Altered 5-HT metabolism with clonazepam, diazepam and diphenylhydantoin

Clonazepam as a therapeutic adjunct to improve the management of depression: a brief review

Clonazepam, first used for seizure disorders, is now increasingly used to treat affective disorders. We summarize the use of clonazepam to improve the management of depression. Clonazepam is useful for treatment-resistant and/or protracted depression, as well as for acceleration of response to conventional antidepressants. Clonazepam is at this time recommended for use in combination with SSRIs (fluoxetine, fluvoxamine, sertraline) as an antidepressant, and should be used at a dosage of 2.5-6.0 mg/day. If clonazepam is effective, a response should be observed within 2-4 weeks. It is significantly more effective for unipolar than for bipolar depression. Low-dose, long-term treatment with clonazepam exhibits a prophylactic effect against recurrence of depression. Although the mechanism of action of clonazepam has not yet been established, some investigators have been suggested that it involves enhancement of anti-anxiety effects, anticonvulsant effects on subclinical epilepsy, increase in 5-HT/monoamine synthesis or decrease in 5-HT receptor sensitivity mediated through the GABA system, and regulate in GABA activity.

Post-traumatic stress disorder: a review of psychobiology and pharmacotherapy

OBJECTIVE

To review the literature on the psychobiology and pharmacotherapy of PTSD.

METHODS

Relevant studies were identified by literature searches (Pub-med, Web of Science) and through reference lists. The search was ended by May 2001.

RESULTS

There is evidence of involvement of opioid, glutamatergic, GABAergic, noradrenergic, serotonergic and neuroendocrine pathways in the pathophysiology of PTSD. Medications shown to be effective in double-blind placebo-controlled trials includes selective serotonin reuptake inhibitors, reversible and irreversible MAO-inhibitors, tricyclic antidepressants and the anticonvulsant lamotrigine. Still more agents appear promising in open-label trials.

CONCLUSION

The complexity of the psychobiology is reflected by the difficulties in treating the disorder. According to the present knowledge, suggestions for drug treatment of PTSD are made.

Clonazepam and sertraline: absence of drug interaction in a multiple-dose study

Thirteen subjects (seven men, six women) completed a placebo-controlled, randomized, double-blind, crossover study to determine whether an interaction occurs between clonazepam and sertraline. Ten days of once-daily doses of either clonazepam 1 mg and placebo (CZ + PL) or clonazepam 1 mg and sertraline 100 mg (CZ + SR) were administered; there was an 11-day washout period. Sertraline did not significantly affect the pharmacokinetics of clonazepam (p > 0.13). Clonazepam apparent oral clearance, volume of distribution, and half-life were 3.9 +/- 0.2 L/hr, 233 +/-11 L, and 40.5 +/- 0.3 hours, respectively. The kinetics of the inactive metabolite 7-aminoclonazepam were marginally affected by sertraline, with a 21% decrease in the elimination half-life (p = 0.03) relative to CZ + PL and no significant difference between treatments in area under the curve or metabolite ratio. Card sorting (CS), digit-symbol substitution test (DSST), nurse-rated sedation scale (NRSS), and self-rated sedation scores were assessed four times daily on days -1 (PL + PL), 1, 4, 7, and 10. There were no differences between treatments in area under the effect curve or maximum observed effect for CS, DSST, or NRSS. Maximum impairment on all assessment days was low, with a less than 10% change from the drug-free values for CS and DSST. Despite higher clonazepam concentrations, predose (time 0) psychomotor and sedation scores did not differ among days -1, 1, 4, 7, and 10 or between treatments. These results in healthy volunteers indicate that sertraline does not affect the pharmacokinetics or pharmacodynamics of clonazepam.

Clonazepam in the treatment of prolonged depression

BACKGROUND

The purpose of this paper was to examine the optimal adjunctive dose of clonazepam for the treatment of prolonged depression.

METHODS

Sixty nine patients with prolonged depression were enrolled in an open trial over a 4 week period during which clonazepam was added to their medication.

RESULTS

A daily dose of 3.0 mg clonazepam as augmentation was significantly more effective than doses of 1.5 mg and below. Most of the improved patients showed a rapid onset of action within 2 weeks, and side effects were not severe.

