The pemoline model of self-injurious behaviour

Traditional models of neuropsychiatric disorders consist of attempts to replicate the broad spectrum of behavioural and neurochemical sequelae that characterize a specific disorder. However, these disorders comprise complex constellations of symptoms, including emotional instability, perseverative thoughts, and aberrant behaviours. Close examination often reveals heterogeneity of symptom expression within patient groups and homogeneity in expression of specific symptoms across diagnostic categories. Accordingly, it may not be possible to model the entire spectrum of characteristics for any one of these disorders in any single animal model. A focus on one or more specific behavioural characteristics (e.g. self-injury) may be a more fruitful strategy. Development of behaviourally focused models yields increased understanding of the genetic basis and biochemical abnormalities that underlie specific psychiatric dysfunctions. Furthermore, by revealing pathophysiology that underlies specific disease characteristics, behaviourally focused models improve translational power and help to identify targets for effective pharmacotherapies. One such behaviourally focused animal model is the pemoline model of self-injurious behaviour.

Delusional parasitosis and the dopamine transporter. A new insight of etiology?

Delusional parasitosis (DP) is a psychotic condition in which a person has the unshakeable and mistaken belief (delusion) and/or aberrant perception (hallucination) of being infested with parasites. The disorder will be usually classified in a primary DP-group without a detectable cause (so-called pure forms), while secondary DP-groups are associated with general organic conditions, psychiatric illnesses and drugs (substance induced). Etiology and pathophysiology of DP remain however unknown. In the present paper we hypothesize for the first time a decreased striatal dopamine transporter (DAT)-functioning (corresponding with an increased extracellular dopamine-level) as etiologic condition for DP (primary and secondary groups). The DAT as key regulator of the dopamine-reuptake in the human brain is well known (regulation of the extracellular dopamine concentration). It is a presynaptic plasma membrane protein highly dense represented in the striatum. The hypothesis of a decreased DAT-functioning as etiologic condition by DP is revealed in case reports which show that DAT-inhibitors, such as cocaine, pemoline, methylphenidate and other amphetamine-derivatives can induce the clinical expression of DP. Several other associated causes of secondary DP-groups (medications, parkinson, chorea huntington, multiple system atrophy, diabetes, cerebrovascular diseases, alcoholism, traumatic brain injury, hyperuricemia, human immunodeficiency virus, iron deficiency, schizophrenia, depression) suggest that the clinical expression of DP may be related to a decreased striatal DAT-functioning (blocking, reduced ligand binding, reduced density, reduced activity). Our examined DP-cases (2-females) show means of magnetic resonance imaging a structurally damaged striatum. Furthermore, we presume that by the primary DP-group, the physiologically age-related decline of the DAT-density is pathologically elevated. Based on this hypothesis we show in the present paper the relation between DP and decreased striatal DAT-functioning, trying to give a new insight into the pathophysiologically mechanism involved. The hypothesis provides supporting evidence that increased levels of extracellular dopamine in the striatum of DP-patients is likely to be the result of decreased DAT-functioning and not increased rates of release. The hypothesis can be investigated simply by dopamine transporter imaging in patients with DP.

Assessing medication effects in the MTA study using neuropsychological outcomes

BACKGROUND

While studies have increasingly investigated deficits in reaction time (RT) and RT variability in children with attention deficit/hyperactivity disorder (ADHD), few studies have examined the effects of stimulant medication on these important neuropsychological outcome measures.

METHODS

316 children who participated in the Multimodal Treatment Study of Children with ADHD (MTA) completed the Conners' Continuous Performance Test (CPT) at the 24-month assessment point. Outcome measures included standard CPT outcomes (e.g., errors of commission, mean hit reaction time (RT)) and RT indicators derived from an Ex-Gaussian distributional model (i.e., mu, sigma, and tau).

RESULTS

Analyses revealed significant effects of medication across all neuropsychological outcome measures. Results on the Ex-Gaussian outcome measures revealed that stimulant medication slows RT and reduces RT variability.

CONCLUSIONS

This demonstrates the importance of including analytic strategies that can accurately model the actual distributional pattern, including the positive skew. Further, the results of the study relate to several theoretical models of ADHD.

Effect of fluoxetine, pemoline and placebo on heart period and QT variability in normal humans

OBJECTIVE

To measure the effects of fluoxetine and pemoline on heart period and QT variability.

