Effects of Increased Central Cholinergic Activity on the Metabolic Challenge Induced by Submaximal Exercise in Rats: Adrenomedullary Secretion Influences.

AIM: The aim of this study was to assess the influence of adrenomedullary secretion on the plasma glucose, lactate, and free fatty acids (FFAs) during running exercise in rats submitted to intracerebroventricular (i.c.v.) injection of physostigmine (PHY). PHY i.c.v. was used to activate the central cholinergic system. METHODS: Wistar rats were divided into sham-saline (sham-SAL), sham-PHY, adrenal medullectomy-SAL, and ADM-PHY groups. The plasma concentrations of glucose, lactate, and FFAs were determined immediately before and after i.c.v. injection of 20 µL of SAL or PHY at rest and during running exercise on a treadmill. RESULTS: The i.c.v. injection of PHY at rest increased plasma glucose in the sham group, but not in the ADM group. An increase in plasma glucose, lactate, and FFAs mobilization from adipose tissue was observed during physical exercise in the sham-SAL group; however, the increase in plasma glucose was greater with i.c.v. PHY. Moreover, the hyperglycemia induced by exercise and PHY in the ADM group were blunted by ADM, whereas FFA mobilization was unaffected. CONCLUSION: These results indicate that there is a dual metabolic control by which activation of the central cholinergic pathway increases plasma glucose but not FFA during rest and exercise, and that this hyperglycemic response is dependent on adrenomedullary secretion.

Targeting increased levels of APP in Down syndrome: Posiphen-mediated reductions in APP and its products reverse endosomal phenotypes in the Ts65Dn mouse model.

OBJECTIVE: Recent clinical trials targeting amyloid beta (Aß) and tau in Alzheimer's disease (AD) have yet to demonstrate efficacy. Reviewing the hypotheses for AD pathogenesis and defining possible links between them may enhance insights into both upstream initiating events and downstream mechanisms, thereby promoting discovery of novel treatments. Evidence that in Down syndrome (DS), a population markedly predisposed to develop early onset AD, increased APP gene dose is necessary for both AD neuropathology and dementia points to normalization of the levels of the amyloid precursor protein (APP) and its products as a route to further define AD pathogenesis and discovering novel treatments. BACKGROUND: AD and DS share several characteristic manifestations. DS is caused by trisomy of whole or part of chromosome 21; this chromosome contains about 233 protein-coding genes, including APP. Recent evidence points to a defining role for increased expression of the gene for APP and for its 99 amino acid C-terminal fragment (C99, also known as ß-CTF) in dysregulating the endosomal/lysosomal system. The latter is critical for normal cellular function and in neurons for transmitting neurotrophic signals. NEW/UPDATED HYPOTHESIS: We hypothesize that the increase in APP gene dose in DS initiates a process in which increased levels of full-length APP (fl-APP) and its products, including ß-CTF and possibly Aß peptides (Aß42 and Aß40), drive AD pathogenesis through an endosome-dependent mechanism(s), which compromises transport of neurotrophic signals. To test this hypothesis, we carried out studies in the Ts65Dn mouse model of DS and examined the effects of Posiphen, an orally available small molecule shown in prior studies to reduce fl-APP. In vitro, Posiphen lowered fl-APP and its C-terminal fragments, reversed Rab5 hyperactivation and early endosome enlargement, and restored retrograde transport of neurotrophin signaling. In vivo, Posiphen treatment (50 mg/kg/d, 26 days, intraperitoneal [i.p.]) of Ts65Dn mice was well tolerated and demonstrated no adverse effects in behavior. Treatment resulted in normalization of the levels of fl-APP, C-terminal fragments and small reductions in Aß species, restoration to normal levels of Rab5 activity, reduced phosphorylated tau (p-tau), and reversed deficits in TrkB (tropomyosin receptor kinase B) activation and in the Akt (protein kinase B [PKB]), ERK (extracellular signal-regulated kinase), and CREB (cAMP response element-binding protein) signaling pathways. Remarkably, Posiphen treatment also restored the level of choline acetyltransferase protein to 2N levels. These findings support the APP gene dose hypothesis, point to the need for additional studies to explore the mechanisms by which increased APP gene expression acts to increase the risk for AD in DS, and to possible utility of treatments to normalize the levels of APP and its products for preventing AD in those with DS. MAJOR CHALLENGES FOR THE HYPOTHESIS: Important unanswered questions are: (1) When should one intervene in those with DS; (2) would an APP-based strategy have untoward consequences on possible adaptive changes induced by chronically increased APP gene dose; (3) do other genes present on chromosome 21, or on other chromosomes whose expression is dysregulated in DS, contribute to AD pathogenesis; and (4) can one model strategies that combine the use of an APP-based treatment with those directed at other AD phenotypes including p-tau and inflammation. LINKAGE TO OTHER MAJOR THEORIES: The APP gene dose hypothesis interfaces with the amyloid cascade hypothesis of AD as well as with the genetic and cell biological observations that support it. Moreover, upregulation of fl-APP protein and products may drive downstream events that dysregulate tau homeostasis and inflammatory responses that contribute to propagation of AD pathogenesis.

