Cannabidiol Partially Blocks the Excessive Sleepiness in Hypocretindeficient Rats: Preliminary Data

BACKGROUND

Excessive daytime sleepiness and cataplexy are among the symptoms of narcolepsy, a sleep disorder caused by the loss of hypocretin/orexin (HCRT/OX) neurons placed into the Hypothalamus (LH). Several treatments for managing narcolepsy include diverse drugs to induce alertness, such as antidepressants, amphetamine, or modafinil, etc. Recent evidence has shown that cannabidiol (CBD), a non-psychotropic derived from Cannabis sativa, shows positive therapeutic effects in neurodegenerative disorders, including Parkinson´s disease. Furthermore, CBD provokes alertness and enhances wake-related neurochemicals in laboratory animals. Thus, it is plausible to hypothesize that excessive somnolence observed in narcolepsy might be blocked by CBD.

OBJECTIVE

Here, we determined whether the systemic injection of CBD (5mg/kg, i.p.) would block the excessive sleepiness in a narcoleptic model.

METHODS

To test this idea, the neurotoxin hypocretin-2-saporin (HCRT2/SAP) was bilaterally injected into the LH of rats to eliminate HCRT leading to the establishment of narcoleptic-like behavior. Since excessive somnolence in HCRT2/SAP lesioned rats has been observed during the lights-off period, CBD was administered at the beginning of the dark phase.

RESULTS

Hourly analysis of sleep data showed that CBD blocked the sleepiness during the lights-off period across 7h post-injection in lesioned rats.

CONCLUSION

Taking together, these preliminary findings suggest that CBD might prevent sleepiness in narcolepsy.

Orexin cell transplant reduces behavioral arrest severity in narcoleptic mice

Narcolepsy is a sleep disorder that has been associated with the loss of orexinergic neurons from the lateral hypothalamic area. This loss leads to dysregulated sleep and cataplexy attacks. Therapeutic options are currently limited to symptom management with pharmacotherapy and nonpharmacological approaches. Nonetheless, cell replacement therapy could offer relief, and research in the field has yielded positive results for other neurodegenerative disorders, such as Parkinson's disease. Thus, we propose that orexin cell rich grafts could help improve narcoleptic symptoms in the orexin/ataxin-3 mouse model of narcolepsy. For this purpose, we isolated EGFP+ cells from either orexin/EGFP or CAG-EGFP mice with the use of a flow cytometer and grafted them into the pedunculopontine and laterodorsal tegmentum nuclei (PPT/LDDT) of orexin/ataxin-3 mice. Our results show that even small orexinergic grafts can reduce the severity of behavioral arrests, with a median reduction of 30.31% in episode duration, 51.35% for number of events and 69.73% in time spent in the behavioral arrest state and help with sleep fragmentation measured in number of bouts per behavioral state. Surprisingly, control grafts made from cerebellar tissue also reduced behavioral arrest severity, but to a lesser degree. Although still at a very early stage, these results show that there is potential in cell grafts for improving aspects of the narcoleptic phenotype and further research could help elucidate realistic expectations of an orexin cell replacement therapy for narcolepsy.

Chronic exercise modulates the cellular immunity and its cannabinoid receptors expression

The impact of performing exercise on the immune system presents contrasting effects on health when performed at different intensities. In addition, the consequences of performing chronic exercise have not been sufficiently studied in contrast to the effects of acute bouts of exercise. The porpoise of this work was to determine the effect that a popular exercise regimen (chronic/moderate/aerobic exercise) has on the proportion of different immune cell subsets, their function and if it affects the cannabinoid system with potentially functional implications on the immune system. A marked increase in several immune cell subsets and their expression of cannabinoid receptors was expected, as well as an enhanced proliferative and cytotoxic activity by total splenocytes in exercised animals. For this study male Wistar rats performed treadmill running 5 times a week for a period of 10 weeks, at moderate intensity. Our results showed a significant decrease in lymphocyte subpopulations (CD4+, Tγδ, and CD45 RA+ cells) and an increase in the cannabinoid receptors expression in those same cell. Although functional assays did not reveal any variation in total immunoglobulin production or NK cells cytotoxic activity, proliferative capability of total splenocytes increased in trained rats. Our results further support the notion that exercise affects the immunological system and extends the description of underlying mechanisms mediating such effects. Altogether, our results contribute to the understanding of the benefits of exercise on the practitioner´s general health.

