Role of noradrenergic and dopaminergic systems in the antinociceptive effect of N-(3-(phenylselanyl)prop-2-yn-1-yl)benzamide in mice

Pain has a negative impact on public health, reducing quality of life. Unfortunately, current treatments are not fully effective and have adverse effects. Therefore, there is a need to develop new analgesic compounds. Due to promising results regarding the antinociceptive effect of N-(3-(phenylselanyl)prop-2-in-1-yl)benzamide (SePB), this study aimed to evaluate the participation of the dopaminergic and noradrenergic systems in this effect in mice, as well as its toxicity. To this, the antagonists sulpiride (D2/D3 receptor antagonist, 5 mg/kg), SCH-23390 (D1 receptor antagonist, 0.05 mg/kg), prazosin (α1 adrenergic receptor antagonist, 0.15 mg/kg), yohimbine (α2-adrenergic receptors, 0.15 mg/kg) and propranolol (non-selective β-adrenergic antagonist, 10 mg/kg) were administered intraperitoneally to mice 15 min before SePB (10 mg/kg, intragastrically), except for propranolol (20 min). After 26 min of SePB administration, the open field test was performed for 4 min to assess locomotor activity, followed by the tail immersion test to measure the nociceptive response. For the toxicity test, animals received a high dose of 300 mg/kg of SePB. SePB showed an increase in the latency for nociceptive response in the tail immersion test, and this effect was prevented by SCH-23390, yohimbine and propranolol, indicating the involvement of D1, α2 and β-adrenergic receptors in the antinociceptive mechanism of the SePB effect. No changes were observed in the open field test, and the toxicity assessment suggested that SePB has low potential to induce toxicity. These findings contribute to understanding SePB's mechanism of action, with a focus on the development of new alternatives for pain treatment.

In Silico Identification of a Potential TNF-Alpha Binder Using a Structural Similarity: A Potential Drug Repurposing Approach to the Management of Alzheimer's Disease

Introduction

Alzheimer's disease (AD) is a neurodegenerative disorder with no conclusive remedy. Yohimbine, found in Rauwolfia vomitoria, may reduce brain inflammation by targeting tumour necrosis factor-alpha (TNFα), implicated in AD pathogenesis. Metoserpate, a synthetic compound, may inhibit TNFα. The study is aimed at assessing the potential utility of repurposing metoserpate for TNFα inhibition to reduce neuronal damage and inflammation in AD. The development of safe and effective treatments for AD is crucial to address the growing burden of the disease, which is projected to double over the next two decades.

Methods

Our study repurposed an FDA-approved drug as TNFα inhibitor for AD management using structural similarity studies, molecular docking, and molecular dynamics simulations. Yohimbine was used as a reference compound. Molecular docking used SeeSAR, and molecular dynamics simulation used GROMACS.

Results

Metoserpate was selected from 10 compounds similar to yohimbine based on pharmacokinetic properties and FDA approval status. Molecular docking and simulation studies showed a stable interaction between metoserpate and TNFα over 100 ns (100000 ps). This suggests a reliable and robust interaction between the protein and ligand, supporting the potential utility of repurposing metoserpate for TNFα inhibition in AD treatment.

Conclusion

Our study has identified metoserpate, a previously FDA-approved antihypertensive agent, as a promising candidate for inhibiting TNFα in the management of AD.

Yohimbine ameliorates liver inflammation and fibrosis by regulating oxidative stress and Wnt/β-catenin pathway

BACKGROUND AND PURPOSE

Chronic liver injury, caused by various aetiologies, causes recurrent tissue damage, culminating in decreased liver regenerative ability and resulting in fibrosis followed by cirrhosis. In this study, the anti-fibrotic activity of Yohimbine hydrochloride (YHC) was investigated using various in vitro models and in vivo models.

METHODS

To assess the anti-inflammatory, antioxidant, and anti-fibrotic effects of YHC, lipopolysaccharide or TGF-β induced differentiation or lipid-induced oxidative-stress models were employed using HLECs, HSC-LX2, and HepG2 cells. Further, thioacetamide (TAA) induced hepatic inflammation/fibrosis models were utilized to validate the YHC's anti-fibrotic activity in rats.

RESULTS

Inflammation/differentiation experiments in HLECs and HSC-LX2 revealed that YHC treatment significantly (p < 0.001) mitigated the lipopolysaccharide or TGF-β induced upregulation of inflammatory and fibrotic markers expression respectively. In addition, YHC dose-dependently reduced the TGF-β induced migration and palmitic acid-induced oxidative stress in HepG2 cells. Further, TAA administration (5 weeks) in vivo rat model showed increased inflammatory marker levels/expression, oxidative stress, and pathological abnormalities. Additionally, TAA administration (9 weeks) elevated the fibrotic marker expression, collagen deposition in liver tissues, and shortened longevity in rats. Treatment with YHC dose-dependently mitigated the TAA-induced abnormalities in both inflammation and fibrosis models and improved the survival of the rats. Further mechanistic approaches revealed that TAA administration elevated the JNK, Wnt components and β-catenin expression in hepatic stellate cells and animal tissues. Further treatment with YHC significantly modulated the JNK/Wnt/β-catenin signaling. Moreover, the β-catenin nuclear translocation results showed that β-catenin levels were significantly elevated in the nuclear fraction of TAA control samples and reduced in YHC-treated samples.

CONCLUSION

Yohimbine treatment significantly improved inflammation and fibrosis by inhibiting differentiation, oxidative stress, and collagen deposition by partly modulating the JNK/Wnt/β-catenin pathway. These results might serve as a foundation for proposing yohimbine as a potential lead compound for liver fibrosis.

α 2 -ADRENORECEPTOR ANTAGONIST AMELIORATES SEPSIS-ASSOCIATED PULMONARY FIBROSIS BY SUPPRESSING NOREPINEPHRINE-MEDIATED FIBROBLAST DIFFERENTIATION VIA INHIBITING PKC ACTIVATION