METHODS

Healthy volunteers were randomly assigned treatment with 20 mg daily of fluoxetine (n=7), 56.25 mg of pemoline (n=7) or placebo (n=9). Twenty-four-hour Holter ECGs were obtained before and after approximately 8 weeks of double-blind treatment.

RESULTS

There were no significant changes in the fluoxetine group. Pemoline was associated with a significant decrease in the high frequency (HF) power (0.15-0.5 Hz, P=.02) and fractal dimension of RR time series (P=.03). QTvi, a measure of QT interval variability, increased in the pemoline group (P=.05).

CONCLUSION

Pemoline, but not fluoxetine, decreases heart period variability (HPV) in the HF power, suggesting a vagolytic effect on cardiac autonomic function. Pemoline is also associated with an increase in QT interval variability, a measure that is sensitive to adrenergic agonists.

Pharmacologic thresholds for self-injurious behavior in a genetic mouse model of Lesch-Nyhan disease

Congenital deficiency of hypoxanthine-guanine phosphoribosyl transferase (HPRT) causes Lesch-Nyhan disease in humans, which is associated with severe and recurrent self-injurious behavior (SIB). The HPRT-deficient knockout mouse model, however, does not display this unusual behavior. The present studies tested whether these mice might be more vulnerable to pharmacologic agents known to cause SIB in normal rodents, including clonidine, Bay K 8644, GBR 12909, methamphetamine, pemoline and caffeine. The results provided three conclusions. First, normal mice did not display SIB using some drugs known to provoke the behavior in rats (GBR 12909, caffeine), indicating important species differences in the expression of the behavior. Second, the C57BL/6J mice did not display SIB using drugs effective for other strains of mice (methamphetamine, pemoline), indicating important strain differences in expression of the behavior. Finally, there was no evidence that the HPRT-deficient mice were more susceptible to SIB when it occurred (clonidine, Bay K 8644).

Effects of pemoline on spontaneous and event-related electrical activity of the brain

The effect of pemoline on the electrical activity of the brain (electroencephalogram, EEG) was studied in relation to time since sleep and time of day in 6 healthy subjects carrying out periods of work lasting 18 h. Power of the spontaneous EEG increased with time since sleep and amplitude of the P3 event-related response decreased. The changes may be interpreted as the reduction in alertness with time awake. In contrast, pemoline decreased power of the spontaneous EEG and increased the amplitude the P3 response, effects that are consistent with improved alertness. The changes in brain activity were paralleled by effects on performance, in terms of percentage of correct responses and reaction time. Performance decreased with time awake, and was improved by pemoline compared with placebo. The drug counteracted the adverse effects of time since sleep, with the beneficial effect of the drug persisting over the 18-hour period of work. The findings emphasise that spontaneous and event-related activity of the EEG may be used both to complement measures of performance in the laboratory and to assess behaviour in occupational situations where performance testing is impractical.

Psychostimulants in supportive care

Psychostimulant medications have been used clinically and investigated in psychiatric populations, the medically ill, cancer patients and healthy people. This article discusses the pharmacology of dextroamphetamine, methylphenidate, pemoline (and other psychostimulants such as caffeine and ephedrine), their use in general medicine and cancer care, side effects, and abuse potential. Therapeutic use in children is addressed only insofar as it illustrates facets of their use in adults.

Dopaminergic and glutamatergic interactions in the expression of self-injurious behavior

Self-injurious behavior occurring in persons with severe mental retardation is a clinically significant and poorly understood problem. Multiple neurotransmitter systems have been implicated in the pathogenesis of this behavior, particularly dopaminergic, opioidergic, and serotonergic systems. Pemoline, a central stimulant, administered systemically at high doses reliably produces self-biting behavior in the rat. The systemic bolus of pemoline produces sustained neostriatal levels of pemoline for over 24 h in a continuous infusion paradigm. Studies of the effect of cortical lesions on pemoline-mediated behaviors reveal that cortical damage, as is common in profound mental retardation, lowers the threshold for pemoline-induced self-biting behavior. Data from the corticostriatal slice suggests that sustained exposure to pemoline produces a shift in N-methyl-D-aspartate receptor-mediated responses rendering them more susceptible to dopaminergic enhancement. Thus, dopaminergic and glutamatergic interactions appear to play an important role in the development and expression of self-biting in the pemoline model.