The Substantia Nigra Is Permissive and Gains Inductive Signals When Lesioned for Dopaminergic Differentiation of Embryonic Stem Cells

Transplantation of dopaminergic (DA) cells into the striatum can rescue from dopamine deficiency in a Parkinson's disease condition, but this is not a suitable procedure for regaining the full control of motor activity. The minimal condition toward recovering the nigrostriatal pathway is the proper innervation of transplanted DA neurons or their precursors from the substancia nigra pars compacta (SNpc) to their target areas. However, functional integration of transplanted cells would require first that the host SNpc is suitable for their survival and/or differentiation. We recently reported that the intact adult SNpc holds a strong neurogenic environment, but primed embryonic stem cells (ie, embryoid body cells, EBCs) could not derive into DA neurons. In this study, we transplanted into the intact or lesioned SNpc, EBCs derived from embryonic stem cells that were prompt to differentiate into DA neurons by the forced expression of Lmx1a in neural precursor cells (R1B5/NesE-Lmx1a). We observed that, 6 days posttransplantation (dpt), R1B5 or R1B5/NesE-Lmx1a EBCs gave rise to Nes⁺ and Dcx⁺ cells within the host SNpc, but a large number of Th⁺ cells derived only from EBCs exogenously expressing Lmx1a. In contrast, when transplantation was carried out into the 6-hydroxidopamine-lesioned SNpc, the emergence of Th⁺ cells from EBCs was independent of exogenous Lmx1a expression, although these cells were not found by 15 dpt. These results suggest that the adult SNpc is not only a permissive niche for initiation of DA differentiation of non-neuralized cells but also releases factors upon damage that promote the acquisition of DA characteristics by transplanted EBCs.

The artificial sweetener Splenda intake promotes changes in expression of c-Fos and NeuN in hypothalamus and hippocampus of rats

BACKGROUND

Obesity is the result of the interaction of multiple variables, including the excessive increase of sugar-sweetened beverages consumption. Diets aimed to treat obesity have suggested the use of artificial sweeteners. However, recent evidence has shown several health deficits after intake of artificial sweeteners, including effects in neuronal activity. Therefore, the influence of artificial sweeteners consumption such as Splenda, on the expression of c-Fos and neuronal nuclear protein (NeuN) in hypothalamus and hippocampus remains to be determined.

OBJECTIVES

We investigated the effects on c-Fos or NeuN expression in hypothalamus and hippocampus of Splenda-treated rats.

METHODS

Splenda was diluted in water (25, 75 or 250 mg/100 mL) and orally given to rats during 2 weeks ad libitum. Next, animals were sacrificed by decapitation and brains were collected for analysis of c-Fos or NeuN immunoreactivity.

RESULTS

Consumption of Splenda provoked an inverted U-shaped dose-effect in c-Fos expression in ventromedial hypothalamic nucleus while similar findings were observed in dentate gyrus of hippocampus. In addition, NeuN immunoreactivity was enhanced in ventromedial hypothalamic nucleus at 25 or 75 mg/100 mL of Splenda intake whereas an opposite effect was observed at 250 mg/100 mL of artificial sweetener consumption. Lastly, NeuN positive neurons were increased in CA2/CA3 fields of hippocampus from Splenda-treated rats (25, 75 or 250 mg/100 mL).

CONCLUSION

Consuming Splenda induced effects in neuronal biomarkers expression. To our knowledge, this study is the first description of the impact of intake Splenda on c-Fos and NeuN immunoreactivity in hypothalamus and hippocampus in rats.

Transcranial magnetic stimulation as an antioxidant

In the last decades, different transcranial magnetic stimulation protocols have been developed as a therapeutic tool against neurodegenerative and psychiatric diseases, although the biochemical, molecular and cellular mechanisms underlying these effects are not well known. Recent data show that those magnetic stimulation protocols showing beneficial effects could trigger an anti-oxidant action that would favour, at least partially, their therapeutic effect. We have aimed to review the molecular effects related to oxidative damage induced by this therapeutic strategy, as well as from them addressing a broader definition of the anti-oxidant concept.

