Antiplatelet Effect of Mirtazapine via Co-blocking of the 5-HT2A and α2-Adrenergic Receptors on Platelets.

Mirtazapine (MTZ) is a noradrenergic and specific serotonergic antidepressant. MTZ is reportedly associated with an increased risk of bleeding. However, the underlying mechanism remains unclear. In this study, we investigated the antiplatelet effect of MTZ in mice via light transmission aggregometry to elucidate the mechanism of MTZ-induced bleeding. The results of the ex vivo study showed that the oral administration of MTZ (20 or 100 mg/kg) significantly suppressed platelet aggregation mediated by the synergic interaction of 5-hydroxytryptamine (5-HT) and adrenaline. Additionally, MTZ significantly suppressed platelet aggregation, mediated by the synergic interaction of ADP and 5-HT or adrenaline. Similar results were obtained in vitro, under the condition of 5-HT- and adrenaline-induced platelet aggregation. Overall, the results suggest that MTZ exerts antiplatelet effect by co-blocking 5-HT2A and α2-adrenergic receptors on platelets and suppresses platelet aggregation mediated by ADP, increased by either 5-HT or adrenaline. Thus, a detailed monitoring of bleeding is recommended for patients taking MTZ.

Mirtazapine-induced steatosis
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Mirtazapine is a commonly used drug indicated for the treatment of severe depression. It works as a presynaptic α2-adrenoreceptor antagonist that increases central noradrenergic and serotonergic neurotransmission, and it is metabolized by the p450 cytochrome oxidase system. There is evidence within the literature to suggest a link between antidepressants and increased liver enzymes, although case reports demonstrating a link between mirtazapine specifically and steatosis are sparse. Here, we present a case of mirtazapine-induced steatosis in a 48-year-old office worker. She presented with painless jaundice of 2 days duration and generalized lethargy and peripheral edema present for 3 weeks beforehand. Extensive investigations were undertaken to identify the cause of her jaundice but no biochemical, blood-borne, or anatomical cause could be found. Mirtazapine was subsequently stopped, and her liver function, both clinically and biochemically, improved rapidly. She made a full recovery after discontinuation of her mirtazapine.
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Impact of Stress and Glucocorticoids on Schema-Based Learning.

Pre-existing knowledge, a 'schema', facilitates the encoding, consolidation, and retrieval of schema-relevant information. Such schema-based memory is key to every form of education and provides intriguing insights into the integration of new information and prior knowledge. Stress is known to have a critical impact on memory processes, mainly through the action of glucocorticoids and catecholamines. However, whether stress and these major stress mediators affect schema-based learning is completely unknown. To address this question, we performed two experiments, in which participants acquired a schema on day 1 and learned schema-related as well as schema-unrelated information on day 2. In the first experiment, participants underwent a stress or control manipulation either immediately or about 25 min before schema-based memory testing. The second experiment tested whether glucocorticoid and/or noradrenergic activation is sufficient to modulate schema-based memory. To this end, participants received orally a placebo, hydrocortisone, the α2-adrenoceptor-antagonist yohimbine, leading to increased noradrenergic stimulation, or both drugs, before completing the schema-based memory test. Our data indicate that stress, irrespective of the exact timing of the stress exposure, impaired schema-based learning, while leaving learning of schema-unrelated information intact. A very similar effect was obtained after hydrocortisone, but not yohimbine, administration. These data show that stress disrupts participants' ability to benefit from prior knowledge during learning and that glucocorticoid activation is sufficient to produce this effect. Our findings provide novel insights into the impact of stress and stress hormones on the dynamics of human memory and have important practical implications, specifically for educational contexts.

Effects of idazoxan on alcohol pharmacokinetics and intoxication: a preliminary human laboratory study.

