Selective delta-opioid receptor ligands: potential PET ligands based on naltrindole

Two series of delta-selective ligands related to the prototypic delta-antagonist naltrindole have been prepared and evaluated in opioid binding assays with the aim of developing new PET ligands for the delta-opioid receptor. One compound (5d) had significantly higher selectivity than naltrindole, but with substantially reduced binding affinity. For those compounds retaining similar affinity to naltrindole, those having ethyl and fluoroethyl substituents afforded the highest levels of selectivity. However, none of the compounds combined the high level of affinity and selectivity ideally suited to the development of an imaging agent.

Venlafaxine occupation at the noradrenaline reuptake site: in-vivo determination in healthy volunteers

Venlafaxine, a serotonin and noradrenaline reuptake inhibitor, is an effective antidepressant at doses of 75 mg p.o. daily and above. Preclinical and healthy volunteer studies have demonstrated that venlafaxine is more potent at the serotonin than at the noradrenaline reuptake site, with noradrenergic blocking effects being observed at doses >75 mg p.o. in man. We used the Multiple Organs Coincidences Counter and [11C] meta hydroxy ephedrine (MHED) to test whether significant occupation of cardiac sympathetic neurones was achieved in man in vivo after the acute administration of venlafaxine 75 mg p.o. in nine healthy volunteers. MHED is a tracer which binds at the noradrenaline reuptake site. This study demonstrates that the [11C]MHED signal is significantly reduced after the administration of venlafaxine 75 mg p.o. thus showing that noradrenaline reuptake blockade is observable at this dose. This effect is predominantly seen in volunteers who received > 1 mg/kg venlafaxine.

The processing of automatic thoughts of drug use and craving in opiate-dependent individuals

This study investigated the processing of sentences describing craving and withdrawal in opiate-dependent individuals. Eighteen patients who attended a methadone maintenance clinic for obtaining methadone, 18 patients who were not treated with methadone, and 18 control family members performed on a computerized contextual priming task. The task was priming sentences (craving, withdrawal, or neutral) to words (addiction, neutral, or nonwords). The methadone group was slower to process all sentences compared with family members. They were also faster to process drug-related words following withdrawal-related sentences compared with neutral words following neutral sentences. Finally, they were slower to recognize neutral words following neutral sentences compared with the nonmethadone group. Results suggest that the processing of information describing withdrawal and craving for drugs plays an important role in opiate dependence.

Addiction and withdrawal--current views

The final common pathway of addiction (the dopamine hypothesis of reward) has recently been evolving, with the mesocorticolimbic dopaminergic system now seen as key to natural rewards and drug-seeking behaviour, though perhaps having less of a role in the maintenance of such behaviour. The perception of a common pathway has meant that treatments for one drug of addiction have 'crossed-over' and become possible treatments for other addictive drugs.

Adenosine receptor subtypes modulate two major functional pathways for hippocampal serotonin release

To clarify the mechanisms of interaction between adenosine A(1) receptor (A1-R) and adenosine A(2) receptor (A2-R) on neurotransmitter release, this study determined the functional interactions among adenosine receptors (AD-Rs), voltage-sensitive Ca(2+) channels (VSCCs), protein kinases (PKs), and synaptic proteins [N-ethylmaleimide-sensitive factor (NSF) attachment protein (SNAP) receptors] on hippocampal serotonin release using in vivo microdialysis in freely moving rat. Basal serotonin release was regulated by two functional complexes: N-type VSCC (N-VSCC)/calcium-phospholipid-dependent protein kinase (PKC)/syntaxin (major pathway) and P-type VSCC (P-VSCC)/cyclic AMP-dependent protein kinase (PKA)/synaptobrevin (minor pathway). However, K(+)-evoked serotonin release was regulated by N-VSCC/PKC/syntaxin (minor pathway) and P-VSCC/PKA/synaptobrevin (major pathway). A1-R antagonists increased basal serotonin release, which was reduced by inhibitors of N-VSCC, PKC, and syntaxin predominantly and by inhibitors of PKA and synaptobrevin weakly, but was not affected by P-VSCC inhibitor. In the presence of A1-R antagonist, A2-R agonists increased basal serotonin release, which was inhibited by inhibitors of P-VSCC, PKA, and synaptobrevin predominantly and reduced by inhibitors of N-VSCC, PKC, and syntaxin weakly. Under the condition of activation of adenylate cyclase in the absence of A1-R antagonists, A2-R agonists increased basal serotonin release. A1-R antagonist and A2-R agonist enhanced K(+)-evoked serotonin release, which was inhibited by inhibitors of P-VSCC, PKA, and synaptobrevin predominantly. These results suggest that an activation of A1-R suppresses serotonin release via inhibition of both N-VSCC/PKC/syntaxin and P-VSCC/PKA/synaptobrevin pathways, and an activation of A2-R stimulates serotonin release via enhancement of the P-VSCC/PKA/synaptobrevin pathway. Therefore, PKA activity plays an important role in the interaction between A1-R and A2-R on hippocampal serotonin release.