Intrastriatal Chromospheres' Transplant Reduces Nociception in Hemiparkinsonian Rats

The present study evaluates the possible antinociceptive effect of chromosphere transplants in rats injected with 6-hydroxydopamine (6-OHDA), a model of Parkinson's disease. Male adult Wistar rats received 40μg/0.5μl of 6-OHDA or 0.5μl of vehicle into the left substantia nigra (SNc). Rats were evaluated for mechanical allodynia, cold allodynia, thermal hyperalgesia and formalin. Rats with altered nociceptive threshold were transplanted with chromospheres. After transplant, rats were evaluated every week. Our results confirm that 6-OHDA injection into rat's SNc reduces mechanical, thermal, and chemical thresholds. Interestingly, chromospheres' transplant reverted 6-OHDA-induced allodynia and hyperalgesia. The antinociceptive effect induced by chromospheres was dopamine D2- and opioid-receptor dependent since sulpiride or naltrexone reverted its effect.

Historical perspective of cell transplantation in Parkinson’s disease

Cell grafting has been considered a therapeutic approach for Parkinson’s disease (PD) since the 1980s. The classical motor symptoms of PD are caused by the loss of dopaminergic neurons in the substantia nigra pars compacta, leading to a decrement in dopamine release in the striatum. Consequently, the therapy of cell-transplantation for PD consists in grafting dopamine-producing cells directly into the brain to reestablish dopamine levels. Different cell sources have been shown to induce functional benefits on both animal models of PD and human patients. However, the observed motor improvements are highly variable between individual subjects, and the sources of this variability are not fully understood. The purpose of this review is to provide a general overview of the pioneering studies done in animal models of PD that established the basis for the first clinical trials in humans, and compare these with the latest findings to identify the most relevant aspects that remain unanswered to date. The main focus of the discussions presented here will be on the mechanisms associated with the survival and functionality of the transplants. These include the role of the dopamine released by the grafts and the capacity of the grafted cells to extend fibers and to integrate into the motor circuit. The complete understanding of these aspects will require extensive research on basic aspects of molecular and cellular physiology, together with neuronal network function, in order to uncover the real potential of cell grafting for treating PD.

Recovery of glomerular morphology in the olfactory bulb of young mice after disruption caused by continuous odorant exposure

Olfactory glomeruli are the first synaptic site of the olfactory system and are formed by the convergence of axons of the same type of sensory neurons onto the olfactory bulbs of the brain. Although the anatomical organization of glomeruli is conserved across species, their particular role in olfactory processing remains uncertain. We studied the composition and maintenance of glomeruli by means of a genetic model, mI7-IRES-tauGFP knock-in young mice, where the cytoskeleton of sensory neurons expressing the mI7 olfactory receptor is tagged with green fluorescent protein. Animals were continuously exposed to heptaldehyde, a cognate ligand of the mI7 receptor, from postnatal days 5-10. We hypothesized that continuous odorant exposure will induce changes in glomerular morphology, and that this can be recovered if the normal odorant environment is reestablished within the early postnatal period. We assessed changes in the distribution of mI7 axons in glomerular morphology, as well as possible changes in the number of the mI7 olfactory sensory neurons. Following odorant exposure the well-defined convergence of mI7 fibers into a single glomerulus was disrupted, producing numerous neighboring glomeruli partially innervated by mI7 fibers. After the normal odor environment was reestablished the number of glomeruli partially innervated by mI7 fibers decreased significantly. Moreover, we found that multiple supernumerary mI7 glomeruli were formed. Our results confirm the significant role of sensory input in glomerular formation and maintenance. Additionally, we show that the developing olfactory system actively maintains glomerular morphology, suggesting the importance of this for olfactory processing.

