Sleep induced by low doses of apomorphine in rats

Sleep loss and recovery after administration of drugs related to different arousal systems in rats

Sleep is homeostatically regulated suggesting a restorative function. Sleep deprivation is compensated by an increase in length and intensity of sleep. In this study, suppression of sleep was induced pharmacologically by drugs related to different arousal systems. All drugs caused non-rapid eye movement (NREM) sleep loss followed by different compensatory processes. Apomorphine caused a strong suppression of sleep followed by an intense recovery. In the case of fluoxetine and eserine, recovery of NREM sleep was completed by the end of the light phase due to the biphasic pattern demonstrated for these drugs first in the present experiments. Yohimbine caused a long-lasting suppression of NREM sleep, indicating that either the noradrenergic system has the utmost strength among the examined systems, or that restorative functions occurring normally during NREM sleep were not blocked. Arousal systems are involved in the regulation of various wakefulness-related functions, such as locomotion and food intake. Therefore, it can be hypothesized that activation of the different systems results in qualitatively different waking states which might affect subsequent sleep differently. These differences might give some insight into the homeostatic function of sleep in which the dopaminergic and noradrenergic systems may play a more important role than previously suggested.

Can pharmaco-electroencephalography help improve survival of central nervous system drugs in early clinical development?

Pharmaco-electroencephalography has significant yet unrealised promise as a translatable intermediate biomarker of central pharmacodynamic activity that could help reduce Phase 2 attrition in the development of central nervous system drugs. In an effort to understand its true potential, a framework for decision-making was proposed and the utility of pharmaco-electroencephalography was assessed through several case studies. A key finding was that lack of standardisation reduces the value of data pooling and meta-analyses and renders assessment of translatability difficult, limiting utility in all but simple cases. Pre-competitive collaboration is essential both to improving understanding of translation and developing modern signal processing techniques.

Vigilance troubles in Parkinson's disease: A subjective and objective polysomnographic study

BACKGROUND AND PURPOSE

To assess the prevalence of vigilance disorders in Parkinson's disease patients, relate the observed phenomena to potential causes and confirm these troubles with polysomnographic analysis.

PATIENTS AND METHODS

A questionnaire was used to gather information on demographic data, previous and current treatments, disease characteristics, sleep and vigilance troubles. Somnolence was measured using the Epworth Sleepiness Scale (ESS). Nocturnal polysomnography (PSG) and multiple sleep latency tests (MSLT) were performed for a sample of parkinsonian patients.

RESULTS

Two hundred twenty-two parkinsonian patients completed the questionnaire, and 36 patients had objective analyses. Of the patients, 43.2% had an ESS score >10, and 28.4% reported somnolence in the hour after taking dopaminergic drugs, whereas 6.8% reported unintended sleep episodes. In view of questionnaire data, these vigilance disorders may be partly explained not only by the impact of nocturnal sleep disorders (e.g. sleep apnea syndromes) but also by dopaminergic therapy (especially with dopaminergic agonists). With PSG and MSLT results, we have shown a significant correlation between mean sleep latency and ESS score. Patients with unintended sleep episodes have severe sleepiness in MSLT compared with others patients.

CONCLUSIONS

Vigilance disorders are frequently observed in Parkinson's disease. We recommend informing patients of the risk of occurrence of such conditions, notably for patients with unintended sleep episodes and with sleepiness in the hour after taking dopaminergic drugs.

Dopamine receptor gene polymorphisms in Parkinson's disease patients reporting "sleep attacks"

Genes encoding proteins involved in dopaminergic transmission are potential candidate genes for the induction of somnolence in Parkinson's disease (PD) because dopaminergic agents have been shown to be associated with sudden onset of sleep (SOS) in PD. We conducted an association study on dopamine D2, D3, and D4 receptor gene polymorphisms comparing 137 PD patients with SOS and 137 PD patients without SOS matched according to drug therapy, disease duration, sex, and age. Our results show a significant association between the dopamine D2 receptor gene polymorphism Taq IA and SOS in PD. No significant association between two other investigated polymorphisms and the phenomenon of "sleep attacks" in PD was observed.

Pharmacogenomics in the treatment of narcolepsy

Narcolepsy is a neurological disorder characterized by excessive daytime sleepiness and cataplexy. Available treatments of narcolepsy include stimulants and antidepressants but the recent discovery of orexin/hypocretin deficiency in narcolepsy opens up new perspectives. Narcolepsy is a complex disorder involving genetic, immune and environmental factors. Although only a strong association is found with the HLA DQB1*0602 gene, other genetic susceptibility factors might be involved. Among these, the functional polymorphism of the catechol-O-methyltransferase (COMT) gene is critically involved in the severity of narcolepsy and in the response to the stimulant modafinil. Other pharmacogenetic targets include the orexinergic, noradrenergic and possibly the serotonergic pathways.