The psychobiology of anxiolytic drug. Part 2: Pharmacological treatments of anxiety

Benzodiazepines have been the mainstay of pharmacological treatment of anxiety over the last 4 decades. The problems associated with their use prompted the research for alternative agents that would be useful in anxiety conditions. Old classes of antidepressants, such as tricyclic antidepressants and monoamine oxidase inhibitors, showed effectiveness in some anxiety syndromes, even in areas where benzodiazepines were not very effective. Newer antidepressants, the selective serotonin-reuptake inhibitors, also appear very useful in some anxiety states, and their favourable side-effect profile has elevated them to first-line treatment tools in these conditions. However, the ideal anxiolytic does not exist. Research with other new compounds is very active, and some experimental drugs show promise for the future.

The psychobiology of anxiolytic drugs. Part 1: Basic neurobiology

The authors provide an overview of the current state of knowledge with regards to the neurobiological mechanisms involved in normal and pathological anxiety. A brief review of the classification and cognitive psychology of anxiety is followed by a more in-depth look at the neuroanatomical and neurochemical processes and their relevance to our understanding of the modes of action of anxiolytic drugs. The serotonergic, noradrenergic, and gamma-aminobutyric acidergic systems are reviewed. The numerous physiological and pharmacological methods of anxiety provocation and the increasing importance of functional neuroimaging are also examined. The review provides an overview of the biology and basic pharmacology of anxiolytic drugs, and compliments the more clinically oriented companion review.

Efficacy of mirtazapine in clinically relevant subgroups of depressed patients

Mirtazapine is a noradrenergic and specific serotonergic antidepressant (NaSSA) with a novel mode of action that differs from other antidepressants that are currently available. Clinical trials have demonstrated it to have good antidepressant efficacy and excellent tolerability. Analysis of the results of placebo-controlled trials in moderately or severely depressed patients have shown mirtazapine to be effective in clinically important subgroups of depressed patients, particularly anxious patients, patients with sleep disturbance, retarded patients, and agitated patients. The efficacy and tolerability of mirtazapine are attributable to its pharmacological profile. It is likely that the overall antidepressant activity arises from its dual action, enhancing both noradrenergic and 5-HT1 receptor-mediated serotonergic neurotransmission, while the anxiolytic and sleep-improving properties of mirtazapine are attributable to the specific blockade of 5-HT2 and 5-HT3 receptors.

Substance P antagonists: novel agents in the treatment of depression

The field of neuropeptides has been expanding very rapidly in recent years. Apart from understanding their physiology and elucidating their functional role as putative neurotransmitters, research has focused on producing drugs that may treat a variety of illnesses in a novel way. Substance P antagonists occupy a central role in this area of intensive scientific activity. Substance P (SP), an undecapeptide, is abundant both in the periphery and in the CNS, where it is usually co-localised with one of the classical neurotransmitters, most commonly serotonin (5-HT). A role for SP is proposed in the regulation of pain, asthma, psoriasis, inflammatory bowel disease and, in the CNS, emesis, migraine, schizophrenia, depression and anxiety. A recently published positive study of MK 869, in depression, a novel SP antagonist has generated excitement amongst psychopharmacologists. It is the first time that a drug, not directly related to monoamine transmitters, has showed efficacy in depression. Although MK 869 has been suspended from further development, a host of other compounds, with similar action and better pharmacological profile, are currently under development. In this review, the pharmacology of central SP and its receptors are discussed, together with the exploration of the prospects and implications for future treatments of depression.

