Competitive Antagonism of Etomidate Action by Diazepam: In Vitro GABAA Receptor and In Vivo Zebrafish Studies.

BACKGROUND: Recent cryo-electron microscopic imaging studies have shown that in addition to binding to the classical extracellular benzodiazepine binding site of the α1ß3γ2L γ-aminobutyric acid type A (GABAA) receptor, diazepam also binds to etomidate binding sites located in the transmembrane receptor domain. Because such binding is characterized by low modulatory efficacy, the authors hypothesized that diazepam would act in vitro and in vivo as a competitive etomidate antagonist. METHODS: The concentration-dependent actions of diazepam on 20 µM etomidate-activated and 6 µM GABA-activated currents were defined (in the absence and presence of flumazenil) in oocyte-expressed α1ß3γ2L GABAA receptors using voltage clamp electrophysiology. The ability of diazepam to inhibit receptor labeling of purified α1ß3γ2L GABAA receptors by [H]azietomidate was assessed in photoaffinity labeling protection studies. The impact of diazepam (in the absence and presence of flumazenil) on the anesthetic potencies of etomidate and ketamine was compared in a zebrafish model. RESULTS: At nanomolar concentrations, diazepam comparably potentiated etomidate-activated and GABA-activated GABAA receptor peak current amplitudes in a flumazenil-reversible manner. The half-maximal potentiating concentrations were 39 nM (95% CI, 27 to 55 nM) and 26 nM (95% CI, 16 to 41 nM), respectively. However, at micromolar concentrations, diazepam reduced etomidate-activated, but not GABA-activated, GABAA receptor peak current amplitudes in a concentration-dependent manner with a half-maximal inhibitory concentration of 9.6 µM (95% CI, 7.6 to 12 µM). Diazepam (12.5 to 50 µM) also right-shifted the etomidate-concentration response curve for direct activation without reducing the maximal response and inhibited receptor photoaffinity labeling by [H]azietomidate. When administered with flumazenil, 50 µM diazepam shifted the etomidate (but not the ketamine) concentration-response curve for anesthesia rightward, increasing the etomidate EC50 by 18-fold. CONCLUSIONS: At micromolar concentrations and in the presence of flumazenil to inhibit allosteric modulation via the classical benzodiazepine binding site of the GABAA receptor, diazepam acts as an in vitro and in vivo competitive etomidate antagonist.

ECHOCARDIOGRAPHIC PARAMETERS IN EIGHT ADULT TIGERS ( PANTHERA TIGRIS) DURING TWO PHASES OF AN ANESTHETIC PROTOCOL.

Eight adult tigers ( Panthera tigris) underwent a complete echocardiographic examination following sedation with medetomidine, midazolam, and induction of general anesthesia using ketamine and isoflurane (phase 1). Atipamezole was used to antagonize medetomidine (phase 2) and a second echocardiographic examination was performed. Physiologic tricuspid and pulmonic regurgitations were common findings in the sample population and one tiger was excluded from final analyses due to the finding of a ventricular septal defect. Measurements and mean arterial pressure were assessed for statistically significant differences between the two examination phases as well as gender and weight. There was a statistically significant difference between interventricular septum thickness at end systole, ejection fraction, and mean arterial pressure between anesthetic phases while fractional shortening and left ventricular internal dimension at end-systole approached, but did not reach, statistical significance between phases. Weight was found to be a statistically significant predictor of stroke volume and left ventricular internal dimension at end-diastole. The echocardiographic measurements obtained during this study can be used as guidelines for future examinations in adult tigers. The effects of medetomidine on these measurements and systolic function should be taken into account when performing echocardiograms and monitoring anesthetic events.

Sedative and cardiopulmonary effects of buccally administered detomidine gel and reversal with atipamezole in dogs.