Narcolepsy and idiopathic hypersomnolence

Narcolepsy is among the leading causes of excessive daytime sleepiness. Its classic form associates daytime sleepiness with cataplexy, sleep paralysis, hypnopompic hallucinations, and nocturnal disrupted sleep. This form is associated with HLA DQ betal-0602 in about 85% to 90% of affected subjects, independently of their ethnicity. But the definition of the variants of narcolepsy remains controversial, despite the fact that, in some cases, narcolepsy may be limited to daytime sleepiness. In its classic form, it is associated with two or more sleep onset rapid eye movement periods at the Multiple Sleep Latency Test. This test, performed after nocturnal polysomnography, can be helpful in diagnosing narcolepsy, in the absence of a convincing history of partial or complete attacks of cataplexy--a pathognomonic symptom. Investigation of narcoleptic Dobermans has indicated that a muscarinic cholinergic hypersensitivity exists in the brain of affected animals and abnormalities involve also the dopaminergic system. Despite its prevalence of 0.03% to 0.05%, it is still a neurologic entity often missed. Investigations of families of narcoleptics, including monozygotic twins, indicate that this syndrome is polygenic in nature with association of environmental factors. As the peak of onset of disabling symptoms occurs between 15 and 25 years of age, it is important to improve the treatment of this lifelong, disabling illness. Stimulants medications, independently of their mode of action, are prescribed to help daytime sleepiness, and tricyclic antidepressant drugs or serotonergic reuptake blockers are used on the other symptoms. But these medications have a limited efficacy. Short naps at regular intervals during the day are a strong therapeutic adjuvent.

Autoradiographic studies of post-mortem human narcoleptic brain

Although the pathological basis for narcolepsy is unknown, studies of human and canine narcolepsy have suggested that monoamine and cholinergic metabolism may be altered. We used quantitative autoradiography to assess binding of dopaminergic, noradrenergic, and cholinergic ligands to basal ganglia and amygdala of five narcoleptic and 17 control human brains. Dopamine receptor studies revealed significant increases in D-1 and D-2 receptor binding in the caudate nucleus, as well as large but not significant increases of D-1 binding in the medial globus pallidus, and D-2 binding in the lateral globus pallidus and the lateral nucleus of the amygdala. Alpha-adrenergic receptor studies revealed a significant increase in alpha-2 receptor binding in the putamen and large but not significant increases of alpha-2 binding in the caudate nucleus, and basal and lateral nuclei of the amygdala. Alpha-1 receptor binding was decreased in several areas but the changes were not statistically significant. Studies of two narcoleptic brains revealed small but not statistically significant increases in muscarinic receptor binding in the caudate nucleus, putamen, and amygdala. Although we cannot exclude the possibility that stimulant medications used before death may be partly responsible for these findings, the results suggest that human narcolepsy is associated with upregulation of dopamine and alpha-2 adrenergic receptors in specific brain regions.

Antiserum to prolactin decreases rapid eye movement sleep (REM sleep) in the male rat

Previous reports suggest that blood-born prolactin (PRL) may selectively promote rapid eye movement sleep (REMS). To study the possible involvement of endogenous PRL in sleep regulation, rats were systemically injected with either antiserum to PRL or normal rabbit serum, and the sleep-wake activity was determined during the subsequent 12-h light cycle. The administration of normal rabbit serum in physiological saline did not alter sleep-wake activity compared to control recordings, whereas the PRL antiserum caused a modest and selective suppression in REMS. Immunoreactive PRL was eliminated from the serial plasma samples obtained between 6 to 11 h after the injection of the antiserum. Brain temperature was not affected by the antiserum. The results indicate that physiological pituitary PRL secretion has a slight REMS-promoting activity in the male rat. It is speculated that an increased release of pituitary PRL or the PRL-like substance previously demonstrated in the brain may significantly stimulate REMS.

Electroencephalographic correlates of the sedative effects of dopamine agonists presumably acting on autoreceptors

Alterations both in the activity of the cortical EEG and behaviour were studied after administration of dopamine receptor agonists. In addition to apomorphine, which provided contrasting effects, both on the EEG and behaviour, when small and large doses were compared, alterations elicited by the D2 agonist, quinpirole and another agonist, with preference for dopamine D2 autoreceptors, talipexole (B-HT 920), were evaluated by using telemetric EEG recordings in rats. Similarly to apomorphine, quinpirole produced opposite effects after small and large doses: a small dose (0.05 mg/kg) led to sedation and an increase of EEG power spectra in all of the bands, except beta 2, whereas a larger dose (0.5 mg/kg) elicited stereotypy and desynchronization of the EEG, with a characteristic increase of power in the alpha 1 band. The effects on the EEG and on behaviour, obtained with the small dose of quinpirole were very similar to those of a small dose of apomorphine (0.05 mg/kg) and a small dose of talipexole (0.02 mg/kg) but even the large dose of talipexole (0.5 mg/kg) produced similar effects: all of these treatments produced behavioural sedation and an increase of power in the EEG in all of the bands, except beta 2; such increases appeared most pronounced in the delta band. The present study provides further evidence that drugs, which are assumed to activate dopamine autoreceptors, are effective in inducing sedation. This sedation was accompanied by a characteristic pattern, observed in EEG power spectra analysis.

A novel effect of MPTP: the selective suppression of paradoxical sleep in cats

We studied the effect of MPTP on sleep-wakefulness cycle in cats. Five mg/kg n-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was administered i.p. for 5 consecutive days. Electrocorticographic, electrooculographic and electromyographic recordings were performed before (5 days), during (5 days) and after (14 days) the treatment. Total selective paradoxical sleep deprivation was observed from the first injection. This effect lasted 6-9 days after the last dose, while the relative amount of slow wave sleep increased. The Berg-Fourier analysis showed no significant change in the EEG power spectra of slow-wave sleep during the paradoxical sleep deprivation compared to control period. Recurrence of paradoxical sleep was parallel to the disappearance of the motor symptoms. Histopathological investigation showed neuronal loss mainly in the substantia nigra. Our present study suggests a complex behavioral effect of MPTP.

