Clonazepam induces decreased serotoninergic activity in the mouse brain

Longitudinal cytokine and multi-modal health data of an extremely severe ME/CFS patient with HSD reveals insights into immunopathology, and disease severity

Introduction

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) presents substantial challenges in patient care due to its intricate multisystem nature, comorbidities, and global prevalence. The heterogeneity among patient populations, coupled with the absence of FDA-approved diagnostics and therapeutics, further complicates research into disease etiology and patient managment. Integrating longitudinal multi-omics data with clinical, health,textual, pharmaceutical, and nutraceutical data offers a promising avenue to address these complexities, aiding in the identification of underlying causes and providing insights into effective therapeutics and diagnostic strategies.

Methods

This study focused on an exceptionally severe ME/CFS patient with hypermobility spectrum disorder (HSD) during a period of marginal symptom improvements. Longitudinal cytokine profiling was conducted alongside the collection of extensive multi-modal health data to explore the dynamic nature of symptoms, severity, triggers, and modifying factors. Additionally, an updated severity assessment platform and two applications, ME-CFSTrackerApp and LexiTime, were introduced to facilitate real-time symptom tracking and enhance patient-physician/researcher communication, and evaluate response to medical intervention.

Results

Longitudinal cytokine profiling revealed the significance of Th2-type cytokines and highlighted synergistic activities between mast cells and eosinophils, skewing Th1 toward Th2 immune responses in ME/CFS pathogenesis, particularly in cognitive impairment and sensorial intolerance. This suggests a potentially shared underlying mechanism with major ME/CFS comorbidities such as HSD, Mast cell activation syndrome, postural orthostatic tachycardia syndrome (POTS), and small fiber neuropathy. Additionally, the data identified potential roles of BCL6 and TP53 pathways in ME/CFS etiology and emphasized the importance of investigating adverse reactions to medication and supplements and drug interactions in ME/CFS severity and progression.

Discussion

Our study advocates for the integration of longitudinal multi-omics with multi-modal health data and artificial intelligence (AI) techniques to better understand ME/CFS and its major comorbidities. These findings highlight the significance of dysregulated Th2-type cytokines in patient stratification and precision medicine strategies. Additionally, our results suggest exploring the use of low-dose drugs with partial agonist activity as a potential avenue for ME/CFS treatment. This comprehensive approach emphasizes the importance of adopting a patient-centered care approach to improve ME/CFS healthcare management, disease severity assessment, and personalized medicine. Overall, these findings contribute to our understanding of ME/CFS and offer avenues for future research and clinical practice.

The role of the serotonergic and GABA system in translational approaches in drug discovery for anxiety disorders

There is ample evidence that genetic factors play an important role in anxiety disorders. In support, human genome-wide association studies have implicated several novel candidate genes. However, illumination of such genetic factors involved in anxiety disorders has not resulted in novel drugs over the past decades. A complicating factor is the heterogeneous classification of anxiety disorders in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) and diverging operationalization of anxiety used in preclinical and clinical studies. Currently, there is an increasing focus on the gene × environment (G × E) interaction in anxiety as genes do not operate in isolation and environmental factors have been found to significantly contribute to the development of anxiety disorders in at-risk individuals. Nevertheless, extensive research on G × E mechanisms in anxiety has not resulted in major breakthroughs in drug discovery. Modification of individual genes in rodent models has enabled the specific study of anxiety in preclinical studies. In this context, two extensively studied neurotransmitters involved in anxiety are the gamma-aminobutyric acid (GABA) and 5-HT (5-hydroxytryptamine) system. In this review, we illustrate the complex interplay between genes and environment in anxiety processes by reviewing preclinical and clinical studies on the serotonin transporter (5-HTT), 5-HT1A receptor, 5-HT2 receptor, and GABAA receptor. Even though targets from the serotonin and GABA system have yielded drugs with known anxiolytic efficacy, the relation between the genetic background of these targets and anxiety symptoms and development of anxiety disorders is largely unknown. The aim of this review is to show the vast complexity of genetic and environmental factors in anxiety disorders. In light of the difficulty with which common genetic variants are identified in anxiety disorders, animal models with translational validity may aid in elucidating the neurobiological background of these genes and their possible role in anxiety. We argue that, in addition to human genetic studies, translational models are essential to map anxiety-related genes and to enhance our understanding of anxiety disorders in order to develop potentially novel treatment strategies.

