Lauri Alanko

Local energy depletion in the basal forebrain increases sleep

Sleep saves energy, but can brain energy depletion induce sleep? We used 2,4‐dinitrophenol (DNP), a molecule which prevents the synthesis of ATP, to induce local energy depletion in the basal forebrain of rats. Three‐hour DNP infusions induced elevations in extracellular concentrations of lactate, pyruvate and adenosine, as well as increases in non‐REM sleep during the following night. Sleep was not affected when DNP was administered to adjacent brain areas, although the metabolic changes were similar. The amount and the timing of the increase in non‐REM sleep, as well as in the concentrations of lactate, pyruvate and adenosine with 0.5–1.0 mm DNP infusion, were comparable to those induced by 3 h of sleep deprivation. Here we show that energy depletion in localized brain areas can generate sleep. The energy depletion model of sleep induction could be applied to in vitro research into the cellular mechanisms of prolonged wakefulness.

Opposite changes in adenosine A1 and A2A receptor mRNA in the rat following sleep deprivation.

Extracellular levels of adenosine increase in basal forebrain following prolonged wakefulness. Moreover, perfusion of adenosine into basal forebrain increases sleep. In this study we have examined the adenosine receptor subtypes, A1 and A2A, for changes in the levels of mRNA using RT-PCR and in situ hybridization and the receptor ligand binding efficiency using autoradiography following 3 and 6 h of sleep deprivation. We observed that A1 receptor mRNA levels increased in basal forebrain with no changes in other forebrain areas examined. A1 receptor binding was not affected. A2A receptor mRNA and ligand binding were undetectable in basal forebrain. However, in the olfactory tubercle, A2A mRNA and receptor binding decreased significantly. Based on the significant increase in the A1 but not in A2A receptor, we hypothesize that the effects of sleep deprivation-induced increased adenosine are mediated by A1 receptor in basal forebrain of rats.

Sleep deprivation increases somatostatin and growth hormone-releasing hormone messenger RNA in the rat hypothalamus

We studied the effect of sleep deprivation (SD) on the amount of somatostatin (SRIF) and growth hormone‐releasing hormone (GHRH) mRNA in rat hypothalamic nuclei. According to earlier studies SRIF possibly facilitates REM sleep and GHRH slow‐wave sleep. Adult male rats were sleep deprived by the gentle handling method either for 6 h during the first half of the light phase or for 12 h during the dark phase. Undisturbed rats sacrificed at the same time as the SD rats served as controls. After oligonucleotide in situ hybridization the amount of SRIF and GHRH mRNA was measured in brain sections by image analysis and cell count. SD increased the amount of SRIF mRNA in the arcuate nucleus (ARC). In the periventricular nucleus (PE) there was no effect. The amount of GHRH mRNA increased in the paraventricular nucleus (PA) in the 6 h SD group but no effect was detected in ARC. In the periventromedial hypothalamic area (pVMH) the amount of GHRH mRNA was higher in the control rats sacrificed in the morning (09.00 hours) than in the afternoon (15.00 hours), and SD had no effect. We conclude that SRIF cells in ARC and GHRH cells in PA are modulated by sleep loss, which is in accordance with the possible sleep regulatory function of these neuropeptides.

The effect of age on prepro-orexin gene expression and contents of orexin A and B in the rat brain

Orexin A and B (hypocretin 1 and 2) are hypothalamic peptides, which are synthesized in the lateral hypothalamus. Orexins participate in the regulation energy balance, food intake, vigilance and several endocrine and autonomic functions. The widespread projections of the orexin neurons suggest that they may have a role in coordination of different brain activities. The effects of ageing on the orexin system have not been studied previously. Prepro-orexin gene expression in the lateral hypothalamus, and the contents of orexin A and B peptides in the lateral hypothalamus and hypothalamus were measured in young, middle-aged and old (3, 12 and 24 months) rats. In the course of ageing, the expression of the prepro-orexin gene and the levels of orexin A and B decreased; the main decrease occurred by 12 months. Sleep deprivation for 6h increased slightly the expression of prepro-orexin gene in young rats. Deterioration of the orexin system may play a role in the phenomenon associated with aging, e.g. decreased consolidation of vigilance states, endocrine changes and dysfunctions of autonomic nervous system.

Insomnia is a frequent finding in adults with Asperger syndrome

BackgroundAsperger syndrome (AS) is a neurodevelopmental disorder belonging to autism spectrum disorders with prevalence rate of 0,35% in school-age children. It has been most extensively studied in childhood while there is scarcity of reports concerning adulthood of AS subjects despite the lifelong nature of this syndrome. In children with Asperger syndrome the initiation and continuity of sleep is disturbed because of the neuropsychiatric deficits inherent of AS. It is probable that sleep difficulties are present in adulthood as well. Our hypothesis was that adults with AS suffer from difficulty in initiating and maintaining sleep and nonrestorative sleep (insomnia).Methods20 AS without medication were compared with 10 healthy controls devoid of neuropsychiatric anamnesis. Clinical examination, blood test battery and head MRI excluded confounding somatic illnesses. Structured psychiatric interview for axis-I and axis-II disorders were given to both groups as well as Beck Depression Inventory and Wechsler adult intelligence scale, revised version.Sleep quality was assessed with sleep questionnaire, sleep diary during 6 consecutive days and description of possible sleep problems by the participants own words was requested.Resultscompared with controls and with normative values of good sleep, AS adults had frequent insomnia. In sleep questionnaire 90% (18/20), in sleep diary 75% (15/20) and in free description 85% (17/20) displayed insomnia. There was a substantial psychiatric comorbidity with only 4 AS subject devoid of other axis-I or axis-II disorders besides AS. Also these persons displayed insomnia. It can be noted that the distribution of psychiatric diagnoses in AS subjects was virtually similar to that found among patient with chronic insomnia.Conclusionsthe neuropsychiatric deficits inherent of AS predispose both to insomnia and to anxiety and mood disorders. Therefore a careful assessment of sleep quality should be an integral part of the treatment plan in these individuals. Conversely, when assessing adults with chronic insomnia the possibility of autism spectrum disorders as one of the potential causes of this condition should be kept in mind.