Understanding sleep-wake mechanisms and drug discovery

INTRODUCTION

Although not discernible at first glance, sleep is a highly active and regulated brain state. Although we spend practically one third of our lifetimes in this stage, its importance is often taken for granted. Sleep loss can lead to disease, error and economic loss. Our understanding of how sleep is achieved has greatly advanced in recent years, and with that, the management of sleep disorders has improved. There is still room for improvement and recently many new compounds have reached clinical trials with a few being approved for commercial use. Areas covered: In this review, the authors make the case of sleep disorders as a matter of public health. The mechanisms of sleep transition are discussed emphasizing the wake and sleep promoting interaction of different brain regions. Finally, advances in pharmacotherapy are examined in the context of chronic insomnia and narcolepsy. Expert opinion: The orexinergic system is an example of a breakthrough in sleep medicine that has catalyzed drug development. Nevertheless, sleep is a topic still with many unanswered questions. That being said, the melanin-concentrating hormone system is becoming increasingly relevant and we speculate it will be the next target of sleep medication.

Lipopolysaccharide Binding Protein and Oxidative Stress in a Multiple Sclerosis Model

Recent findings in experimental autoimmune encephalomyelitis (EAE) suggest that altering certain bacterial populations present in the gut may lead to a proinflammatory condition, that could result in the development of multiple sclerosis (MS). Also, Reactive Oxygen Species seem to be involved in the course of MS. In this study, it has been aimed to relate all these variables starting from an analysis of the lipopolysaccharide (LPS) and LPS-binding protein (LBP) with the determination of parameters related to oxidative stress in the blood, brain and spinal cord. For this purpose, samples obtained from EAE rats and relapsing-remitting (RRMS) MS patients were used. In addition, EAE rats were treated with Natalizumab, N-acetyl-cysteine and dimethyl fumarate. Natalizumab was also employed in RRMS. The results of this study revealed an improvement in the clinical symptoms of the EAE and MS with the treatments, as well as a reduction in the oxidative stress parameters and in LBP. Correlations between the clinical variables of the disease, i.e. oxidative damage and LBP, were established. Although the conclusions of this research are indeed relevant, further investigation would be necessary to establish the intrinsic mechanisms of the MS-oxidative stress-microbiota relationship.

Mouse embryonic stem cell-derived cells reveal niches that support neuronal differentiation in the adult rat brain

A neurogenic niche can be identified by the proliferation and differentiation of its naturally residing neural stem cells. However, it remains unclear whether "silent" neurogenic niches or regions suitable for neural differentiation, other than the areas of active neurogenesis, exist in the adult brain. Embryoid body (EB) cells derived from embryonic stem cells (ESCs) are endowed with a high potential to respond to specification and neuralization signals of the embryo. Hence, to identify microenvironments in the postnatal and adult rat brain with the capacity to support neuronal differentiation, we transplanted dissociated EB cells to conventional neurogenic and non-neurogenic regions. Our results show a neuronal differentiation pattern of EB cells that was dependent on the host region. Efficient neuronal differentiation of EB cells occurred within an adjacent region to the rostral migratory stream. EB cell differentiation was initially patchy and progressed toward an even distribution along the graft by 15-21 days post-transplantation, giving rise mostly to GABAergic neurons. EB cells in the striatum displayed a lower level of neuronal differentiation and derived into a significant number of astrocytes. Remarkably, when EB cells were transplanted to the striatum of adult rats after a local ischemic stroke, increased number of neuroblasts and neurons were observed. Unexpectedly, we determined that the adult substantia nigra pars compacta, considered a non-neurogenic area, harbors a robust neurogenic environment. Therefore, neurally uncommitted cells derived from ESCs can detect regions that support neuronal differentiation within the adult brain, a fundamental step for the development of stem cell-based replacement therapies.