5-HT1A receptor blockade reverses GABA(A) receptor alpha3 subunit-mediated anxiolytic effects on stress-induced hyperthermia

RATIONALE

Stress-related disorders are associated with dysfunction of both serotonergic and GABAergic pathways, and clinically effective anxiolytics act via both neurotransmitter systems. As there is evidence that the GABA(A) and the serotonin receptor system interact, a serotonergic component in the anxiolytic actions of benzodiazepines could be present.

OBJECTIVES

The main aim of the present study was to investigate whether the anxiolytic effects of (non-)selective alpha subunit GABA(A) receptor agonists could be reversed with 5-HT(1A) receptor blockade using the stress-induced hyperthermia (SIH) paradigm.

RESULTS

The 5-HT(1A) receptor antagonist WAY-100635 (0.1-1 mg/kg) reversed the SIH-reducing effects of the non-alpha-subunit selective GABA(A) receptor agonist diazepam (1-4 mg/kg) and the GABA(A) receptor alpha(3)-subunit selective agonist TP003 (1 mg/kg), whereas WAY-100635 alone was without effect on the SIH response or basal body temperature. At the same time, co-administration of WAY-100635 with diazepam or TP003 reduced basal body temperature. WAY-100635 did not affect the SIH response when combined with the preferential alpha(1)-subunit GABA(A) receptor agonist zolpidem (10 mg/kg), although zolpidem markedly reduced basal body temperature.

CONCLUSIONS

The present study suggests an interaction between GABA(A) receptor alpha-subunits and 5-HT(1A) receptor activation in the SIH response. Specifically, our data indicate that benzodiazepines affect serotonergic signaling via GABA(A) receptor alpha(3)-subunits. Further understanding of the interactions between the GABA(A) and serotonin system in reaction to stress may be valuable in the search for novel anxiolytic drugs.

A double-blind, placebo-controlled trial of clonazepam in obsessive-compulsive disorder

Selective serotonin reuptake inhibitors (SSRIs) are currently the first-line pharmacological agents in treating obsessive-compulsive disorder (OCD). Appropriate treatment for OCD also involves cognitive behavioural therapy (CBT), including exposure and response prevention. As there is a time delay in seeing full therapeutic response, and not all patients tolerate SSRIs, there remains an unmet need for additional treatment approaches in OCD. In addition, most responders report only a partial reduction in symptoms. Clonazepam has demonstrated effectiveness in several preliminary reports in treating OCD. Twenty-seven patients with OCD were entered into a 10 week, double-blind, parallel design trial of clonazepam vs. placebo. Overall, only 3 out of 25 patients who had >/= 1 rating on clonazepam/placebo were judged to be treatment responders, by scoring a 1 (very much improved) or 2 (much improved) on the CGI improvement scale. Responders included 2 of 9 in the placebo group and 1 of 16 in the clonazepam group. No significant difference was found between clonazepam and placebo groups on responder/non responder status (Chi(2 )=1.39, df =1,24, p=0.238), nor on change in YBOCS, Ham-A, Ham-D or NIMH scales from beginning to last evaluation carried forward. These findings suggest that clonazepam is not effective as monotherapy in treating OCD. Its effectiveness in specific subgroups of OCD patients with co-morbid anxiety disorders or as an augmentation strategy added to SSRIs remains to be determined.