Perioperative use of physostigmine to reduce opioid consumption and peri-incisional hyperalgesia: a randomised controlled trial.

BACKGROUND: Several studies have shown that cholinergic mechanisms play a pivotal role in the anti-nociceptive system by acting synergistically with morphine and reducing postoperative opioid consumption. In addition, the anti-cholinesterase drug physostigmine that increases synaptic acetylcholine concentrations has anti-inflammatory effects. METHODS: In this randomised placebo-controlled trial including 110 patients undergoing nephrectomy, we evaluated the effects of intraoperative physostigmine 0.5 mg h-1 i.v. for 24 h on opioid consumption, hyperalgesia, pain scores, and satisfaction with pain control. RESULTS: Physostigmine infusion did not affect opioid consumption compared with placebo. However, the mechanical pain threshold was significantly higher (2.3 [sd 0.3]) vs 2.2 [0.4]; P=0.0491), and the distance from the suture line of hyperalgesia (5.9 [3.3] vs 8.5 [4.6]; P=0.006), wind-up ratios (2.2 [1.5] vs 3.1 [1.5]; P=0.0389), and minimum and maximum postoperative pain scores at 24 h (minimum 1.8 [1.0] vs 2.4 [1.2]; P=0.0451; and maximum 3.2 [1.4] vs 4.2 [1.4]; P=0.0081) and 48 h (minimum 0.9 [1.0] vs 1.6 [1.1]; P=0.0101; and maximum 2.0 [1.5] vs 3.2 [1.6]; P=0.0029) were lower in the study group. Pain Disability Index was lower and satisfaction with pain control was higher after 3 months in the physostigmine group. CONCLUSIONS: In contrast to previous trials, physostigmine did not reduce opioid consumption. As pain thresholds were higher and hyperalgesia and wind-up lower in the physostigmine group, we conclude that physostigmine has anti-hyperalgesic effects and attenuates sensitisation processes. Intraoperative physostigmine may be a useful and safe addition to conventional postoperative pain control. CLINICAL TRIAL REGISTRATION: EudraCT number 2012-000130-19.

Combined Pre- and Posttreatment of Paraoxon Exposure.

AIMS: Organophosphates (OPCs), useful agents as pesticides, also represent a serious health hazard. Standard therapy with atropine and established oxime-type enzyme reactivators is unsatisfactory. Experimental data indicate that superior therapeutic results can be obtained when reversible cholinesterase inhibitors are administered before OPC exposure. Comparing the protective efficacy of five such cholinesterase inhibitors (physostigmine, pyridostigmine, ranitidine, tacrine, or K-27), we observed best protection for the experimental oxime K-27. The present study was undertaken in order to determine if additional administration of K-27 immediately after OPC (paraoxon) exposure can improve the outcome. METHODS: Therapeutic efficacy was assessed in rats by determining the relative risk of death (RR) by Cox survival analysis over a period of 48 h. Animals that received only pretreatment and paraoxon were compared with those that had received pretreatment and paraoxon followed by K-27 immediately after paraoxon exposure. RESULTS: Best protection from paraoxon-induced mortality was observed after pretreatment with physostigmine (RR = 0.30) and K-27 (RR = 0.34). Both substances were significantly more efficacious than tacrine (RR = 0.67), ranitidine (RR = 0.72), and pyridostigmine (RR = 0.76), which were less efficacious but still significantly reduced the RR compared to the no-treatment group (paraoxon only). Additional administration of K-27 immediately after paraoxon exposure (posttreatment) did not further reduce mortality. Statistical analysis between pretreatment before paraoxon exposure alone and pretreatment plus K-27 posttreatment did not show any significant difference for any of the pretreatment regimens. CONCLUSIONS: Best outcome is achieved if physostigmine or K-27 are administered prophylactically before exposure to sublethal paraoxon dosages. Therapeutic outcome is not further improved by additional oxime therapy immediately thereafter.