Cerebral functional magnetic resonance imaging activation modulated by a single dose of the monoamine neurotransmission enhancers fluoxetine and fenozolone during hand sensorimotor tasks

Fluoxetine inhibits the reuptake of serotonin, and dextroamphetamine enhances presynaptic release of monoamines. Although the excitatory effect of both noradrenaline and dopamine on motor behavior generally is accepted, the role of serotonin on motor output is under debate. In the current investigation, the authors evidenced a putative role of monoamines and, more specifically, of serotonin in the regulation of cerebral motor activity in healthy subjects. The effects on cerebral motor activity of a single dose of fluoxetine (20 mg), an inhibitor of serotonin reuptake, and fenozolone (20 mg/50 kg), an amphetamine-like drug, were assessed by functional magnetic resonance imaging. Subjects performed sensorimotor tasks with the right hand. Functional magnetic resonance imaging studies were performed in two sessions on two different days. The first session, with two scan experiments separated by 5 hours without any drug administration, served as time-effect control. A second, similar session but with drug administration after the first scan assessed drug effects. A large increase in evoked signal intensity occurred in the ipsilateral cerebellum, and a parallel, large reduction occurred in primary and secondary motor cortices (P < 10(-3)). These results are consistent with the known effects of habituation. Both drugs elicited comparable effects, that is, a more focused activation in the contralateral sensorimotor area, a greater involvement of posterior supplementary motor area, and a widespread decrease of bilateral cerebellar activation (P < 10(-3)). The authors demonstrated for the first time that cerebral motor activity can be modulated by a single dose of fluoxetine or fenozolone in healthy subjects. Drug effects demonstrated a direct or indirect involvement of monoamines and serotonin in the facilitation of cerebral motor activity.

Paradoxical effects of serotonin and opioids in pemoline-induced self-injurious behavior

Self-injurious behavior (SIB) is a symptom of various psychiatric disorders with differing etiologies. Although no generally effective pharmacological treatment of SIB is available, subsets of individuals exhibiting SIB have been found to respond to opioid antagonists and selective serotonin reuptake inhibitors (SSRIs). The present study evaluated the efficacy of these two treatments in the pemoline-induced model of self-biting behavior (SBB) in rats. Using a factorial design, adult rats receiving daily pemoline at 100 mg/kg or the peanut oil vehicle were pretreated with either distilled water vehicle (1 cc/kg), naltrexone (1 mg/kg), or paroxetine (1 mg/kg). Each day, animals were rated on the severity of SBB and also periodically behavioral changes were evaluated using various other outcome measures. Paroxetine significantly increased the severity of SBB induced by pemoline, while naltrexone only marginally increased the SBB. These results were not expected and suggest that further studies into the role of serotonin agonists and antagonists are needed in evaluating this model.

Intensive and sustained air operations: potential use of the stimulant, pemoline

BACKGROUND

Intensive and sustained military operations involve long periods of overnight work and the occasional use of a stimulant to maintain performance may be beneficial. In this context a dose response study was carried out to investigate the effects of pemoline, a dopamimetic agent, on overnight work and to assess potential residual effects on subsequent sleep.

METHODS

Six healthy volunteers participated in a placebo-controlled, double-blind, cross-over trial involving a 12-h period of work during which subjective alertness and performance on a range of tasks were assessed at 1.5 h intervals following ingestion at 2000 hours of pemoline (10, 20, 30 and 40 mg) and, on two occasions, placebo. The work period was preceded by a 6-h sleep period with temazepam 20 mg, and followed by a 4-h recovery sleep with no medication. All sleep periods were recorded electroencephalographically.

RESULTS

There was no difference between sleep periods preceding the work period. Subjective alertness and performance on all tasks deteriorated significantly during the work period, with the earliest impairments in performance observed at 0200 hours. Pemoline increased subjective alertness and performance on all but two tasks, compared with placebo. The onset of activity was seen 4.5 h after drug ingestion and alerting effects of 30 and 40 mg pemoline persisted beyond the work period, disturbing morning recovery sleep. Doses of 10 and 20 mg pemoline had no effect on recovery sleep.

CONCLUSION

The present studies indicate that a 20 mg dose of pemoline may be suitable for maintaining nocturnal performance without having adverse effects on recovery sleep.