Modification of the anxiolytic action of 5-HT1A compounds by GABA-benzodiazepine agents in rats

The general purpose of the present study was to analyze the possible interactions between the GABA benzodiazepine and the serotonin systems in the mediation of the antianxiety actions of 5-HT1A compounds. The anxiolytic effect of buspirone (5 mg/kg), ipsapirone (5 mg/kg), indorenate (5 mg/kg), and 8-OH-DPAT (0.5 mg/kg) was established in the rat burying behavior test. Flumazenil (5 mg/kg), but not bicuculline (2.5 mg/kg), effectively counteracted the reduction in burying behavior produced by buspirone, ipsapirone, and 8-OH-DPAT. These same 5-HT1A compounds, at subthreshold doses, produced an important reduction in burying behavior when combined with diazepam (0.25 mg/kg). The effect of indorenate was not altered by any of the antagonists and, when combined with diazepam it produced large increases in burying behavior latency. Only buspirone alone and in combination with bicuculline or flumazenil impaired motor coordination as tested in the rota rod. Data are discussed on the bases of the interaction between the GABAergic and serotonergic systems, stressing species differences and variations due to the animal model of anxiety.

Regionally specific effects of diazepam on brain serotonin metabolism in rats: sustained effects following repeated administration

The effects of single (1mg/kg) and repeated (1mg/kg 2* daily for 4 days) diazepam administration are investigated on brain regional 5-hydroxytryptamine (5-HT; serotonin) and 5-hydroxy indoleacetic acid (5-HIAA) concentration in rats. Daily treatment decreased food intakes but body weights did not decrease. Administration of diazepam (1mg/kg) to 4 day saline injected rats on the 5th day decreased 5-HT levels in the hippocampus and increased it in the hypothalamus. 5-HIAA levels were increased in the striatum and decreased in the hypothalamus 4 day diazepam injected rats injected with saline on the 5th day also exhibited similar changes of 5-HT and 5-HIAA. Cortical levels of 5-HIAA were also smaller in these rats. Administration of diazepam to 4 day diazepam injected rats again decreased 5-HT in the hippocampus and 5-HIAA in the hypothalamus. 5-HT and 5-HIAA were both decreased in the striatum. Regionally specific effects of diazepam on brain serotonin metabolism are discussed in relation to their possible functions.

Serotonin turnover rate, [3H]paroxetine binding sites, and 5-HT1A receptors in the hippocampus of rats subchronically treated with clonazepam

Selective central benzodiazepine agonists, such as clonazepam, are known to modify serotonin and 5-hydroxyindoleacetic content in the brain. In order to further study the effect of this benzodiazepine on serotonin turnover rate, rats received clonazepam, 10 mg/kg for 10 days, and the concentrations of serotonin and 5-hydroxyindoleacetic acid were determined in the hippocampus after inhibition of monoamineoxidase with pargyline. The results indicate a reduction in the turnover rate of the monoamine. In addition, the systemic administration of clonazepam produced a decrease in the Bmax of [3H]DPAT binding to 5-HT1A sites in the hippocampus. By contrast, this effect was not observed if clonazepam was delivered into the dorsal raphe nucleus by osmotic minipumps. The binding of [3H]paroxetine to 5-HT reuptake sites was increased by the treatment with clonazepam. The present observations indicate that clonazepam produces a reduction of serotonin turnover rate in the hippocampus of the rat concomitant with a down-regulation of 5-HT1A binding sites, probably by an effect at the forebrain projections. There is also an up-regulation of the serotonin transporter, which might contribute to a reduction in the synaptic availability of serotonin during clonazepam treatment.

Biological characterization of social phobia

As social phobia has become clinically more clearly characterized, the search for biologic features of the disorder has been instituted. As with most psychiatric disorders, this undertaking is difficult, because of the heterogeneity of the disorder in affected individuals. However, with investigation into several different areas, i.e., the neuroendocrine system, neurotransmitter function via naturalistic challenges, chemical and pharmacologic probes, response to pharmacologic interventions, and neuroimaging, theories about the biologic characteristics of social phobia have been advanced. Neuroendocrine studies have not yet revealed any clear abnormalities specific to individuals with social phobia. Based on studies of neurotransmitter functions and pharmacologic response, the major neurotransmitter systems that have been implicated are the serotonergic, dopaminergic, and noradrenergic. Neuroimaging studies have demonstrated possible structural and metabolic differences in some patients with social phobia.