Delirium due to the use of topical cyclopentolate hydrochloride.

Introduction - Our aim is to present a rare case where a child had delirium manifestation after instillation of cyclopentolate. Case presentation - A 7-year old patient was seen in our outpatient clinic, and cyclopentolate was dropped three times at 10 minutes intervals in both eyes. The patient suddenly developed behavioral disorders along with gait disturbance, and complained of visual hallucinations 20-25 minutes after the last drop. The patient was transferred to intensive care unit and 0.02 mg/kg IV. physostigmine was administered. The patient improved after minutes of onset of physostigmine, and was discharged with total recovery after 30 minutes. Conclusion - Delirium is a rare systemic side effect of cyclopentolate. The specific antidote is physostigmine, which can be used in severely agitated patients who are not responding to other therapies.

(-)-Phenserine tartrate (PhenT) as a treatment for traumatic brain injury.

AIM: Traumatic brain injury (TBI) is one of the most common causes of morbidity and mortality of both young adults and the elderly, and is a key contributing factor in about 30% of all injury-associated deaths occurring within the United States of America. Albeit substantial impact has been made to improve our comprehension of the mechanisms that underpin the primary and secondary injury stages initiated by a TBI incident, this knowledge has yet to successfully translate into the development of an effective TBI pharmacological treatment. Developing consent suggests that a TBI can concomitantly trigger multiple TBI-linked cascades that then progress in parallel and, if correct, the multifactorial nature of TBI would make the discovery of a single effective mechanism-targeted drug unlikely. DISCUSSION: We review recent data indicating that the small molecular weight drug (-)-phenserine tartrate (PhenT), originally developed for Alzheimer's disease (AD), effectively inhibits a broad range of mechanisms pertinent to mild (m) and moderate (mod)TBI, which in combination underpin the ensuing cognitive and motor impairments. In cellular and animal models at clinically translatable doses, PhenT mitigated mTBI- and modTBI-induced programmed neuronal cell death (PNCD), oxidative stress, glutamate excitotoxicity, neuroinflammation, and effectively reversed injury-induced gene pathways leading to chronic neurodegeneration. In addition to proving efficacious in well-characterized animal TBI models, significantly mitigating cognitive and motor impairments, the drug also has demonstrated neuroprotective actions against ischemic stroke and the organophosphorus nerve agent and chemical weapon, soman. CONCLUSION: In the light of its tolerability in AD clinical trials, PhenT is an agent that can be fast-tracked for evaluation in not only civilian TBI, but also as a potentially protective agent in battlefield conditions where TBI and chemical weapon exposure are increasingly jointly occurring.

Continuous infusion of physostigmine in patients with perioperative septic shock: A pharmacokinetic/pharmacodynamic study with population pharmacokinetic modeling.

BACKGROUND: In the context of the cholinergic anti-inflammatory pathway, the clinical trial Anticholium® per Se (EudraCT Number: 2012-001650-26, ClinicalTrials.gov NCT03013322) addressed the possibility of taking adjunctive physostigmine salicylate treatment in septic shock from bench to bedside. Pharmacokinetics (PK) are likely altered in critically ill patients; data on physostigmine PK and target concentrations are sparse, particularly for continuous infusion. Our objective was to build a population PK (popPK) model for physostigmine, and further evaluate pharmacodynamics (PD) and concentration-response relationship in this setting. METHODS: In the randomized, double-blind, placebo-controlled trial, 20 patients with perioperative septic shock either received an initial dose of 0.04 mg/kg physostigmine salicylate, followed by continuous infusion of 1 mg/h for up to 120 h, or equivalent volumes of 0.9% sodium chloride (placebo group). Physostigmine plasma concentrations and acetylcholinesterase (AChE) activity were measured; concentration-response associations were evaluated, and popPK and PD modeling was performed with NONMEM. RESULTS: Steady state physostigmine plasma concentrations reached 7.60 ±â€¯2.81 ng/mL (mean ±â€¯standard deviation [SD]). PK was best described by a two-compartment model with linear clearance. Significant covariate effects were detected for body weight and age on clearance, as well as a high inter-individual variability of the central volume of distribution. AChE activity was significantly reduced to 30.5%-50.6% of baseline activity during physostigmine salicylate infusion. A sigmoidal direct effect PD model best described enzyme inhibition by physostigmine, with an estimated half maximal effective concentration (EC50) of 5.99 ng/mL. CONCLUSIONS: PK of physostigmine in patients with septic shock displayed substantial inter-individual variability with body weight and age influencing the clearance. Physostigmine inhibited AChE activity with a sigmoidal concentration-response effect.