BACKGROUND: Preliminary basic and human studies suggest that the α2 -adrenergic antagonist idazoxan may represent a novel medication for alcohol dependence. The goal of this study was to evaluate the safety and tolerability of the co-administration of idazoxan with alcohol and explore whether pharmacokinetics (PK) and biobehavioral mechanisms of idazoxan may alter alcohol's effects. METHODS: This was a preliminary double-blind, single-dose, placebo-controlled, crossover, randomized human laboratory study. Ten social drinkers were dosed, in 2 different alcohol challenge studies (ACS), with a single oral dose of idazoxan (40 mg) or placebo, followed by a fixed alcohol dose 60 minutes later. Participants returned after a 1-week washout, and they were crossed over to the opposite medication condition. RESULTS: There were no significant differences in adverse events between idazoxan and placebo. Moreover, during the ACS paradigm, 40 mg idazoxan was well tolerated with no significant autonomic effects compared to placebo; idazoxan reduced the peak blood alcohol level (p < 0.01) and time to peak (p < 0.05) compared to placebo. A PK/pharmacodynamic model aligned the biobehavioral effects, demonstrating that the co-administration of 40 mg idazoxan with alcohol decreased alcohol-related stimulation (p < 0.05) and increased alcohol-related sedation (p < 0.05). CONCLUSIONS: This study supports the safety and tolerability of 40 mg idazoxan when co-administered with alcohol. Additionally, this study suggests that idazoxan may alter the biphasic effects of alcohol by decreasing stimulation and increasing sedation. These findings have implications for further investigation of using idazoxan as a probe to develop potential novel medications to treat alcoholic patients.

Istradefylline is recommended for morning use: a report of 4 cases.

We herein describe four cases of patients with Parkinson's disease who were treated with istradefylline (ISD) in the evening and had severe daytime sleepiness. The time to onset of sleepiness varied between 2 weeks to 3 months. All patients recovered after changing the timing of the ISD dosage from evening to morning. ISD is an A2A receptor antagonist with a caffeine-like arousal effect that may worsen the quality of sleep and thus increase daytime sleepiness. This report provides the first evidence of daytime sleepiness induced by evening ISD treatment. We propose that ISD should therefore only be used in the morning, particularly if taken by professional drivers.

A double-blind, randomized, placebo-controlled crossover trial of the α2C-adrenoceptor antagonist ORM-12741 for prevention of cold-induced vasospasm in patients with systemic sclerosis.

OBJECTIVES: Our primary purpose was to evaluate the efficacy of the high-potency α2C-adrenoceptor antagonist ORM-12741 in the attenuation of a cold-induced reduction in finger blood flow and temperature in patients with RP secondary to SSc. Secondary objectives were to assess safety and tolerability. METHODS: This was a phase IIa, randomized, double-blind, crossover, single-dose, placebo-controlled, single-centre study. Patients attended five times: initial screening, treatment visits 1-3 (each at least 1 week apart) and 1-2 weeks after the last treatment. At each treatment visit, each subject received a single oral dose of 30 mg or 100 mg of ORM-12741 or placebo. Thirty minutes later the subject underwent a cold challenge. Blood flow to the fingers was assessed by three methods [temperature by probe, laser Doppler imaging (LDI) and infrared thermography] performed before, during and after the cold challenge. RESULTS: Twelve patients (10 female, mean age 58 years) were included. The area under the rewarming curve (LDI) of the right index finger (arbitrary flux units × time) was lower for both 30 mg (P = 0.043) and 100 mg (P = 0.025) of ORM-12741 compared with placebo, indicating delayed reperfusion. The time to 70% temperature recovery (middle finger probe) was longer with active than placebo treatment: mean (s.d.) values for placebo, 30 mg of ORM-12741 and 100 mg of ORM-12741 were 21.4 min (12.4), 25.7 min (12.2) and 26.9 min (13.9), respectively. Overall ORM-12741 was well tolerated. CONCLUSION: ORM-12741 did not expedite recovery from a cold challenge in the fingers of patients with SSc. TRIAL REGISTRATION: https://www.clinicaltrialsregister.eu/; no. 2010-024005-13.

Acute stressor effects on goal-directed action in rats.