Apomorphine-induced alterations in cortical EEG activity of rats. Involvement of D-1 and D-2 dopamine receptors

EEG activity after activation of dopamine receptors of D-1 and/or D-2 type was studied by using telemetric recordings in rats. Apomorphine, a preferential D-2 agonist, produced a characteristic increase in the power of alpha-1 band (7.00-9.50 Hz) when given in doses mediating stereotypies (0.2 or 0.5 mg/kg s.c.). Low doses produced a general increase in the power of all of the bands except beta-2. In particular, delta activity was enhanced which seems to be in correspondence with the sedation observed after these doses (0.02 and 0.05 mg/kg). Haloperidol in a dose which is assumed to block both D-1 and D-2 receptors (0.1 mg/kg i.p.) completely antagonized the alpha-1 activation produced by apomorphine (0.5 mg/kg). A similar, although not complete inhibition of alpha-1 activation was found after administration of a large dose of the selective D-1 antagonist SCH 23390 (0.2 mg/kg i.p.). The selective agonist at D-2 receptors quinpirole (1.0 mg/kg s.c.) produced a less pronounced activation of the power in the alpha-1 band than apomorphine. In general, there was found to be a good correlation between the activation of the alpha-1 activity and stereotyped behaviour. The results suggest that for the full expression of alpha-1 activation, a pronounced activation of D-2 receptors and at least a minimal activation of D-1 receptors, for instance by the endogenous dopamine, is necessary.

Effects of the selective dopamine D-2 receptor agonist, quinpirole on sleep and wakefulness in the rat

The effects of the dopamine D-2 receptor agonist, quinpirole, were compared with those produced by dopamine D-2 antagonist, YM-09151-2, in rats implanted with electrodes for chronic sleep recordings. Quinpirole (0.015-1.0 mg/kg) induced biphasic effects such that low doses decreased wakefulness and increased sleep, while higher doses induced the opposite effects. At 0.015 mg/kg, YM-09151-2 slightly augmented wakefulness, while at 1.0-2.0 mg/kg it significantly increased light sleep but depressed REM sleep. Pretreatment with YM-09151-2 in a dose which preferentially acts at presynaptic sites reversed the suppressant effects of a low dose of quinpirole on wakefulness and slow wave sleep. In contrast, the administration of YM-09151-2 in a dose which blocks postsynaptic D-2 receptors prevented the effect of a high dose of quinpirole on wakefulness and slow wave sleep; the depression of REM sleep was not affected. The opposite effects observed on the waking EEG after activation of either dopamine autoreceptors or postsynaptic D-2 receptors with adequate doses of quinpirole tend to indicate an active role for DA in the control of the waking state.

Inhibition by pertussis toxin of the soporific effects induced by stimulation of dopamine D2 autoreceptors in the ventral tegmental area in rats

The behavioural and ECoG spectrum power effects of agonists at dopamine D2 autoreceptors, both after systemic or intracerebral administration, were studied in rats. It was shown that the bilateral injection of apomorphine or (+) 3PPP (0.1, 0.5 and 1.0 nmol for each compound) into the ventral tegmental area produced behavioural and ECoG sleep, accompanied by a statistically-significant increase in ECoG total spectrum power. These effects were completely antagonized by a pretreatment (24, 48 or 72 hr before) with pertussis toxin (0.34 and 3.4 micrograms), given into the same site. Similarly, behavioural sleep and an increase in ECoG total voltage power, produced by systemic administration of apomorphine (263 nmol/kg i.p.), were abolished by pertussis toxin (3.4 micrograms) injected bilaterally into the ventral tegmental area 24, 48 or 72 hr before. In conclusion, the present results suggest that behavioural and ECoG spectrum power effects, triggered by stimulation of dopamine D2 autoreceptors in the ventral tegmental area of rats, seem to be linked to the inhibition of adenylate cyclase activity through a Gi protein and or to other biochemical events linked to Gi proteins.

Antagonism of ethanol effects by Ro 15-4513: an electrophysiological analysis

Ethanol (ETH) and general anesthetics have been reported to facilitate the chloride channel opening, possibly, or at least partly, through an interaction with the GABA-benzodiazepine (BZ) receptor-gated chloride ionophore "supramolecular complex". Recently Ro 15-4513, a novel BZ ligand, has been indicated as a potent and selective antagonist of various ETH-induced behavioral and biochemical effects. However, since its precise characterization is still a matter of debate, we have tested and compared the effect of Ro 15-4513, as well as its antagonism against ETH, in two objective electrophysiological parameters, i.e., the electroencephalograph (EEG) pattern in freely moving rats and single unit activity of reticulata neurons. Ro 15-4513 produced an EEG state of alertness and antagonized the behavioral impairment and the EEG deterioration by ETH. However, while its protective action was consistent against moderate doses (2 g/kg) of ETH, it was much less evident versus higher doses (4 and 8 g/kg). On reticulata cells, Ro 15-4513 potently stimulated their spontaneous firing and reversed the depression by both ETH and Na-pentobarbital. Moreover, the beta-carboline DMCM also had similar effects. The "pure" BZ antagonist Ro 15-1788 was completely inefective against ETH, yet fully cancelled the reversing actions of Ro 15-4513 and DMCM upon ETH or Na-pentobarbital effects. It is concluded that Ro 15-4513 behaves as a BZ inverse agonist, so that its opposition to ETH and Na-pentobarbital is probably the result of its "negative" coupling with the BZ recognition site that triggers the closing of chloride channels. It suggests that BZ inverse agonists might constitute, in the near future, a new class of analeptic drugs.