The 5-HT2 receptor antagonist ketanserine prevents electroconvulsive shock- and clonidine-induced amnesia

The 5-HT2-selective antagonist ketanserine was examined for its ability to prevent electroconvulsive shock (ECS)- or clonidine-induced performance deficit in the passive avoidance situation (step-down) in rats. The posttrain intraperitoneal injection of ketanserine at doses of 3 and 10 mg/kg prevented the ECS- or clonidine-provoked amnesia upon retention tests given 3 h, 24 h, and 7 days after training. The present data favor the view that the selective modification of 5-HT2 receptors after training can prevent the performance deficit in step-down-trained rats and suggest a role of the 5-HTergic neurotransmitter system in memory. The results of this study further suggest that 5-HTergic receptor antagonists might be useful in treatment of cognitive disorders.

Modulation of 5HT1A receptors in the hippocampus and the raphe area of rats treated with clonazepam

1. Clonazepam is one of the most potent benzodiazepines known to decrease the activity of the central serotonergic systems. The acute and subchronic administration of clonazepam reduced serotonin (5HT) turnover rate in the hippocampus of the rat, as determined by the ratio of the monoamine and its metabolite, 5-hydroxyindoleacetic acid. 2. The modulation of 5HT binding sites and 5HT1A receptors by the administration of clonazepam for various periods of time were studied in the hippocampus and the raphe area by experiments with radioligands. 3. The density of [3H]5HT recognition sites increased in the hippocampus of clonazepam-treated rats in a dose- and time-dependent manner. This increase was impaired by the simultaneous administration of the 5HT agonist 5-methoxy-N,N-dimethyltryptamine. The affinity of this binding did not significantly change. This observation might indicate an increase in some of the 5HT receptors or an increase of the uptake site. 4. The binding parameters for [3H]DPAT, Bmax and Kd, decreased in the hippocampus but not in the raphe area of clonazepam-treated rats. It seems that the presynaptic reduction in 5HT function, resulting in the decrease of its availability at the synaptic space, modifies the corresponding 5HT recognition sites. 5. These changes could be related to the anxyolitic activity or the withdrawal symptoms of benzodiazepines.

Interaction of GABA and serotonin in the anxiolytic action of diazepam and serotonergic anxiolytics

The general purpose of the present study was to analyze the possible interactions between the GABA-benzodiazepine and the serotonergic (5-HT) systems in the anxiolytic action of diazepam and the 5-HT1A agonists, ipsapirone, indorenate, and 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). The effect of the benzodiazepine receptor antagonist, flumazenil (10.0 mg/kg), on the anxiolytic action of ipsapirone (5.0 mg/kg), indorenate (5.0 mg/kg), and 8-OH-DPAT (0.125 mg/kg) was examined on the avoidance exploratory behavior paradigm in mice. The effect of the 5-HT1 blockers, methiotepin (0.31 mg/kg), pindolol (3.1 mg/kg), and alprenolol (5.0 mg/kg), on the anxiolytic action of diazepam (0.5 mg/kg) was also studied. In the last part of this work, the putative potentiation between diazepam (0.25 mg/kg) and each of the serotonergic anxiolytics was investigated. The antianxiety effect of diazepam, ipsapirone, indorenate, and 8-OH-DPAT was prevented by flumazenil. The serotonergic/beta-blocker, alprenolol, partially antagonized the diazepam effect. Finally, a potentiation of suboptimal doses of diazepam and ipsapirone, but not with indorenate or 8-OH-DPAT, was observed. The findings suggest an interaction between both systems on the anxiolytic action of diazepam and the 5-HT1A agonists.