Here we examined effects of acute stressors that involve either systemic coadministration of corticosterone/yohimbine (3 mg/kg each) to increase glucocorticoid/noradrenaline activity (denoted as "pharmacological" stressor) or one or several distinct restraint stressors (denoted as "single" vs. "multiple" stressor) on performance of goal-directed actions. Rats were trained over 11 d to perform two instrumental actions, one for food pellets the other for sucrose solution, followed by two consecutive tests days. On each test day, rats were first sated in a counterbalanced manner on one of the two outcomes by prefeeding (selective outcome devaluation), then subjected to an acute stressor, and tested afterward in a two-lever choice task in extinction to assess whether instrumental performance is goal-directed, i.e., sensitive to changes in outcome value. Like in control rats, in rats subjected to the pharmacological or single restraint stressor prior to the choice test, performance of instrumental action was goal-directed, i.e., sensitive to outcome devaluation. By contrast, in rats exposed to the multiple stressor prior to the choice test, performance of instrumental action was habitual, i.e., insensitive to outcome devaluation. Pretreatment with diazepam (1 and 2 mg/kg) did not alleviate (or only marginally) this multiple stressor-induced effect. Thus, an intense acute stressor can render performance of previously acquired instrumental action habitual, possibly due to a compromised retrieval of encoded relationships between actions and their outcome value. Our observation in rats that an acute stressor can shift instrumental responding from goal-directed to habitual control is consistent with similar findings in humans.

Predictors and mediators of add-on mirtazapine-induced cognitive enhancement in schizophrenia--a path model investigation.

We aimed to evaluate predictors and mediators of enhancing effect of adjunctive mirtazapine on cognition in schizophrenia. Patients with difficult-to-treat schizophrenia received either mirtazapine (n = 19) or placebo (n = 18) in a double-blind fashion for six weeks. Mirtazapine outperformed placebo on the Block Design and Stroop Dots. In the present subsidiary study, factors underlying this difference were explored with Path Analysis. Add-on mirtazapine had an independent enhancing effect on the Block Design-measured visuo-spatial functioning. Further, this effect was mediated via changes in positive, depressive and parkinsonism symptoms, but not in negative symptoms. This effect was predicted by higher doses of FGAs, longer duration of illness and lower initial Block Design scores. Path Analysis model fit was good. Mirtazapine may have direct and indirect favorable effects on visuo-spatial functioning, but further research is needed. Path analysis may be a feasible statistical method for further research of neurocognition in psychopharmacological interventions in schizophrenia. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Involvement of α2-adrenoceptors, imidazoline, and endothelin-A receptors in the effect of agmatine on morphine and oxycodone-induced hypothermia in mice.

Potentiation of opioid analgesia by endothelin-A (ET(A)) receptor antagonist, BMS182874, and imidazoline receptor/α2-adrenoceptor agonists such as clonidine and agmatine are well known. It is also known that agmatine blocks morphine hyperthermia in rats. However, the effect of agmatine on morphine or oxycodone hypothermia in mice is unknown. The present study was carried out to study the role of α2-adrenoceptors, imidazoline, and ET(A) receptors in morphine and oxycodone hypothermia in mice. Body temperature was determined over 6 h in male Swiss Webster mice treated with morphine, oxycodone, agmatine, and combination of agmatine with morphine or oxycodone. Yohimbine, idazoxan, and BMS182874 were used to determine involvement of α2-adrenoceptors, imidazoline, and ET(A) receptors, respectively. Morphine and oxycodone produced significant hypothermia that was not affected by α2-adrenoceptor antagonist yohimbine, imidazoline receptor/α2 adrenoceptor antagonist idazoxan, or ET(A) receptor antagonist, BMS182874. Agmatine did not produce hypothermia; however, it blocked oxycodone but not morphine-induced hypothermia. Agmatine-induced blockade of oxycodone hypothermia was inhibited by idazoxan and yohimbine. The blockade by idazoxan was more pronounced compared with yohimbine. Combined administration of BMS182874 and agmatine did not produce changes in body temperature in mice. However, when BMS182874 was administered along with agmatine and oxycodone, it blocked agmatine-induced reversal of oxycodone hypothermia. This is the first report demonstrating that agmatine does not affect morphine hypothermia in mice, but reverses oxycodone hypothermia. Imidazoline receptors and α2-adrenoceptors are involved in agmatine-induced reversal of oxycodone hypothermia. Our findings also suggest that ET(A) receptors may be involved in blockade of oxycodone hypothermia by agmatine.