Dopaminergic agents and stimulants as antidepressant augmentation strategies

Dopaminergic agents and stimulants have been used to manage depression when conventional antidepressant treatments fail. We reviewed evidence for the role of dopaminergic dysfunction in depression, the use of dopaminergic agents as antidepressants, and the use of dopaminergic agents and stimulants as antidepressant adjuncts. Dopamine may be part of the pathophysiology of depression for a subset of patients. When used with caution and an appreciation of the potential risk of abuse, dopaminergic agents and stimulants may be useful for patients refractory to antidepressants alone.

Pemoline alters dopamine modulation of synaptic responses of neostriatal neurons in vitro

Pemoline, a central stimulant, administered systemically at high doses (300 mg/kg) reliably produces self-biting behavior in rats. Pemoline-induced self-biting shares many similarities with self-injury seen in certain human disorders. Recent evidence has shown that alterations in neostriatal neurochemistry accompany the self-biting behavior seen in the rat. The present study used intracellular electrophysiological techniques to reveal changes in neostriatal cellular physiology in slices from rats which had displayed self-injury. Depolarizing postsynaptic potentials (DPSPs) were examined in neostriatal slices from rats that received pemoline and had been engaging in self-injurious behavior and from two control populations: rats that received the same concentration of pemoline and did not engage in self-biting, and rats that received vehicle alone (peanut oil). Data were acquired in standard artificial cerebral spinal fluid. DPSPs were evoked by cortical electrical stimulation in the slice. In neurons from rats that received the vehicle or that had received pemoline but had not engaged in self-injury, dopamine (DA, 20 microM) application produced a significant decrease in the size of the cortically evoked neostriatal DPSP. In contrast, DA application produced an increase in DPSP size in neurons from rats which had received pemoline and had engaged in self-injury. Bath application of a combination of D1 and D2 receptor agonists best replicated the enhancing effect of DA. Furthermore, the enhancement could be blocked by pretreatment with the competitive N-methyl-d-aspartate receptor antagonist, 2-amino-5-phosphonopentanoic acid. The results indicate that alterations in neostriatal DA-glutamate interactions accompany pemoline injections which produce self-injurious behavior.

Pemoline produces ipsilateral turning behavior in unilateral 6-OHDA-lesioned rats

1. Male Sprague-Dawley rats received either a unilateral injection of 6-hydroxy-dopamine or vehicle injection into the medial forebrain bundle. 2. Two weeks post surgery, all rats received a pemoline challenge (250 mg/kg s.c.), and rotational and stereotyped behaviors were videotaped and analyzed. 3. All rats regardless of injection expressed stereotyped behaviors and hyper-locomotion after pemoline challenge. 4. High performance liquid chromatography (HPLC) with electrochemical detection was used to evaluate changes in the levels of dopamine, serotonin and their metabolites in neostriata. 5. Rats with dopamine depleting lesions exhibited ipsilateral rotational behavior, indicating that pemoline, a central stimulant, is an indirect dopamine agonist in the rat. 6. The extent of dopamine depletion and serotonin elevation in the neostriatum in lesioned animals was related to the expression and degree of rotational behavior.

Pretreatment with MK-801 inhibits pemoline-induced self-biting behavior in prepubertal rats

The indirect dopamine agonist, pemoline (120-300 mg/kg s.c.), can induce self-biting behavior in the rat. The present study demonstrates that the non-competitive N-methyl-D-aspartate (NMDA) antagonist, dizocilpine (MK-801, 0.2 mg/kg s.c.), significantly attenuates pemoline-induced self-biting behavior, while simultaneously increasing locomotor activity. When animals received a fixed dose of MK-801 with increasing doses of pemoline, a competitive relationship emerged such that high-dose pemoline surmounted the antagonistic effect of MK-801. In contrast to spiperone, delayed administration of MK-801 was ineffective in blocking the subsequent expression of self-biting behavior, suggesting that dizocilpine exerts its protective effect early in the cascade of events which eventually leads to self-biting behavior in this paradigm.

