Interaction effects of intracerebroventricular injection of crocin with the α2-adrenoceptors on memory deficit and hippocampal synaptic plasticity following chronic pain in rat.

Patients with chronic pain exhibit anxiety and deficits in memory. Additionally, α2-adrenoceptors that are wildly expressed in the brain have an important role in modulating both pain and memory formation. In the present study, we investigated the interaction effects of crocin with central α2-adrenoceptors on pain comorbidity and hippocampal synaptic plasticity changes following chronic constriction injury (CCI) of the sciatic nerve in rats. All the drugs (crocin, an antagonist (yohimbine) and agonist (clonidine) of α2-adrenergic receptors) were injected (via intracerebroventricular injection) from the day of CCI operation (day 0) and continued daily (once per day) until the 14th day post-CCI. The effects of drugs on the cold allodynia (using acetone test) and anxiety-like behaviors (using elevated plus maze, EPM and open field tests) were assessed. Spatial memory (using Barnes maze) was assessed on day 14 post-CCI operation. Hippocampal synaptic plasticity (using in-vivo extracellular field potential recording) was performed on day 14 post-CCI operation. We observed that crocin induced analgesic, anxiolytic and memory enhancer action following CCI surgery. Furthermore, crocin significantly increased long-term potentiation (LTP) (increased fEPSP slope and population spike amplitude). Furthermore, the co-injection of yohimbine effectively decreased analgesic, anxiolytic and enhancer action of crocin on the LTP parameters (fEPSP slope and population spike amplitude). Our study provided information that protective effects of crocin on pain/anxiety responses and synaptic plasticity were possibly mediated by central α2-adrenoceptor in the rats with chronic pain.

Intracranial hemorrhage after a single dose of Yohimbine in a chronic user of clonidine.

INTRODUCTION: Yohimbine, an alpha-2 adrenoreceptor antagonist found in a variety of supplements, has been historically used to treat libido, erectile dysfunction, xerostomia, and as a weight loss enhancement. Yohimbine toxicity causes a sympathomimetic syndrome as demonstrated by the case below of a female who developed an intracranial hemorrhage (ICH) following an ingestion of yohimbine. CASE: This case follows a 39-year-old female who presented to the emergency department (ED) with complaints of nausea, emesis, and flushing following the ingestion of a female sexual enhancement supplement labeled to contain yohimbine (BioXgenic Nature's Desire) one hour prior. The patient took her prescribed 0.1 mg clonidine when the symptoms commenced. Upon arrival, the patient's blood pressure was 198/93. She developed neurological sequelae including a left-sided facial droop and weakness of her right extremities. A computed tomography scan demonstrated an acute basal ganglia hemorrhage with mild mass effect and mild subarachnoid hemorrhage. She was transferred to a regional referral hospital and discharged 16 days later to a rehabilitation center with persistent neurological sequelae. DISCUSSION: This patient exhibited sympathetic toxicity temporally associated with yohimbine ingestion. Our patient also had a variety of risk factors that increased the likelihood of a poor outcome with yohimbine. Chronic use of clonidine is known to down-regulate alpha-2 receptors. This leads to dependence of clonidine to maintain adrenergic homeostasis and could potentiate the effects of yohimbine. To compound effects, our patient was also taking bupropion and desvenlafaxine, which inhibit norepinephrine reuptake, likely worsening our patient's sympathomimetic response. Despite the temporal relationship of our patient's ICH and ingestion of yohimbine, a definitive relationship cannot be inferred due to our lack of confirmatory testing of yohimbine content and possibility of adulterants. The U.S. Food and Drug Administration (FDA) does not regulate the supplement market strictly, with multiple studies illustrating variation among ingredients of supplements despite stated quantities on the labels. CONCLUSION: Dietary supplements are not required by the FDA to undergo efficacy or safety testing, necessitating clear post-marketing communication regarding potential adverse events from various supplements. Users should be aware of yohimbine-containing products and the possible side effects of toxicity. It is crucial that physicians and patients be aware of possible drug-supplement interactions of yohimbine and the presentation of sympathomimetic syndromes.

Antisecretory and Spasmolytic Activities of Aqueous and Ethanolic Stem Bark Extracts of Nauclea diderrichii in Wistar Rats.