OBJECTIVE To evaluate hemodynamic, respiratory, and sedative effects of buccally administered detomidine gel and reversal with atipamezole in dogs. ANIMALS 8 adult purpose-bred dogs. PROCEDURES Arterial and venous catheters were placed. Baseline heart rate, respiratory rate, cardiac output (determined via lithium dilution with pulse contour analysis), oxygen delivery, systemic vascular resistance, arterial blood gas values, and sedation score were obtained. Detomidine gel (2.0 mg/m2) was administered on the buccal mucosa. Cardiopulmonary data and sedation scores were obtained at predetermined times over 180 minutes. Atipamezole (0.1 mg/kg) was administered IM at 150 minutes. Reversal of sedation was timed and scored. Data were analyzed with an ANOVA. RESULTS Compared with baseline values, heart rate was lower at 45 to 150 minutes, cardiac output and oxygen delivery were lower at 30 to 150 minutes, and systemic vascular resistance was increased at 30 to 150 minutes. There were no significant changes in Paco2, Pao2, or lactate concentration at any time point, compared with baseline values, except for lactate concentration at 180 minutes. All dogs became sedated; maximum sedation was detected 75 minutes after administration of detomidine. Mean ± SD time to recovery after atipamezole administration was 7.55 ± 1.89 minutes; sedation was completely reversed in all dogs. No adverse events were detected. CONCLUSIONS AND CLINICAL RELEVANCE Buccally administered detomidine gel was associated with reliable and reversible sedation in dogs, with hemodynamic effects similar to those induced by other α2-adrenoceptor agonists. Buccally administered detomidine gel could be an alternative to injectable sedatives in healthy dogs.

Sedative effect of intramuscular medetomidine with and without vatinoxan (MK-467), and its reversal with atipamezole in sheep.

OBJECTIVE: To evaluate the effect of the peripherally acting α2-adrenoceptor antagonist vatinoxan (MK-467) on the sedative properties of medetomidine (MED) when injected intramuscularly (IM) in the same syringe and on reversal of this sedation with atipamezole in sheep. STUDY DESIGN: Randomized, blinded, crossover experimental trial. ANIMALS: Eight healthy adult female sheep. METHODS: Sheep received MED (30 µg kg-1 IM) alone or combined in the same syringe with vatinoxan (300 µg kg-1 IM, MED+VAT) with a 2 week washout period. Atipamezole (150 µg kg-1 IM) was administered 30 minutes later for reversal. Sedation was assessed using two sedation scores, a visual analog score and a descriptive scale before treatments (T0) and at intervals up to 5 hours thereafter. Pulse rate (PR) was counted at T0 and at 30 (T30) and 90 (T90) minutes. Rectal temperature was measured at T0 and T90 postinjection. Plasma samples were analyzed for drug concentrations at T30 and T90. RESULTS: The first signs of sedation were seen significantly earlier after MED+VAT (4.6 ± 1.7 minutes versus 9.4 ± 2.6 minutes after MED) and the sedation scores were significantly higher after MED+VAT than MED. All animals laid with head down 10.0 ± 3.4 minutes after MED+VAT, whereas three MED animals did not become recumbent before atipamezole was administered. The plasma concentrations of dexmedetomidine were significantly higher at T30 (2.47 ± 0.2 ng mL-1) and significantly lower at T90 (1.23 ± 0.3 ng mL-1) with MED+VAT than with MED (1.19 ± 0.8 and 1.83 ± 0.4 ng mL-1, respectively). While no significant differences were observed between treatments in PR at T30, PR at T90 was significantly higher with MED+VAT than with MED. CONCLUSIONS AND CLINICAL RELEVANCE: When administered IM in the same syringe, vatinoxan hastened and intensified the initial sedative effects of MED and enhanced the sedation reversal by atipamezole.

Efficacy and safety of flumazenil injection for the reversal of midazolam sedation after elective outpatient endoscopy.

OBJECTIVE: Midazolam sedation during elective endoscopy is widely performed and flumazenil is frequently administered after endoscopy to reverse sedation in clinical practice. This study aimed to investigate the safety and efficacy of flumazenil injections after elective endoscopy under midazolam sedation. METHODS: Participants who underwent an upper endoscopy under midazolam sedation were randomly divided into two groups. In group I, flumazenil was administered i.v. 10 min after the patient's transfer to the recovery room, and no antidote was injected in group II. The time of stay in the recovery room and adverse events were reviewed through the nursing records. We asked the patients about their pain and degree of satisfaction according to a visual analogue scale (VAS), their memory of the procedure, mental status and the presence of uncomfortable symptoms on the day of the procedure and the day afterwards. RESULTS: The length of stay in recovery was significantly shorter in group I than in group II. No significant differences were found in the number of patients with pain (VAS ≥1), adverse events and discomfort between the two groups. Additionally, there were no differences in the patients' memory of the procedure, satisfaction with sedation, willingness to repeat the endoscopy and mental status. CONCLUSIONS: The time in the recovery room after flumazenil administration was significantly shortened, and the use of the drug did not increase the risk of adverse events or discomfort. The use of flumazenil for reversing midazolam sedation seems to be safe and effective.