The neuroanatomical basis of anxiety

This review details the neural systems that are important in anxiety-related behaviours. In particular, the role of the amygdaloid complex, Papez circuit, septohippocampal formation and raphe nuclei are described and discussed. Evidence is gathered from a variety of experimental approaches. These include behavioural assessment of anxiety in animals after intracerebral injection of pharmacological agents and following lesions of discrete brain nuclei and selective neurotransmitter pathways. Further evidence is provided by functional brain mapping studies applied to animals and humans. It is proposed that the neural systems recruited in different experimental conditions of anxiety may differ, supporting the notion that clinical anxiety exists in several forms. This has implications for the identification of new anxiolytic treatments. In particular, the findings suggest that approaches aimed at identifying new anxiolytic agents must take into account both the distribution of receptors for the drug and the neuronal systems activated by the experimental protocol.

Region-selective reduction of brain serotonin turnover rate and serotonin agonist-induced behavior in mice treated with clonazepam

Evidence supports a complex interaction between benzodiazepines and the central serotonergic system. This study attempts to correlate biochemical changes in the serotonin (5HT) system induced by clonazepam (CLON) with the behavioural response to a 5HT agonist. The acute administration of CLON to mice produced a time-dependent decrease in 5HT turnover rate in the raphe area (dorsal and medial raphe nuclei) and modified the serotonergic syndrome induced by 5-methoxy-N,N,-dimethyltryptamine (DMT). One hour after CLON administration, a dose-dependent increase in 5HT concentration was found in the raphe area, while 5-hydroxyindoleacetic acid (5HIAA) levels remained stable, leading to an increase in 5HT/5HIAA ratio, indicative of reduced 5HT turnover rate. No significant changes were detected in the frontal cortex of CLON-treated mice. After 4 days of CLON treatment, the 5HT turnover rate was still decreased in the raphe area and unchanged in the frontal cortex. Acute CLON administration produced dose-dependent alterations in locomotor activity, not observed after subchronic administration. Lateral head weaving, a motor manifestation of the serotonergic syndrome produced by DMT, was less intense in CLON-treated animals. The modifications in the 5HT system induced by CLON are region selective, suggesting differences in the receptors implicated in the interaction. Altered synaptic availability of 5HT as a result of CLON administration may be responsible for the differential response to DMT in control and CLON-treated mice.

Interaction of cholecystokinin and diazepam: effects on brain monoamines

An antagonism between cholecystokinin (CCK) peptides and benzodiazepines (BZD) has been described in various paradigms. We sought to determine whether CCK and BZD are also antagonistic in their effects on brain neurotransmitter levels in the rat. No effect on the noradrenergic system was induced in any brain area by CCK 8 S and diazepam alone or in combination. Administered alone, sulfated CCK octapeptide (CCK 8 S) (5 micrograms/kg ip) and diazepam (5 mg/kg ip) were found to decrease DOPAC levels in the cortex and to induce 5-hydroxy-tryptamine accumulation in the hippocampus. When administered together, these variations were no longer observed. However, a slight tendency by each substance to decrease 3-methoxy-tyramine levels in the striatum, became significant when given in association. The differences in CCK-BZD interactions observed in the striatum, cortex and hippocampus suggest that different mechanisms of action are involved. The addition of the effects occurring in the striatum might involve a GABA-ergic mechanism.

Brain benzodiazepine receptors in fathead minnows and the behavioral response to alarm pheromone

Fathead minnows (Pimephales promelas) exposed to 1 or 10 mg/l chlordiazepoxide showed normal alarm behavior during the presentation of alarm pheromone. Fish exposed to 20 mg/l drug, however, showed little or no behavioral alarm and did not appear sedated. A food extract stimulus presented after alarm pheromone led to a large foraging response by fish exposed to 20 mg/l chlordiazepoxide. Control fish or fish exposed to 1 to 10 mg/l drug showed less tendency to begin foraging. Exposure to 1, 10, or 20 mg/l chlordiazepoxide for 3 hr did not affect whole-brain concentrations of tryptophan, 5-hydroxytryptamine, 5-hydroxyindoleacetic acid, tyrosine, or dopamine. The binding of [3H]diazepam to specific brain receptor sites (KD = 10 nM, estimated Bmax = 3.3 fmol/mg wet weight) could be displaced by chlordiazepoxide (IC50 = 1.6 microM). These results suggest that benzodiazepine receptors in the central nervous system of lower vertebrates may function in ways similar to those in mammals, i.e., in the modulation of behavior in anxiety-like states.