Sleep deprivation induces differential morphological changes in the hippocampus and prefrontal cortex in young and old rats

Sleep is a fundamental state necessary for maintenance of physical and neurological homeostasis throughout life. Several studies regarding the functions of sleep have been focused on effects of sleep deprivation on synaptic plasticity at a molecular and electrophysiological level, and only a few studies have studied sleep function from a structural perspective. Moreover, during normal aging, sleep architecture displays some changes that could affect normal development in the elderly. In this study, using a Golgi-Cox staining followed by Sholl analysis, we evaluate the effects of 24 h of total sleep deprivation on neuronal morphology of pyramidal neurons from Layer III of the prefrontal cortex (PFC) and the dorsal hippocampal CA1 region from male Wistar rats at two different ages (3 and 22 months). We found no differences in total dendritic length and branching length in both analyzed regions after sleep deprivation. Spine density was reduced in the CA1 of young-adults, and interestingly, sleep deprivation increased spine density in PFC of aged animals. Taken together, our results show that 24 h of total sleep deprivation have different effects on synaptic plasticity and could play a beneficial role in cognition during aging.

Global actions of nicotine on the striatal microcircuit

The question to solve in the present work is: what is the predominant action induced by the activation of cholinergic-nicotinic receptors (nAChrs) in the striatal network given that nAChrs are expressed by several elements of the circuit: cortical terminals, dopamine terminals, and various striatal GABAergic interneurons. To answer this question some type of multicellular recording has to be used without losing single cell resolution. Here, we used calcium imaging and nicotine. It is known that in the presence of low micromolar N-Methyl-D-aspartate (NMDA), the striatal microcircuit exhibits neuronal activity consisting in the spontaneous synchronization of different neuron pools that interchange their activity following determined sequences. The striatal circuit also exhibits profuse spontaneous activity in pathological states (without NMDA) such as dopamine depletion. However, in this case, most pathological activity is mostly generated by the same neuron pool. Here, we show that both types of activity are inhibited during the application of nicotine. Nicotine actions were blocked by mecamylamine, a non-specific antagonist of nAChrs. Interestingly, inhibitory actions of nicotine were also blocked by the GABA_A-receptor antagonist bicuculline, in which case, the actions of nicotine on the circuit became excitatory and facilitated neuronal synchronization. We conclude that the predominant action of nicotine in the striatal microcircuit is indirect, via the activation of networks of inhibitory interneurons. This action inhibits striatal pathological activity in early Parkinsonian animals almost as potently as L-DOPA.

Retracted: Hypocretin (orexin) cell transplantation diminishes narcoleptic-like sleep behavior in rats

Arias-Carrión, O.; Drucker-Colín, R.; Murillo-Rodríguez, E. "Hypocretin (orexin) cell transplantation diminishes narcoleptic-like sleep behavior in rats." CNS Neurol. Disord. Drug Targets, 2011,11(7). The above-cited paper has been retracted from CNS & Neurological Disorders-Drug Targets at the request of the authors. The authors advised the Journal of their intention to perform additional experiments in order to strengthen their initial results, at which time an amended manuscript may be submitted.

Odor memory stability after reinnervation of the olfactory bulb

The olfactory system, particularly the olfactory epithelium, presents a unique opportunity to study the regenerative capabilities of the brain, because of its ability to recover after damage. In this study, we ablated olfactory sensory neurons with methimazole and followed the anatomical and functional recovery of circuits expressing genetic markers for I7 and M72 receptors (M72-IRES-tau-LacZ and I7-IRES-tau-GFP). Our results show that 45 days after methimazole-induced lesion, axonal projections to the bulb of M72 and I7 populations are largely reestablished. Furthermore, regenerated glomeruli are re-formed within the same areas as those of control, unexposed mice. This anatomical regeneration correlates with functional recovery of a previously learned odorant-discrimination task, dependent on the cognate ligands for M72 and I7. Following regeneration, mice also recover innate responsiveness to TMT and urine. Our findings show that regeneration of neuronal circuits in the olfactory system can be achieved with remarkable precision and underscore the importance of glomerular organization to evoke memory traces stored in the brain.