ABSTRACT

Pulmonary fibrosis is an important factor affecting the prognosis of severe septic patients with acute lung injury. The objective of this study was to explore the effect of norepinephrine (NE) and α 2 -adrenoreceptor (AR) on sepsis-associated pulmonary fibrosis and the mechanism underlying these effects. We found pulmonary fibrotic changes, and increased NE production and α 2A -AR expression in the pulmonary tissue of mice subjected to cecal ligation and puncture surgery. Reserpine and yohimbine alleviated pulmonary fibrosis in mice with sepsis by exhausting NE derived from the lung's adrenergic nerve and blocking α 2 -AR, respectively. There was no significant difference in the expression of the three α 1 -AR subtypes. The effect of NE on promoting pulmonary fibroblast differentiation in vitro was suppressed by yohimbine. Both the protein and mRNA expression levels of α 2A -AR were increased in pulmonary fibroblasts treated with LPS. Clonidine, a selective α 2 -AR agonist, enhanced LPS-induced differentiation in pulmonary fibroblasts, as indicated by the increase in α-smooth muscle actin and collagen I/III, which was mitigated by inhibiting PKC and p38. Further in vivo results indicated that yohimbine alleviated pulmonary fibrosis and inhibited the phosphorylation of PKC, p38, and Smad2/3 in lung tissue of mice exposed to LPS for 4 weeks. Clonidine showed the opposite effect to yohimbine, which aggravated LPS-induced pulmonary fibrosis. These findings demonstrated that the sepsis-induced increase in NE promoted fibroblast differentiation via activating α 2 -AR. Blockage of α 2 -AR effectively ameliorated sepsis-associated pulmonary fibrosis by abolishing NE-induced lung fibroblast differentiation and inhibiting the PKC-p38-Smad2/3 pathway.

Dexmedetomidine Ameliorated Cognitive Dysfunction Induced by Intestinal Ischemia Reperfusion in Mice with Possible Relation to the Anti-inflammatory Effect Through the Locus Coeruleus Norepinephrine System

Cognitive impairment is a common central nervous system complication that occurs following surgery or organs damage outside the nervous system. Neuroinflammation plays a key role in the molecular mechanisms of cognitive impairment. Dexmedetomidine alleviates neuroinflammation and reduces cognitive dysfunction incidence; however, the mechanism by which dexmedetomidine alleviates cognitive dysfunction remains unclear. This study evaluated the effect of dexmedetomidine on attenuation of early cognitive impairment induced by intestinal ischemia–reperfusion in mice and examined whether the locus coeruleus norepinephrine (LCNE) system participates in the anti-inflammatory effect of dexmedetomidine. The superior mesenteric artery was clamped for 45 min to induce intestinal ischemia reperfusion injury. Dexmedetomidine alone or combined with DSP-4, a selective locus coeruleus noradrenergic neurotoxin, was used for pretreatment. Postoperative cognition was assessed using the Morris water maze. Serum and hippocampal levels of IL-1β, TNF-α, norepinephrine (NE), and malondialdehyde (MDA) were assessed by enzyme-linked immunosorbent assay. Immunofluorescence, immunohistochemistry, and hematoxylin and eosin staining were used to evaluate the expression of tyrosine hydroxylase (TH) in the locus coeruleus, hippocampal microglia, and intestinal injury. Pretreatment with dexmedetomidine alleviated intestinal injury and decreased the serum and hippocampal levels of NE, IL-1β, TNF-α, and MDA at 24 h after intestinal ischemia reperfusion, decreased TH-positive neurons in the locus coeruleus, and ameliorated cognitive impairment. Similarly, DSP-4 pre-treatment alleviated neuroinflammation and improved cognitive function. Furthermore, α2-adrenergic receptor antagonist atipamezole or yohimbine administration diminished the neuroprotective effects and improved cognitive function with dexmedetomidine. Therefore, dexmedetomidine attenuated early cognitive dysfunction induced by intestinal ischemia–reperfusion injury in mice, which may be related to its anti-inflammatory effects through the LCNE system.

Yohimbine hydrochloride ameliorates collagen type-II-induced arthritis targeting oxidative stress and inflammatory cytokines in Wistar rats

Rheumatoid arthritis (RA) is the most common type of chronic inflammatory disease which is triggered by dysfunction in the immune system which in turn affects synovial joints. Current treatment of RA with NSAIDs and DMRDs is limited by their side effect. As a result, the interest in alternative, well tolerated anti-inflammatory remedies has re-emerged. Our aim was to evaluate the antioxidant and anti-inflammatory activities underlying the anti-RA effect of Yohimbine hydrochloride (YCL) in collagen induced arthritis (CIA) in Wistar rats. The YCL was administered at doses of 5 and 10 mg kg^-1 body weight once daily for 28 days. The effects of treatment in the rats were assessed by biochemical parameter (articular elastase, LPO, GSH, catalase, SOD), hematological parameter (ESR, WBC, C-reactive protein (CRP), immunohistochemical expression (COX2, TNF-α, and NF-κB), and histological changes in joints. YCL showed anti-RA efficacy as it significantly reduced articular elastase, LPO and catalase level and ameliorates histological changes. This is in addition to its antioxidant efficacy as YCL shown a significant increase in GSH and SOD level. Also, YCL showed effective anti-inflammatory activity as it significantly decreased the expression of COX-2, TNF-α, and NF-ĸB. The therapeutic effect of YCL against RA was also evident from lower arthritis scoring and reduced hematological parameter (ESR, WBC, and C-reactive protein level). The abilities to inhibit proinflammatory cytokines and modulation of antioxidant states that the protective effect of YCL on arthritis rats might be mediated via the modulation of the immune system. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 619-629, 2017.

Berberine in combination with yohimbine attenuates sepsis-induced neutrophil tissue infiltration and multiorgan dysfunction partly via IL-10-mediated inhibition of CCR2 expression in neutrophils

Infiltration of activated neutrophils into the vital organs contributes to the multiple organ dysfunctions in sepsis. In the present study, we investigated the effects of berberine in combination with yohimbine (BY) on neutrophil tissue infiltration and multiple organ damage during sepsis, and further elucidated the involved mechanisms. Sepsis was induced in mice by cecal ligation and puncture (CLP). BY or CCR2 antagonist was administered 2h after CLP, and anti-IL-10 antibody (IL-10 Ab) or control IgG was injected intraperitoneally just before BY treatment. We found that IL-10 production was enhanced by BY therapy in septic mice. BY significantly attenuated neutrophil tissue infiltration and multiple organ injury in CLP-challenged mice, all of which were completely reversed by IL-10 Ab pretreatment. The levels of KC, MCP-1, MIP-1α and MIP-2 in the lung, liver and kidney were markedly increased 6h after CLP. BY reduced the tissue concentrations of these chemokines in septic mice, but IL-10 Ab pretreatment did not completely eliminate these inhibitory effects of BY. Particularly, dramatically increased CCR2 expression in circulating neutrophils of septic mice was reduced by BY and this effect was completely abolished by IL-10 Ab pretreatment. Furthermore, CCR2 antagonist also inhibited lung and renal injury and neutrophil infiltration in septic mice. Taken together, our data strongly suggest that BY therapy attenuates neutrophil tissue infiltration and multiple organ injury in septic mice, at least in part, via IL-10-mediated inhibition of CCR2 expression in circulating neutrophils.

