Evidence that behavioural and electrocortical sleep induced by guanfacine is due to stimulation of alpha 2-adrenoceptors

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.

Pediatric Sleep Pharmacology: A Primer

"What will you give my child to help him sleep?" is a common question parents ask and some health care providers abhor hearing. Entire families may suffer when one member does not sleep well. Poor sleep may complicate the management of other comorbid conditions. Health care providers may have received only limited education on sleep disorders and are frequently forced to choose between treatment options that are poorly studied in children. Fortunately, when addressed correctly, many children with chronic sleep disorders may improve their sleep and daytime behavior in a relatively short time. This review provides a framework to help understand the causes of poor sleep in children and the potential pharmacologic options.

Catecholaminergic involvement in the control of aggression: hormones, the peripheral sympathetic, and central noradrenergic systems

Noradrenaline is involved in many different functions, which all are known to affect behaviour profoundly. In the present review we argue that noradrenaline affects aggression on three different levels: the hormonal level, the sympathetic autonomous nervous system, and the central nervous system (CNS), in different, but functionally synergistic ways. Part of these effects may arise in indirect ways that are by no means specific to aggressive behaviour, however, they are functionally relevant to it. Other effects may affect brain mechanisms specifically involved in aggression. Hormonal catecholamines (adrenaline and noradrenaline) appear to be involved in metabolic preparations for the prospective fight; the sympathetic system ensures appropriate cardiovascular reaction, while the CNS noradrenergic system prepares the animal for the prospective fight. Indirect CNS effects include: the shift of attention towards socially relevant stimuli; the enhancement of olfaction (a major source of information in rodents); the decrease in pain sensitivity; and the enhancement of memory (an aggressive encounter is very relevant for the future of the animal). Concerning more aggression-specific effects one may notice that a slight activation of the central noradrenergic system stimulates aggression, while a strong activation decreases fight readiness. This biphasic effect may allow the animal to engage or to avoid the conflict, depending on the strength of social challenge. A hypothesis is presented regarding the relevance of different adrenoceptors in controlling aggression. It appears that neurons bearing postsynaptic alpha2-adrenoceptors are responsible for the start and maintenance of aggression, while a situation-dependent fine-tuning is realised through neurons equipped with beta-adrenoceptors. The latter phenomenon may be dependent on a noradrenaline-induced corticosterone secretion. It appears that by activating very different mechanisms the systems working with adrenaline and/or noradrenaline prepare the animal in a very complex way to answer the demands imposed by, and to endure the effects caused by, fights. It is a challenge for future research to elucidate how precisely these mechanisms interact to contribute to functionally relevant and adaptive aggressive behaviour.

Skin conductance response after 6-hydroxydopamine lesion of central noradrenaline system in cats

Absence of skin conductance response (SCR) is a psychophysiological sign frequently observed among schizophrenic patients. This alteration of electrodermal activity can be reproduced in cats and rats by intraventricular administration of 6-hydroxydopamine (6-OHDA), a neurotoxin selectively destroying catecholamine neurons. The finding appears to be quite consistent with the catecholamine hypothesis of schizophrenia. To determine which catecholamine system--the dopamine (DA) or the noradrenaline (NA)--is responsible for the induction of this abnormality, the same dose of 6-OHDA was microinjected to either the ventral tegmental area (VTA, n = 3), through which most DA fibers ascend, or to the ascending noradrenergic bundle (ANB, n = 3), through which most NA fibers ascend. Four cats remained intact as a control for later brain catecholamine estimation. The skin conductance of all pretreatment intact cats (n = 10) showed not only spontaneous fluctuations but also SCRs to auditory stimuli (5 kHz, 100 dB, 1 sec) which habituated with repetition. In contrast, ANB-lesioned cats showed a complete abolition of auditory SCRs, few spontaneous fluctuations, and a low basal skin conductance level. These abnormalities were statistically significant. On the other hand, no change was found in the skin conductance activity of the VTA-lesioned cats. Catecholamine estimation after the experiment confirmed selective destruction of the appropriate system corresponding to each type of lesion. These findings are discussed in the context of the DA or NA theory of schizophrenia, and involvement of the NA system in the pathogenesis of this illness is suggested.

Evidence that locus coeruleus is the site where clonidine and drugs acting at alpha 1- and alpha 2-adrenoceptors affect sleep and arousal mechanisms

The behavioural and electrocortical (ECoG) effects of clonidine were studied after microinjection into the third cerebral ventricle, or microinfusion into some specific areas of the rat brain rich in noradrenaline-containing cell bodies (locus coeruleus) or into areas receiving noradrenergic terminals (dorsal hippocampus, amygdaloid complex, thalamus, frontal and sensimotor cortex). The ECoG effects were continuously analysed and quantified by means of a Berg-Fourier analyser as total power and as power in preselected bands of frequency. Clonidine (9.4 to 75 nmol) given into the third cerebral ventricle produced behavioural sedation and sleep and a dose-dependent increase in ECoG total voltage power as well as in the lower frequency bands. Much lower doses were required to produce similar behavioural and ECoG spectrum power effects after either unilateral or bilateral microinfusion of clonidine into the locus coeruleus. Doses of clonidine equimolar to those given into the third cerebral ventricle, were almost ineffective in inducing behavioural and ECoG sleep after their microinfusion into the dorsal hippocampus. In addition, a dose (0.56 nmol) of clonidine which, given into the locus coeruleus, produced marked behavioural sleep and ECoG synchronization, lacked effects when given into the ventral or anterior thalamus, into the amygdaloid complex or onto the frontal and sensimotor cortex. The behavioural and ECoG spectrum power effects of clonidine given into the third cerebral ventricle or into the locus coeruleus were prevented by antagonists of alpha 2-adrenoceptors but not by alpha 1-adrenoceptor antagonists. Intraventricular microinjection, or microinfusion into the locus coeruleus, of yohimbine, a selective alpha 2-adrenoceptor antagonist, produced behavioural arousal, increase in locomotor and exploratory activity, tachypnoea and ECoG desynchronization with a significant reduction in total voltage power. Similar stimulatory effects were also observed after microinjection of phentolamine into the same sites. No significant effects on behaviour and ECoG activity were evoked after intraventricular injection or microinfusion into the locus coeruleus of prazosin or methoxamine.

Chronic treatment with antidepressant drugs and ECT differentially modifies the hypothermic action of clonidine and guanfacine

The hypothermia inducing action of clonidine and guanfacine was abolished by yohimbine and idazoxan pretreatment which suggests an alpha 2-adrenoceptor involvement in this effect. The effects of acute and chronic treatment with the antidepressant drugs desipramine (DMI), amitriptyline (AMI), maprotiline (MAP), mianserin (MIAN), iprindol (IPR), alaproclate (ALA) and electroconvulsive treatment (ECT) on the hypothermic action of the alpha 2-adrenoceptor agonists clonidine and guanfacine were studied. Acute administration of MIAN potentiated clonidine induced hypothermia whereas acute MIAN, IPR and ALA potentiated guanfacine induced hypothermia. Repetitive DMI, AMI and MAP treatment attenuated clonidine-induced hypothermia whereas guanfacine-induced hypothermia was potentiated by chronic treatment with DMI, AMI, MAP and MIAN, ECT applied without anaesthesia attenuated both clonidine and guanfacine hypothermia, however, under ethyl ether anaesthesia ECT was effective only towards guanfacine hypothermia. This discrepancy is discussed in terms of the relative selectivity of the agonists used, the reliability of agonist studies for indexing receptor function, and possible pharmacokinetic interaction.