Fetal substantia nigra and adrenal medullary grafts placed contralateral to the nigrostriatal lesion side induce a decrease in turning behavior but not in dopamine receptor density

Motor asymmetries as well as changes in the density of postsynaptic dopamine receptors produced by unilateral denervation of the striatum have been reduced by both substantia nigra (SN) and adrenal medullary (AM) grafts. Since to this date all studies have placed the grafts on the side ipsilateral to the lesion, the purpose of this study was to determine whether similar effects can be obtained when grafts are placed contralateral to the denervated side. The results of this study showed that 6-hydroxydopamine-lesioned rats followed up to 150 days with contralaterally placed intraventricular fetal substantia nigra grafts and fetal adrenal medulla grafts have a reduction of turning behavior of 41% and 34% respectively. However, contrary to ipsilateral grafts no normalization of dopamine receptor density as measured by [3H]spiperone autoradiography was observed 6 months after SN grafts, however, after AM grafts normalization did occur except in the anterior portion of the striatum. These results suggest that the compensatory motor changes induced by the grafted tissues could be mediated by mechanisms unrelated to changes in receptor density.

Transcranial magnetic stimulation reduces nociceptive threshold in rats

Transcranial magnetic stimulation (TMS) is a procedure that uses magnetic fields to stimulate or inhibit nerve cells in the brain noninvasively. TMS induces an electromagnetic current in the underlying cortical neurons. Varying frequencies and intensities of TMS increase or decrease excitability in the cortical area directly targeted. It has been suggested that TMS has potential in the treatment of some neurological disorders such as Parkinson's disease, stroke, and depression. Initial case reports and open label trials reported by several groups support the use of TMS in pain treatment. In the present study, we evaluated the effect of TMS on the nociceptive threshold in the rat. The parameters used were a frequency of 60 Hz and an intensity of 2 and 6 mT for 2 hr twice per day. After 5 days of TMS treatment, rats were evaluated for mechanical, chemical, and cold stimulation. We observed a significant reduction in the nociceptive threshold in TMS-treated rats but not in sham-treated rats in all behavioral tests evaluated. When TMS treatment was stopped, a slow recovery to normal mechanic threshold was observed. Interestingly, i.c.v. MK-801 or CNQX administration reverted the TMS-induced pronociception. The results suggest that high-frequency TMS can alter the nociceptive threshold and produce allodynia in the rats; results suggest the involvement of NMDA and AMPA/KA receptors on TMS-induced allodynia in the rat.

Cellular viability effects of fatty acid amide hydrolase inhibition on cerebellar neurons

The endocannabinoid anandamide (ANA) participates in the control of cell death inducing the formation of apoptotic bodies and DNA fragmentation. The aim of this study was to evaluate whether the ANA degrading enzyme, the fatty acid amide hydrolase (FAAH), would induce cellular death. Experiments were performed in cerebellar granule neurons cultured with the FAAH inhibitor, URB597 (25, 50 or 100 nM) as well as endogenous lipids such as oleoylethanolamide (OEA) or palmitoylethanolamide (PEA) and cellular viability was determined by MTT test. Neurons cultured with URB597 (25, 50 or 100 nM) displayed a decrease in cellular viability. In addition, if cultured with OEA (25 nM) or PEA (100 nM), cellular death was found. These results further suggest that URB597, OEA or PEA promote cellular death.

Administration of URB597, oleoylethanolamide or palmitoylethanolamide increases waking and dopamine in rats

Background

Oleoylethanolamide (OEA) and palmitoylethanolamide (PEA) are amides of fatty acids and ethanolamine named N-acylethanolamines or acylethanolamides. The hydrolysis of OEA and PEA is catalyzed by the fatty acid amide hydrolase (FAAH). A number of FAAH inhibitors that increase the levels of OEA and PEA in the brain have been developed, including URB597. In the present report, we examined whether URB597, OEA or PEA injected into wake-related brain areas, such as lateral hypothalamus (LH) or dorsal raphe nuclei (DRN) would promote wakefulness (W) in rats.

Methodology and Principal Findings

Male Wistar rats (250–300 g) were implanted for sleep studies with electrodes to record the electroencephalogram and electromyogram as well as a cannulae aimed either into LH or into DRN. Sleep stages were scored to determine W, slow wave sleep (SWS) and rapid eye movement sleep (REMS). Power spectra bands underly neurophysiological mechanisms of the sleep-wake cycle and provide information about quality rather than quantity of sleep, thus fast Fourier transformation analysis was collected after the pharmacological trials for alpha (for W; α = 8–12 Hz), delta (for SWS; δ = 0.5–4.0 Hz) and theta (for REMS; θ = 6.0–12.0 Hz). Finally, microdialysis samples were collected from a cannula placed into the nucleus accumbens (AcbC) and the levels of dopamine (DA) were determined by HPLC means after the injection of URB597, OEA or PEA. We found that microinjection of compounds (10, 20, 30 µg/1 µL; each) into LH or DRN during the lights-on period increased W and decreased SWS as well as REMS and enhanced DA extracellular levels.