CONCLUSION

A daily dose of at least 3.0 mg clonazepam as augmentation of ongoing antidepressant treatment should be considered in prolonged depressive patients with suboptimal improvement.

LIMITATIONS

The effect on clonazepam alone on prolonged depression was not established, and its effect of on severe depression is unknown. High dose treatment was not carried out in this study.

Melatonin as a therapy in REM sleep behavior disorder patients: an open-labeled pilot study on the possible influence of melatonin on REM-sleep regulation

REM sleep behavior disorder (RBD) is clinically impressive by virtue of its vigorous sleep behaviors usually accompanying vivid, striking dreams. The main feature of the disorder, REM sleep without muscle atonia, has been shown in a variety of diseases; therefore, the disorder might possibly be underestimated. In an open-labeled trial, we treated six consecutive RBD patients over a 6-week period with 3 mg melatonin given within 30 minutes before bedtime. There was a dramatic clinical improvement in five of the six patients within a week which extended beyond the end of treatment for weeks or months. A second polysomnogram performed 6 weeks after the beginning of treatment showed a significant tendency toward normalization of the percentage of REM sleep, a significant reduction of 30-second epochs, scored as REM sleep without muscle atonia, a significant reduction of stage-shifts in REM, and a significant reduction in epochs considered as movement time in REM. All other sleep parameters were not changed consistently. We hypothesize that internal desynchrony might be a part of the underlying pathophysiology in RBD. Our data might give first evidence to the hypothesis that exogenous melatonin, administered to patients with internal desynchrony at the time of the maximal rise of melatonin secretion, might increase the overall amplitude of the circadian pacemaker by reentraining the suprachiasmatic nucleus and thereby restore circadian driven rhythms, one of them being the circadian modulation of REM sleep.

Pharmacologic treatment of tremor

Tremor is a common neurologic symptom that can also be incapacitating to the patient, so effective therapy is needed. The causes of tremor are heterogeneous. Essential tremor (ET) and the tremor associated with Parkinson's disease (PD) are the most common encountered in clinical practice. Beta-adrenergic blockers and primidone remain the mainstay of treatment for ET, whereas carbidopa/levodopa and anticholinergics are most beneficial in PD. However, the efficacy of various other medications has been studied in ET and PD, and also in patients with tremor resulting from other conditions, with varying results.

Clonazepam as a therapeutic adjunct to improve the management of psychiatric disorders

Clonazepam, which is a benzodiazepine structurally related to chlordiazepoxide hydrochloride, diazepam and nitrazepam, has been available for the treatment of seizure disorders in the USA since 1976 and in Japan since 1981. Increasingly, clonazepam has been used in the treatment of a variety of psychiatric disorders. Six representative case studies are presented and specific guidelines for the use of clonazepam are discussed.

The effect of chronic cyclodiene insecticide treatment on some pharmacological actions of diazepam in rats

The sedative and hypnotic effects of diazepam were tested in rats following chronic treatment with subconvulsive doses of the cyclodiene insecticides, endosulfan and aldrin. The anticonvulsant effect of diazepam was determined on picrotoxin-induced convulsions in insecticide-treated and control animals. Both endosulfan and aldrin promoted the convulsant action of picrotoxin indicating that the insecticides were able to show proconvulsant action following chronic administration. Interestingly, the protective effect of diazepam against picrotoxin-induced convulsions was greater in endosulfan- and aldrin-treated animals than in control animals. The sedative and hypnotic effects of diazepam were also increased in insecticide-treated animals. The mechanisms involved in the interaction were discussed with the support of the findings reported by the present and other investigators on the central and hepatic effects of chronic endosulfan and aldrin treatment.