Milacemide increases 5-hydroxytryptamine and dopamine levels in rat brain--possible mechanisms of milacemide antimyoclonic property in the p,p'-DDT-induced myoclonus

Milacemide, a glycine prodrug that is able to enter the brain readily, has been shown to have an antimyoclonic property in the p,p'-DDT-induced myoclonus syndrome. Milacemide increased regional 5-HT and dopamine and decreased 5-HIAA, DOPAC and HVA levels in naive rats. In p,p'-DDT-treated rats, 5-HT levels were unchanged at the time the rats experienced spontaneous myoclonus in all brain regions except in the striatum, where it increased. 5-HIAA levels increased but did not reach significant levels except in the striatum. Dopamine, DOPAC, HVA and norepinephrine were unchanged. When rats were treated concurrently with both p,p'-DDT and milacemide, regional 5-HT levels were increased and NE levels in the brainstem and cerebellum decreased. Depletion of brain serotonin by pretreatment with PCPA or with 5,7-DHT, or blocking 5-HT receptors with different 5-HT antagonists, failed to eliminate the antimyoclonic property of milacemide. This antimyoclonic effect of milacemide may be mediated through other mechanisms besides its ability to increase brain 5-HT levels. Possible mechanisms to be considered are its antiepileptic property, and its ability to increase brain glycine levels. Milacemide may have potential for therapeutic trials in patients with myoclonus.

The effects of diazepam on brain 5-HT and 5-HIAA in stressed and unstressed rats

Diazepam, administered to rats at a high dose (25 mg/kg PO) has been shown to have no effect on the plasma corticosterone response to the stress of an elevated open platform. It did however, reduce the plasma corticosterone in rats repeatedly exposed to the apparatus. Diazepam-withdrawal from stress-habituated rats increased plasma corticosterone (p less than 0.01) whereas withdrawal of diazepam from unstressed rats had no effect on plasma corticosterone. It is concluded that this effect of diazepam-withdrawal may reflect the development of dependence upon the drug. Significant effects were not observed following the administration of a lower non-selective dose (5 mg/kg PO) of diazepam and, therefore, it is not clear whether dependence to its sedative, rather than the anxiolytic properties have been measured. Acute diazepam (25 mg/kg) increased (p less than 0.05) hippocampal 5-hydroxyindoleacetic acid; its withdrawal from unstressed rats after 40 days reduced (p less than 0.01) hypothalamic 5-hydroxytryptamine. There was no evidence that the effects of diazepam or its withdrawal on plasma corticosterone in stressed rats were associated directly with changes in brain 5-hydroxyindoles.

Neurotransmitters, anxiety and benzodiazepines: a behavioral review

The possible involvement of serotonin, GABA and opioid peptides in anxiety and in the mechanism of action of benzodiazepine tranquilizers have recently been the subjects of intensive biochemical, neurophysiological and behavioral research. The present review examines the behavioral evidence, viewing anxiety and benzodiazepine action as far as possible separately. Four behavioral paradigms of experimental anxiety or "conflict behaviors" are described and assessed for soundness with some practical considerations. The functional significance and pharmacology of benzodiazepine receptors are discussed, and the cases for a number of putative endogenous ligands are examined. Conflict behavior is attenuated by drugs which reduce functional serotonin activity and enhanced by serotonin agonists, but there is little evidence to implicate serotonin in benzodiazepine action. GABA antagonists both intensify conflict and reduce benzodiazepine effects, but evidence of the reverse effects with GABA agonists is more equivocal. The interpretation of behavioral effects of opiate agonists and antagonists and their interactions with benzodiazepines is hindered by their actions on motivational systems other than anxiety, and evidence for an important role of opioid peptides is only suggestive. Some promising lines for future research are indicated.