Sleep changes during long-term treatment of depression with fluvoxamine--a home-based study

RATIONALE

The effects of antidepressants on sleep in depression have been extensively investigated, although to date there have been relatively few studies of newer drug classes such as specific serotonin reuptake inhibitors (SSRIs). All reported studies on SSRIs have been conducted in patients admitted to sleep laboratories and very few longitudinal studies have continued to measure sleep beyond 5 weeks of treatment. The growing trend towards outpatient and community care has highlighted the need for studies of sleep in depression in a more naturalistic setting, and during longer periods of treatment in line with recommended clinical practice.

OBJECTIVES

To establish if the changes in sleep architecture and continuity described during early treatment with SSRIs persist after 3 months, to relate these changes to clinical state, and to establish whether home recordings would yield similar results to previous laboratory studies.

METHODS

We have recorded objective sleep parameters in 12 depressed patients before and during 12-week treatment with an SSRI, fluvoxamine. All the sleep recordings were performed in the patients' own homes, using the Oxford Medilog system.

RESULTS

At 12 weeks, 7/12 patients had responded (HAM-D decreased by > 50%). REM latency showed the expected increase early in treatment; this change was less obvious at weeks 3 and 12. Amount of REM sleep was decreased at day 2 and week 3, but returned to baseline by week 12. Slow wave sleep was slightly increased at day 2 and decreased at week 12. Of the sleep continuity measures, the only significant change was in sleep onset latency, which was increased at week 3; the other measures showed non-significant worsening at night 2 and week 3, but most were better than baseline by 12 weeks. Subjective sleep (the three sleep items on the HAM-D) showed a progressive improvement over time, especially in the responders.

CONCLUSIONS

The effects of the SSRI fluvoxamine on objective sleep measures are in the direction predicted by its pharmacological actions and some persist for at least 12 weeks. In addition subjective appraisal of sleep is strongly affected by mood state. All patients found the home recording procedure acceptable and only minimally disruptive.

Behavioural and physiological effects induced by an infusion of antisense to alpha(2D)-adrenoceptors in the rat

1. The aim of this study was to investigate the behavioural and physiological effects of an i.c.v. infusion of antisense oligonucleotide to the alpha(2D)-adrenoceptor subtype. Behavioural and physiological parameters were monitored for 2 days before the infusion, throughout the 3-day infusion period and for 3 days following the end of the infusion. 2. The antisense infusion resulted in a significant increase in behavioural activity characterized by increased locomotion and grooming scores. Behavioural activity scores of rats treated with antisense to alpha(2D)-adrenoceptors were significantly higher than those of rats treated with vehicle (H(2)O) or the mismatch toxicity control on day 4 and day 5 and, significantly higher than vehicle controls on day 6. 3. Body weight gain was significantly reduced in the antisense-treated rats at the end of the study compared to the vehicle (34%) and mismatch groups (30%), although daily food and water intakes were not significantly different at any time point. 4. Pupil diameters of rats infused with antisense to alpha(2D)-adrenoceptors were significantly greater than those of animals treated either with vehicle or mismatch oligonucleotide on day 5 of the study. On day 6, the pupil diameters of these animals were still significantly greater than the mismatch group. 5. In conclusion, an i.c.v. infusion of antisense to the alpha(2D)-adrenoceptor induced behavioural activation in rats, increased pupil diameter and reduced total weight gain. These effects were specific to the antisense-treated group and were fully reversed post-infusion.