Resolution of dysarthria in multiple sclerosis by treatment with weak electromagnetic fields

It has been reported that 50% or more of patients diagnosed with multiple sclerosis (MS) exhibit speech impairment (dysarthria) which in some cases can be exceedingly disabling. Currently there is no effective medical treatment for the dysarthria of MS which occurs as a result of lesions to the cerebellum and its outflow tracts. It was reported recently that extracranial application of brief AC pulsed electromagnetic fields (EMFs) in the picotesla (pT) range intensity produced in patients with MS sustained improvement in motor functions including cerebellar symptomatology. This communication concerns two MS patients with a chronic progressive course who exhibited severe dysarthria which improved already during the initial treatment with pulsed EMFs and which resolved completely 3-4 weeks later. Since application of EMFs has been shown to alter: (a) the resting membrane potential and synaptic neurotransmitter release through an effect involving changes in transmembrane calcium flux; and (b) the secretion of pineal melatonin which in turn influences the synthesis and release of serotonin (5-HT) and gamma-amino butyric acid (GABA) in the cerebellum, it is suggested that the immediate improvement of the dysarthria occurred as a result of changes in cerebellar neurotransmitter functions particularly 5-HT and GABA rather than from remyelination.

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.

Enhancement of acetylcholine release by flumazenil in the hippocampus of rats chronically treated with diazepam but not with imidazenil or abecarnil

The effects of long-term treatment (three times a day for 3 weeks) with pharmacologically active doses of the novel anxiolytics and anticovulsants abecarnil (0.5 mg/kg, IP) and imidazenil (0.5 mg/kg, IP) on basal hippocampal acetylcholine release in freely moving rats were compared with those of diazepam (3 mg/kg, IP). Challenge doses of diazepam, abecarnil, and imidazenil decreased the extracellular acetyl-choline concentration in the hippocampus by the same extent in animals chronically treated with the respective drug or vehicle. Moreover, the abrupt discontinuation of long-term treatment with diazepam, abecarnil, or imidazenil failed to affect hippocampal acetylcholine release during the first 5 days of withdrawal. In contrast, the acute administration of the benzodiazepine receptor antagonist flumazenil (1 mg/kg, IP) 2 days after diazepam withdrawal elicited a marked increase (65%) in acetylcholine release in the hippocampus. Flumazenil failed to induce the same effect 5 days after diazepam withdrawal or 2 or 5 days after discontinuation of long-term treatment with abecarnil or imidazenil. These results indicate that (i) the inhibitory effects of full (diazepam), partial (imidazenil), and selective (abecarnil) benzodiazepine receptor agonists on acetylcholine output in rat hippocampus are not affected by repeated drug administration; (ii) discontinuation of long-term treatment with each type of agonist does not affect hippocampal cholinergic mechanisms; and (iii) flumazenil increases acetylcholine release only in the hippocampus of rats chronically treated with diazepam. Together, these data further differentiate the pharmacology of benzodiazepine receptor full agonists from that of partial and selective agonists.

Weak electromagnetic fields attenuate tremor in multiple sclerosis

It has been estimated that about 75% of patients diagnosed with multiple sclerosis (MS) have tremor which can be exceedingly disabling. The most common tremor observed in patients with MS is a cerebellar intention tremor ('kinetic tremor') although postural tremor ('static tremor') is also common and often extremely incapacitating. Currently there is no effective medical treatment for the tremor of MS which, in some severe cases, may be abolished by stereotactic thalamotomy. It was reported recently that extracranial application of brief AC pulsed electromagnetic fields (EMFs) in the picotesla (pT) range produced improvement in motor and cognitive functions in patients with MS. The present communication concerns three MS patients with a chronic progressive course of the disease (mean age: 39.3 +/- 8.3 years; mean duration of illness: 11.3 +/- 3.2 years) in whom brief external applications of pulsed EMFs of 7.5 pT intensity reduced intention and postural tremors resulting in significant functional improvement. The report suggests that these extremely low intensity EMFs are beneficial also in the treatment of tremors in MS and that this treatment may serve as an alternative method to stereotactic thalamotomy in the management of tremor in MS. The mechanisms by which EMFs attenuate the tremors of MS are complex and are thought to involve augmentation of GABA and serotonin (5-HT) neurotransmission in the cerebellum and its outflow tracts.