Ventral tegmental area: site through which dopamine D2-receptor agonists evoke behavioural and electrocortical sleep in rats

1. In freely moving rats the effects on behaviour and electrocortical (ECoG) spectrum power of some dopamine agonists, i.e. apomorphine and (+)-3PPP, given directly into different areas of the rat brain were studied. In particular, dopamine agonists were microinfused in the ventral tegmental area (VTA) and substantia nigra (SN) or into the caudate nucleus, n. accumbens and prefrontal cortex. The ECoG spectrum power effects were continuously analysed by means of a computerized Berg-Fourier analyser as total spectrum power and power in preselected frequency bands. 2. Apomorphine and (+)-3PPP (0.01, 0.1 and 1.0 nmol) given bilaterally into the VTA produced behavioural and ECoG sleep in a dose-dependent fashion. A statistically significant (P less than 0.01) increase in ECoG total spectrum power with a predominant increase in the lower frequency bands (0.25-3, 3-6 and 6-9 Hz) occurred. No behavioural and ECoG changes were evoked by the same doses of apomorphine bilaterally microinfused into the SN or into the caudate nucleus or by (+)-3PPP (1.0 nml) microinjected into the n. accumbens or applied onto the prefrontal cortex. 3. Behavioural and ECoG sleep was also induced in rats after systemic administration of apomorphine (263 nmol kg-1, i.p.). 4. The behavioural and ECoG spectrum power effects of apomorphine (1.0 nmol) bilaterally micro-infused into the VTA were prevented by a previous microinjection into the same site of (-)-sulpiride (9.8 nmol). Similarly, behavioural and ECoG effects evoked by (+)-3PPP (0.1 nmol) given bilaterally into the VTA, were completely antagonized by a previous injection into the same site of haloperidol (16 pmol given 10 min before). In contrast, pretreatment with SCH 23390 (50 pgkg-1, s.c.), a selective antagonist at dopamine Dl-receptors, was unable to antagonize the behavioural and ECoG spectrum power effects of ( +)-3PPP. 5. Soporific effects induced by systemic administration of apomorphine were antagonized by (-)- sulpiride (9.8 nmol) given bilaterally into the VTA 10min before, whereas, yohimbine (1.3 nmol), (an antagonist at alpha 2-adrenoceptors) bilaterally microinfused into the VTA, was ineffective in this respect. 6. The present experiments provide evidence suggesting that stimulation of dopamine D2-receptors located at the cell body level and/or the dendrites of dopaminergic neurones in the VTA may represent the mechanism through which apomorphine or (+)-3PPP exert their soporific effects in rats.

Apomorphine in the evaluation of dopaminergic function in man

1. Apomorphine (Apo), a short acting dopamine (DA) receptor agonist, stimulates growth hormone (GH) secretion, decreases prolactin secretion, induces yawning, penile erections and other physiological effects in man. An effect on behavior, movement disorders and alcoholism has also been described. 2. Apo-mediated responses are used to evaluate DA function in psychiatric and neurological disorders. Many of the studies in schizophrenia using the GH response to Apo as an index of central DA function are difficult to interpret because of failure to control for key variables. 3. The GH response to Apo is a useful system to evaluate the effects of various drugs including peptides which may not cross the blood brain barrier on DA function in man. 4. Apo is a potent sedative. Specific antimanic, antischizophrenic, and anticraving effects in alcoholics have not been convincingly demonstrated. Side effects of Apo and failure to use active placebo make double-blind studies difficult. 5. Apo improves parkinsonian symptoms and certain forms of reflex epilepsy but beneficial effects in other involuntary movement disorders requires further documentation. 6. Apo may be a useful agent to evaluate DA function in impotent patients and predict a therapeutic response to long-acting dopaminergic agents. 7. Impairment of DA function may play a role in diabetic impotence. 8. The development of a simple polygraphic method to monitor the yawning response to Apo may facilitate clinical studies on the basic physiology of yawning in man and the use of the yawning response as a measure of central DA function in schizophrenia and other clinical disorders. 9. The use of Apo with 18F-fluorodeoxyglucose positron emission tomography to examine regional DA function in man opens up a promising area of research. 10. Though long-acting orally active aporphine DA agonists and antagonists have been developed the problem of tolerance may limit their therapeutic potential.

Behavioural and ECoG spectrum power effects after intraventricular injection of drugs altering dopaminergic transmission in rats

In rats with cannulae permanently implanted into the third cerebral ventricle, the effects of different pharmacological manipulations affecting dopaminergic mechanisms, were studied on behaviour and electrocorticographic (ECoG) activity, continuously quantified in its spectrum power. The intraventricular injection (0.1-1 nmol) of (-)3PPP[3-(3-hydroxyphenyl) N-n-propylpiperidine], a specific agonist at dopamine (DA) autoreceptors, produced dose-dependent behavioural sedation or sleep and an increase in ECoG spectrum power, with a predominant increase in the lower frequency bands. Short episodes of stereotyped movements, wet-dog syndrome, penile grooming and erection were also observed. Similar behavioural and ECoG effects were elicited by the intraventricular injection of R-(+)-8-chloro-2,3,4,5-tetrohydro-3-methyl-5-phenyl-1H-3-benzazepi ne-7-ol (SCH 23390), a selective antagonist at D1 postsynaptic receptors, although these were preceded by a short period of behavioural and sexual stimulation. In addition, the intraventricular administration of some neuroleptics, chloropromazine and haloperidol, produced behavioural and ECoG slow wave sleep. No significant changes were observed with a neuroleptic drug, 1-sulpiride, which is reputed to act selectively as an antagonist at dopamine D2 receptors. In conclusion, the present experiments add new evidence in favour of the idea that dopaminergic mechanisms are involved in mammalian species in the control of arousal and that both post-synaptic D1 and D2 receptors may take part in such a control.