Evaluation of [O-methyl-11C]RS-15385-197 as a positron emission tomography radioligand for central alpha2-adrenoceptors

Carbon-11 labelled RS-15385-197 and its ethylsulphonyl analogue, RS-79948-197, were evaluated in rats as potential radioligands to image central alpha2-adrenoceptors in vivo. The biodistributions of both compounds were comparable with that obtained in an earlier study using tritiated RS-79948-197 and were consistent with the known localisation of alpha2-adrenoceptors. The maximal signals (total to non-specific binding) were, however, reduced, in the order [11C]RS-79948-197 < [11C]RS-15385-197 < [3H]RS-79948-197, primarily due to the difference in radiolabel position (O-methyl for carbon- 11 compared with S-ethyl for tritium). This resulted in the in-growth of radiolabelled metabolites in plasma, which, in turn, contributed to the non-specific component of brain radioactivity. Nonetheless, the signal ratio of approximately 5 for a receptor-dense tissue compared with the receptor-sparse cerebellum, at 90-120 min after radioligand injection, encouraged the development of [O-methyl-11C]RS-15385-197 for human positron emission tomography (PET). Unfortunately, in two human PET scans (each of 90 min), brain extraction of the radioligand was minimal, with volumes of distribution more than an order of magnitude lower than that measured in rats. Following intravenous injection, radioactivity was retained in plasma and metabolism of the radiolabelled compound was very low. Retrospective measurements of in vitro plasma protein binding and in vivo brain uptake index (BUI) in rats demonstrated a higher protein binding of the radioligand in human compared with rat plasma and a lower BUI in the presence of human plasma. It is feasible that a higher affinity of RS-15385-197 for human plasma protein compared with receptor limited the transport of the radioligand. Although one of the PET scans showed a slight heterogeneity in biodistribution of radioactivity which was consistent with the known localisation of alpha2-adrenoceptors in human brain, it was concluded that [O-methyl-11C]RS-15385-197 showed little promise for routine quantification of alpha2-adrenoceptors in man.

Consensus statement on posttraumatic stress disorder from the International Consensus Group on Depression and Anxiety

OBJECTIVE

To provide primary care clinicians with a better understanding of management issues in posttraumatic stress disorder (PTSD) and guide clinical practice with recommendations on the appropriate management strategy.

PARTICIPANTS

The 4 members of the International Consensus Group on Depression and Anxiety were James C. Ballenger (chair), Jonathan R. T. Davidson, Yves Lecrubier, and David J. Nutt. Other faculty invited by the chair were Edna B. Foa, Ronald C. Kessler, Alexander C. McFarlane, and Arieh Y. Shalev.

EVIDENCE

The consensus statement is based on the 6 review articles that are published in this supplement and the scientific literature relevant to the issues reviewed in these articles.

CONSENSUS PROCESS

Group meetings were held over a 2-day period. On day 1, the group discussed the review articles and the chair identified key issues for further debate. On day 2, the group discussed these issues to arrive at a consensus view. After the group meetings, the consensus statement was drafted by the chair and approved by all attendees.

CONCLUSION

PTSD is often a chronic and recurring condition associated with an increased risk of developing secondary comorbid disorders, such as depression. Selective serotonin reuptake inhibitors are generally the most appropriate choice of first-line medication for PTSD, and effective therapy should be continued for 12 months or longer. The most appropriate psychotherapy is exposure therapy, and it should be continued for 6 months, with follow-up therapy as needed.

The psychobiology of posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) develops after exposure to events that are threatening and/or intensely distressing. Accumulating evidence suggests that intense psychological trauma can cause long-standing alterations in the neurobiological response to stress. These alterations translate into a number of symptoms commonly experienced by patients with PTSD. Current treatments for this disorder are only partially effective in managing the disease, and patients have to endure unpleasant symptoms associated with hyperarousal. As a result, they often withdraw from social interaction and increase the use of central nervous system depressants. Data suggest that biological dysregulation of the glutamatergic, amine neurotransmitter (noradrenergic and serotonergic), and neuroendocrine pathways plays a fundamental part in the pathology of PTSD and may cause brain structural as well as functional abnormalities. Knowledge of these pathologic changes in PTSD provides direction for the development of new treatments that will offer more comprehensive management of PTSD and enable patients to enjoy a much improved quality of life. This article reviews current knowledge regarding the psychobiology of PTSD and considers specific agents that are emerging as key modulators of this pathological process.