Clomipramine and clonazepam increase cholecystokinin levels in rat ventral tegmental area and limbic regions

Recent reports suggest that a cholecystokinin (CCK)-related dysfunction may be a target by which drugs can modulate anxiety and panic disorders. In the present study, effects of subchronic (14 days) treatment with the monoamine uptake inhibitors nortriptyline (30 mumol/kg per day), amitriptyline (29 mumol/kg per day), clomipramine (32 mumol/kg per day) and alaproclate (39 mumol/kg per day), as well as with the benzodiazepine clonazepam (0.25 mumol/kg per day), on rat brain levels of CCK- and substance P-like immunoreactivity, were compared. The drugs were administered by continuous s.c. infusion using implanted osmotic pumps. The plasma concentrations of the monoamine uptake inhibitors were similar after 1 and 2 weeks of treatment, indicating that steady-state plasma levels had been reached during the first week. Treatment with clomipramine or clonazepam increased the CCK-like immunoreactivity level in the ventral tegmental area (by 64.4 +/- 28.8% and 105.1 +/- 28.8%, respectively) and in the cingulate cortex (by 30.3 +/- 10.1% and 36.0 +/- 11.8%, respectively) (P < 0.05 or P < 0.01). Clomipramine also significantly increased the CCK-like immunoreactivity level in the periaqueductal grey by 85.1 +/- 29.7%. Neither nortriptyline nor amitriptyline or alaproclate produced any significant alterations in the CCK- or substance P-like immunoreactivity levels in the areas examined. The present results may suggest that an altered utilization of CCK in limbic circuits could be of importance for the well documented clinical effect of clomipramine and clonazepam in panic 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.

From the jumping Frenchmen of Maine to post-traumatic stress disorder: the startle response in neuropsychiatry

The startle response is a universal and phylogenetically ancient reflex. Pathological exaggerations and modifications of startle underlie the symptomatology of a surprisingly diverse range of neuropsychiatric disorders, a fact that seems to have gone largely unappreciated. We review the available literature on the physiology of the normal human startle response and examine the neuropsychiatric conditions characterized by pathological startle. Startle epilepsy and primary hyperekplexia are considered as neurological disorders involving abnormal startle. Patients with hyperstartle and exotic culture-bound syndromes characterized by excessive startle are considered by the authors to represent extreme variants of the normal startle response. Post-traumatic stress disorder, drug and alcohol withdrawal states and schizophrenia all have abnormal startle as a clinical feature secondary to increased arousal and presumed disturbance of central neurotransmitter systems. The neurophysiological mechanisms by which abnormalities of the startle response may occur are discussed and a system of classification of neuropsychiatric hyperstartles is suggested.

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.

Monoamine turnover in the brain of mice during development of tolerance to the anticonvulsant effect of clonazepam

Mice were treated for 14 days with clonazepam, 0.5 mg/kg i.p. twice daily, during which time partial tolerance to the anticonvulsant effect against pentetrazole developed. The development of tolerance was paralleled by a reduced turnover of noradrenaline in the whole brain, and of dopamine in the midbrain. The turnover of 5-HT was increased during the first week of treatment, but decreased thereafter. These changes in monoamine turnover, which are thought to be GABA-mediated, are consistent with an increased seizure susceptibility, and may contribute to the development of tolerance to the anticonvulsant effect of benzodiazepines.

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.

Anticonvulsant activity of di-n-propylacetate and brain monoamine metabolism in the rat

1. Sodium di-n-propylacetate (DPA) treatment induced significant increases in brain contents of gamma-aminobutyric acid (GABA), 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA). Furthermore, the threshold for pentylenetetrazol (PTZ) clonic convulsions was also increased in response to DPA administration. 2. Pretreatment with inhibitors of monoamine synthesis alpha-methyl-p-tyrosine (AMPT) and p-chlorophenylalanine (PCPA) did not alter the anticonvulsant activity of DPA, but when given alone, both AMPT and PCPA caused significant decreases in brain monoamine contents and PTZ threshold seizures. 3. Experiments using probenecid suggest that the increases in 5-HIAA and HVA seen after DPA treatment could have resulted from inhibition of their active transport out of the brain. These data indicate that the anticonvulsant action of DPA is not dependent on changes in monoamine metabolism in the brain.

Biochemical pharmacology of Gilles de la Tourette's syndrome

A comprehensive brief review of Tourette's syndrome has been presented. This included description of various symptoms display, neuropathological findings, biochemical and pharmacological studies. An outline of pharmacotherapy and pharmacological properties of agents used in management of Tourette's syndrome has been made. They were classified according to their effect in modulating biogenic amine systems. Drugs producing exacerbation of Tourette's syndrome were also surveyed. Biochemical and pharmacological hypotheses relevant to the underlying pathology of the disease have been addressed and discussed.