Background: Diarrheal diseases are a major cause of morbidity and mortality throughout the world and particularly in developing countries. Nauclea diderrichii is a plant used in traditional medicine in the treatment of anemia, fever, gastric ulcer, malaria, abdominal pain, skin infections, and diarrhea. The present work is aimed at evaluating the antisecretory and spasmolytic activities of aqueous and ethanolic stem bark extracts of Nauclea diderrichii in Wistar rats. Methods: The effect of aqueous and ethanolic extracts of Nauclea diderrichii was tested at doses of 100, 200, and 300 mg/kg on castor oil-induced secretory diarrhea, misoprostol-induced fluid accumulation, and the effect of pretreatment with yohimbine and glibenclamide. They were also tested on normal motility and castor oil- and carbachol-induced hypermotility. Results: The results showed that the aqueous and ethanolic extracts of Nauclea diderrichii significantly (p < 0.001) inhibited castor oil-induced secretory diarrhea at all the doses. Both extracts significantly (p < 0.001) inhibit fluid accumulation induced by misoprostol. The pretreatment with glibenclamide reduced the antidiarrheal activity of aqueous extract of Nauclea diderrichii. The pretreatment with yohimbine did not alter the effect of the aqueous extract of Nauclea diderrichii. On intestine transit as on castor oil- and carbachol-induced motility, the aqueous and ethanolic extracts at doses of 100 and 200 mg/kg reduced significantly (p < 0.05, p < 0.01, and p < 0.001) the travelled distance by charcoal and peristaltic index. Conclusions: The study demonstrated that the aqueous and ethanolic extracts of Nauclea diderrichii possess antisecretory and antispasmolytic properties hence its use in traditional medicine against diarrhea.

Severe acute intoxication with yohimbine: Four simultaneous poisoning cases.

Yohimbine is an indole alkaloid from the leaves and bark of the Pausinystalia johimbe tree that has acquired an enviable reputation in treating erectile dysfunction. This report presents four simultaneous severe poisoning/death cases caused by yohimbine. The test samples comprised the venous blood of four middle-aged men (aged 47-65) who were suspected of poisoning; one of the men died due to ineffective rescue. Ethanol concentration determination and toxicological routine screening were performed using gas chromatography with flame ionization detection (GC-FID) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). A specific LC-MS/MS method was developed to quantify yohimbine, which showed concentrations of 459, 249, and 301ng/mL in three poisoned blood samples and concentrations as high as 5631ng/mL in the deceased. Moreover, the deceased's autopsy ruled out death from trauma and previous illness, and no other common toxic components were detected in his blood. Therefore, yohimbine poisoning appears to be the most likely cause of death. As a type of alkaloid that can be employed in the treatment of clinical diseases and additives for supplements, the danger of yohimbine should be of widespread concern in society.

Neuropharmacological effects of d-pinitol and its possible mechanisms of action.

The aim was to evaluate the diuretic and neuropharmacological actions of d-pinitol and describe a possible mechanism of action. The diuretic effects of d-pinitol were evaluated using mice placed in metabolic cages. The sedative, anxiolytic-like, antidepressant-like, and anticonvulsant effects of 1-100 mg/kg d-pinitol were assessed. The possible mechanisms of action of the anxiolytic-like, antidepressant-like, and anticonvulsant effects of d-pinitol were evaluated using inhibitors. d-pinitol lacked diuretic effects. However, d-pinitol showed the highest anxiolytic-like actions (ED50  = 70 mg/kg p.o. in mice) in the cylinder exploratory test and the highest antidepressant-like activity in the forced swimming test (ED50  = 26 mg/kg p.o. in mice). d-pinitol (100 mg/kg) exerted anticonvulsant actions in the pentylenetetrazole-induced seizures test. The pre-treatment with 2 mg/kg flumazenil reverted the anxiolytic-like actions and the anticonvulsant effects of d-pinitol, whereas the pre-treatment with 1 mg/kg yohimbine and 0.05 mg/kg prazosin abolished the antidepressant effects of d-pinitol. PRACTICAL APPLICATIONS: d-pinitol (3-O-methyl-d-chiro-inositol) is a polyol found in many fruits, as well as in many members of the Leguminosae and Fabaceae families. The results propose that this compound could contribute in the treatment of anxiety, depression, and convulsions. The findings suggest the possible participation of the GABAergic system in the anxiolytic-like and anticonvulsant actions of d-pinitol, whereas the noradrenergic system is probably involved in the antidepressant effects of d-pinitol. This study provides new information about other pharmacological uses for d-pinitol.