Flumazenil challenge in social phobia

The benzodiazepine antagonist, flumazenil, can provoke panic attacks in some panic disorder patients. It has been predicted that panic responses to flumazenil may be associated with situational fear. Patients with social phobia frequently experience situational anxiety and panic attacks. The current study tested whether flumazenil induces panic in patients with social phobia. Fourteen patients with social phobia (DSM-III-R) and 14 age- and sex-matched controls were tested in a single session, double blind crossover challenge design, using intravenous flumazenil 2 mg/20 ml or matched placebo infusions 1 hour apart. Panic attacks occurred during flumazenil challenge in 2/14 subjects with social phobia. The rate of panic attacks and the severity of panic symptoms following flumazenil were not significantly greater in patients than in controls. Situational fears that are provoked by social cues therefore do not predict panic responses to flumazenil.

Probes for imidazoline binding sites: synthesis and evaluation of a selective, irreversible I2 ligand

An irreversible ligand (7) has been prepared based on the selective I2 ligand 2-BFI. Compound 7 displayed high affinity and selectivity for I2-sites and has been shown to irreversibly bind to these sites in rat brain. Compound 7 should, therefore, prove an invaluable tool for the further elucidation of I2-site function.

Desipramine binding to noradrenaline reuptake sites in cardiac sympathetic neurons in man in vivo

Noradrenergic reuptake blockade is a recognised mechanism of antidepressant action, but the extent of the blockade necessary for therapeutic effect is not known and plasma levels do not provide a guide to therapy. We report a method to assess noradrenaline reuptake blockade in vivo in man using [11C]meta-hydroxyephedrine and the multiple organs' coincidences counter. Eight healthy volunteers had two scans, one with tracer alone and one after preloading with desipramine 50-75 mg p.o. In all subjects, there was an increased washout rate of the radioligand from the heart following preloading (t=4.38; P<0.003) as well as a decrease of the area under the [11C]meta-hydroxyephedrine time activity curve (t=7. 4; P=0.001). In one subject who had three doses of desipramine, the increase in washout rate was dose-dependent. In conclusion, [11C]meta-hydroxyephedrine in the multiple organs' coincidences counter gives a valid, low radiation method to assess noradrenergic reuptake blockade in the clinic.

Evidence-based guidelines for treating depressive disorders with antidepressants: a revision of the 1993 British Association for Psychopharmacology guidelines. British Association for Psychopharmacology

A revision of the British Association for Psychopharmacology guidelines for treating depressive disorders with antidepressants was undertaken in order to specify the scope and target of the guidelines and to update the recommendations based explicitly on the available evidence. A consensus meeting, involving experts in depressive disorders and their treatment, reviewed key areas and considered the strength of evidence and clinical implications. The guidelines were drawn up after extensive feedback from participants and interested parties. A literature review is given which identifies the quality of evidence followed by recommendations, the strength of which are based on the level of evidence. The guidelines cover the nature and detection of depressive disorders, acute treatment with antidepressant drugs, choice of drug versus alternative treatment, practical issues in prescribing, management when initial treatment fails, continuation treatment, maintenance treatment to prevent recurrence and stopping treatment.

Chest pain: panic attack or heart attack?

Chest pain is a common presentation to both primary and secondary care physicians but is often non-cardiac in origin. Patients presenting with chest pain may be experiencing a panic attack. Panic disorder is a disabling psychiatric condition with serious consequences, such as impaired social functioning and increased risk of suicide. Comorbidity of panic disorder with other psychiatric conditions is common and often leads to increased severity of anxiety symptoms and a poorer prognosis. The cost of misdiagnosing non-cardiac chest pain is high. It is important for physicians to be able to recognise panic attacks and to distinguish them from cardiac disease, thus avoiding unnecessary use of healthcare resources. This review discusses the prevalence and diagnosis of panic attack and panic disorder in patients presenting with chest pain to primary care physicians and cardiologists. Treatment options for panic disorder are considered, particularly the selective serotonin reuptake inhibitors, which are emerging as the first-line choice for the treatment of panic disorder.