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.

Brain neurotransmitters in dystonia musculorum deformans

We examined histologically and biochemically the brains of two patients with generalized childhood-onset dystonia musculorum deformans. We found no important histologic changes in the basal ganglia, cerebral cortex, higher brain-stem nuclei, locus ceruleus, or raphe nuclei. Similarly, the activity of choline acetyltransferase and the levels of gamma-aminobutyric acid and glutamic acid in the cerebral cortex and basal ganglia were within the control range. In contrast, the norepinephrine concentrations were markedly and consistently decreased in the lateral and posterior hypothalamus, mamillary body, subthalamic nucleus, and locus ceruleus. The serotonin level was subnormal in the dorsal raphe nucleus, as was the dopamine level in the nucleus accumbens and, in one of the two cases, in the striatum. Elevated concentrations of norepinephrine were found in the septum, thalamus, colliculi, red nucleus, and dorsal raphe nucleus; of serotonin, in the globus pallidus, subthalamic nucleus, and locus ceruleus; and of 5-hydroxyindoleacetic acid, in the globus pallidus, subthalamic nucleus, and nuclei raphe centralis inferior and obscurus. The level of homovanillic acid showed little consistent change in the regions examined. We conclude that some of these monoamine changes, especially the pronounced apparent disturbance of noradrenergic brain mechanisms, may represent a basic neurochemical abnormality in dystonia musculorum deformans and may thus be relevant to the pathoneurophysiology and treatment of this disorder.

A comparison between chlordiazepoxide and CL 218,872, a synthetic non-benzodiazepine ligand for benzodiazepine receptors, on serotonin and catecholamine turnover in brain

Serotonin (5-HT) and catecholamine (CA) turnover rates in midbrain-hindbrain were investigated in rats treated with the benzodiazepine chlordiazepoxide (CDP) or with the anxiolytic triazolopyridazine CL 218,872. A single injection of CDP (2.5-20 mg/kg) decreased 5-HT but not CA turnover rates. Seven daily CDP injections decreased the turnover rates of both 5-HT and CA. In contrast, neither acute nor chronic administration of CL 218,872 (2.5-20 mg/kg) altered baseline turnover rates of 5-HT or CA. Since CL 218,872 has a selective affinity for Type I benzodiazepine receptors, these results suggest that stimulation of Type I receptors is not sufficient to decrease 5-HT or CA turnover rates in midbrain-hindbrain. More importantly, these results question the long-held belief that benzodiazepines exert their anxiolytic and depressant effects through reductions in 5-HT and CA turnover respectively.

Non-benzodiazepine anxiolytics: potential activity of phenylpiperazines without 3H-diazepam displacing action

Four phenylpiperazine derivatives exhibited an activity similar to benzodiazepines and meprobamate in the 4-plate test. One of these (compound IV) demonstrated anxiolytic like activity in a step-down avoidance technique, in electroshock induced aggression and in the staircase test. In contrast to benzodiazepines, compound IV was not anticonvulsant, myorelaxant or sedative. Confirmation of the anxiolytic activity of compound IV in animal models was obtained in 3 separate clinical trials in anxious patients. The mechanism of action of these phenylpiperazines appears to be different from the benzodiazepines as they do not displace 3H-diazepam binding nor do they interact with other elements of the GABA receptor macromolecular complex. Instead, compound IV interacts with both dopaminergic and serotoninergic neuron systems. Thus, from this data it would appear that an activity at the benzodiazepine recognition site is not obligatory for anxiolytic activity in man or in animals models.

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.

Evidence for excitatory and depressant non-receptor-mediated membrane effects of benzodiazepines in the crayfish

Oxazepam produced a significant reversible monophasic concentration-dependent (50-500 mumol/l) depression of stretch-induced discharge frequency of the isolated crayfish sensory neuron. In total contrast, flurazepam (10-200 mumol/l) evoked reversible excitation of the neuronal firing rate but at concentrations greater than 300 mumol/l it induced transient excitation followed by secondary total depression. The benzodiazepine antagonist flumazepil (less than or equal to 1 mmol/l) also produced an inherent increase in neuronal discharge frequency, though respective concentrations of 50 and 100 mumol/l failed to block flurazepam-excitation or oxazepam-depression. It is suggested that these high concentration qualitatively divergent neuronal effects are not mediated through specific benzodiazepine receptors.