Dopaminergic transmission and the sleep-wakefulness continuum in man

Modulation of dopaminergic transmission on daytime alertness and performance and on nocturnal sleep were studied in man using 30, 60 and 90 mg pemoline, a dopamimetic drug, and 2, 4 and 6 mg pimozide, a dopamine receptor antagonist. Pemoline lengthened daytime sleep latencies and improved attention, and increased wakefulness during nocturnal sleep. Rapid eye movement (REM) sleep was reduced with 90 mg pemoline, but this was due entirely to increased wakefulness. Pimozide had little effect on overnight sleep, but increased the tendency to fall asleep and impaired performance during the day. These studies suggest that the effects of certain drugs which modulate the activity of neurotransmitters, involved in the control of sleep and wakefulness, may be related to the inherent level of activity of the central nervous system. Modulation of the dopaminergic system can have a profound influence on the manifestation of wakefulness and vigilance, but is unlikely to modify directly the elaboration of REM sleep in man.

Stimulant medication therapy in the treatment of children with attention deficit hyperactivity disorder

Despite the tremendous research advances that have increased our knowledge regarding the pharmacodynamics, clinical pharmacology, pharmacokinetics, and adverse effects of stimulant medications in the treatment of children with ADHD, our knowledge is yet incomplete. Perhaps the most central unresolved issue concerns our understanding of the pathogenesis, pathophysiology, and diagnosis of ADHD. This review has touched briefly on the controversy and confusion surrounding this issue. Although our understanding of the use of stimulant medications in this disorder is similarly incomplete, a review of the literature does allow certain conclusions to be made that are helpful to the practitioner. 1. Stimulant medications are an effective treatment modality for most children with ADHD. Short-term efficacy is well documented, and long-term outcome may be improved when stimulants are used with other therapeutic strategies. Stimulants in and of themselves are not a panacea. 2. It is impossible to predict which children will have a favorable response to stimulant medications and which children may have a placebo response. The use of individual single-blind medication trials is a practical solution to this problem and should be considered for all children who are candidates for stimulant therapy as a means for preventing overuse or inappropriate use of these medications. 3. The precise mechanism of action of stimulants is not yet completely understood, but stimulants appear to exert their therapeutic effects through their influence on multiple neurotransmitters in the catecholamine, dopamine, norepinephrine axis in the central nervous system. 4. The three major stimulants--methylphenidate, dextroamphetamine, and pemoline--appear to be equally efficacious, although methylphenidate has emerged as the most commonly used and most studied drug. Because of its potential for causing liver toxicity, pemoline has remained a second-line medication. 5. The three major stimulants appear to have somewhat different mechanisms of action so that failure of a patient to respond to one medication does not mean that he or she will not respond to another. 6. The recommended starting doses for the stimulants are 0.3 mg per kg of methylphenidate, 0.15 mg per kg of dextroamphetamine, and 37.5 mg of pemoline. There is a great deal of individual variability in dose response, so doses must be titrated for optimal effects in each child. Sustained release preparations are much more expensive than regular preparations and may be less effective. 7. There is no evidence that stimulants have any effect on ultimate adult height. 8. Although relatively uncommon, motor tics have been observed in children on stimulants, and all children on stimulants need to be carefully monitored for the development of tics. (ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of rapid eye movement sleep in humans by drugs that modify monoaminergic and purinergic transmission

Modulation of rapid eye movement (REM) sleep is a well-established effect of many centrally acting drugs. However, there is uncertainty concerning the nature of the changes and their significance, and it is in this context that we have analyzed the effects of several groups of drugs that alter monoaminergic or purinergic transmission on sleep in humans. The analysis shows that drugs that modulate noradrenergic and serotonergic transmission lead to marked suppression of REM sleep, irrespective of any increase or decrease in sleep duration. There is no evidence that the timing of the ultradian cycle of REM sleep relative to sleep onset is altered by these drugs. On the other hand, reduced REM sleep with dopamimetic drugs is due solely to increased wakefulness. However, there can be more subtle effects of some drugs on REM sleep. Benzodiazepine receptor agonists and drugs that modify purinergic transmission modulate the appearance of early REM activity. There may, therefore, be two discrete systems that control entry into REM sleep, and that are responsive to drugs. The exact appearance and timing of REM periods may be modulated by a feedback mechanism involving GABAergic, or possibly purinergic, transmission, while monoaminergic and cholinergic influences exert a reciprocal and overriding control of REM sleep.