Effects of apomorphine and (+/-)-3-(3-hydroxyphenyl)-N-n-propylpiperidine, injected into the striatum, on the caudate spindle in the rat

The caudate spindle in rats was observed following bilateral application of apomorphine (1.5-50 micrograms) and (+/-)-3-(3-hydroxyphenyl)-N-n-propylpiperidine (3-PPP, 0.3-3 micrograms) into the striatum. The smallest dose (1.5 micrograms) of apomorphine enhanced the spindle whereas with a larger dose (50 micrograms), suppression occurred. The preferential dopamine (DA) autoreceptor (inhibitory-receptor) agonist, (+/-)-3-PPP, enhanced the spindle, in a dose-dependent manner. The enhancing effect of apomorphine (1.5 micrograms) and (+/-)-3-PPP (3 micrograms) was prevented by neuroleptics, such as haloperidol (20 micrograms/kg, i.v.) and sulpiride (2 mg/kg, i.v.) at doses which, per se, did not affect the spindle. Small doses of neuroleptics are thought to block DA autoreceptors, suggesting that the enhancing effects of the DA agonists are mediated by autoreceptors. These results lend further support to the assumption that the development of the caudate spindle involves activation or DA receptors. Enhancement of the spindle, induced by injections of apomorphine into the striatum (small dose) and (+/-)-3-PPP, may be mediated by DA autoreceptors (inhibitory-receptors) located at presynaptic elements of the nigro-striatal DA system, while suppression may be due to stimulation of the postsynaptic DA receptors.

Different epileptogenic activities of murine and ovine corticotropin-releasing factor

The behavioral and EEG effects of rat and ovine corticotropin releasing factor (r- and o-CRF) were compared. Both peptides were injected intracerebroventricularly into rats through chronically implanted cannulae. At the doses of 0.1 and 1 microgram both peptides activated the EEG and stimulated motor activity. At the dose of 10 micrograms they produced spiking activity. However, while o-CRF-induced spiking activity was present both in the hippocampus and in the cortical leads and was associated with generalized myoclonic movements, that induced by r-CRF was confined in the hippocampus and was not accompanied by myoclonic movements. Spiking activity induced by r-CRF was suppressed by verapamil, but was not influenced by naloxone.

The dose-response effects of caffeine on sleep in rats

Caffeine at doses of 0.125, 1.25, 12.5 and 25 mg/kg was administered to rats and the subsequent effects on the sleep-wake cycle were measured. The 12.5 and 25 mg/kg doses of caffeine increased wakefulness, and decreased slow wave sleep-1 (SWS1), SWS2, rapid eye movement (REM) sleep and total sleep time (P less than or equal to 0.05). The 0.125 and 1.25 mg/kg doses of caffeine increased SWS1 at the expense of SWS2 (P less than or equal to 0.05), and did not affect total sleep time in any time period measured. Adenosine or adenosine agonists have been shown to increase SWS2 at the expense of waking or SWS1 with an increase in total sleep time. The effects of caffeine on sleep reported in this study suggest that caffeine administration not only antagonizes the effects of adenosine at the receptor level, but also at the behavioral level.

Effects of acute and chronic treatment with an atypical antidepressant drug, nomifensine, on the sleep-wake activity in rats

After the chronic administration of saline, rats were treated with nomifensine (0.1 or 1.0 mg/kg, twice a day, at light and dark onset) for 11 days. The sleep-wake activity was recorded for 24 h on the baseline day (saline), on nomifensine days 1, 5 and 11, and also on day 12, when saline was injected again (withdrawal day). Another group of rats was treated with saline throughout the experiment, without significant effect on the sleep-wake activity. The smaller dose of nomifensine increased non-REM sleep (NREMS) at the expense of wakefulness (W) in the light period. The effect persisted throughout the chronic treatment. A late increase in REM sleep (REMS) was noted on nomifensine days 5 and 11. Nomifensine failed to affect the sleep-wake activity in the dark period. On withdrawal, the baseline percentages of the vigilance states were recovered. As evaluated through spectral analysis of the EEG, the increase in NREMS was accompanied by an increase in slow wave activity. The higher dose of nomifensine elicited an increase in W and a reduction in both sleep states, followed by changes in W and NREMS in the opposite directions. These effects were evident in both the light and the dark periods of the day. Chronic treatment resulted in circadian variations in the effects. Withdrawal of the drug abolished the arousal reaction, but the late increase in NREMS persisted. The dose-dependent biphasic effects of nomifensine on sleep-wake activity can be explained by considering the proposed indirect dopamine and possibly noradrenaline agonist activity of the drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Dopamine autoreceptor antagonists: effects on sleep-wake activity in the rat

The effects of the putative dopamine (DA) autoreceptor antagonists cis-(+)-5-methoxy-1-methyl-2-(di-n-propylamino)tetralin, (+)-UH 232, and cis-(+)-5-methoxy-1-methyl-2-(n-propylamino)tetralin, (+)-AJ 76, on sleep-wake activity, EEG, and motor activity in the rat were studied. Both drugs induced a dose-dependent increase in wakefulness (W) and a reduction in non-REM sleep (NREMS). A definite tendency to a suppression of REM sleep (REMS) could also be observed. The results of spectral analysis indicated that EEG slow wave activity, a marker of sleep intensity, was particularly sensitive to the drugs. Slight differences between the two drugs were observed: (+)-AJ 76 seemed to be more efficacious than (+)-UH 232 in stimulating motor activity. (+)-UH 232 tended to suppress slow wave activity more strongly than (+)-AJ 76. It is suggested that the increase in W following administration of (+)-AJ 76 resulted predominantly from locomotor activation, while (+)-UH 232 might also act on dopaminergic mechanisms involved in the regulation of sleep.