Effects of noradrenergic stimulation on memory in patients with major depressive disorder

Major depressive disorder (MDD) has been associated with alterations in the noradrenergic system and impaired memory function. In turn, enhanced memory function has been associated with noradrenergic stimulation. In this study, we examined whether noradrenergic stimulation would differentially improve memory function in patients with MDD and healthy controls. In a placebo-controlled crossover study, 20 patients with MDD and 18 age- and sex-matched healthy controls received either placebo or 5 mg of yohimbine, an alpha-2-adrenoceptor antagonist that causes increased noradrenergic activity, orally before memory testing. A word list paradigm was used to test memory consolidation. Furthermore, the autobiographical memory test assessing memory retrieval and a working memory test were administered. Salivary alpha-amylase and blood pressure were measured. Yohimbine improved memory consolidation (word list learning) across groups (main effect of yohimbine: p = 0.05). This effect was more prominent in depressed patients compared with controls (post hoc t-test: MDD p = 0.01, controls p = 0.77). Memory retrieval (autobiographical memory specificity) and working memory were not affected by yohimbine. Across groups, yohimbine administration resulted in an increase in blood pressure and alpha-amylase. In sum, these results further support the hypothesis that noradrenergic stimulation enhances memory consolidation. The mechanism by which yohimbine leads to stronger memory consolidation in depressed patients compared with healthy controls remains to be elucidated.

Berberine protects against lipopolysaccharide-induced intestinal injury in mice via alpha 2 adrenoceptor-independent mechanisms

AIM

To investigate the mechanisms responsible for the protective action of berberine (Ber) against gut damage in endotoxemic mice.

METHODS

Male BALB/c mice were administered intragastrically with distilled water (0.1 mL/10 g), Ber (50 mg/kg) alone, yohimbine (2 mg/kg) alone, or Ber (50 mg/kg) in combination with yohimbine (2 mg/kg) for 3 d. On the third day, lipopolysaccharide (LPS, 18 mg/kg) or normal saline was intraperitoneally injected one hour after the intragastric administration. Following the treatment, intestinal injury in the ileum was histopathologically accessed; enterocyte apoptosis was examined using TUNEL method; Toll-like receptor 4 (TLR4) mRNA expression was measured using RT-PCR assay; inhibitor protein-κBα (I-κBα) phosphorylation and myeloperoxidase content were examined using Western blloting. The macrophage inflammatory protein-2 (MIP-2) production was measured using ELISA assay.

RESULTS

Mice challenged with LPS caused extensive ileum injury, including a significantly increased injury score, decreased intestinal villus height, reduced gut mucosal weight and increased intestinal permeability. Furthermore, LPS significantly induced enterocyte apoptosis, increased TLR4 mRNA expression, I-κBα phosphorylation, MIP-2 production and myeloperoxidase content in the ileum. Pretreatment with Ber significantly alleviated all the alterations in the ileum in the endotoxemic mice. Pretreatment with the α2-adrenoceptor antagonist yohimbine did not block the protective action of Ber against LPS-induced intestinal injury. In addition, treatment with yohimbine alone did not prevent LPS-induced intestinal injury.

CONCLUSION

Pretreatment with Ber provides significant protection against LPS-induced intestinal injury in mice, via reducing enterocyte apoptosis, inhibiting the TLR4-nuclear factor κB-MIP-2 pathway and decreasing neutrophil infiltration that are independent of α2-adrenoceptors.

Paradoxical effect of noradrenaline-mediated neurotransmission in the antinociceptive phenomenon that accompanies tonic-clonic seizures: role of locus coeruleus neurons and α(2)- and β-noradrenergic receptors

The postictal state is generally followed by antinociception. It is known that connections between the dorsal raphe nucleus, the periaqueductal gray matter, and the locus coeruleus, an important noradrenergic brainstem nucleus, are involved in the descending control of ascending nociceptive pathways. The aim of the present study was to determine whether noradrenergic mechanisms in the locus coeruleus are involved in postictal antinociception. Yohimbine (an α(2)-receptor antagonist) or propranolol (a β-receptor antagonist) was microinjected unilaterally into the locus coeruleus, followed by intraperitoneal administration of pentylenetetrazole (PTZ), a noncompetitive antagonist that blocks GABA-mediated Cl(-) influx. Although the administration of both yohimbine and propranolol to the locus coeruleus/subcoeruleus area resulted in a significant decrease in tonic or tonic-clonic seizure-induced antinociception, the effect of yohimbine restricted to the locus coeruleus was more distinct compared with that of propranolol, possibly because of the presynaptic localization of α(2)-noradrenergic receptors in locus coeruleus neurons. These effects were related to the modulation of noradrenergic activity in the locus coeruleus. Interestingly, microinjections of noradrenaline into the locus coeruleus also decrease the postictal antinociception. The present results suggest that the mechanism underlying postictal antinociception involves both α(2)- and β-noradrenergic receptors in the locus coeruleus, although the action of noradrenaline on these receptors causes a paradoxical effect, depending on the nature of the local neurotransmission.

Yohimbine protects against endotoxin-induced acute lung injury by blockade of alpha 2A adrenergic receptor in rats

BACKGROUND

Alpha 2A adrenergic receptor (AR) is a subtype of α2 AR belonging to G protein-coupled receptors, and exerts a variety of biological effects. Recent studies have demonstrated that the α2A AR activation was closely related with inflammatory reaction. The present study aimed to investigate the influence of α2A AR antagonist, yohimbine, on the severity of endotoxin-induced acute lung injury in rats.

METHODS

A total of 72 male Sprague-Dawley rats were randomly divided into three groups: control group, lipopolysaccharide (LPS) group and LPS + yohimbine group. Rats were intratracheally administrated with normal saline or LPS (300 µg), and the rats in the LPS + yohimbine group were treated with additional yohimbine (2 mg/kg, i.p) soon after LPS administration. Six, 24 and 48 hours after treatment, arterial blood gas analysis was carried out, and optical microscopy was performed to evaluate pathological changes in the lung, and lung injury score was assessed. The count of white blood cells in bronchoalveolar lavage fluid (BALF) was determined. The levels of norepinephrine, tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 in BALF were measured with enzyme-linked immunosorbent assay. Immunocytochemistry was performed for the detection of α2A AR on inflammatory cells in BALF.