A Comparison of Resource Utilization in the Management of Anticholinergic Delirium Between Physostigmine and Nonantidote Therapy.

Background: Antimuscarinic delirium is associated with significant morbidity, and its management requires substantial resource allocation, including intubation, restraint, and intensive care unit (ICU) placement. There is controversy over the management of these patients. Physostigmine can rapidly reverse antimuscarinic delirium but has been associated with adverse effects. Objective: This study aims to assess the effect of physostigmine use on resource allocation and adverse events. Methods: This is a retrospective chart review of patients with an antimuscarinic toxidrome at a single hospital approved by the local institutional review board. A blinded abstractor recorded data from patient charts. Whether the patient was given physostigmine, intubated, restrained, or admitting to critical care was recorded. We recorded instances of seizure, vomiting, or bradycardia. The primary aim was to compare frequency of intubation as a function of physostigmine administration. Results: A total of 141 patients were identified. We found no difference between the groups in age, gender, or initial heart rate; 65 (46%) were given physostigmine, 45 (32%) were admitted to the ICU, and 29 (20%) were intubated. Patients who received physostigmine in the first 24 hours were less likely to be intubated and less likely to be admitted to an ICU. The instance of bradycardia (n = 16), vomiting (n = 27), and seizures (n = 7) was limited, and there were no significant differences between the groups. There were no associations noted between physostigmine administration and adverse effects. Conclusion and Relevance: This study demonstrated that physostigmine use is associated with decreased resource utilization (including intubation and ICU placement) without increasing rates of bradycardia, vomiting, or seizures.

Effect of physostigmine on recovery from septic shock following intra-abdominal infection - Results from a randomized, double-blind, placebo-controlled, monocentric pilot trial (Anticholium® per Se).

PURPOSE: The cholinergic anti-inflammatory pathway has been shown to be accessible by physostigmine salicylate in animal models. However, the cholinesterase inhibitor is not approved for adjunctive therapy in sepsis, and tolerability and safety of high initial doses followed by continuous infusion have not been investigated. MATERIALS AND METHODS: In this trial, 20 patients with perioperative septic shock due to intra-abdominal infection were eligible. The physostigmine group received an initial dose of 0.04 mg/kg physostigmine salicylate, followed by continuous infusion of 1 mg/h for 120 h; the placebo group was treated with 0.9% sodium chloride. Primary outcome was the mean Sequential Organ Failure Assessment (SOFA) score during treatment and up to 14 days. RESULTS: Administration of physostigmine salicylate was well tolerated. Mean SOFA scores were 8.9 ±â€¯2.5 and 11.3 ±â€¯3.6 (mean ±â€¯SD) for physostigmine and placebo group, respectively. Adjusted for age, difference between means was not statistically significant (-2.37, 95% CI: -5.43 to 0.70, p = 0.121). Norepinephrine doses required only appeared lower in the physostigmine group (p = 0.064), along with a more rapid reduction from an elevated heart rate possibly indicating less hemodynamic instability. CONCLUSIONS: Treatment with physostigmine salicylate was feasible and safe. Further studies are justified to assess the effect on recovery from septic shock. TRIAL REGISTRATION: EudraCT Number 2012-001650-26, ClinicalTrials.gov identifier NCT03013322.

Physostigmine is superior to non-antidote therapy in the management of antimuscarinic delirium: a prospective study from a regional poison center.