Modifications of sleep parameters in the rat by (+)- and (-)-3-PPP

The effects of subcutaneous administration of the two enantiomers of 3-(3-hydroxyphenyl)-N-n-propylpiperidine (3-PPP), a new dopamine analogue, were studied with regard to their effects on sleep parameters in the rat. The studies with both enantiomers were carried out taking into account their different effects on central dopaminergic receptors. At low doses they act preferentially as autoreceptor agonists; at higher doses the (+)-form is also an agonist while the (-)-form acts as an antagonist at postsynaptic dopamine receptors. The results showed the following: (1) with the high dose of (+)-3-PPP there was no change in REM sleep, but a marked increase in wakefulness; (2) with the high dose of (-)-3-PPP there was a significant increase in REM sleep and in the mean duration of REM episodes; (3) with the low dose of (+)-3-PPP similar results to those described for high-dose (-)-3-PPP were obtained; (4) there was no significant alteration of sleep parameters with the low dose of (-)-3-PPP. The data are discussed in terms of an active role for dopamine in the regulation of REM sleep.

Effects on the caudate spindle in rats of dopamine microinjected into the caudate nucleus

We examined the caudate spindle in control and pargyline-pretreated rats following bilateral application of 3 doses (15, 50 and 150 micrograms/site) of dopamine (DA) into the caudate nucleus. The highest dose of DA (150 micrograms) suppressed the spindle, whereas lower doses (15, 50 micrograms) enhanced the spindle in control rats. Haloperidol given into the bilateral caudate nucleus increased the spindle in control rats. In pargyline-pretreated rats, 50 and 150 micrograms DA caused marked suppression, but 15 micrograms DA caused enhancement. These findings indicate that the DA system may mediate the development of the caudate spindle. Suppression of the caudate spindle induced by intracaudate DA injection may be due to stimulation of postsynaptic DA receptors and enhancement mediated by DA autoreceptors on the DA nerve terminals in the caudate nucleus with a subsequent inhibition of DA neurotransmission.

Sedation and sleep induced by high doses of apomorphine after blockade of D-1 receptors by SCH 23390

The effect of SCH 23390, a selective blocker of D-1 receptors, on apomorphine-induced behavioural and EEG changes was studied in rats. In control rats, a low dose of apomorphine (50 micrograms/kg s.c.) produced sedation associated with EEG synchronization. A high dose of apomorphine (1 mg/kg s.c.) produced stereotypy associated with EEG desynchronization. At the dose of 1 mg/kg i.p., SCH 23390 decreased motor activity but failed to alter the EEG pattern. The administration of either the low or high dose of apomorphine to SCH 23390-treated rats elicited a marked sedative response associated with EEG synchronization. The EEG synchronization produced by apomorphine (50 micrograms/kg) in SCH 23390-treated rats was prevented by (-)-sulpiride (25 mg/kg i.p.), a D-2 receptor blocker. It is concluded that by preventing the excitatory response to apomorphine SCH 23390 discloses the existence of a population of D-2 receptors mediating sedation and sleep.

Response changes after repeated low apomorphine: dopamine autoreceptor desensitization or learning?

Repeated injection of rats with low doses of apomorphine (APO), which selectively interact with dopamine (DA) autoreceptors, caused a change in yawning responses that suggests initial low-APO-induced desensitization of DA autoreceptors, followed by a long-lasting rebound hypersensitivity. Repeated treatment with low APO followed by open-field testing, however, yielded totally different results. APO accelerated intrasession response decrement and upon repeated administration enhanced the intersession response decrement. Both for yawning and open-field behavior, the response change after the second dose of APO was only evident when the first as well as the second APO injection were followed by exposure of the rat to the same test situation. These results indicate that response changes after repeated treatment with low APO are not due to a simple DA-agonist-induced change in receptor sensitivity but that drug experience combined with environmental influences play a decisive role.

Effects of amphetamine and apomorphine on locomotor activity after 6-OHDA and electrolytic lesions of the nucleus accumbens septi

Spontaneous locomotor activity was markedly elevated by electrolytic lesions of the nucleus accumbens. This was true whether or not the dopaminergic input to this nucleus was previously destroyed by injection of 6-hydroxydopamine (6-OHDA) into the region. In animals with electrolytic lesions the locomotor stimulant action of d-amphetamine sulfate (1.5 mg/kg SC) was occluded, while a moderately low dose of apomorphine (0.25 mg/kg SC) produced a striking decrease of locomotor activity. The results are consistent with the view that the efferents of neurons in the nucleus accumbens exert an inhibitory influence on locomotor activity. Hyperactivity results when these efferents are destroyed. The results are also consistent with the view that the locomotor depressant action of apomorphine is mediated, at least partly, by an action at a site other than the nucleus accumbens.

Unilateral dopamine deficit and lateral eeg asymmetry: sleep abnormalities in hemi-Parkinson's patients

The hypothesis was tested that unilateral dopamine deficiency leading to the contralateral extrapyramidal syndrome (hemi-parkinsonism) would cause distinctly asymmetric EEG sleep patterns. In 7 hemi-Parkinson's patients 2 nights of sleep were monitored along with pre-sleep waking periods. No medication was given prior to the first night. The second night followed at least 2 months of L-DOPA medication. Although in all patients sleep architecture was disturbed, no statistically significant asymmetries of sleep patterns were obtained. L-DOPA medication improved the quality of sleep. Delta sleep was most visibly improved. Also, post-treatment enhancement of the mean delta power over the parkinsonian hemisphere was supported statistically. The role of dopamine in slow wave sleep control and mechanisms of contralateral hemisphere involvement are discussed.