RESULTS

When compared with the control group, the oxygenation index in the LPS group was significantly decreased, and white blood cell count, the lung histopathological scores, levels of norepinephrine and IL-6 as well as α2A AR expression on inflammatory cells in the BALF were dramatically increased at different time points, and the concentrations of TNF-α and IL-1β were also increased except at 48 hours after LPS administration. The oxygenation index decreased while white blood cell count in BALF and the lung histopathological scores were obviously increased in the LPS + yohimbine group. The level of norepinephrine in BALF was increased at each time interval in the LPS + yohimbine group, and so did the levels of TNF-α, IL-1β and IL-6 at 6 and 48 hours after LPS administration respectively. When compared with the LPS group, the oxygenation index, white blood cell count, the lung histopathological scores and the level of IL-6 in the LPS + yohimbine group were significantly improved at each time interval, and the concentrations of TNF-α and IL-1β were also lower at 24 hours of LPS administration (all P < 0.05). Correlation analysis indicated the level of norepinephrine was related to the levels of TNF-α, IL-1β and IL-6 in the BALF and the lung histopathological scores (r = 0.703, r = 0.595, r = 0.487 and r = 0.688, respectively, P < 0.001) and the intensity scores of immunoreactivity to α2A AR on inflammatory cells were also associated with the levels of TNF-α, IL-1β and IL-6 as well as the lung histopathologial scores (r = 0.803, r = 0.978, r = 0.716 and r = 0.808, respectively, P < 0.001).

CONCLUSIONS

Yohimbine can inhibit TNF-α, IL-1β and IL-6 overproduction and relieve the severity of pulmonary inflammation induced by endotoxin, which is maybe mediated by blockade of α2A AR on inflammatory cells.

Almitrine-Raubasine combination for dementia

BACKGROUND

Almitrine-raubasine combination (brand name Duxil), has been considered as an alternative treatment for dementia.

OBJECTIVES

To determine the clinical efficacy and safety of Duxil in the treatment of patients with dementia.

SEARCH STRATEGY

We searched the Cochrane Dementia and Cognitive Improvement Group Specialised Register (now known as ALOIS) (September 2009), the China Biological Medicine Database (CBM-disc 1979 to December 2009), the Chinese National Knowledge Infrastructure (www.cnki.net 1979 to December 2009), the Stroke Trials Registry at www.strokecentre.org/trials/index.aspx. We searched identified citations for additional trials, contacted the first author of identified trials for additional references and unpublished data. We also contacted the pharmaceutical company manufacturing Duxil (Servier Pharmaceutical Co Ltd) for additional unpublished data.

SELECTION CRITERIA

Randomised controlled trials studying the efficacy and safety of Duxil for dementia were included, irrespective of blinding, publication status, or language. If the trial was cross-over in nature, only data from the first period were included.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion, assessed trial quality and extracted the data.

MAIN RESULTS

Three trials involving a total of 206 participants were included, all patients with vascular dementia. All three included studies were assessed as being at high risk of bias. When analysing these trials together, there was significant beneficial effect of Duxil on the improvement of cognitive function measured by MMSE (WMD 2.04, 95% CI 1.43 to 2.66). No data on behaviour and death at the end of treatment and follow-up were available from the included trials. Two trials failed to show an improvement of functional performance measured by ADL (WMD -1.68; 95% CI -3.70 to 0.35). Of the three included trials, all described the adverse events in detail, there were no statistically significant differences across the trials (OR 4.84, 95%CI 0.55 to 42.67). Behaviour disturbance, quality of life, caregiver burden were not undertaken in the included trials.

AUTHORS' CONCLUSIONS

Due to the low methodological quality of included trials, small number of trials and probable publication bias, this review did not provide sufficient evidence to support the routine use of Duxil for the treatment of patients with dementia. High-quality and large-scale randomised controlled trials are needed to confirm or refute these results.

Treatment options for female sexual arousal disorder: part II

Female sexual arousal disorder (FSAD) occurs when a woman experiences distress due to the inability to attain or maintain adequate vaginal lubrication. Many treatments are still under investigation, and at this time, there are no FDA-approved medications available for the treatment of FSAD. Treatment options include "off-label" medications, vaginal estrogen, compounded preparations, and over-the-counter products.

Alpha(1) and alpha(2)-adrenoreceptor antagonists in streptozotocin- and vincristine-induced hyperalgesia

The effect of alpha(1)- and alpha(2)-adrenoreceptor antagonists (prazosin and yohimbine, respectively) on streptozotocin (STZ)- and vincristine (VIN)-induced hyperalgesia in rats was studied. In two experimental models, yohimbine (1.0 mg/kg ip) completely abolished STZ and VIN-induced hyperalgesia. This effect was markedly prolonged in diabetic rats. Prazosin (0.3 mg/kg ip) attenuated and delayed development of STZ-induced hyperalgesia. In VIN-elicited neuropathy, the administration of prazosin not only delayed hyperalgesia but also produced antinociception. After cessation of drug administration, a significant decrease in nociceptive threshold was observed. The obtained results seem to indicate that both alpha(1)- and alpha(2)-adrenoreceptors are engaged in diabetic (STZ) and toxic (VIN) neuropathy.

Dietary supplements and nutraceuticals in the management of andrologic disorders

Dietary supplements and nutraceuticals are commonly used by men with erectile dysfunction, decreased libido, BPH, and concerns about developing prostate cancer. Many preparations do not contain the advertised dosages of the active ingredient or are contaminated. Dietary supplements and nutraceuticals, particularly those addressing erectile dysfunction and libido, need to undergo rigorous testing before they can be wholeheartedly recommended.

Yohimbine in the treatment of orgasmic dysfunction

AIM

To study the effect of yohimbine in the treatment of men with orgasmic dysfunction.

METHODS

A 20-mg dose of yohimbine was first given to 29 men with orgasmic dysfunction of different aetiology in the clinic. Patients were then allowed to increase the dose at home (titration) under more favourable circumstances. The outcome and side effects were subsequently assessed.

RESULTS

The patients were classified into three groups of orgasmic dysfunction: primary complete (13), primary incomplete (8) and secondary (8). Nocturnal emissions were present in 75%, 40% and 50% of patients in the above groups, respectively (overall average 62%). The men presented because of fertility problems (52%) or because they wanted to experience the pleasure of orgasm (48%). Of the 29 patients who completed the treatment, 16 managed to reach orgasm and were able to ejaculate either during masturbation or sexual intercourse. A further three achieved orgasm, but only with the additional stimulation of a vibrator. A history of preceding nocturnal emissions was present in 69% of the men in whom orgasm was induced but only 50% who failed treatment. Of the patients, two have subsequently fathered children (one set of twins) and another 3 men were also cured. Side effects were not sufficient to cause the men to cease treatment.

CONCLUSION

Yohimbine is a useful treatment option in orgasmic dysfunction.