Evaluation of severe insomnia in the general population: results of a European multinational survey

The epidemiology of severe insomnia and its effect on quality of life and healthcare consumption was assessed in a survey of the general population of five northern European countries. Applying established consumer sampling techniques, insomnia sufferers were selected from the general population using a questionnaire, conducted by face-to-face interview, and severity of insomnia was ranked (severe, mild/moderate, no sleep complaint) using a specific algorithm. Population samples were matched according to case control methodology for age, gender and geographical region. A second questionnaire gathered information on sleep problems, quality of life (SF-36 scores) and healthcare consumption. The prevalence of severe insomnia ranged from 4% to 22%, was higher in females than in males, but did not increase significantly with age. Patients with severe insomnia had been experiencing sleeping problems for a median of 2-6 years. In all countries, insomnia had a negative impact on quality of life, and the degree of impairment in quality of life was directly related to the severity of insomnia. Individuals with severe insomnia also showed a higher level of healthcare consumption. Despite this, severe insomnia did not appear to feature prominently in the doctor-patient relationship.

Isolation of RP-HPLC pure clonidine-displacing substance from NG108-15 cells

A crude extract of clonidine-displacing substance (CDS) has previously been extracted from the NG108-15 cell line. This study aimed to purify CDS extracted from this cell line further, by the technique of reverse phase-HPLC (RP-HPLC), and subsequently determine whether this refined CDS bears any similarity to CDS's extracted from other tissues. Crude CDS was extracted from NG108-cells and fractionated by RP-HPLC eluting with a linear gradient of methanol (5-65%; 1 ml min(-1) flow rate) over 50 min., and collected at 1 min. intervals. The pharmacological activities of the CDS fractions were determined by their abilities to displace bound [3H]clonidine to alpha(2)-adrenoceptors in rat brain membranes. RP-HPLC analysis of CDS revealed a pharmacologically active fraction distinct from agmatine, eluting at 24 min, corresponding to an absorbance peak observed at this time. Collectively, these results confirmed that CDS was present in the NG108-15 cell line. However, the RP-HPLC analysis showed the pharmacological activity to elute at a more hydrophobic gradient than previously observed with CDS's extracted from bovine tissues. These results support the notion of the existence of several CDS's.

In vitro and in vivo approaches to the characterization of the alpha2-adrenoceptor

1. In order to more fully understand the role of the alpha2-adrenoceptor in brain function, a combination of in vitro and in vivo techniques were utilized including radioligand binding, autoradiography, brain microdialysis and antisense oligonucleotides. 2. Binding studies showed the tritiated form of the selective alpha2-adrenoceptor antagonist, RX821002 (methoxy-idazoxan) labelled an apparent single population of sites in rat brain membranes with high affinity (1 nM), for which prazosin had low affinity (1107 nM). Similar studies in rabbit brain membranes found that prazosin and oxymetazoline were able to displace [3H]-RX821002 in a biphasic manner indicating the presence of subtypes of alpha2-adrenoceptors. 3. Receptor autoradiography revealed a distribution of [3H]-RX821002 binding in rat brain consistent with the labelling of all alpha2-adrenoceptor subtypes, namely alpha(2A/D-), alpha2B and alpha2C. 4. In rat, in vivo brain dialysis experiments demonstrated peripherally administered RX821002 elevated basal noradrenaline in frontal cortex and also, although to a lesser extent, in ventral hippocampus. RX821002 was also able to elevate extracellular dopamine in the striatum. 5. A 7-day i.c.v. infusion of an antisense oligonucleotide targeting the alpha(2A/D)-adrenoceptor, resulted in a significant reduction in the autoradiographic density of [3H]-RX821002 binding in specific brain areas, notably the lateral septal nuclei and anterior hypothalamic area. 6. Several years of research by our group has extended our knowledge of the pharmacology and function of the alpha2-adrenoceptor and has provided evidence of the roles of this receptor in the control of monoamine turnover. The successful use of antisense technology to knockdown expression of the alpha(2A/D) subtype provides future opportunities to explore the physiology of this receptor subtype.