Catecholamines and the sleep-wake cycle. I. EEG and behavioral arousal

The exact role of catecholamines (CA) on the sleep-wake cycle is still controversial. Critical analysis of lesion studies tends to suggest a neuromodulatory role for both dopamine (DA) and norepinephrine (NE) on EEG and behavioral arousal. Support for this view is provided by pharmacological studies in which catecholaminergic systems are activated or inhibited. Taken together they show that disturbances in the dynamic balance between neurochemical systems may alter the conditions for wake-triggering mechanisms to express at optimal levels. Large electrolytic or neurotoxic lesions which affect noradrenergic and dopaminergic structures are associated with marked and prolonged EEG changes and decreased behavioral arousal, respectively. In contrast, specific and circumscribed damage restricted to these systems is followed by a transient decrease in waking activity. Thus, results observed after large central lesions are most probably related to destruction of non-catecholaminergic neurons. Inhibition of brain CA synthesis causes behavioral sedation and a decrease in waking activity. Selective pharmacological stimulation of presynaptic alpha-adrenergic (alpha 2) receptors tends to decrease waking, while opposite effects result from alpha 2-receptor blockade. Drugs with agonistic activity at postsynaptic alpha-adrenergic (alpha 1) sites increase EEG desynchronization, but specific blockade of alpha 1-receptor does not result in marked decreases of waking EEG. In contrast, treatments which simultaneously block NE and DA receptors significantly affect waking. Beta-adrenergic receptor blockers show no conclusive effects on waking or sleep. Selective DA-receptor agonists induce biphasic effects, with low doses decreasing and large doses increasing cortical desynchronization and motility. Opposite effects are observed in laboratory animals after injection of specific DA-receptor blockers.

Effect of domperidone on apomorphine-induced growth hormone secretion in normal men

Domperidone, a peripheral dopamine (DA) receptor blocker which poorly crosses the blood-brain barrier and which is inactive towards dopamine-sensitive adenylate cyclase, in a dose (100 micrograms/kg) sufficient to increase serum prolactin levels at least 5-fold, decreased the growth hormone (GH) response to the DA receptor agonist, apomorphine HCI (Apo) (0.5 gm s.c.) in each of six normal men examined. The mean GH increment at 30, 45, 60 and 75 min following Apo injection, the mean individual peak increment and the mean individual GH secretion (ng min) was significantly decreased by domperidone pretreatment (p less than 0.005 -p less than 0.002). These results indicate that in man Apo stimulates GH secretion by an effect on DA receptors which are not linked to adenylate cyclase and which are situated at a locus in the hypothalamic-pituitary axis that lies outside the blood-brain barrier.

Inhibition of evoked dopamine release by monopropionylcadaverine in vitro

A naturally occurring diamine, cadaverine, and one of its acyl derivatives, monopropionylcadaverine, were tested for their effects on the in vitro release of endogenous dopamine from slices of the rat neostriatum. Dopamine release was allowed to occur spontaneously and was evoked by elevating the potassium concentration in the incubation medium or by electric field stimulation. Monopropionylcadaverine had no effect on spontaneous release of dopamine and little effect on potassium-evoked release of dopamine, but at concentrations as low as 10(-8) M in the medium it significantly depressed the electrically induced dopamine release.

Detailed analysis of the effects of apomorphine and d-amphetamine on spontaneous locomotor behaviour of rats as measured in a TV-based, automated open-field system

Rat open field behaviour was measured in a TV-based, automated system. Habituation was evident in saline-treated rats. Most variables measured declined over a 10 min period. Apomorphine affected rat open-field behaviour bimodally, i.e. low doses of apomorphine (0.02-0.08 mg/kg, s.c.) decreased most aspects of rat open-field behaviour, whereas at higher doses (0.2 and 0.5 mg/kg, s.c.) various aspects of open-field behaviour were stimulated. Rearing and average speed, however, were monotonically depressed. Amphetamine (1 and 2 mg/kg) stimulated most aspects of rats open-field behaviour, including rearing. Speed was not affected by amphetamine. Habituation was more pronounced after low doses of apomorphine than after saline treatment and was absent after high doses of apomorphine and after amphetamine. The results represent a detailed analysis of apomorphine and amphetamine effects on rat open-field behaviour and show that the distinct components of this behaviour are affected differentially.

Pharmacologic manipulations of brain catecholamines and the behavior of Callithrix jacchus (marmoset)

In experiment 1, groups of marmosets were injected with 50 - 200 mg/kg L-dopa, 0.5 - 2.0 mg/kg apomorphine (AP), or 0.5 - 5.0 mg/kg methamphetamine. The number of head movements, number of body movements, number of times the tongue was extended, and the time the animal remained in an upright posture were scored during a 90-min period after the injections. L-Dopa and AP induced large dose-dependent increases in body movements and time in upright posture. Furthermore, the smallest dose of AP induced self-destructive behavior. The main effect produced by methamphetamine was a constant turning of the head with the body remaining still. In experiment 2, the marmosets were treated with alpha-methyl-p-tyrosine (AMPT) or haloperidol prior to challenge with AP or methamphetamine. Haloperidol blocked most of the effects of both drugs, while AMPT blocked only methamphetamine effects. In experiment 3, marmosets were injected with increasing doses of haloperidol for 22 days. Upon withdrawal of the neuroleptic, methamphetamine and AP effects were not increased, suggesting absence of supersensitivity of dopaminergic receptors.