Sleep deprivation increases brain serotonin turnover in the rat.

IN order to study possible time-dependent changes in serotonin metabolism in rat brain, male Wistar rats were subjected to 3, 6 or 12 h total sleep deprivation (SD) by gentle handling. In addition two groups of rats subjected first to 6 h SD were allowed 2 or 4 h rebound sleep. Tissue concentrations of serotonin (5-HT) and 5-hydroxyin-doleacetic acid (5-HIAA) were measured from several brain areas using HPLC/ECD. SD significantly increased the 5-HIAA/5-HT ratio in frontal cortex, hippocampus, hypothalamus and brain stem, indicating increased 5-HT turnover in those areas. After 2 and 4 h rebound sleep, the 5-HIAA/5-HT ratio was similar to that in controls. We conclude that a short SD increases 5-HT turnover in the rat brain for the duration of SD only.

REM sleep deprivation induces galanin gene expression in the rat brain

Rats were deprived of REM sleep for 24 h by keeping them on small platforms that were placed in a water bath (the platform method). Galanin coding mRNA was visualized using in situ hybridization, and cells expressing galanin mRNA were counted. In REM sleep-deprived animals the cell count was higher in the preoptic area and periventricular nucleus. Lesions of this area have been reported to induce wakefulness in cats and rats. Galanin administered into the lateral ventricle had no effect on sleep. We conclude that REM sleep deprivation can induce galanin gene expression in some brain areas, but galanin alone does not modify spontaneous sleep.

The effect of REM sleep deprivation on somatostatin and growth hormone-releasing hormone gene expression in the rat hypothalamus

Growth hormone‐releasing hormone (GHRH) and somatostatin (SRIF) have been implicated as sleep factors. We studied how the hypothalamic SRIF/GHRH system is affected by possible feedback regulation resulting from REM sleep deprivation at the level of gene expression and how this is reflected in serum growth hormone (GH) content. Male rats were deprived of REM sleep on small platforms for 24 or 72 h, and one group was allowed a rebound sleep of 24 h after 72 h deprivation. Animals maintained on large platforms and animals taken directly from their home cages served as controls. In situ hybridization was made from 20 μm cryosections through the periventricular, paraventricular and arcuate hypothalamic nuclei using oligonucleotide probes for GHRH and SRIF. The number of cells expressing SRIF or GHRH was counted. Serum GH was measured by means of radioimmunoassay in similarly treated rats. Fewer cells expressed GHRH in the paraventricular nucleus of animals subjected to 24 and 72 h of REM sleep deprivation than in home control animals. A similar trend was observed in the arcuate nucleus. The number of cells expressing SRIF was elevated in the arcuate nucleus after 24 h of REM sleep deprivation but not after 72 h. In the periventricular nucleus the number of cells expressing SRIF was higher after 72 h of deprivation when compared to expression in animals maintained on large platforms. Serum GH levels were decreased in animals maintained on either small or large platforms. It is concluded that the expression of the SRIF and GHRH genes is modulated by REM sleep deprivation.

Adenosine, Energy Metabolism, and Sleep

While the exact function of sleep remains unknown, it is evident that sleep was developed early in phylogenesis and represents an ancient and vital strategy for survival. Several pieces of evidence suggest that the function of sleep is associated with energy metabolism, saving of energy, and replenishment of energy stores. Prolonged wakefulness induces signs of energy depletion in the brain, while experimentally induced, local energy depletion induces increase in sleep, similarly as would a period of prolonged wakefulness. The key molecule in the induction of sleep appears to be adenosine, which induces sleep locally in the basal forebrain.

Nitrobenzylthioinosine (NBMPR) binding and nucleoside transporter ENT1 mRNA expression after prolonged wakefulness and recovery sleep in the cortex and basal forebrain of rat

We have previously shown that extracellular adenosine levels increase locally in the basal forebrain (BF) during prolonged wakefulness, yet the cellular mechanisms of this local accumulation have remained unknown. The extracellular adenosine levels are strictly regulated by adenosine metabolism and its transport through cell membrane by the nucleoside transporters. As we previously showed that the key adenosine metabolizing enzymes were not affected by prolonged wakefulness, we now focussed on potential changes in the nucleoside transporters. In the present study, we measured the binding of nitrobenzylthioinosine (NBMPR), an ENT1 transporter inhibitor, and the ENT1 transporter mRNA after prolonged wakefulness and recovery sleep. Rats were sleep‐deprived for 3 or 6 h using gentle handling. After 6 h one group was allowed to sleep for 2 h. NBMPR binding was determined from BF and cortex by incubating tissue extracts with [3H] NBMPR. The in situ hybridization was carried out on 20 μm cryosections using [35S]dATP‐labelled oligonucleotide probe for ENT1 mRNA. The NBMPR binding was significantly decreased in the BF, but not in the cortex, after 6 h sleep deprivation when compared with the time‐matched controls, suggesting a decline in adenosine transport. The expression of ENT1 mRNA did not change during prolonged wakefulness or recovery sleep in either cortex or the BF, although circadian variations were measured in both areas. We conclude that the regional decrease in adenosine transport could contribute to the gradual accumulation of extracellular adenosine in the basal forebrain during prolonged wakefulness.