Antinociceptive and anti-inflammatory effects of octacosanol from the leaves of Sabicea grisea var. grisea in mice.

Sabicea species are used in the Amazon for treatment of fever and malaria, which suggests that its chemical constituents may have some effect on pain and inflammation. Phytochemical analysis of the hexane fraction obtained from the crude ethanol extract from Sabicea grisea var. grisea Cham. & Schltdl (Rubiaceae), an endemic plant in Brazil, resulted in the isolation of octacosanol. This study investigated the antinociceptive and anti-inflammatory effects of the octacosanol in different experimental models. The crude ethanolic extract and hexane fraction obtained from the leaves of S. grisea produced an inhibition of acetic acid-induced pain. Moreover, octacosanol isolated from the hexane fraction produced a significant inhibition of pain response elicited by acetic acid. Pre-treatment with yohimbine, an alpha 2-adrenergic receptor antagonist, notably reversed the antinociceptive activity induced by octacosanol in the abdominal constriction test. Furthermore, mice treated with octacosanol did not exhibit any behavioral alteration during the hot plate and rota-rod tests, indicating non-participation of the supraspinal components in the modulation of pain by octacosanol with no motor abnormality. In the formalin test, octacosanol did not inhibit the licking time in first phase (neurogenic pain), but significantly inhibited the licking time in second phase (inflammatory pain) of mice. The anti-inflammatory effect of octacosanol was evaluated using carrageenan-induced pleurisy. The octacosanol significantly reduced the total leukocyte count and neutrophils influx, as well as TNF-α levels in the carrageenan-induced pleurisy. This study revealed that the mechanism responsible for the antinociceptive and anti-inflammatory effects of the octacosanol appears to be partly associated with an inhibition of alpha 2-adrenergic transmission and an inhibition of pathways dependent on pro-inflammatory cytokines. Finally, these results demonstrated that the octacosanol from the leaves of S. grisea possesses antinociceptive and anti-inflammatory activities, which could be of relevance for the pharmacological control of pain and inflammatory processes.

Stimulation of the noradrenergic system during memory formation impairs extinction learning but not the disruption of reconsolidation.

The noradrenergic system plays a critical role in the 'consolidation' of emotional memory. If we are to target 'reconsolidation' in patients with anxiety disorders, the noradrenergic strengthening of fear memory should not impair the disruption of reconsolidation. In Experiment I, we addressed this issue using a differential fear conditioning procedure allowing selective reactivation of one of two fear associations. First, we strengthened fear memory by administering an α(2)-adrenergic receptor antagonist (ie, yohimbine HCl; double-blind placebo-controlled study) 30 min before acquisition (time for peak value yohimbine HCl <1 h). Next, the reconsolidation of one of the fear associations was manipulated by administering a ß-adrenergic receptor antagonist (ie, propranolol HCl) 90 min before its selective reactivation (time for peak value propranolol HCl <2 h). In Experiment II, we administered propranolol HCl after reactivation of the memory to rule out a possible effect of the pharmacological manipulation on the memory retrieval itself. The excessive release of noradrenaline during memory formation not only delayed the process of extinction 48 h later, but also triggered broader fear generalization. Yet, the ß-adrenergic receptor blocker during reconsolidation selectively 'neutralized' the fear-arousing aspects of the noradrenergic-strengthened memory and undermined the generalization of fear. We observed a similar reduction in fear responding when propranolol HCl was administered after reactivation of the memory. The present findings demonstrate the involvement of noradrenergic modulation in the formation as well as generalization of human fear memory. Given that the noradrenergic strengthening of fear memory impaired extinction learning but not the disruption of reconsolidation, our findings may have implications for the treatment of anxiety disorders.