[Clinical research of effect of Yishen Yangnao capsule on vascular dementia]

OBJECTIVE

To find a good way to diagnose VD, value the effect of Yishen Yangnao capsule on VD and try to find some rules of changes in Chinese medicine syndromes.

METHOD

Patients were randomly divided into treating group and western medicine comparison group. It's the phase III clinical research of Rishen Yangnao capsule curing VD, judging the validity and security of it, using dukexi slice as comparison drug. Some of the patients did the examination of P300.

RESULT

The total validity of Yishen Yangnao capsule is 56.3% (contract team is 60.0%). The improve rate of ADL is 0.1069% (contract team is 0.1134%). The scores of Chinese medicine syndrome descend.

CONCLUSION

Yishen Yangnao capsule has the same effect as dukexi slice in curing VD at the side of intelligence situation and life ability.

Pharmacological effects on sexual function

Many drugs may have effects on sexual function. Sexual function is complex and psychological and relationship issues are likely to have greater impacts on sexual function in women than drugs. Although it is important to understand the effects of drugs on sexual function, physicians should use caution in "medicalization" of sexual function in women [106].

Individualisierung der Evidenz – Single Case Randomized Trial

Ein 64-jähriger Patient mit gut eingestellter essentieller Hypertonie berichtet überzeugend vom Therapieerfolg mit Yohimbin in der Akutbehandlung seiner erektilen Dysfunktion. Er wünscht die Verschreibung dieser Substanz, wovon wiederum sein Arzt nicht begeistert ist, da Akuteffekte dieser Behandlung ungewöhnlich sind und die Blockade von α2-adrenergen Rezeptoren den Blutdruck erhöhen kann. Sie einigen sich auf die Objektivierung von Wirksamkeit oder Versagen von Yohimbin in einer experimentellen Untersuchung nach einem Single Case Randomized Trial Design, also einer kontrollierten Versuchsanordnung in einem Einzelpatienten mit doppelblinder Durchführung. Der zehnmalige Vergleich von Placebo und oralem Yohimbin ließ keinen Unterschied erkennen und verhinderte, dass der Patient mit einer potenziell schädlichen Arzneimittel-Kombination exponiert wurde.

A pharmacological modulation of opiate withdrawal using an up-/down-regulation of the noradrenergic system in opiate-dependent rats

Chronic opioid exposure induces neuroadaptative changes in several brain systems. Amongst others the alpha adrenergic system appears to be extremely sensitive to opioid exposure and has, therefore, been proposed to play a key role in opiate withdrawal symptoms. In order to better understand the influence of the noradrenergic system in opioid withdrawal and be able to develop new therapeutic strategies, we studied the effect of pre-treatment with the alpha2 agonist (clonidine) and alpha2 antagonist (yohimbine) on naloxone-precipitated withdrawal in opiate-dependent rats. As is already known clonidine pre-treatment significantly enhances autonomic and behavioural signs of opioid withdrawal whereas yohimbine significantly attenuates them with dose-related effect. We also tested the effect of clonidine (0.1 mg/kg) during naloxone-precipitated opiate withdrawal in rats pre-treated with yohimbine (5 mg/kg) and we observed that yohimbine pre-treatment potentiates clonidine efficiency in decreasing opiate withdrawal signs. This study supports the possibility of using a noradrenergic antagonist in order to regulate adrenoreceptors chronically exposed to opioids, therefore interfering with the intensity of naloxone-precipitated opiate withdrawal and potentiating later effectiveness of noradrenergic agonists like clonidine. These results may have various applications in clinical opiate detoxification protocols and are discussed through an up-/down- regulation of adrenoreceptors.

On the mechanism of carbamazepine-induced antinociception in the formalin test

In the present study, the effect of lidocaine (a sodium channel blocker) on carbamazepine-induced antinociception, in formalin test was investigated. Intraperitoneal (i.p.) administration of different doses of carbamazepine (3.5, 7, 15, and 30 mg/kg) induced a dose-dependent antinociception in mice, in the first and second phases of the test. Different doses of lidocaine as a sodium channel blocker (5, 10, and 20 mg/kg, i.p.) also induced antinociception in both phases of the formalin test. It is noted that lidocaine could potentiate the response of carbamazepine in the first, but not in the second, phase of the formalin test. Meanwhile i.p. administration of different doses of Prazosin, alpha1 adrenoceptor antagonist (0.125, 0.25, and 0.5 mg/kg), Yohimbine, alpha2 adrenoceptor antagonist (0.25, 0.5, and 1 mg/kg), Bicuculline, GABAA receptor antagonist (1.5 and 3 mg/kg), and CGP 35348, GABAB receptor antagonist (100 and 200 mg/kg) exert dose-dependent antinociceptive effect in both phases of the formalin test. It should be noted that bicuculline 0.75 mg/kg by itself increased pain score in the second phase of the formalin test, indicating that blockade of GABAA receptor subtype may induce chronic pain. None of the aforementioned drugs could alter the antinociceptive response of carbamazepine in the formalin test. It is concluded that sodium channel mechanisms may be involved partly in the antinociceptive induced by carbamazepine.

Potentiation of cue-induced reinstatement of cocaine-seeking in rats by the anxiogenic drug yohimbine

Stress and drug-associated cues can trigger drug desire and relapse in abstinent cocaine users. Although the role of these two factors in relapse is well documented, it remains unclear as to whether an interaction between stress and drug-associated cues can lead to an enhancement in cocaine-seeking behavior. Here, we assessed the effects of the anxiogenic alpha2-noradrenergic receptor antagonist, yohimbine, on reinstatement of cocaine-seeking in rats either in the presence or absence of cocaine-associated cues. Yohimbine pretreatment in the absence of cocaine-associated cues or cues by themselves reliably reinstated responding on the previously cocaine-paired lever (3-4 times higher than extinction levels). However, animals showed greatly potentiated responding if yohimbine preceded cue-induced reinstatement (10-13 times higher than extinction levels, or 3-5 times over cues or yohimbine alone). While cocaine self-administration produced a significant increase in plasma corticosterone, plasma corticosterone levels did not show a clear relationship to cocaine-paired lever responding during cue and/or yohimbine-induced reinstatement. These results demonstrate that exposure to drug-paired cues during a stressful state can greatly potentiate cocaine-seeking and suggest that future treatment interventions should target multiple modalities.