Pharmacokinetics after a single dose of naloxone administered as a nasal spray in healthy volunteers.

BACKGROUND: There is increasing interest in the use of intranasal naloxone to reverse adverse opioid effects during management of procedural pain in children and in adults after overdose. There are limited data on the pharmacokinetics of intranasal naloxone so in this study we aimed to detail the pharmacokinetic profile of the commercially marketed injectable solution of naloxone 0.4 mg/ml when administered as an intranasal spray. METHODS: Twenty healthy volunteers received naloxone as an intranasal spray at a dose of 10 µg/kg. Venous blood sampling was carried out for 90 min after administration to determine the time profile of the plasma concentrations of using tandem mass spectrometry. Pharmacokinetic parameters were calculated using a one-compartment model. RESULTS: Median time to maximum naloxone concentration (Tmax) was 14.5 (95% CI: 9.0-16.5) min, mean maximum naloxone concentration (Cmax) was 1.09 ± 0.56 ng/ml and mean AUC0-90 min was 37.1 ± 15.0 ng*min/ml. Elimination half-life estimated from the median concentration data was 28.2 min. CONCLUSION: Our results show a faster uptake of intranasal naloxone to maximum concentration compared with previous studies although with a marked variation in maximum concentration. The findings are consistent with our clinical experience of the time profile for reversing the effects of sufentanil sedation in children.

A Review of the use of Flumazenil for the Reversal of Midazolam Conscious Sedation in Dentistry.

The practice of midazolam conscious sedation is well established in dentistry. The drug flumazenil is a specific benzodiazepine antagonist and is an essential requirement in settings where midazolam is used. A literature review has been carried out, examining the available information regarding flumazenil's safety, administration, potential complications and the regulatory documentation which governs its use. Flumazenil is a safe drug to use for the reversal of midazolam induced conscious sedation although the evidence surrounding its use is limited.

Propofol-medetomidine-ketamine total intravenous anaesthesia in thiafentanil-medetomidine-immobilized impala (Aepyceros melampus).

OBJECTIVE: To characterize a propofol-medetomidine-ketamine total intravenous anaesthetic in impala (Aepyceros melampus). STUDY DESIGN: Prospective clinical study. ANIMALS: Ten adult female impala. MATERIALS AND METHODS: Impala were immobilized at 1253 m above sea level with 2.0 mg thiafentanil and 2.2 mg medetomidine via projectile darts. Propofol was given to effect (0.5 mg kg-1 boluses) to allow endotracheal intubation, following which oxygen was supplemented at 2 L minute-1. Anaesthesia was maintained with a constant-rate infusion of medetomidine and ketamine at 5 µg kg-1 hour-1 and 1.5 mg kg-1 hour-1, respectively, and propofol to effect (initially 0.2 mg kg-1 minute-1) for 120 minutes. The propofol infusion was titrated according to reaction to nociceptive stimuli every 15 minutes. Cardiopulmonary parameters were monitored continuously and arterial blood gas samples were analysed intermittently. After 120 minutes' maintenance, the thiafentanil and medetomidine were antagonized using naltrexone (10:1 thiafentanil) and atipamezole (5:1 medetomidine), respectively. RESULTS: All impala were successfully immobilized. The median dose [interquartile range (IQR)] of propofol required for intubation was 2.7 (1.9-3.3) mg kg-1. The propofol-medetomidine-ketamine combination abolished voluntary movement and ensured anaesthesia for the 120 minute period. Propofol titration showed a generally downward trend. Median (IQR) heart rate [57 (53-61) beats minute-1], respiratory rate [10 (9-12) breaths minute-1] and mean arterial blood pressure [101 (98-106) mmHg] were well maintained. Arterial blood gas analysis indicated hypoxaemia, hyper- capnia and acidaemia. Butorphanol (0.12 mg kg-1) was an essential rescue drug to counteract thiafentanil-induced respiratory depression. All impala regurgitated frequently during the maintenance period. Recovery was calm and rapid in all animals. Median (IQR) time to standing from antagonist administration was 4.4 (3.2-5.6) minutes. CONCLUSIONS AND CLINICAL RELEVANCE: A propofol-medetomidine-ketamine combination could provide adequate anaesthesia for invasive procedures in impala. The propofol infusion should begin at 0.2 mg kg-1 minute-1 and be titrated to clinical effect. Oxygen supplementation and airway protection with a cuffed endotracheal tube are essential.