CONTEXT: Poison centers (PCs) frequently manage patients with antimuscarinic delirium. However, controversy surrounds the antidotal use of physostigmine for its treatment. The aim of this study was to prospectively investigate physostigmine versus non-antidote therapy for the management of antimuscarinic delirium in a single regional PC. METHODS: This was a prospective observational analysis of patients diagnosed with antimuscarinic delirium and treated in consultation with a regional PC. Certified Specialists in Poison Information (CSPIs) use a clinical guideline to recommend the use of physostigmine. Using a previously derived altered mental status score, we quantified the rate of delirium improvement with physostigmine compared to non-antidote therapy two hours after initial patient identification. We also recorded adverse events (defined a priori as bradycardia, vomiting, seizures) and resource utilization (intubation and physical restraint). RESULTS: We identified 245 patients and included 154 in the analysis. The most common exposure classes were antihistamines (68%), analgesics (19%), and antipsychotics (19%). CSPIs recommended physostigmine in 81% (125) of cases and the treatment team administered it in 37% (57) of these. We observed delirium control in 79% of patients who received physostigmine versus 36% of those who did not. The odds of delirium control were six times greater for patients receiving physostigmine than for patients treated with non-antidote therapy (OR 6.6). Adverse events were rare and did not differ significantly between the groups. Physostigmine was not associated with changes in the incidence of intubation or restraint. CONCLUSIONS: This study provides further evidence of both the safety and efficacy of physostigmine in the treatment of antimuscarinic delirium.

Physostigmine-loaded liposomes for extended prophylaxis against nerve agent poisoning.

Pre-administration of physostigmine can prevent poisoning against nerve agent exposure by reversibly binding to cholinesterase. However, its cholinesterase protection-based prophylactic effect can be eliminated rapidly due to short biological half-life. Liposomes are useful for encapsulating hydrophilic drugs like physostigmine, and can be used for sustained release after parenteral injection. Thus, physostigmine liposomes were prepared by the pH-gradient condition-based remote-loading method for subcutaneous injection. In addition, polyethylene glycol (PEG)-lipid was applied to further extend the release of physostigmine and its prophylactic action. In vitro release of physostigmine, pharmacokinetics and duration of prophylactic effect were then evaluated. Physostigmine was dissolved in distilled water and used as a solution group for comparison. The prepared liposomes showed spherical shape and their particle size was around 130 µm. Addition of PEG-lipid in liposomes significantly increased the entrapment efficiency of physostigmine. Both control and PEG liposomes exhibited sustained release pattern compared to the solution. Moreover, the release of PEG liposomes was relatively slower than that of the control liposomes. Pharmacokinetic study in rats revealed that physostigmine liposomes exhibited lower maximum plasma concentration and longer half-life compared to the solution. Plasma cholinesterase inhibition ratio in the liposomal group decreased more gradually compared to the solution. Moreover, PEG liposomes showed higher plasma concentration of physostigmine and cholinesterase inhibition ratio compared to the control liposomes. These results suggest that PEG liposomes have potential to enhance the duration of cholinesterase-protecting effect of physostigmine.

[Promethazine - an old pharmaceutical that has got a renaissance. An avalanche-like increase in the number of overdose cases in Sweden]. / Renässans för Lergigan med kraftig ökning av intoxikationsfall - Korrekt användning av fysostigmin vid överdosering medför minimal risk.

Promethazine is a phenothiazine derivative antihistamine first introduced in the 1940s that is used in multiple medical conditions as a sedative/hypnotic agent. The drug is not addictive, which probably explains why it is increasingly used in the care of drug addicts. During the recent decade the sales of promethazine in Sweden have increased threefold while the yearly number of overdose cases with this drug at the Swedish Poisons Centre has increased from 100 to nearly 700. The anticholinergic delirium that may be provoked by this poisoning carries a symptomatology which may resemble the symptoms seen after an intracranial catastrophe, wherefore some cases are exposed to unnecessary diagnostic measures and invasive ventilator treatment. The case report and literature review presented in this paper conclude that physostigmine is the drug of choice in delirium provoked by overdose of promethazine, and that its use in this setting carries a minimal risk of serious side effects.

Cromakalim, a Potassium Channel Opener, Ameliorates the Organophosphate and Carbamate-Induced Seizure in Mice.