Dopaminergic and non-dopaminergic neurons in substantia nigra: differential response to bromocriptine

Bromocriptine reduces the spontaneous firing rate of neurons in the pars compacta of the substantia nigra but does not change the electrical activity of the neurons located in the pars reticulata. On the other hand, bromocriptine induces contralateral circling behaviour in rats with unilateral 6-hydroxydopamine nigral lesion. This increased motor activity follows an initial period of hypomotility. The decrease of the neuronal firing rate in the pars compacta of the substantia nigra coincides with the hypomotility observed in the lesioned rats.

Psychopharmacological effects of low and high doses of apomorphine during ontogeny

The effects of low (0.05 and 0.1 mg/kg) and high (1.0 and 3.0 mg/kg) doses of apomorphine on locomotor activities and stereotypies of 7, 14, 21, 28 and 35 day old rats were measured using a behavioral time-sampling procedure. High doses of apomorphine induced increases in matrix crossings and locomomtor movements at all ages tested. Apomorphine also induced wall climbing behavior in 7 and 14 day olds, but not older animals. A low dose suppression of activity was not seen until beginning at 28 days after birth using matrix crossings as a response measure, or at 35 days after birth using locomotor movements as a response measure. Stereotyped sniffing was not significantly increased by apomorphine until 21 days after birth and thereafter. Results are discussed in terms of differential maturation of dopamine auto- and postsynaptic receptors.

The effects of an alpha-adrenergic agonist or antagonist on sleep during blockade of catecholamine synthesis in the cat

The effects of clonidine (CLO) and phentolamine (PHE) on the sleep-waking cycle in the cat treated with alpha-methyl-p-tyrosine (AMPT) were investigated with continuous 16--24 h polygraphic recordings. For the evaluation of possible cholinergic interactions in the paradoxical sleep (PS) increasing effect of AMPT, an atropine pretreatment was given to a group of cats receiving AMPT. Results were compared with those from previous experiments with PHE and atropine. When given alone, AMPT (150 mg/kg) decreased waking and increased deep slow wave sleep. Consistent with other reports PS was enhanced. These results support the hypothesis that moderate inhibition of catecholaminergic transmission favors the execution of PS in the cat. Previous studies have shown that CLO inhibits and PHE increases PS in the cat. In the present study administration of AMPT (150 mg/kg) did not alter the effect of CLO (0.01 mg/kg) or PHE (20 mg/kg) on PS; if anything, a slight potentiation was observed. These results support the view that stimulation of alpha 2-adrenoceptors is of major importance in the effect of CLO on PS and that in certain situations blockade of these receptors by PHE may contribute to its PS increasing action. The increase in PS induced by AMPT was moderate when compared with PS increase after injection of PHE (20 mg/kg) which enhances significantly both the number of PS episodes and their mean length. Atropine at a small dose of 0.075 mg/kg reverses the effect of PHE on PS, whereas it did not affect the sleep pattern induced by AMPT.

Polygraphic evidence against a critical role of the raphe nuclei in sleep in the rat

The role of the raphe nuclei (RN) in sleep and waking has been investigated in 35 male Wistar rats. After an habituation period to their environment, the rats were continuously recorded (24 h/day), during a 5 day period prior to the lesioning of one or several RN and thereafter during 22 days. The daily slow wave sleep (SWS) and paradoxical sleep (PS) amounts from the 18th to the 22nd day after the lesion were used to classify the rats. Most of the lesions of the RN had no effect, or only transient ones, upon sleep whereas some rats with a long-lasting decrease in both sleep stages had no lesions at the level of the RN. Specific PS alterations were observed after lesions around the A 10 area and specific SWS alterations occur following lesions in the lateral part of the periaqueductal central gray at the level of the rostral end of nucleus raphe dorsalis (RD).

Electrically and chemically induced spindling and slow waves in the encéphale isolé rat: a possible role for dopamine in the regulation of electrocortical activity

The effects of electrical and chemical stimulation of brain areas known to contain dopaminergic cell bodies or terminals on electrocortical activity have been studied in the encéphale isolé rat. Electrical stimulation of medial basal midbrain areas with single stimuli resulted in a single evoked spindle but stimulation of more lateral areas resulted in the appearance of slow waves and spindling. These effects were blocked or reduced by prior treatment with 6-hydroxydopamine. Electrical stimulation of the caudate nucleus also produced a single evoked spindle. Local injection of dopamine into the caudate nucleus induced spindling, with higher doses also resulting in slow waves. Electrical stimulation of the basal forebrain brought about slow waves, an effect which was also seen following injection of dopamine into this area. It appears that electrical stimulation of certain brain areas produces similar effects to those produced by the injection of dopamine. This suggests the involvement of dopaminergic pathways in the production of cortical spindling and slow waves and also the involvement of neurones of both limbic and striatal systems.

Suppression of REM and delta sleep by apomorphine in man: a dopamine mimetic effect

Apomorphine, a direct stimulant of dopamine receptors, was given in nonemetic doses by continuous IV infusion for 180-240 min during night sleep in normal subjects. During apomorphine infusion, a significant reduction of stage (S)4 and an abolition of rapid eye movement (REM) sleep occurred. The percent duration of S2 was significantly increased. In the 240 min following interruption of 240-min infusion of apomorphine, a significant increase of S4 and REM percent duration was observed. The effect of apomorphine infusion on sleep was prevented by the administration of haloperidol or sulpiride, two dopamine receptor blocking agents. This suggests that it is due to a dopamine mimetic action.