Conclusions

URB597, OEA or PEA promoted waking and enhanced DA if injected into LH or DRN. The wake-promoting effects of these compounds could be linked with the enhancement in levels of DA and indirectly mediated by anandamide.

Narcolepsy and orexins: an example of progress in sleep research

Narcolepsy is a chronic neurodegenerative disease caused by a deficiency of orexin-producing neurons in the lateral hypothalamus. It is clinically characterized by excessive daytime sleepiness and by intrusions into wakefulness of physiological aspects of rapid eye movement sleep such as cataplexy, sleep paralysis, and hypnagogic hallucinations. The major pathophysiology of narcolepsy has been recently described on the bases of the discovery of the neuropeptides named orexins (hypocretins) in 1998; considerable evidence, summarized below, demonstrates that narcolepsy is the result of alterations in the genes involved in the pathology of the orexin ligand or its receptor. Deficient orexin transmission is sufficient to produce narcolepsy, as we describe here, animal models with dysregulated orexin signaling exhibit a narcolepsy-like phenotype. Remarkably, these narcoleptic models have different alterations of the orexinergic circuit, this diversity provide us with the means for making comparison, and have a better understanding of orexin-cell physiology. It is of particular interest that the most remarkable findings regarding this sleep disorder were fortuitous and due to keen observations. Sleep is a highly intricate and regulated state, and narcolepsy is a disorder that still remains as one of the unsolved mysteries in science. Nevertheless, advances and development of technology in neuroscience will provide us with the necessary tools to unravel the narcolepsy puzzle in the near future. Through an evaluation of the scientific literature we traced an updated picture of narcolepsy and orexins in order to provide insight into the means by which neurobiological knowledge is constructed.

Infusion of modafinil into anterior hypothalamus or pedunculopontine tegmental nucleus at different time-points enhances waking and blocks the expression of recovery sleep in rats after sleep deprivation

Clinical studies have indicated that the primary pharmacological activity of modafinil (MOD) is inducing wakefulness; however, the brain targets that underlie its wake-promoting activity have not been described. In the present study, we show that MOD injected into sleep-wake related brain areas promoted alertness. If administered (10, 20, or 30 μg/1 μL) into either anterior hypothalamus (AH) or pedunculopontine tegmental nucleus (PPTg) at 08:00, 12:00 or 16:00 h, MOD enhanced wakefulness whereas diminished slow wave sleep as well as rapid eye movement sleep. In addition, microinjection of MOD (10, 20, or 30 μg/1 μL) either into AH or PPTg after total sleep deprivation prevented the sleep rebound. Taken together, these observations suggest that AH and PPTg play a key role in the wake-inducing effects of MOD and encourage further experimentation to draw a possible mechanism of action.

Growth hormone improves hippocampal adult cell survival and counteracts the inhibitory effect of prolonged sleep deprivation on cell proliferation