Chlordiazepoxide and tonic immobility: a paradoxical enhancement

Four experiments were conducted with chickens to examine the effects of chlordiazepoxide on tonic immobility, which has been implicated as an innate fear response. Not only did chlordiazepoxide produce a paradoxical dose-dependent increase in the duration of tonic immobility, but birds treated with chlordiazepoxide showed significantly enhanced shock-termination thresholds. Using two separate tolerance paradigms, the enhancement due to chlordiazepoxide was shown to be independent of the sedative and/or muscle relaxant effects of the drug. These findings have interesting implications for the supposed anxiolytic effects of the benzodiazepines and the relationship between fear and serotonin in avian species.

5-HT and anxiety: promises and pitfalls

This review examines the evidence implicating serotonergic systems in the control of anxiety. The effects of manipulations of 5-HT, including 5-HT lesions, pharmacological reduction and enhancement of serotonergic function in animal tests of anxiety are reviewed. Biochemical and behavioral evidence implicating serotonergic pathways in the anxiolytic action of benzodiazepines is presented. In each section the promises of a serotonergic involvement, as indicated by positive findings, and the pitfalls, evidenced by inconsistent and conflicting results, are discussed. Finally the dangers of a superficial interpretation of the behavioral and biochemical findings is stressed.

Are serotonergic neurons involved in the control of anxiety and in the anxiolytic activity of benzodiazepines?

Several studies have shown that, like benzodiazepines (BZP), treatments able to reduce or block the activity of CNS serotonergic (5-HT) neurons released punished behavior. Therefore, 5-HT mechanisms have been tentatively implicated in the anti-punishment (anxiolytic?) activity of BZP. Numerous data, however, are not in keeping with this hypothesis. Since not responding enables the animals to avoid punishment but also delays the receipt of food-reward, one of these factors could be an alteration of waiting capacities. Indeed, we have shown that diazepam released behavioral suppression in conflict schedules only when the duration of the punished periods exceeded 1 minute. Moreover, in rats allowed to choose in a T-maze between immediate-but-small vs. delayed-but-large reward, BZP significantly decreased the frequency with which the delayed reward was chosen, with 5-HT uptake blockers producing opposite effects. Therefore, one can hypothesize that BZP render the animals less prone than controls to tolerate delay of reward and that 5-HT mechanisms may be involved in this phenomenon. An altered tolerance to delay of reward should be taken into account when interpreting the BZP-induced release of behavioral inhibition in classical conflict procedures.

Clonazepam-induced up-regulation of serotonin1 binding sites in frontal cortex of rat

Chronic administration of the benzodiazepine, clonazepam, increased the number of [3H]5-hydroxytryptamine (5-HT1) binding sites in the frontal cortex of the rat. The increase reflected a change in the maximum density of binding sites (Bmax) with no change in ligand affinity (Kd). Increased binding occurred after continued exposure (10 days) to large (5.0 mg/kg) doses of clonazepam. The changes in [3H]5-HT binding were regional in that they occurred in membranes from the frontal cortex but not the brainstem. The effects were also at least partially selective for 5-HT receptors since the binding of the beta-adrenergic radioligand, [3H]dihydroalprenolol, was not affected by clonazepam. A second benzodiazepine, diazepam, did not affect the binding of [3H]5-HT at doses of 30 mg/kg per day. The latter data suggest that the effects of benzodiazepines on serotonin 5-HT1 receptors are unique to clonazepam.

Chlordiazepoxide, go-nogo successive discrimination and brain biogenic amines in cats

Chlordiazepoxide (CDP; 0.4 mg/kg/day, per os) was administered to cats during either the acquisition (CDP 21-22 days) of a go-nogo successive discrimination task (SD) or the performance (CDP 10 days) of the previously learned SD task. Endogenous levels of serotonin, 5-hydroxyindoleacetic acid, noradrenaline and dopamine were assayed in 12 brain areas, in trained as well as in untrained cats. This study has shown that (1) CDP strongly impaired the acquisition but not performance of the SD task, revealing a dissociation of the effects of CDP on these two stages of training; (2) the CDP administration, as well as the SD training, produced regional changes in brain levels of biogenic amines, suggesting the involvement of particular monoaminergic neurons in the behavioral effects of CDP and in operant behavior; and (3) in particular brain areas, interactions were observed between the effects of the SD training and those of the CDP administration on monoamines, indicating that the behavioral state may interfere with the neurochemical effects of CDP.