Comparison of the effects of racemic ketamine and S-ketamine for anesthesia in Rheem gazelles (Gazella subgutturosa marica) and Subgutturosa gazelles (Gazella subgutturosa subgutturosa).

OBJECTIVE: To evaluate effects of racemic ketamine and S-ketamine in gazelles. ANIMALS: 21 male gazelles (10 Rheem gazelles [Gazella subgutturosa marica] and 11 Subgutturosa gazelles [Gazella subgutturosa subgutturosa]), 6 to 67 months old and weighing (mean±SD) 19 ± 3 kg. PROCEDURES: In a randomized, blinded crossover study, a combination of medetomidine (80 µg/kg) with racemic ketamine (5 mg/kg) or S-ketamine (3 mg/kg) was administered i.m.. Heart rate, blood pressure, respiratory rate, rectal temperature, and oxygen saturation (determined by means of pulse oximetry) were measured. An evaluator timed and scored induction of, maintenance of, and recovery from anesthesia. Medetomidine was reversed with atipamezole. The alternate combination was used after a 4-day interval. Comparisons between groups were performed with Wilcoxon signed rank and paired t tests. RESULTS: Anesthesia induction was poor in 2 gazelles receiving S-ketamine, but other phases of anesthesia were uneventful. A dominant male required an additional dose of S-ketamine (0.75 mg/kg, i.m.). After administration of atipamezole, gazelles were uncoordinated for a significantly shorter period with S-ketamine than with racemic ketamine. Recovery quality was poor in 3 gazelles with racemic ketamine. No significant differences between treatments were found for any other variables. Time from drug administration to antagonism was similar between racemic ketamine (44.5 to 53.0 minutes) and S-ketamine (44.0 to 50.0 minutes). CONCLUSIONS AND CLINICAL RELEVANCE: Administration of S-ketamine at a dose 60% that of racemic ketamine resulted in poorer induction of anesthesia, an analogous degree of sedation, and better recovery from anesthesia in gazelles with unremarkable alterations in physiologic variables, compared with racemic ketamine.

Pharmacologically induced alcohol craving in treatment seeking alcoholics correlates with alcoholism severity, but is insensitive to acamprosate.

Modulation of alcohol craving induced by challenge stimuli may predict the efficacy of new pharmacotherapies for alcoholism. We evaluated two pharmacological challenges, the α(2)-adrenergic antagonist yohimbine, which reinstates alcohol seeking in rats, and the serotonergic compound meta-chlorophenylpiperazine (mCPP), previously reported to increase alcohol craving in alcoholics. To assess the predictive validity of this approach, the approved alcoholism medication acamprosate was evaluated for its ability to modulate challenge-induced cravings. A total of 35 treatment seeking alcohol dependent inpatients in early abstinence were randomized to placebo or acamprosate (2997 mg daily). Following two weeks of medication, subjects underwent three challenge sessions with yohimbine, mCPP or saline infusion under double blind conditions, carried out in counterbalanced order, and separated by at least 5 days. Ratings of cravings and anxiety, as well as biochemical measures were obtained. In all, 25 subjects completed all three sessions and were included in the analysis. Cravings were modestly, but significantly higher following both yohimbine and mCPP challenge compared with saline infusion. The mCPP, but not yohimbine significantly increased anxiety ratings. Both challenges produced robust ACTH, cortisol and prolactin responses. There was a significant correlation between craving and the degree of alcoholism severity. Acamprosate administration did not influence craving. Both yohimbine and mCPP challenges lead to elevated alcohol craving in a clinical population of alcoholics, and these cravings correlate with alcoholism severity. Under the experimental conditions used, alcohol cravings induced by these two stimuli are not sensitive to acamprosate at clinically used doses.