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.

Hyperekplexia: a syndrome of pathological startle responses

We describe a family and three sporadic cases of startle disease, or hyperekplexia. Sudden unexpected noises caused the patients to fall rigidly, often injuring themselves but retaining consciousness. This unusual entity differs from startle epilepsy and cataplexy. Clonazepam proved ineffective in three patients. Valproic acid, 5-hydroxytryptophan, or piracetam markedly reduced the abnormal startle in three patients.

Benzodiazepine inhibition of adenosine uptake is not prevented by benzodiazepine antagonists

Uptake of [3H]adenosine into rat cerebral cortex synaptosomes was studied. Hexobendine (10(-5) M) and the benzodiazepine agonists diazepam (10(-5) M) and flurazepam (10(-4) M) significantly inhibited this uptake, but only if the compounds were pre-incubated for 10 min in the case of the benzodiazepines. The benzodiazepine antagonists Ro15-1788 (10(-5) M) and CGS 8216 (10(-5) M) failed to reverse the action of benzodiazepine agonists or hexobendine on [3H]adenosine uptake. The results add weight to the view that inhibition of adenosine uptake processes by benzodiazepines do not contribute to their behavioural effects.

Raphe unit activity in freely moving cats: effects of benzodiazepines

Benzodiazepines (chlordiazepoxide and diazepam) produced a dose-dependent decrease in the discharge rate of serotonin-containing neurons in the dorsal raphe nucleus of freely moving cats. This ranged from no significant change at doses of 0.5 and 1.0 mg/kg (i.p.), to greater than 90% reductions in unit activity at 10 mg/kg. The effects of benzodiazepines on raphe units occurred within 15-30 min of injection and the duration of action was dose-dependent and lasted from 1 to more than 6 hr. Doses of benzodiazepines that significantly decreased raphe unit activity (i.e. 2.5-10 mg/kg) also produced ataxia and decreased EMG activity. These data suggest that benzodiazepine-induced suppression of raphe unit activity is closely related to general motor behavior. Raphe unit activity remained suppressed during phasic increases in EMG activity during eating, grooming, or predatory behavior, suggesting that benzodiazepines also have a direct inhibitory action on raphe cells. The present results are discussed in the context of the serotonergic hypothesis of anxiety.

Attenuation of induced-anxiety in rats by chlordiazepoxide: role of raphe dorsalis benzodiazepine binding sites and serotoninergic neurons

In chronically implanted awake rats, microinjections of chlordiazepoxide (5 x 10(-7) M) into the dorsal raphé significantly attenuated the inhibition of lever-pressing for food elicited by a signal of punishment. This effect is abolished by prior application of 5,7-dihydroxytryptamine into the dorsal raphé (3 weeks after the infusion of the neurotoxin, dorsal raphé tryptophan hydroxylase activity was reduced to 25% of control values). Furthermore, the disinhibitory effect of intra raphé chlordiazepoxide can be mimicked or potentiated by intra raphé dorsalis application of serotonin (10(-7) or 10(-8) M, respectively). Further evidence for a crucial interaction between benzodiazepines and serotoninergic processes are provided by in vitro experiments showing that chlordiazepoxide or diazepam (10(-5) M) are able to facilitate the K+-evoked [3H]serotonin release from rat midbrain slices. Finally, a high density of [3H]flunitrazepam binding sites was found in the dorsal (and the median) raphé nucleus, the Kd and Bmax values being not altered by prior infusion of 5,7-dihydroxytryptamine. These in vitro data suggest possible means by which intra raphé (and perhaps peripherally administered) benzodiazepines may affect the activity of serotoninergic neurons and thereby produce their effects on experimental anxiety.