Tryptamine-induced myoclonus in guinea-pigs pretreated with a monoamine oxidase inhibitor indicates pre- and post-synaptic actions of tryptamine upon central indoleamine systems

Tryptamine (1-320 mg/kg) evoked only slight muscle jerking in naive guinea-pigs but, in animals pretreated with pargyline (75 mg/kg; 1 hr previously), tryptamine induced a dose-dependent (6-160 mg/kg) myoclonus. The myoclonus induced by tryptamine (40 mg/kg) plus pargyline (75 mg/kg) was differentially inhibited by the indoleamine receptor antagonists, methergoline (5 mg/kg) which was more potent than methysergide (10 mg/kg), mianserin (10 mg/kg) which was more potent that cyproheptadine (10 mg/kg) and propranolol (20 mg/kg) which was more potent than cinanserin (10 mg/kg). This rank order of potency differed from that observed for the order of potency of these drugs in inhibiting the myoclonus induced by L-5-hydroxytryptophan (5HTP) plus carbidopa in guinea-pigs (Luscombe, Jenner and Marsden, Neuropharmacology, 1981), perhaps indicating involvement of pharmacologically distinct indoleamine receptors. Manipulation of presynaptic function of 5-hydroxytryptamine (5HT) by tryptophan hydroxylase inhibition with p-chlorophenylalanine to produce depletion of cerebral 5HT, or by an L-tryptophan load to elevate 5HT in brain, suggested that the functional integrity of serotonergic neurones is required for the expression of myoclonus induced by tryptamine plus pargyline. A range of blockers of 5HT re-uptake did not alter the jerking produced by tryptamine (40 mg/kg) in guinea pigs pretreated with pargyline (75 mg/kg; 1 hr previously), or the threshold myoclonus induced by a smaller dose of tryptamine (10 mg/kg; plus pargyline 75 mg/kg). It is suggested that myoclonus induced by tryptamine in guinea pigs pretreated with pargyline involves activation of post-synaptic indoleamine receptors by tryptamine by a mechanism which requires intact presynaptic function of 5HT.

Depletion in amygdaloid 5-hydroxytryptamine concentration and changes in social and aggressive behaviour

5,7-Dihydroxytryptamine (10 and 20 microgram) was microinjected bilaterally into the amygdaloid complex of rats and resulted in 55% and 80% depletion in 5-hydroxytryptamine concentration, respectively. The lesioned animals exhibited fewer dominance behaviours and submitted more often to an intruder into their home-cages than did the vehicle-injected controls. The lesioned rats were also more submissive than were the controls when they were intruding into another rat's territory. Only the higher dose of toxin altered social investigatory behaviour when this was measured in an arena in which neither rat had established territory. The lesioned rats displayed less social interaction and had reduced levels of motor activity. The results are compared with those of other studies in which there has been regional or general depletion of brain 5-hydroxytryptamine concentration.

Effect of dialysis on plasma and CSF tryptophan and CSF 5-hydroxyindoleacetic acid in advanced renal disease

Patients with uraemic encephalopathy were previously found to have low total tryptophan (bound plus free), but high free tryptophan concentrations in the plasma and high CSF tryptophan concentrations. The 5-hydroxytryptamine metabolite 5-hydroxyindoleacetic acid was also raised in the CSF. A study of the effect of dialysis treatment on these substances in chronic uraemic patients with and without dialysis dementia is described. After an episode of dialysis the patients without dialysis dementia showed increased plasma total tryptophan and decreased free tryptophan. These changes were associated with a decrease of plasma free fatty acid. The patients with dialysis dementia did not show changes in tryptophan, but plasma free fatty acid rose. CSF concentrations of 5-hydroxyindoleacetic acid fell moderately in both groups of patients on dialysis.