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.

A Comparison of the Anorectic Effect and Safety of the Alpha2-Adrenoceptor Ligands Guanfacine and Yohimbine in Rats with Diet-Induced Obesity.

The search for drugs with anorectic activity, acting within the adrenergic system has attracted the interest of researchers. Partial α2-adrenoceptor agonists might offer the potential for effective and safe treatment of obesity. We compared the effectiveness and safety of α2-adrenoceptor ligands in reducing body mass. We also analyzed if antagonist and partial agonists of α2-adrenoceptor--yohimbine and guanfacine--act similarly, and determined which course of action is connected with anorectic activity. We tested intrinsic activity and effect on the lipolysis of these compounds in cell cultures, evaluated their effect on meal size, body weight in Wistar rats with high-fat diet-induced obesity, and determined their effect on blood pressure, heart rate, lipid profile, spontaneous locomotor activity, core temperature and glucose, as well as glycerol and cortisol levels. Both guanfacine and yohimbine showed anorectic activity. Guanfacine was much more effective than yohimbine. Both significantly reduced the amount of intraperitoneal adipose tissue and had a beneficial effect on lipid profiles. Decreased response of α2A-adrenoceptors and partial stimulation of α2B-receptors seem to be responsible for the anorectic action of guanfacine. The stimulation of α1-adrenoceptors by guanfacine is responsible for cardiovascular side effects but may also be linked with improved anorexic effect. α1-adrenoceptor blockade is connected with the side effects of yohimbine, but it is also associated with the improvement of lipid profiles. Guanfacine has been approved by the Food and Drug Administration (FDA) to treat hypertension and conduct disorder, but as it reduces body weight, it is worth examining its effectiveness and safety in models of obesity.

Manic psychosis associated with ginseng: a report of two cases and discussion of the literature.

BACKGROUND: Herbal medicine use, highly prevalent in the general population, is often a neglected component of the medical history. Herbs are presumed safe because they are "natural" self-care products. We call attention to the following issues: Panax ginseng, one of the most frequently used herbal medicines, has complex pharmacological activity, and can be associated with severe psychiatric symptoms. Physicians may be unfamiliar with herbal therapy risks, and the need for further education and systematic research is highlighted. OBJECTIVE: To describe two cases of new onset manic psychoses associated with high dose, chronic ginseng use, and review the relevant literature. CASE REPORTS: A 23-year-old man developed acute mania after one month of daily ginseng use and intermittent cannabis use. A 79-year-old man developed hypomania while using ginseng and yohimbine for erectile dysfunction, and had a recurrence of mania after stopping yohimbine but increasing his daily intake of ginseng. CONCLUSIONS/SUMMARY: Symptoms of mania fully remitted within days upon discontinuation of ginseng and supportive treatment. Available data prevent a clear determination of causation; however, ginseng-induced mania in the these and previous case reports is suggested by the following: patients had no prior psychiatric history, daily use of ginseng was temporally associated with mania onset, patients ingested much higher doses for a longer duration than recommended in Traditional Chinese Medicine (TCM), and withdrawal of ginseng led to rapid remission. Generally well tolerated, many physicians are unaware that ginseng may be associated with acute and significant psychiatric disturbances for certain at-risk individuals.

Bulk muscles, loose cables.

The accessibility and usage of body building supplements is on the rise with stronger internet marketing strategies by the industry. The dangers posed by the ingredients in them are underestimated. A healthy young man came to the emergency room with palpitations and feeling unwell. Initial history and clinical examination were non-contributory to find the cause. ECG showed atrial fibrillation. A detailed history for any over the counter or herbal medicine use confirmed that he was taking supplements to bulk muscle. One of the components in these supplements is yohimbine; the onset of symptoms coincided with the ingestion of this product and the patient is symptom free after stopping it. This report highlights the dangers to the public of consuming over the counter products with unknown ingredients and the consequential detrimental impact on health.

Sexual enhancement products for sale online: raising awareness of the psychoactive effects of yohimbine, maca, horny goat weed, and Ginkgo biloba.