PHARMACOLOGICAL ASSESSMENT OF HISPIDULIN - A NATURAL BIOACTIVE FLAVONE.

Hispidulin is well-known natural bioactive flavone on behalf of its pharmacological aspects. This review contains data on isolation, synthetic methodology, pharmacokinetics and bioactivities of hispidulin. The article provides a critical assessment of present knowledge about hispidulin with some clear conclusions, perspectives and directions for future research in potential applications.

The Toxicology Investigators Consortium Case Registry-the 2015 Experience.

The American College of Medical Toxicology established the Toxicology Investigators Consortium (ToxIC) Case Registry in 2010. The Registry contains all medical toxicology consultations performed at participating sites. The Registry has continued to grow since its inception, and as of December 31, 2015, contains 43,099 cases. This is the sixth annual report of the ToxIC Registry, summarizing the additional 8115 cases entered in 2015. Cases were identified by a query of the Registry for all cases entered between January 1 and December 31, 2015. Specific data reviewed for analysis included demographics (age, race, gender), source of consultation, reason for consultation, agents and agent classes involved in exposures, signs, symptoms, clinical findings, fatalities, and treatment. By the end of 2015, there were 50 active sites, consisting of 101 separate health-care facilities; 51.2 % of cases involved females. Adults between the ages of 19 and 65 made up the majority (64.2 %) of Registry cases. Caucasian race was the most commonly reported (55.6 %); 9.6 % of cases were identified as Hispanic ethnicity. Inpatient and emergency department referrals were by far the most common referral sources (92.9 %). Intentional pharmaceutical exposures remained the most frequent reason for consultation, making up 52.3 % of cases. Of these intentional pharmaceutical exposures, 69 % represented an attempt at self-harm, and 85.6 % of these were a suicide attempt. Nonopioid analgesics, sedative-hypnotics, and antidepressant agents were the most commonly reported agent classes in 2015. Almost one-third of Registry cases involved a diagnosed toxidrome (32.8 %), with a sedative-hypnotic toxidrome being the most frequently described. Significant vital sign abnormalities were recorded in 25.3 % of cases. There were 98 fatalities reported in the Registry (1.2 %). Adverse drug reactions were reported in 4.3 % of cases. Toxicological treatment was given in 65.3 % of cases, with 33.0 % receiving specific antidotal therapy. Exposure characteristics and trends overall were similar to prior years. While treatment interventions were required in the majority of cases, fatalities were rare.

Acute Administration of Diazepam Provokes Redox Homeostasis Imbalance in the Rat Brain: Prevention by Simvastatin.

We investigated the effects of acute diazepam (DZP) administration on thiobarbituric acid-reactive substance (TBARS) levels, protein carbonyl content, and on the activities of the antioxidant enzymes catalase, glutathione peroxidase, and superoxide dismutase in the brain of rats. Additionally, we investigated the antioxidant role of chronic pretreatment with simvastatin on the effects provoked by DZP. Simvastatin was administered (1 or 10 mg/kg by oral gavage) for 30 days. On the 30th day of treatment, groups were randomized and DZP was administered (0.5 or 1.0 mg/kg by intraperitoneal injection). Control groups received saline. Results showed that DZP enhanced TBARS levels and protein carbonyl content and altered enzymatic activity in the brain of rats. Simvastatin prevented most of the alterations caused by DZP on the oxidative stress parameters. Data indicate that DZP administration causes an oxidative imbalance in the brain areas studied; however, in the presence of simvastatin, some of these alterations in oxidative stress were prevented.

Inhibitors of Calcium-Activated Anion Channels Modulate Hypnotic Ethanol Responses in Adult Sprague Dawley Rats.