Repeated pemoline produces self-injurious behavior in adult and weanling rats

Self-injurious behavior (SIB) is a serious problem among the mentally handicapped and is often accompanied by other repetitive or stereotyped behaviors. Acute administration of high doses of amphetamine or pemoline to rats produces transient SIB which is accompanied by severe deterioration of the behavioral repertoire. Repeated subcutaneous (SC) administration of pemoline to rats produces a high incidence of SIB without the dramatic behavioral changes produced by high doses of oral pemoline. Repeated pemoline increased locomotions and rears and produced intermittent stereotyped sniffing and licking/biting. However, the animals were still able to eat, drink, sleep and groom. Hotplate tests provided no evidence for analgesia. Because SIB is often associated with human developmental disorders, the effects of repeated SC administration of pemoline to weanling rats was also investigated. SC injections every 12 hours produced a high rate of SIB in weanling rats.

Effects of the indirect dopaminomimetic diethylpemoline on local cerebral glucose utilization and local cerebral blood flow in the conscious rat

The changes in local cerebral glucose utilization (LCGU) and local cerebral blood flow (LCBF) following the systemic application of the indirect dopaminomimetic diethylpemoline (50 mg/kg i.v.) were measured in conscious rats using the autoradiographic [14C]2-deoxyglucose and the [14C] iodoantipyrine technique. Increased rates of glucose utilization were observed in the sensorimotor cortex, parafascicular nucleus, ventrolateral nucleus of the thalamus, substantia nigra, caudate nucleus, globus pallidus, red nucleus, subthalamic nucleus, cerebellar cortex and vermis. Cingulate cortex, anteromedial, anteroventral nucleus of the thalamus, habenula and nucleus accumbens showed a decreased LCGU. The determination of LCBF revealed a similar pattern of altered blood flow values. Statistical evaluation of the relationship between glucose utilization and blood flow by regression analysis did not reveal any distinguishable difference between diethylpemoline-treated rats and controls. The data suggest that it is mainly the altered neuronal activity and metabolic demand after dopaminergic stimulation that effect the changes in blood flow rather than a direct dopaminergic effect on brain vasculature.

Pharmacologic control of pemoline induced self-injurious behavior in rats

Administration of oral Pemoline produces long lasting amphetamine-type stereotyped behavior and persistent self-biting behavior in rats. The effects of haloperidol, pimozide, diazepam, and serotonin depletion by pretreatment with p-chlorophenylalanine (PCPA) or chronic pretreatment with p-chloroamphetamine (PCA) on abnormal behavior produced by pemoline were studied. Diazepam consistently increased the duration of stereotyped behavior. It also reduced licking/biting and self-biting but the latter effects were not consistent. Pretreatment with PCA had negligible effects on stereotyped behavior. Pretreatment with PCPA dramatically increased locomotion and rearing without affecting the other components of stereotypy--stereotyped head movements, licking/biting, and self-biting. Haloperidol (0.2 and 0.3 mg/kg) produced a dose related normalization of pemoline induced behaviors, including elimination of self-biting. Pimozide (0.5, 0.8 and 1.3 mg/kg) had little or no effect on behaviors such as locomotions, rears, licking/biting, or stereotyped head movements but eliminated self-biting at 1.3 mg/kg. These data suggest that pemoline, like amphetamine, produces stereotyped behavior through central dopaminergic mechanisms. Dopaminergic mechanisms also appear to be involved in pemoline induced self-biting. pemoline is apparently pharmacologically and behaviorally very similar to amphetamine. Pemoline may provide a useful animal model for syndromes characterized by self-injurious behavior and other repetitive behaviors.

Effects of Mg-pemoline on the central catecholaminergic system

Acute or repeated treatment with Mg-Pemoline (Mg-Pg) did not modify the endogenous level of brain catecholamines (CA) of rats. However, a single dose (30 mg/kg) produced a significant decrease of brain CA turnover, measured either by the rate of conversion of 14C-tyrosine to CA or by the rate of disappearance of CA after alpha-MT. Mg-Pe (0.01-0.1 mM) did not modify the basal outflow nor the release of 3H-DA elicited by high K+ in slices of corpus striatum. At the same concentrations, Mg-Pe inhibited uptake of DA (competitively) or NA (uncompetitively) in synaptosomes from corpus striatum and hypothalamus, respectively. Turning-behavior in mice lesioned in corpus striatum with 6-OH-DA, indicated that this drug acts like amphetamine as an indirect DA agonist. These results suggest that central stimulant effects of Mg-Pe may be the consequence of CA-uptake inhibition and this effect may also account for the decrease of brain CA turnover.