INTRODUCTION: The use of unlicensed food and herbal supplements to enhance sexual functions is drastically increasing. This phenomenon, combined with the availability of these products over the Internet, represents a challenge from a clinical and a public health perspective. METHODS: A comprehensive multilingual assessment of websites, drug fora, and other online resources was carried out between February and July 2013 with exploratory qualitative searches including 203 websites. Additional searches were conducted using the Global Public Health Intelligence Network (GPHIN). Once the active constitutes of the products were identified, a comprehensive literature search was carried out using PsycInfo and PubMed. RESULTS: The most common sexual enhancement products available on the Internet were identified. Their active ingredients included yohimbine, maca, horny goat weed and Ginkgo biloba. These four substances were reported with the occurrence of adverse events and the induction of psychological symptoms, such as mood changes, anxiety, and hallucinations as well as addictive behaviours. CONCLUSIONS: Uncontrolled availability of sexual enhancement products that contain potentially harmful substances is a major public health concern. The possible impact on population health, particularly among subjects with psychiatric disorders, usually at risk for sexual dysfunction, may be significant. This new trend needs to be extensively studied and monitored.

Synthesis of 2´-hydroxy-4´-isoprenyloxychalcone derivatives with potential antidepressant-like activity.

A series of 2´-hydroxy-4´-isoprenyloxychalcone derivatives was synthesized and evaluated for its antidepressant- like activity using the FST and TST. All compounds exhibited the potential antidepressant-like activity in the FST and the TST through intraperitoneal injection. Among them, compounds 4i, 4l and 4n exhibited more potent antidepressant- like activity at a dose of 10 mg/kg. And, compounds 4i, 4l and 4n were also adequately absorbed in mice after oral administration at a dose of 30 mg/kg. In the 5-HT induced head-twitch test and yohimbine induced mortality test, compound 4i could increase the head-twitch and rise mortality in mice. The results suggested that the antidepressant effects of compound 4i may be related to via the serotonergic and noradrenergic system.

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.

Norepinephrine and impulsivity: effects of acute yohimbine.

RATIONALE: Rapid-response impulsivity, characterized by inability to withhold response to a stimulus until it is adequately appraised, is associated with risky behavior and may be increased in a state-dependent manner by norepinephrine. OBJECTIVE: We assessed effects of yohimbine, which increases norepinephrine release by blocking alpha-2 noradrenergic receptors, on plasma catecholamine metabolites, blood pressure, subjective symptoms, and laboratory-measured rapid-response impulsivity. METHODS: Subjects were 23 healthy controls recruited from the community, with normal physical examination and ECG, and negative history for hypertension, cardiovascular illness, and axis I or II disorder. Blood pressure, pulse, and behavioral measures were obtained before and periodically after 0.4 mg/kg oral yohimbine or placebo in a randomized, counterbalanced design. Metabolites of norepinephrine [3-methoxy-4-hydroxyphenylglycol (MHPG) and vanillylmandelic acid (VMA)] and dopamine [homovanillic acid (HVA)] were measured by high-pressure liquid chromatography with electrochemical detection. Rapid-response impulsivity was measured by commission errors and reaction times on the immediate memory task (IMT), a continuous performance test designed to measure impulsivity and attention. RESULTS: Yohimbine increased plasma MHPG and VMA but not HVA. Yohimbine increased systolic and diastolic blood pressure and pulse rate. On the IMT, yohimbine increased impulsive errors and impulsive response bias and accelerated reaction times. Yohimbine-associated increase in plasma MHPG correlated with increased impulsive response rates. Time courses varied; effects on blood pressure generally preceded those on metabolites and test performance. CONCLUSIONS: These effects are consistent with increased rapid-response impulsivity after pharmacological noradrenergic stimulation in healthy controls. Labile noradrenergic responses, or increased sensitivity to norepinephrine, may increase risk for impulsive behavior.

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.

Yohimbine increases opioid-seeking behavior in heroin-dependent, buprenorphine-maintained individuals.