BACKGROUND: Ethanol is widely known for its depressant effects; however, the underlying neurobiological mechanisms are not clear. Calcium-activated anion channels (CAACs) contribute to extracellular chloride levels and thus may be involved in regulating inhibitory mechanisms within the central nervous system. Therefore, we hypothesized that CAACs influence ethanol behavioral sensitivity by altering CAAC expression. METHODS: We assessed the role of CAACs in ethanol-induced loss of righting reflex (LORR) and locomotor activity using intracerebroventricular infusions of several nonselective CAAC blockers. CAAC expression was determined after ethanol exposure. RESULTS: Ethanol-induced LORR (4.0 g/kg, intraperitoneally [i.p.]) was significantly attenuated by all 4 CAAC blockers. Blocking CAACs did not impact ethanol's low-dose (1.5 g/kg, i.p.) locomotor-impairing effects. Biochemical analysis of CAAC protein expression revealed that cortical Bestrophin1 (Best1) and Tweety1 levels were reduced as early as 30 minutes following a single ethanol injection (3.5 g/kg, intraperitoneally [i.p.]) and remained decreased 24 hours later in P2 fractions. Cortical Best1 levels were also reduced following 1.5 g/kg. However, CAAC expression was unaltered in the striatum following a single ethanol exposure. Ethanol did not affect Tweety2 levels in either brain region. CONCLUSIONS: These results suggest that CAACs are a major target of ethanol in vivo, and the regulation of these channels contributes to select behavioral actions of ethanol.

Effects of MK-467 on the antinociceptive and sedative actions and pharmacokinetics of medetomidine in dogs.

We investigated the influence of the peripherally acting α2 -adrenoceptor antagonist MK-467 on the sedative and antinociceptive actions and plasma drug concentrations of medetomidine, an α2 -adrenoceptor agonist that is used in veterinary medicine as a sedative and analgesic agent. Eight healthy beagle dogs received intravenous medetomidine (10 µg/kg) or medetomidine with MK-467 (250 µg/kg) in a randomized crossover design. A standardized nociceptive pressure stimulus was applied to a nail bed of a hindlimb. Times for withdrawal of the limb and for head lift were measured, and sedation was scored. EEG data were collected prior to and after stimulation. Plasma drug concentrations were measured. Co-administration of MK-467 significantly attenuated medetomidine analgesia, as assessed with limb withdrawal, and also shortened the duration of sedation. The apparent plasma clearance of both enantiomers of medetomidine, dexmedetomidine and levomedetomidine, was more than doubled in the presence of MK-467. Antagonism by MK-467 of medetomidine-evoked vasoconstriction is seen as the mechanism behind this pharmacokinetic drug interaction. Thus, MK-467 attenuated the antinociceptive and sedative effects of medetomidine. This can probably be explained by increased clearance and decreased concentrations of dexmedetomidine in plasma after co-administration of MK-467 with racemic medetomidine.

Risk Factors and Outcomes of Reversal Agent Use in Moderate Sedation During Endoscopy and Colonoscopy.

BACKGROUND: Moderate sedation has been standard for noninvasive gastrointestinal procedures for decades yet there are limited data on reversal agent use and outcomes associated with need for reversal of sedation. AIM: To determine prevalence and clinical significance of reversal agent use during endoscopies and colonoscopies. METHODS: Individuals with adverse events requiring naloxone and/or flumazenil during endoscopy or colonoscopy from 2008 to 2013 were identified. A control group was obtained by random selection of patients matched by procedure type and date. Prevalence of reversal agent use and statistical comparison of patient demographics and risk factors against controls were determined. RESULTS: Prevalence of reversal agent use was 0.03% [95% confidence interval (CI), 0.02-0.04]. Events triggering reversal use were oxygen desaturation (64.4%), respiration changes (24.4%), hypotension (8.9%), and bradycardia (6.7%). Two patients required escalation of care and the majority of patients were stabilized and discharged home. Compared with the control group, the reversal group was older (61±1.8 vs. 55±1.6, P=0.01), mostly female (82% vs. 50%, P<0.01), and had lower body mass index (24±0.8 vs. 27±0.7, P=0.03) but received similar dosages of sedation. When adjusted for age, race, sex, and body mass index, the odds of reversal agent patients having a higher ASA score than controls was 4.7 (95% CI, 1.7-13.1), and the odds of having a higher Mallampati score than controls was 5.0 (95% CI, 2.1-11.7) with P<0.01. CONCLUSIONS: Prevalence of reversal agent use during moderate sedation is low and outcomes are generally good. Several clinically relevant risk factors for reversal agent use were found suggesting that certain groups may benefit from closer monitoring.