Available and future treatments for erectile dysfunction

There is now a range of treatments for patients with erectile dysfunction (ED) beyond the psychosexual counselling and surgical implants that were the only available management options for many years. Oral treatments, which are minimally invasive, are the favoured first-line option for treatments and include the phosphodiesterase-5 (PDE5) inhibitors, and dopamine agonists such as apomorphine. Psychosexual counselling may still be an appropriate treatment, on its own or in combination, in a minority of patients who do not respond to oral treatment, or where an origin for the ED is likely from the history. The PDE5 inhibitors, sildenafil, tadalafil, and vardenafil, have proven to be effective and well tolerated and facilitate erectile function. Apomorphine is also effective, but causes nausea in a minority of men. The alpha-receptor antagonist yohimbine has been found to be effective in some placebo-controlled trials, but its effectiveness is probably inadequate for treatment of most ED. Intracavernosal injection of drugs such as prostaglandin E1, papaverine, and phentolamine (sometimes in combination) is an effective but invasive treatment. Other treatments include testosterone, vacuum-pump treatment, surgery, and surgical implants, and tend to be used where patients do not respond to oral treatment and counselling.

[An evidence-based approach to writing reviews as illustrated by treatment of erectile dysfunction]

Reviews integrate the data from original sources of information on the given topic. The quality of the review of literature depends on the quality of initial information. The development of evidence-based medicine demands higher standards from clinical trials. The authors analyse available information on the treatment of erectile dysfunction basing on standard international requirements for clinical trials. A checking list is available for standardization of clinical assessment. The data obtained is ranged by the degree of statistical significance. Basing on the evidence-based approach, the conclusion on efficacy of the following modern drugs in the treatment of erectile dysfunction are made: sildenafil, iochimbin, prostaglandin E1 and tadalafil. The conclusion on efficacy of the other drugs against erectile dysfunction is impossible in view of methodological drawbacks of the trials.

[Pharmacotherapy for erectile dysfunction]

In the recent few years, especially since the introduction of phosphodiesterase-5 inhibitor, sildenafil, most researchers have focused their researches on biochemistry and physiology of erectile function. New progress has been made made in basic and clinic researches on pharmacotherapy for ED. In this article, the putative molecular or cellular mechanism of actions of the available centrally and peripherally acting drugs are reviewed, providing details about the current and most explosive area of drug research and development in erectile dysfunction.

Norepinephrine Increases Alveolar Fluid Reabsorption and Na,K-ATPase Activity

The purpose of this study was to determine whether alpha-adrenergic receptor agonists have a role in alveolar fluid reabsorption, via Na,K-ATPase, in the alveolar epithelium. Alveolar fluid reabsorption increased approximately twofold with increasing concentrations of norepinephrine (NE) as compared with control rats. Treatment with the nonselective alpha-adrenergic receptor agonist, octopamine, and the specific alpha(1) agonist, phenylephrine, increased alveolar fluid reabsorption by 54 and 40%, respectively, as compared with control. The specific alpha(1)-adrenergic receptor antagonist, prazosin, inhibited the stimulatory effects of NE by approximately 30%, whereas alpha(2)-adrenergic antagonist, yohimbine, did not prevent the stimulatory effects of NE. The administration of ouabain, Na,K-ATPase inhibitor, prevented the NE-mediated increase in alveolar fluid reabsorption. In parallel with these changes, NE increased Na,K-ATPase activity and protein abundance in alveolar epithelial type II cells via the alpha(1)- and beta-adrenergic receptor. We report here that NE increased alveolar fluid reabsorption via the activation of both alpha(1)- and beta-adrenergic receptors, but not alpha(2)-adrenergic receptors. These effects are due to increased activity and abundance of the Na,K-ATPase in the basolateral membrane of ATII cells.

Addition of the alpha2-antagonist yohimbine to fluoxetine: effects on rate of antidepressant response

Electrophysiological studies suggest that alpha2-adrenoceptors profoundly affect monoaminergic neurotransmission by enhancing noradrenergic tone and serotonergic firing rates. Recent reports suggest that alpha2-antagonism may hasten and improve the response to antidepressant medications. To test this hypothesis, a randomized double-blind controlled trial was undertaken to determine if the combination of an alpha2-antagonist (yohimbine) with a selective serotonin reuptake agent (SSRI) (fluoxetine) results in more rapid onset of antidepressant action than an SSRI agent alone. In all, 50 subjects with a DSM-IV diagnosis of major depressive disorder confirmed by SCID interview were randomly assigned to receive either fluoxetine 20 mg plus placebo (F/P) or fluxetine 20 mg plus a titrated dose of yohimbine (F/Y). The yohimbine dose was titrated based on blood pressure changes over the treatment period, in a blind-preserving manner. Hamilton depression scale ratings (HDRS) and clinical global impression (CGI) ratings were obtained weekly over a period of 6 weeks. The rate of achieving categorical positive responses was significantly more rapid in the F/Y group compared to the F/P group using both the HDRS and the CGI scales as outcome measures in a survival analysis using a log-rank test (chi2(1) = 5.86, p = 0.016 and chi2(1) = 5.29, p = 0.021, respectively). At the last observed visit, 18 (69%) of the 26 F/Y subjects met the response criteria for CGI compared to 10 (42%) of 24 F/P subjects. Using the HDRS criteria, 17 (65%) of 26 F/Y subject vs 10 (42%) of 24 F/P subjects were responders. The addition of the alpha2-antagonist yohimbine to fluoxetine appears to hasten the antidepressant response. There is also a trend suggesting an increased percentage of responders to the combined treatment at the end of the 6-week trial.

Assessment of the therapeutic activity of a combination of almitrine and raubasine on functional rehabilitation following ischaemic stroke

BACKGROUND AND OBJECTIVES

Stroke is a major cause of disability. Certain experimental studies have suggested that a combination of almitrine + raubasine (Duxil) increases the supply of oxygen to cerebral tissues and may be beneficial in post-stroke rehabilitation. This multicentre clinical study was carried out in order to assess the efficacy of this combination on poststroke rehabilitation.

METHODS

The trial was a randomised, double-blind, placebo-controlled study. Patients that had experienced an ischaemic cerebrovascular accident (confirmed by CT scan) were included 4-6 weeks after the acute onset and received randomised treatment of either almitrine + raubasine or placebo 2 tablets daily for 3 months. Before treatment, there was a 2-week washout period for stopping all other drugs, except for antihypertensive and antidiabetic drugs. We assessed the patients by Barthel Index (BI), Neurological Functional Deficit Scores (NFDS), and Hasagawa Dementia Scales (HDS) each month after treatment.