Comparative studies of the effects of 5-hydroxytryptamine and noradrenaline on the rat anococcygeus muscle

The effects of 5-hydroxytryptamine (5HT) and noradrenaline (NA) have been studied on rat anococcygeus muscle. 1. 5HT and NA produced a dose-dependent contraction of rat anococcygeus muscle. Cyproheptadine (1.0 X 10(-6) M), a specific 5HT receptor blocker, failed to inhibit the responses to either 5HT or NA. 2. However, phentolamine, a specific alpha receptor antagonist competitively blocked the responses to 5HT and NA. 3. The responses to 5HT were inhibited in the reserpinized (5 mg/kg i.p. 24 h) and 6-hydroxydopamine (6-OHDA) pre-treated preparations. 6-OHDA produced a leftward shift of the dose-response curve of NA. Reserpine pre-treatment potentiated lower doses of NA and the threshold dose of NA was significantly decreased. 4. Nialamide (2.2 x 10(-6) M), the mono-amine oxidase inhibitor produced a significant leftward shift of the dose-response curve of both 5HT and NA. Pyrogallol (2.3 x 10(-5) M), the catechol-o-methyl transferase inhibitor also potentiated the responses to both 5HT and NA, but the potentiation was significant at lower doses of 5HT and NA. 5. Our data suggest that 5HT- and NA-induced contractions in rat anococcygeus muscle are mediated through common alpha adrenoceptors. 5HT actions are probably indirect, mediated through the release of NA.

An endogenous ligand to the benzodiazepine receptor: preliminary evaluation of its bioactivity

Chromatographic separation of aqueous brain extracts yields a peptide containing fraction which competitively inhibits 3H-diazepam binding to its receptor. An intracerebral-ventricular injection of this isolated fraction results in altered responses in pharmacological and behavioral tests which are similar to those observed when diazepam is administered in the same fashion. The most pronounced effect was obtained in the conflict test. Changes observed in other tests, such as blocking pentylenetetrazole convulsions, altering motility or reducing hyperthermia, were also consistent with the actions of diazepam. At the dose used, neither diazepam nor the brain extract altered muscular co-ordination in two ataxia evaluations. Thus, the animals' performance in the other paradigms would not be adversely influenced by immobilization side-effects. The results reported here support the notion that an endogenous factor does exist in brain which can act like the benzodiazepine drugs when tested for bioactivity in animal studies.

Postanoxic myoclonus. Treatment of a case with 5-hydroxytryptophane and a decarboxylase inhibitor

Postanoxic myoclonus was first accepted as being related to a dysfunction of the ventrolateral thalamic nucleus. Several stereotaxic studies have invalidated this hypothesis. The neurochemical approach, in particular the measure of 5-hydroxyindolacetic acid in the cerebrospinal fluid, has opened new theoretical and therapeutic possibilities involving serotoninergic pathways. A typical case is presented who improved markedly under a combined therapy with 5-hydroxytryptophan and a decarboxylase inhibitor. A review of the pathogenesis and therapeutic approach to postanoxic myoclonus is presented.

Effect of prenatal phenytoin administration on brain tryptophan metabolism of rat offspring during the preweaning period

Serum 5-hydroxytryptamine (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) concentrations in control rat offspring increased progressively during the preweaning period reaching adult values by day 21. It has been shown the prenatal phenytoin administration (100 mg kg-1 orally, days 7-19 of pregnancy) increased serum tryptophan and brain tryptophan, 5-HT and 5-HIAA of rat offspring at 3 days of age but not at 4, 15 or 21 days of age. The effect of prenatal phenytoin administration on the offspring at 3 days of age was not observed when these pups were cross-fostered to control mothers at 2 days of age suggesting that the alteration in rain tryptophan metabolism during the development of tryptaminergic neurons in rat offspring, as a result of prenatal phenytoin administration is mediated through changes in lactation or nursing ability of the mothers. It is important that such non-specific factors are controlled when studying the effect of prenatally administered drugs on neonatal brain transmitter concentrations.

Transient effect of L-tryptophan in progressive myoclonus epilepsy without Lafora bodies: clinical and electrophysiological study

A double-blind crossover trial with 2 g L-tryptophan and placebo was carried out with five familial and two sporadic patients with progressive myoclonus epilepsy (PME) without Lafora bodies. L-Tryptophan improved the clinical condition in six out of seven patients. Clinical improvement in ambulation, myoclonic jerks, and general condition was most evident. The change was statistically significant. In visual assessment of EEGs, the amount of paroxysmal activity and dysrhythmia of the background activity decreased in six out of seven patients on L-tryptophan. The quantitative EEG revealed a decrease in the power bands of theta, alpha, and beta activity in five of six patients on the second day of L-tryptophan treatment. In familial PME cases, the responses were consistently beneficial. With long-term L-tryptophan therapy, the effect disappeared or was even reversed in three of seven patients after 3 to 4 weeks. These findings indicate that therapy with serotonin precursors is worthy of further trial in PME and that deficient tryptophan metabolism may play a part in the etiology of PME without Lafora bodies.