Organophosphates (OPs) and carbamates are acetylcholine esterase inhibitors (AChEIs), which can cause seizure and lethality. Anticonvulsant properties of potassium channel openers including cromakalim have been determined in previous studies. In the present experiment, the possible effect of cromakalim on the convulsion and death induced by OPs and carbamates was studied in mice. Dichlorvos (an OP, 50 mg/kg) and physostigmine (a carbamate, 2 mg/kg) were used to induce seizure in animals. Cromakalim at doses of 0.1, 10, and 30 µg/kg was injected 30 min before dichlorvos and physostigmine, and 5 min before glibenclamide (a potassium channel blocker, 1 mg/kg) administration. All injections were performed intraperitoneally. After drugs administration, the onset of convulsion, death, the severity of seizure, and rate of mortality were investigated. Results revealed that both dichlorvos and physostigmine induced seizure activity and lethality in 100% of the animals. Cromakalim at doses of 0.1, 10, and 30 µg/kg significantly increased the latency of both seizure and death (P<0.05). Also, cromakalim decreased the mortality rate induced by dichlorvos and physostigmine (P<0.05). On the other hand, glibenclamide blocked all aspects of the anticonvulsant effect of cromakalim (P<0.05). This study revealed for the first time that cromakalim (a KATP channel opener) diminishes the seizure and death induced by dichlorvos and physostigmine in mice, and introduces a new aspect to manage the patients who suffer from OPs/carbamates-induced seizure.

Increased cell proliferation and neural activity by physostigmine in the telencephalon of adult zebrafish.

Physostigmine, an acetylcholinesterase inhibitor, is known to affect the brain function in various aspects. This study was conducted to test whether physostigmine affects cell proliferation in the telencephalon of zebrafish. BrdU-labeled cells was prominently observed in the ventral zone of the ventral telencephalon of zebrafish. The increased number of BrdU- and proliferating cell nuclear antigen-labeled cells were shown in zebrafish treated with 200µM physostigmine, which was inhibited by pretreatment with 200µM scopolamine. iNOS mRNA expression was increased in the brain of zebrafish treated with 200µM physostigmine. Consistently, aminoguanidine, an iNOS inhibitor, attenuated the increase in the number of BrdU-labeled cells by physostigmine treatment. Zebrafish also showed seizure-like locomotor activity characterized by a rapid and abrupt movement during a 30min treatment with 200µM physostigmine. Neural activity in response to an electrical stimulus was increased in the isolated telencephalon of zebrafish continuously perfused with 200µM physostigmine. None of the number of BrdU-labeled cells, neural activity, or locomotor activity was affected by treatment with 20µM physostigmine. These results suggest that 200µM physostigmine increased neural activity and induced cell proliferation via nitric oxide production in zebrafish.

Cognitive Impairments Induced by Concussive Mild Traumatic Brain Injury in Mouse Are Ameliorated by Treatment with Phenserine via Multiple Non-Cholinergic and Cholinergic Mechanisms.

Traumatic brain injury (TBI), often caused by a concussive impact to the head, affects an estimated 1.7 million Americans annually. With no approved drugs, its pharmacological treatment represents a significant and currently unmet medical need. In our prior development of the anti-cholinesterase compound phenserine for the treatment of neurodegenerative disorders, we recognized that it also possesses non-cholinergic actions with clinical potential. Here, we demonstrate neuroprotective actions of phenserine in neuronal cultures challenged with oxidative stress and glutamate excitotoxicity, two insults of relevance to TBI. These actions translated into amelioration of spatial and visual memory impairments in a mouse model of closed head mild TBI (mTBI) two days following cessation of clinically translatable dosing with phenserine (2.5 and 5.0 mg/kg BID x 5 days initiated post mTBI) in the absence of anti-cholinesterase activity. mTBI elevated levels of thiobarbituric acid reactive substances (TBARS), a marker of oxidative stress. Phenserine counteracted this by augmenting homeostatic mechanisms to mitigate oxidative stress, including superoxide dismutase [SOD] 1 and 2, and glutathione peroxidase [GPx], the activity and protein levels of which were measured by specific assays. Microarray analysis of hippocampal gene expression established that large numbers of genes were exclusively regulated by each individual treatment with a substantial number of them co-regulated between groups. Molecular pathways associated with lipid peroxidation were found to be regulated by mTBI, and treatment of mTBI animals with phenserine effectively reversed injury-induced regulations in the 'Blalock Alzheimer's Disease Up' pathway. Together these data suggest that multiple phenserine-associated actions underpin this compound's ability to ameliorate cognitive deficits caused by mTBI, and support the further evaluation of the compound as a therapeutic for TBI.