RESULTS

A total of 83 patients were entered into the study and data were available for 74. Of these, 38 patients received almitrine + raubasine and 36 received placebo. The baseline characteristics were comparable between both groups. Almitrine + raubasine was significantly more effective than placebo at increasing BI at 1, 2 or 3 months (14.6 +/- 13.8 versus 3.3 +/- 13.2, p = 0.01; 19.3 +/- 13.6 versus 8.8 +/- 14.0, p = 0.02; 22.6 +/- 14.7 versus 10.7 +/- 17.0, p = 0.02 respectively) and reducing NFDS at 1 month (3.6 +/- 3.2 versus 1.9 +/- 3.5, p = 0.034) after treatment. More almitrine + raubasine-treated patients' NFDS had improved compared with placebo-treated patients at 2 and 3 months (97 versus 78%, p = 0.013; 100 versus 86%, p = 0.023 respectively). Compared with pretreatment, there was a strong tendency towards an improvement of HDS with almitrine + raubasine. The number of adverse events reported was low for the almitrine + raubasine-treated group and the placebo group and all events were mild, of short duration and resolved without treatment. Almitrine + raubasine had no clinically significant effect on blood pressure, heart rate or other laboratory tests.

CONCLUSION

The results indicate that almitrine + raubasine can accelerate neurological function recovery after stroke to some degree and is well tolerated.

Nutrients and botanicals for erectile dysfunction: examining the evidence

Erectile dysfunction affects 50 percent of men ages 40-70 in the United States and is considered an important public health problem by the National Institutes of Health. Consumers are exposed to a plethora of natural products claiming to restore erection and sexual vitality. A review of the available empirical evidence reveals most naturally occurring compounds lack adequate clinical trials to support efficacy. However, arginine, yohimbine, Panax ginseng, Maca, and Ginkgo biloba all have some degree of evidence they may be helpful for erectile dysfunction. Improvements in penile endothelial L-arginine-nitric oxide activity appear to be a unifying explanation for the actions of these naturally occurring agents.

Magnitude of abdominal incision affects the duration of postoperative ileus in rats

BACKGROUND

The pathogenesis of reduced postoperative ileus (POI) in laparoscopic gastrointestinal (GI) surgery still remains controversial. The aim of this study was to investigate the effect of surgical incision on postoperative ileus.

METHODS

The effects of length, depth, and site of the incision on GI transit were compared using the geometric center of 51Cr in rats. The inhibitory mechanism of abdominal incision on GI transit also was studied.

RESULTS

The findings showed that 5 cm of abdominal skin and the 5-cm back muscle incision had no significant effect on GI transit. However, the 5-cm abdominal muscle-fascia incision and a 5-cm laparotomy significantly delayed GI transit. Gastrointestinal transit after a 5-cm laparotomy was significantly delayed, as compared with that of a 1-cm laparotomy regardless whether intestinal manipulation was performed or not. Guanethidine and yohimbine, but not propranolol, significantly improved the impaired GI transit after a 5-cm laparotomy.

CONCLUSIONS

The results suggest that the longer and deeper abdominal incision more profoundly inhibits GI transit. The inhibitory effect of abdominal incision is mediated via the activation of the somatosympathetic reflex and alpha-2 adrenoceptors.

[Effect of rilmenidine on intraocular pressure in rabbits, interaction with efaroxan and rauwolscine]

PURPOSE

Glaucoma is the main cause of blindness in the developed countries. Its progress can be diminished by decreasing intraocular pressure (IOP) using pharmacological or surgical treatment. Antiglaucoma agents, alpha 2-adrenergic's receptor agonists have been known for several years as IOP lowering. Due to the fact that the majority of them turned out to be imidazoline receptor agonists, it is worth checking if selective imidazoline receptor (l1) agonists alter IOP. Preliminary animal experiments show that they lower IOP. In our study we examined the influence of rilmenidine, a potent l1 receptor agonist, on IOP in rabbits. Furthermore, we tried to find out whether l1 and alpha 2 receptor antagonists (efaroxan and rauwolscine) counteract the pharmacological effect of rilmenidine.

MATERIAL AND METHODS

The study was conducted on adult male White New Zealand rabbits. All the substances were administered topically, and IOP was measured by applanation tonometry after topical anaesthesia before and 1, 3 and 5 hours after drug instillation.

RESULTS

Rilmenidine showed the lowering effect on IOP at the concentration of 0.4%. Efaroxan and rauwolscine partly inhibited rilmenidine effect.

CONCLUSIONS

Rilmenidine is a potential antiglaucoma agent, though further studies are necessary.

Medikament�se Therapie der erektilen Dysfunktion?derzeitiger Stand

In the medicinal therapy of erectile dysfunction (ED), both oral as well as local application are possible. The introduction of the PDE-5 inhibitor Sildenafil, as the first highly potent oral therapy for ED, caused dramatic changes in the diagnostic and therapeutic strategies in this area. The later PDE-5 inhibitors Tadalafil and Vardenafil show, as far as it is currently possible to judge, a similar profile to Sildenafil. The only previously available oral therapeutic, Yohimbin, plays an insignificant role, and the initial hopes for Apomorphin as an ED therapeutic have settled to a realistic level. Local application therapies have also become less important, with the intra-urethral application of PGE(1) being reduced to a few clinical indicated situations. The intra-cavernosal pharmacotherapy with PGE(1) is considered the gold standard when oral therapies do not work or can not be used.

[A 47-year-old man with "pure autonomic failure" and pernicious anemia]

HISTORY AND CLINICAL FINDINGS

A 47-year-old man with a known and substituted vitamin B12 deficiency presented with increasing symptoms associated with orthostatic hypotension, neck pain and micturitional and visual disturbances.

CLINICAL AND LABORATORY TESTS

Catecholamines were strongly reduced in plasma and urine.

DIAGNOSIS, TREATMENT AND CLINICAL COURSE

A pure autonomic failure was diagnosed and therapy with fludrocortisone, yohimbine and erythropoetine was started. Symptoms with the exception of micturitional disturbances improved strongly.

CONCLUSIONS

Multiple-drug treatment of pure autonomic failure is successful. The prognosis is good.

The comparative efficacy of yohimbine and atipamezole to treat amitraz intoxication in dogs

This study compared the efficacy of yohimbine with atipamezole, a new alpha2 adrenergic antagonist, to treat canine amitraz intoxication. Thirty dogs were divided equally into 3 groups (A, AY, and AA). Group A received 2.5% amitraz iv at 1 mg/kg; Group AY received the same dose of amitraz followed 30 min later by 0.1 mg/kg (2 mg/mL) yohimbine iv; and Group AA received the same dose of amitraz followed 30 min later by 0.2 mg/kg (5 mg/ mL) atipamezole iv. Temperature, heart rate, respiratory frequency, mean arterial pressure, degree of sedation, mean time of tranquilization and diameter of pupils were monitored for 360 min. Sedation, loss of reflexes, hypothermia, bradycardia, hypotension, bradypnea and mydriasis were observed in Group A, with 3rd eyelid prolapse, increased diuresis and vomiting in some animals. Yohimbine reversed all alterations induced by amitraz, but induced significant cardiorespiratory effects such as tachycardia and tachypnea. Atipamezole was a useful antagonist for amitraz, with less cardiorespiratory effects, suggesting its potential role as an alternative treatment of amitraz intoxication in dogs.