Conditioned suppression of behavior: its reversal by intra raphe microinjection of chlordiazepoxide and GABA

Chlordiazepoxide and GABA (5 X 10(-5) M; 0.2 microliters) applied into the nucleus raphe dorsalis significantly reduced behavioral suppression induced in rats by a 10-min presentation of a signal previously associated with the punishment of lever pressing for food. As compared to saline control rats, this reduction was of the same order of magnitude as that obtained after intraperitoneal administration of chlordiazepoxide (8 mg X kg-1). Chlordiazepoxide or GABA (5 X 10(-5) M) failed to alter response maintained under non-aversive conditions. These data suggest the involvement of GABAergic neurons of the raphe dorsalis in the 'disinhibitory' effects of benzodiazepines.

Tryptophol-induced change in Brain 5-hydroxytryptamine Metabolism

The effects of tryptoiphol (TOL) on brain 5-hydroxytryptamine (5-HT) metabolism were studied. After TOL injection (200 mg/kg IP), brain 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) levels were increased, 5-HT synthesis rate was decreased, and monoamine oxidase (MAO) activity remained unchanged. Pretreatment of mice with p-chlorophenylalanine (PCPA), a potent inhibitor of 5-HT synthesis, did not affect the anticonvulsant action of TOL.. These results suggest that alteration of 5-HT metabolism after TOL injection is not directly related to the anticonvulsant action of TOL

Effect of p-chlorophenylalanine on diazepam withdrawal signs in rats

The effect of p-chlorophenylalanine (PCPA), a specific serotonin (5-HT) depleter, on diazepam withdrawal signs was studied. Rats were made dependent on diazepam by the chronic administration of this drug in the diet. At the time of diazepam withdrawal, the animals were treated with PCPA (200 mg/kg, IP) or the corresponding vehicle (control). After diazepam withdrawal, the maximal body weight losses of control and PCPA-treated animals were 4.1% and 9.0%, respectively. In naive animals, PCPA did not cause any change in body weight. These results suggest that depletion of central 5-HT by PCPA may potentiate the severity of diazepam withdrawal signs.

Serotonergic mechanisms in myoclonus

Post-hypoxic intention myoclonus is a specific myoclonic syndrome in which central serotonergic tone may be deficient. Tryptophan and 5-hydroxytryptophan administration to patients with post-hypoxic intention myoclonus increases pre-existing low levels of 5-hydroxyindoleacetic acid levels in the cerebrospinal bluid, and also suppresses myoclonus. Serotonin precursor administration does not help all patients with myoclonus and may actually worsen some myoclonic syndromes, including those secondary to lipid storage diseases. Treatments that alter serotonin metabolism can also produce myoclonus in experimental animals but their relevance to myoclonic syndromes in humans remains uncertain.

Anticonvulsant action of cannabis in the rat: role of brain monoamines

The role of brain monoamines in the anticonvulsant action of Cannabis indica resin (CI), against maximal electroshock-induced seizures in albino rats, was investigated by using pharmacologic agents that influence brain monoamine activity. Delta-9-tetrahydrocannabinol content of cannabis resin was estimated to be 17%. The anticonvulsant action of CI (200 mg/kg, i.p.) was significantly inhibited after pretreatment with drugs that reduce brain serotonin activity but not by drugs that reduce brain catecholamine activity. Similarly, the anticonvulsant action of a subanticonvulsant dose (50 mg/kg, i.p.) of CI was potentiated by serotonin precursors but not by catecholamine precursors. Potentiation of the anticonvulsant action of CI by nialamide or by imipramine was inhibited after pretreatment with 5,6-dihydroxytryptamine. The results suggest that the anticonvulsant action of CI in the rat is serotonin- and not catecholamine-mediated.