Pemoline-induced self-biting in rats and self-mutilation in the deLange syndrome

Self-mutilation in humans occasionally accompanies physiological disorders such as the deLange syndrome. If pemoline-induced self-biting is behaviorally similar to self-mutilation in the deLange syndrome, similar neurochemical mechanisms may be involved in both. Oral administration of 140 and 220 mg/kg pemoline reliably induced persistent self-biting in rats. This behavior was indistinguishable from stereotyped grooming and its most common target was the medial digits of the foreleg. Pemoline-induced self-biting was accompanied by hyperactivity, stereotyped behavior, abnormal social behavior, abnormal sensorimotor behavior, and unresponsiveness or avoidance of moderate levels of sensory stimuli. Several of these behaviors have also been reported in deLange patients.

Wakefullness and reduced rapid eye movement sleep: studies with prolintane and pemoline

1 Effects of prolintane (15 and 30 mg) and pemoline (60 and 100 mg) on sleep were studied in six healthy adult males. Sleep was assessed by electroencephalography and by analogue scales. 2 Prolintane (15 and 30 mg) reduced rapid eye movement (REM) sleep both by delaying the first period (P < 0.05 and < 0.001 respectively) and by reducing total REM sleep (P < 0.05 and < 0.001 respectively). In some subjects there were increased awakenings during the early part of the night, and in two subjects long periods of wakefulness occurred. 3 With pemoline (60 and 100 mg) sleep duration was marked reduced (P < 0.001). There was evidence in some subjects of delay to the first REM period, and reduced percentage REM sleep (P < 0.01). Shortened and fragmented sleep with 60 and 100 mg were associated with reduced sleep efficiency indices (P < 0.001), and shorter sleep period times led to reduced REM/NREM ratios. Absence of an effect on REM latency for the subjects as a group may be related to relatively slow absorption. 4 The heterocyclic amphetamine derivatives have variable effects on sleep. The differences may be dose related, and wakefulness and reduced REM sleep may be seen together or separately. Alterations in sleep occur with doses of pemoline and prolintane which also modify performance.

Heterocyclic amphetamine derivatives and caffeine on sleep in man

1 Effects of the heterocyclic amphetamine derivatives, pemoline (20 and 40 mg), prolintane hydrochloride (5 and 10 mg), methylphenidate hydrochloride (10 and 20 mg) and fencamfamine hydrochloride (10 and 20 mg), and of caffeine anhydrous (100, 200 and 300 mg) on sleep, were compared with placebo in six young adults (20-31 years) using electroencephalography for sleep measures and analogue scales for subjective assessments of well-being and sleep quality. The study was double-blind.

2 No consistent effect was found with pemoline.

3 With prolintane there were no changes in sleep latencies, or in slow wave sleep (SWS). Rapid eye movement (REM) sleep was reduced during the first 2 h after sleep onset.

4 With methylphenidate and fencamfamine latencies to sleep onset and to stage 3 sleep were unchanged. The higher dose of each drug delayed the first and subsequent REM periods. Both drugs reduced the duration of REM sleep, and the higher dose of each drug reduced the percentage REM sleep. Methylphenidate also reduced total sleep time (TST). There was no evidence of reduced SWS with either drug. Impairment of sleep was reported with each drug.

5 With caffeine there were no changes in latencies to sleep onset or to the first REM period, though in one study with 300 mg subsequent REM periods were delayed. Awake activity and drowsy sleep were increased and TST and SWS were decreased. With 300 mg only, REM sleep was decreased though percentage REM sleep was not altered. Impaired sleep was reported with all doses of caffeine.

Four stimulants of the central nervous system: effects on short-term memory in young versus aged monkeys