[Erectile dysfunction: reasonable diagnostics and treatment in general practice]

The availability of efficacious oral drugs has radically changed the diagnostic and therapeutic approach to erectile dysfunction. Complicated examinations as well as invasive treatment options have been widely abandoned. Instead the management of impotent men has become much more pragmatic and focused on the symptom. Consequently only a minority of impotent men needs to be referred to an urologist, which makes the therapy of erectile dysfunction increasingly attractive for general practitioners. However, successful treatment first of all still needs time and a genuine interest in the field of erectile dysfunction. In this article a reasonable diagnostic evaluation of impotent patients in general practice is described. Furthermore indication and use of little or non-invasive therapies are discussed.

[Yohimbine in the treatment of erectile dysfunction]

Iochimbin hydrochloride was given to 153 men with erectile dysfunction. The results are available for 140 of them. The ability of iochimbin in a single dose of 5-10 mg to enhance arterial blood inflow to cavernous bodies of the penis was confirmed by dynamic angiopenoscintigraphy and Doppler ultrasonography. Iochimbin hydrochloride in a mean daily dose of 15-20 mg proved effective in erectile dysfunction--38 to 84% responders depending on the type of erectile dysfunction. Occasional side effects can be relieved by reducing the drug dose.

Erectile dysfunction: oral pharmacotherapy options

Erectile dysfunction (ED) (impotence) is a widespread, age-related problem, which affects 52% of men between 40 and 70 years of age. It is classified as psychogenic, organic, or mixed psychogenic and organic. ED is not a problem only of men, because the relationship between partners can also be disturbed. Therefore, adequate treatment of ED is needed and the most convenient and simplest way is oral drug therapy. Sildenafil, phosphodiesterase-(PDE)-5-selective inhibitor has been the drug of choice for patients with ED since it has been launched in March 1998. The results of various studies have confirmed the efficacy of the drug in men with ED of various etiologies, as well as the positive effect of sildenafil on the quality of a partnership. The most frequent adverse effects documented with sildenafil usage are headache, flushes, dyspepsia, visual disturbances and nasal congestion/rhinitis. These adverse effects are dose-related, usually transient and mild, with low withdrawal rate. Several studies performed recently have shown that sildenafil is a safe and effective treatment of ED in patients with cardiovascular disease, who do not take nitrates or nitrate donors concomitantly. Other oral medications for ED include apomorphine, phentolamine, yohimbine, trazodone, testosterone and new PDE-5 inhibitors in Phase III clinical trials, such as vardenafil and tadalafil. It is obvious, according to recent data, that the concept of PDE-5 inhibition has a central position in oral pharmacotherapy of ED. However, larger clinical studies of efficacy and safety should be carried out using most of the other above-mentioned oral agents and these may also gain a place in the therapy of ED. There are no studies directly comparing sildenafil and other treatments of ED or assessing its role in combination with other therapies. According to the present knowledge, the quality of life, not only of patients but also of their sexual partners, will be improved significantly with sildenafil usage and this is an important precondition for overall health ofboth. Sildenafil is thus a highly effective peroral treatment for ED in patients without contraindications for its use, which can be considered as the firstline therapy with an acceptable risk-benefit ratio.

The effects of yohimbine plus L-arginine glutamate on sexual arousal in postmenopausal women with sexual arousal disorder

This study examined the effects of the nitric oxide-precursor L-arginine combined with the alpha 2-blocker yohimbine on subjective and physiological sexual arousal in postmenopausal women with Female Sexual Arousal Disorder. Twenty-four women participated in three treatment sessions in which self-report and physiological (vaginal photoplethysmograph) sexual responses to erotic stimuli were measured following treatment with either L-arginine glutamate (6 g) plus yohimbine HCl (6 mg), yohimbine alone (6 mg), or placebo, using a randomized, double-blind, three-way cross-over design. Sexual responses were measured at approximately 30, 60, and 90 min postdrug administration. The combined oral administration of L-arginine glutamate and yohimbine substantially increased vaginal pulse amplitude responses to the erotic film at 60 min postdrug administration compared with placebo. Subjective reports of sexual arousal were significantly increased with exposure to the erotic stimuli but did not differ significantly between treatment groups.

Yohimbine administration prevents over-responsiveness to epinephrine induced by simulated microgravity

BACKGROUND

Simulated microgravity produces sustained inhibition of sympathoneural release, turnover, and synthesis of norepinephrine (NE) and hypersensitization of beta-adrenergic pathways. These changes may explain the orthostatic intolerance experienced by astronauts returning from spaceflights.

HYPOTHESIS

Chronic administration of yohimbine would prevent the increase of beta-adrenergic hypersensitivity to epinephrine (Epi) induced by simulated microgravity.

METHODS

Eight healthy young subjects received 8 mg of yohimbine (an antagonist of alpha2adrenoceptors) orally twice a day during the simulated microgravity achieved through -6 degrees head-down bed rest (HDBR). The catecholamine-induced lipolysis was studied on isolated fat cells from subcutaneous adipose tissue before HDBR and on the fifth day of HDBR. Epi was infused at three graded rates (0.01, 0.02, and 0.03 microg x kg(-1) x min(-1) for 40 min each) before and at the end of the HDBR period. The effects of Epi on the sympathetic nervous system (SNS) activity-assessed by plasma NE levels and spectral analysis of systolic BP and heart rate variability-and on plasma levels of glycerol, non-esterified fatty acids, glucose, and insulin and on energy expenditure were evaluated.

RESULTS

Under yohimbine treatment, HDBR failed to modify urinary NE excretion and spectral variability of systolic BP in the mid-frequency range. The beta- and alpha-adrenergic sensitivity of fat cells were not modified by HDBR nor were plasma NE levels and spectral variability of systolic BP induced by Epi infusion. No alteration of Epi-induced changes in heart rate and systolic and diastolic BPs were observed after HDBR. Epi-induced increases in plasma glucose, insulin, glycerol, and non-esterified fatty acid levels as well as energy expenditure were also unmodified by HDBR. Only the Epi-induced plasma lactate level was increased by HDBR.

CONCLUSION

Our data suggest that the increase in the effects of Epi induced during microgravity could be attenuated by chronic administration of yohimbine. An explanation for this effect could be SNS activation brought about by the alpha2-adrenoceptor antagonist properties of yohimbine.