Tramadol state-dependent memory: involvement of dorsal hippocampal muscarinic acetylcholine receptors.

The effects on tramadol state-dependent memory of bilateral intradorsal hippocampal (intra-CA1) injections of physostigmine, an acetylcholinesterase inhibitor, and atropine, a muscarinic acetylcholine receptor antagonist, were examined in adult male NMRI mice. A single-trial step-down passive avoidance task was used for the assessment of memory retention. Post-training intra-CA1 administration of an atypical µ-opioid receptor agonist, tramadol (0.5 and 1 µg/mouse), dose dependently impaired memory retention. Pretest injection of tramadol (0.5 and 1 µg/mouse, intra-CA1) induced state-dependent retrieval of the memory acquired under the influence of post-training tramadol (1 µg/mouse, intra-CA1). A pretest intra-CA1 injection of physostigmine (1 µg/mouse) reversed the memory impairment induced by post-training administration of tramadol (1 µg/mouse, intra-CA1). Moreover, pretest administration of physostigmine (0.5 and 1 µg/mouse, intra-CA1) with an ineffective dose of tramadol (0.25 µg/mouse, intra-CA1) also significantly restored retrieval. Pretest administration of physostigmine (0.25, 0.5, and 1 µg/mouse, intra-CA1) by itself did not affect memory retention. A pretest intra-CA1 injection of the atropine (1 and 2 µg/mouse) 5 min before the administration of tramadol (1 µg/mouse, intra-CA1) dose dependently inhibited tramadol state-dependent memory. Pretest administration of atropine (0.5, 1, and 2 µg/mouse, intra-CA1) by itself did not affect memory retention. It can be concluded that dorsal hippocampal muscarinic acetylcholine receptor mechanisms play an important role in the modulation of tramadol state-dependent memory.

Physostigmine and Methylphenidate Induce Distinct Arousal States During Isoflurane General Anesthesia in Rats.

BACKGROUND: Although emergence from general anesthesia is clinically treated as a passive process driven by the pharmacokinetics of drug clearance, agents that hasten recovery from general anesthesia may be useful for treating delayed emergence, emergence delirium, and postoperative cognitive dysfunction. Activation of central monoaminergic neurotransmission with methylphenidate has been shown to induce reanimation (active emergence) from general anesthesia. Cholinergic neurons in the brainstem and basal forebrain are also known to promote arousal. The objective of this study was to test the hypothesis that physostigmine, a centrally acting cholinesterase inhibitor, induces reanimation from isoflurane anesthesia in adult rats. METHODS: The dose-dependent effects of physostigmine on time to emergence from a standardized isoflurane general anesthetic were tested. It was then determined whether physostigmine restores righting during continuous isoflurane anesthesia. In a separate group of rats with implanted extradural electrodes, physostigmine was administered during continuous inhalation of 1.0% isoflurane, and the electroencephalogram changes were recorded. Finally, 2.0% isoflurane was used to induce burst suppression, and the effects of physostigmine and methylphenidate on burst suppression probability (BSP) were tested. RESULTS: Physostigmine delayed time to emergence from isoflurane anesthesia at doses ≥0.2 mg/kg (n = 9). During continuous isoflurane anesthesia (0.9% ± 0.1%), physostigmine did not restore righting (n = 9). Blocking the peripheral side effects of physostigmine with the coadministration of glycopyrrolate (a muscarinic antagonist that does not cross the blood-brain barrier) produced similar results (n = 9 each). However, during inhalation of 1.0% isoflurane, physostigmine shifted peak electroencephalogram power from δ (<4 Hz) to θ (4-8 Hz) in 6 of 6 rats. During continuous 2.0% isoflurane anesthesia, physostigmine induced large, statistically significant decreases in BSP in 6 of 6 rats, whereas methylphenidate did not. CONCLUSIONS: Unlike methylphenidate, physostigmine does not accelerate time to emergence from isoflurane anesthesia and does not restore righting during continuous isoflurane anesthesia. However, physostigmine consistently decreases BSP during deep isoflurane anesthesia, whereas methylphenidate does not. These findings suggest that activation of cholinergic neurotransmission during isoflurane anesthesia produces arousal states that are distinct from those induced by monoaminergic activation.