimuscarinic agents at the hypoglossal motor nucleus in vivo in rats.

Successful cholinergic-noradrenergic pharmacotherapy for obstructive sleep apnea (OSA) is thought to be due to effects at the hypoglossal motor nucleus (HMN). Clinical efficacy varies with muscarinic-receptor (MR) subtype affinities. We hypothesized that oxybutynin (cholinergic agent in successful OSA pharmacotherapy) is an effective MR antagonist at the HMN and characterized its efficacy with other antagonists. We recorded tongue muscle activity of isoflurane anesthetized rats (121 males and 60 females, 7-13 per group across 13 protocols) in response to HMN microperfusion with MR antagonists with and without: (i) eserine-induced increased endogenous acetylcholine at the HMN and (ii) muscarine. Eserine-induced increased acetylcholine decreased tongue motor activity (p < 0.001) with lesser cholinergic suppression in females versus males (p = 0.017). Motor suppression was significantly attenuated by the MR antagonists atropine, oxybutynin, and omadacycline (MR2 antagonist), each p < 0.001, with similar residual activity between agents (p ≥ 0.089) suggesting similar efficacy at the HMN. Sex differences remained with atropine and oxybutynin (p < 0.001 to 0.05) but not omadacycline (p = 0.722). Muscarine at the HMN also decreased motor activity (p < 0.001) but this was not sex-specific (p = 0.849). These findings have translational relevance to antimuscarinic agents in OSA pharmacotherapy and understanding potential sex differences in HMN suppression with increased endogenous acetylcholine related to sparing nicotinic excitation.

Ovariectomy reduces cholinergic modulation of excitatory synaptic transmission in the rat entorhinal cortex.

Estrogens are thought to contribute to cognitive function in part by promoting the function of basal forebrain cholinergic neurons that project to the hippocampus and cortical regions including the entorhinal cortex. Reductions in estrogens may alter cognition by reducing the function of cholinergic inputs to both the hippocampus and entorhinal cortex. In the present study, we assessed the effects of ovariectomy on proteins associated with cholinergic synapses in the entorhinal cortex. Ovariectomy was conducted at PD63, and tissue was obtained on PD84 to 89 to quantify changes in the degradative enzyme acetylcholinesterase, the vesicular acetylcholine transporter, and muscarinic M1 receptor protein. Although the vesicular acetylcholine transporter was unaffected, ovariectomy reduced both acetylcholinesterase and M1 receptor protein, and these reductions were prevented by chronic replacement of 17ß-estradiol following ovariectomy. We also assessed the effects of ovariectomy on the cholinergic modulation of excitatory transmission, by comparing the effects of the acetylcholinesterase inhibitor eserine on evoked excitatory synaptic field potentials in brain slices obtained from intact rats, and from ovariectomized rats with or without 17ß-estradiol replacement. Eserine is known to prolong the effects of endogenously released acetylcholine, resulting in an M1-like mediated reduction of glutamate release at excitatory synapses. The reduction in excitatory synaptic potentials in layer II of the entorhinal cortex induced by 15-min application of 10 µM eserine was greatly reduced in slices from ovariectomized rats as compared to intact rats and ovariectomized rats with replacement of 17ß-estradiol. The reduced modulatory effect of eserine is consistent with the observed changes in cholinergic proteins, and suggests that reductions in 17ß-estradiol following ovariectomy lead to impaired cholinergic function within the entorhinal cortex.

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.