Findings of a Naloxone Database and its Utilization to Improve Safety and Education in a Tertiary Care Medical Center.

INTRODUCTION: Analyzing hospital naloxone use may assist in identification of areas for quality and safety improvement. Our primary objective is to quantitate the incidence of hospital naloxone use and to assess certain patient populations at risk. METHODS: During the years 2008 to 2011, each clinical scenario where naloxone was administered on an in-patient care ward was reviewed. The events were assessed to separate situations where naloxone rescue was effective in reversing opioid-induced intoxication vs. others. Further analysis was conducted to stratify patient populations at greatest risk. RESULTS: Naloxone was administered for well-defined opioid-induced respiratory depression and oversedation 61% of the time, the remainder used for patient deterioration of other etiology. Surgical populations are at risk with an incidence of 3.8/1,000 hospitalized patients, and this is the greatest within 24 hours of surgery. General surgical patients represent the highest surgical patient risk at 5.5/1,000. Medical patients represent lower risk at 2.0/1,000. Patients with patient-controlled analgesia and epidural opioid infusion are high risk at 12.1 and 13.1/1,000 patients, respectively. Many quality and safety interventions were gradually implemented in response to this data and are summarized. These include nursing and provider education, electronic medical record modification, and more stringent patient monitoring practices. CONCLUSION: Examination of naloxone use can assist in the identification and stratification of patients at risk for opioid-induced respiratory depression and oversedation and can serve as a driver for improvements in hospital patient safety. This information can also guide other institutions interested in similar improvements.

A preliminary trial of the sedation induced by intranasal administration of midazolam alone or in combination with dexmedetomidine and reversal by atipamezole for a short-term immobilization in pigeons.

OBJECTIVE: To assess the sedative and immobilization effect of intranasal administration (INS) of midazolam (MID) without or with INS dexmedetomidine (DXM), and some physiological changes induced by the drugs. The ability of INS atipamezole to reverse the DXM component was also assessed. STUDY DESIGN: Prospective 'blinded' experimental study. ANIMALS: In total, 15 pigeons. METHODS: Pigeons were sedated by INS MID alone at a dose of 5 mg kg(-1) (group MID, n = 6) or in combination with INS DXM at a dose 80 µg kg(-1) (group MID-DXM, n = 6). Measurements were made of heart rate (HR), respiratory rate (fR ) and cloacal temperature (CT). The degree of sedation was assessed at 15 minutes prior to, immediately after, and at intervals until 100 minutes after drug administrations. Following MID-DXM, INS atipamezole (250 µg kg(-1) ) was administered and the same indices measured 5 and 10 minutes later. RESULTS: MID had no effect on HR and fR , and although CT decreased, it remained within physiological range. MID-DXM caused significant falls in HR, fR and CT that persisted until the end of sedation. Atipamezole antagonized sedation and cardiorespiratory side effects of MID-DXM within 10 minutes of application. In addition, for MID compared to MID-DXM, the lowest sedation scores [10 (7-14) and 10.5 (5-14) versus 2 (1-4) and 2 (1-5)] were achieved in the 10th and 20th minute versus the 20th and 30th minute of the sedation, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: MID alone, given INS had minimal side effects on vital functions but caused inadequate immobilization of pigeons for restraint in dorsal recumbency. MID-DXM caused an effective degree of immobilization from 20 to 30 minutes after administration, at which time birds tolerated postural changes without resistance. Atipamezole antagonized both side effects and sedation, but complete recovery had not occurred within 10 minutes after its application.

Phenylephrine potentiates the anticonvulsant effect and neutralizes the sedative effect of diazepam in rats upon combined intragastric administration.