Aged Rhesus monkeys and young control monkeys were tested in a delayed-response procedure to assess the effects of central-nervous-system (CNS) stimulants on short-term memory (STM). Previous research had established that the aged monkeys showed specific impairments of STM in this procedure. Four different CNS stimulants (methylphenidate, magnesium pemoline, a pentylenetetrazole/niacin mixture, and caffeine) were chosen for evaluation on the basis of their relevancy to current geriatric-psychopharmacologic research. Four different doses of each of the four CNS stimulants were given to each monkey, counter-balanced for possible order effects. Methylphenidate and caffeine impaired the performance of both age groups in this non-human primate cognitive task, even at relatively low dose levels. Magnesium pemoline produced fewer adverse effects and some evidence of improving STM in the aged monkeys, although not within the levels of statistical significance. The pentylenetetrazole/niacin mixture produced a three-way interaction involving age, dose and retention interval. This reflected the fact that although no definite effects were noted under the zero-sec control condition, statistically significant age-related deficits did occur in the STM-dependent retention interval as the dose varied. The data demonstrate that, of these four CNS stimulants, none radily improves (and often may impair) performance of tasks requiring STM. Thus the results of this study offer little support for the hypothesis that general CNS stimulation may constitute significant therapy for cognitive impairments associated with advanced age.

Alterations in cartilage metabolism by neurostimulant drugs

Suppression of growth without significant alterations in hormonal patterns has been demonstrated for the neurostimulant drug pemoline. Comparison of the in vitro effect of pemoline, methylphenidate, and methamphetamine on somatomedin-stimulated sulfate uptake by cartilage showed all three drugs to be inhibitory. Sulfate uptake by cartilage can be directly related to growth and glycosaminoglycan biosynthesis. Assay of two of the enzymes involved in the glycosaminoglycan biosynthetic pathway showed that methamphetamine and methylphenidate caused a marked depression of xylosyl- and galactosyltransferase enzyme activity. These data suggest an interference with cartilage metabolism as one possible mechanism for the growth retardation observed in children on neurostimulant drug therapy.

[Effects of levophacetoperane, pemoline, fenozolone, and centrophenoxine on catecholamines and serotonin uptake in various parts of the rat brain]

These drugs, except centrophenoxine, inhibit in vitro in a competitive manner, norepinephrin uptake in Rat hypothalamus and cortex, and dopamine uptake in corpus striatum and cortex, at higher concentrations than d.l. amphetamine; this alone inhibits serotonin uptake in hypothalamus.

The hyperkinetic child syndrome and brain monoamines: pharmacology and therapeutic implications

Decreased catecholaminergic activity within the central nervous system has been associated with altered arousal, attention, learning, and kinetic function in animals and humans. The hyperkinetic child syndrome (HCS) involves dysfunction in all these spheres and may thus reflect diminished catecholamine activity, particularly as related to brain dopamine. Accordingly, the efficacy of catecholaminergic agents in treating the HCS is a predictable rather than a paradoxical effect of these agents. Sufficient evidence is now available to strongly implicate catecholamine hypoactivity in the pathopharmacology of the HCS.

Tape test as a simple new method for the study of compounds increasing the problem-solving ability of the rat

A simple new method, the "tape test" has been developed for studying the enhancement of learning by drugs in "learning-dull" rats. A piece of adhesive tape is pressed on the left front pad of the rats. The time of tape removal by the animal, i.e., the problem-solving time is measured. In our experiments the selected learning-dull rats were used which were unable to remove the tape within 60 s observed on 3 consecutive days. The problem-solving ability of the rats was studied on 4 consecutive days, by posttrial administration. The problem-solving ability was found to be increased after treatment with different drugs such as para-chlorphenylalanine (PCPA), pemolin, orotic acid, vitamin B12. The stimulatory effect of vitamin B12 could be inhibited by vincristine.

Antidepressant and anticonvulsant activity of 1-(5-phenyl-4-oxazolin-2-yl)-4-substituted piperazines

1-(5-Phenyl-4-oxo-2-oxazolin-2-yl)-4-substituted cinnamoylpiperazines and 1-(5-phenyl-4-oxo-2-oxazolin-2-yl)-4-carbamoylpiperazine and derivatives were synthesized and evaluated for antidepressant activity in the mouse Dopa potentiation test. 1-(5-Phenyl-4-oxo-2-oxazolin-2-yl)-4-carbamoylpiperazine and derivatives were further evaluated for anticonvulsant activity in the audiogenic seizure test in mice.

Antagonistic effects of pemoline to colchicine and caffeine

Pemoline, the constituent of Tradon, is able to slow down the decrease of the mitotic index caused by 0.1% caffeine in roots of Vicia faba, and mitotic aberrations are reduced. With 0.005% colchicine and 3 x 10(-4) g/ml pemoline, no metaphase-accumulation can be observed, and anaphase-disorder is delayed.