RATIONALE: In laboratory animals, the biological stressor yohimbine (α(2)-noradrenergic autoreceptor antagonist) promotes drug seeking. Human laboratory studies have demonstrated that psychological stressors can increase drug craving but not that stressors alter drug seeking. OBJECTIVES: This clinical study tested whether yohimbine increases opioid-seeking behavior. METHODS: Ten heroin-dependent, buprenorphine-stabilized (8 mg/day) volunteers sampled two doses of hydromorphone [12 and 24 mg IM in counterbalanced order, labeled drug A (session 1) and drug B (session 2)]. During each of six later sessions (within-subject, double-blind, randomized crossover design), volunteers could respond on a 12-trial choice progressive ratio task to earn units (1 or 2 mg) of the sampled hydromorphone dose (drug A or B) vs money ($2) following different oral yohimbine pretreatment doses (0, 16.2, and 32.4 mg). RESULTS: Behavioral economic demand intensity and peak responding (O (max)) were significantly higher for hydromorphone 2 than 1 mg. Relative to placebo, yohimbine significantly increased hydromorphone demand inelasticity, more so for hydromorphone 1-mg units (P (max) = 909, 3,647, and 3,225 for placebo, 16.2, and 32.4 mg yohimbine doses, respectively) than hydromorphone 2-mg units (P (max) = 2,656, 3,193, and 3,615, respectively). Yohimbine produced significant but clinically modest dose-dependent increases in blood pressure (systolic ≈ 15 and diastolic ≈ 10 mmHg) and opioid withdrawal symptoms, and decreased opioid agonist symptoms and elated mood. CONCLUSIONS: These findings concur with preclinical data by demonstrating that yohimbine increases drug seeking; in this study, these effects occurred without clinically significant subjective distress or elevated craving, and partly depended on opioid unit dose.

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.

Mifepristone in the central nucleus of the amygdala reduces yohimbine stress-induced reinstatement of ethanol-seeking.

Chronic ethanol exposure leads to dysregulation of the hypothalamic-pituitary-adrenal axis, leading to changes in glucocorticoid release and function that have been proposed to maintain pathological alcohol consumption and increase vulnerability to relapse during abstinence. The objective of this study was to determine whether mifepristone, a glucocorticoid receptor antagonist, plays a role in ethanol self-administration and reinstatement. Male, Long-Evans rats were trained to self-administer either ethanol or sucrose in daily 30 min operant self-administration sessions using a fixed ratio 3 schedule of reinforcement. Following establishment of stable baseline responding, we examined the effects of mifepristone on maintained responding and yohimbine-induced increases in responding for ethanol and sucrose. Lever responding was extinguished in separate groups of rats and animals were tested for yohimbine-induced reinstatement and corticosterone release. We also investigated the effects of local mifepristone infusions into the central amygdala (CeA) on yohimbine-induced reinstatement of ethanol- and sucrose-seeking. In addition, we infused mifepristone into the basolateral amygdala (BLA) in ethanol-seeking animals as an anatomical control. We show that both systemic and intra-CeA (but not BLA) mifepristone administration suppressed yohimbine-induced reinstatement of ethanol-seeking, while only systemic injections attenuated sucrose-seeking. In contrast, baseline consumption, yohimbine-induced increases in responding, and circulating CORT levels were unaffected. The data indicate that the CeA plays an important role in the effects of mifepristone on yohimbine-induced reinstatement of ethanol-seeking. Mifepristone may be a valuable pharmacotherapeutic strategy for preventing relapse to alcohol use disorders and, as it is FDA approved, may be a candidate for clinical trials in the near future.

Psychological and neuroendocrine responses to social stress and to the administration of the alpha-2-receptor antagonist, yohimbine, in highly trained endurance athletes in comparison to untrained healthy controls.

INTRODUCTION: Several clinical studies suggest antidepressive and anxiolytic effects of regular endurance training. The mechanisms by which exercise exerts these effects are still unclear. It was hypothesized that athletes might show a diminished reaction to psychosocial stress and noradrenergic stimulation. METHODS: 12 male athletes and 12 healthy untrained male controls underwent a challenge paradigm on 3 separate days: the alpha-2-receptor antagonist yohimbine (0.4 mg/kg), placebo or a psychosocial stress test (SST) were administered. Responses were measured by psychometric scales, plasma cortisol, blood pressure and heart rate. RESULTS: Before testing, psychometric variables and cortisol levels were not different between the 2 groups. In comparison to placebo conditions, both the social stress test and the administration of yohimbine were followed by significant increases of anxiety symptoms, plasma cortisol, heart rate and blood pressure in both groups. However, these responses were not significantly different between the group of athletes and the control group. DISCUSSION: These results do not support the hypotheses that high aerobic fitness is associated with attenuated psychological and neuroendocrine responses to yohimbine or to psychosocial stress.

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.