High doses of phenylephrine and diazepam (1 and 10 mg/kg, respectively) suppressed the development of generalized tonic-clonic pentylenetetrazole-induced convulsions in 86-100% rats, but did not prevent local clonic pentylenetetrazole-induced convulsions. Diazepam in the specified dose produced strong sedation, while phenylephrine had no sedative effect in the open-field test. Combined intragastric administration of phenylephrine in a medium and individually ineffective dose (0.3 mg/kg) and diazepam in a high dose (10 mg/kg) potentiated the anticonvulsant effect of diazepam: it prevented not only tonic-clonic, but also clonic pentylenetetrazole-induced convulsions in 100% rats and 2.6-fold increased anticonvulsant activity of diazepam. The specified combination of diazepam and phenylephrine had no sedative effect. The mechanism of potentiation of the anticonvulsive effect and elimination of the sedative side effect is based on stimulation of gastric mucosa afferents by phenylephrine.

N(6)-(3-methoxyl-4-hydroxybenzyl) adenine riboside induces sedative and hypnotic effects via GAD enzyme activation in mice.

BACKGROUND AND PURPOSE: N(6)-(3-methoxyl-4-hydroxybenzyl) adenine riboside (B2) is an analog of N(6)-(4-hydroxybenzyl) adenine riboside (NHBA), which was originally isolated from Gastrodia elata Blume. Our laboratory has previously demonstrated that B2 can produce strong sedative and hypnotic effects, but the mechanism remains to be determined. There is evidence that gamma-aminobutyric acid (GABA) acts as an inhibitory neurotransmitter in the brain, plays a major role in sleep regulation, and participates in the sedative and hypnotic effects of B2. Therefore, we studied the interactions between B2 and several GABAergic neurochemical parameters based on the sedative and hypnotic effects of B2. EXPERIMENTAL APPROACH: The GABA and glutamic acid (Glu) in the mouse brain were derivatized with o-phthalaldehyde (OPA) and measured by high performance liquid chromatography-electrochemical detection (HPLC-ECD). The GAD and GABA-T enzyme activities were determined by measuring GABA and NADH production, respectively. The sleep structure analyses were performed by EEG studies in mice. KEY RESULTS: B2 increased the GABA levels and GAD enzyme activity in the mouse hypothalamus and cortex. The EEG results confirmed that B2 significantly shortened the sleep latency and increased the amount of NREM sleep. The GAD enzyme inhibitor semicarbazide (SCZ) blocked the sedative and hypnotic effects of B2. CONCLUSIONS AND IMPLICATIONS: These findings suggest that the GAD enzyme plays a significant role in the sedative and hypnotic effects of B2. Therefore B2 may be a promising candidate for further clinical studies and the appropriate use of GAD agonist may be a promising approach for sleep disorders.

Ameliorating effect of spinosin, a C-glycoside flavonoid, on scopolamine-induced memory impairment in mice.

Spinosin is a C-glycoside flavonoid isolated from the seeds of Zizyphus jujuba var. spinosa. This study investigated the effect of spinosin on cholinergic blockade-induced memory impairment in mice. Behavioral tests were conducted using the passive avoidance, Y-maze, and Morris water maze tasks to evaluate the memory-ameliorating effect of spinosin. Spinosin (10 or 20mg/kg, p.o.) significantly ameliorated scopolamine-induced cognitive impairment in these behavioral tasks with a prolonged latency time in the passive avoidance task, an increased percentage of spontaneous alternation in the Y-maze task and a lengthened swimming time in target quadrant in the Morris water maze task. In addition, a single administration of spinosin in normal naïve mice also enhanced the latency time in the passive avoidance task. To identify the mechanism of the memory-ameliorating effect of spinosin, receptor antagonism analysis and Western blotting were performed. The ameliorating effect of spinosin on scopolamine-induced memory impairment was significantly antagonized by a sub-effective dose (0.5mg/kg, i.p.) of 8-hydroxy-2-(di-N-propylamino)tetralin, a 5-HT1A receptor agonist. In addition, spinosin significantly increased the expression levels of phosphorylated extracellular signal-regulated kinases and cAMP response element-binding proteins in the hippocampus. Taken together, these results indicate that the memory-ameliorating effect of spinosin may be, in part, due to the serotonergic neurotransmitter system, and that spinosin may be useful for the treatment of cognitive dysfunction in diseases such as Alzheimer's disease.