Sleep deprivation (SD) produces numerous deleterious changes in brain cells, including apoptosis. It has been demonstrated that growth hormone (GH) stimulates cell growth and counteracts apoptosis, although this anti-apoptotic effect has not been tested against SD. To determine the protective effect of GH administration on cell proliferation and survival in the dentate gyrus (DG) of the hippocampus after sleep deprivation; we injected Wistar adult rats with a low dose of recombinant human GH (rhGH 5 ng/kg) per seven days and then we gently sleep deprived the animals for 48 consecutive hours. 5-Bromodeoxiuridine (BrdU) was administered to assess cell proliferation after the GH treatment and NeuN was used as marker of cell fate. Our results indicate that GH produced a three fold increase in the number of BrdU positive cells within the DG [Control = 1044 ± 106.38 cells, rhGH = 2952 ± 99.84 cells, P<0.01]. In contrast, 48 h of SD significantly reduced cell proliferation but this effect was antagonized by the GH administration [SD = 540 ± 18.3 cells, rhGH + SD = 1116 ± 84.48 cells, P<0.004]. Paradoxically, SD and GH administration increased cell survival separately but no significantly compared with control animals. However, cell survival was increased in animals treated with rhGH+SD compared to rats injected with saline solution [P<0.04]. Within the survival cells, the percentage of neurons was higher in SD animals [95%] compared with saline group, while this percentage (NeuN positive cells) was increased in animals treated with rhGH+SD [120%] compared with rhGH [25%] alone. Our findings indicate that GH strongly promotes cell proliferation in the adult brain and also protects the hippocampal neuronal precursors against the deleterious effect of prolonged sleep loss.

Protective effect of nicotine on oxidative and cell damage in rats with depression induced by olfactory bulbectomy

We evaluated the effects of nicotine on cell and oxidative damage caused by olfactory bulbectomy (OBX). The rats were divided into seven groups as follows: i) control; ii) vehicle (6% ethanol); iii) treated with nicotine; iv) sham operated; v) olfactory bulbectomy (OBX); vi) OBX+vehicle; and vii) OBX+Nic. The OBX was performed using the trepanation of frontal bone. The olfactory bulbs were cut and removed without damage to the frontal cortex. Two weeks after surgery nicotine was administered chronically once daily for 14 days, intraperitoneally (i.p.) in doses of 1.5 mg/kg, two weeks after surgery. OBX caused an increase in lipid peroxidation products and caspase-3 but prompted a reduction in reduced glutathione (GSH) content and antioxidative enzyme activity. All these changes were reverted by treatment of nicotine (14 days). In conclusions: i) OBX induces oxidative stress and cell death by apoptosis; and ii) nicotine presents antidepressant and antioxidant effect. All these findings suggest that nicotine would be a therapeutic tool for depression, although more studies are needed in this area to define the appropriate treatment regime.

Promoting of wakefulness by administrations of modafinil into anterior hypothalamus and into the pedunculopontine tegmental nucleus in rats

We investigated whether administration of MOD in rats during the lights-on period into wake-promoting areas, such as anterior hypothalamus (AH) or into the pedunculopontine tegmental nucleus (PPTg) would enhance waking. Results showed that microinjections of 1 microL of MOD (10, 20, or 30 microg) into both brain areas increased the total time of alertness and decreased sleep. Additionally, MOD-treated rats showed an enhancement in alpha power spectra but delta power spectra was diminished. Finally, c-Fos expression was found increased into either AH or the PPTg. Collectively, these results suggest that MOD induces waking via the activity of two wake-related brain areas such as AH and the PPTg.

[Neurogenesis as a therapeutic strategy to regenerate central nervous system]

INTRODUCTION

In the past few years, it has been demonstrated that the adult mammalian brain maintains the capacity to generate new neurons from neural stem/progenitor cells. These new neurons integrate into pre-existing systems through a process referred to as 'neurogenesis in the adult brain'.

DEVELOPMENT

This discovery has modified our understanding of how the central nervous system functions in health and disease. Until today, a great effort has been made attempting to decipher the mechanisms regulating adult neurogenesis, which might help to induce neuronal endogenous cell replacement in various neurological diseases.

CONCLUSIONS

In this revision, we will attempt to shed some light on the neurogenesis process with respect to diseases of the central nervous system and we will describe some therapeutic potentials in relation to neurodegenerative diseases.

Long-term changes in sleep and depressive symptoms of smokers in abstinence

Few studies have evaluated the impact of smoking cessation on objective measures of sleep. The present study assessed the long-term effects of tobacco smoking abstinence on sleep and depression. A total of 15 chronic smokers with Hamilton Rating Scale for Depression (HAM-D) scores of less than 9 were evaluated. Subjects were screened for baseline data when they were smoking chronically. They underwent a 5-week psychological treatment for tobacco smoking, after which their depressive symptoms and sleep architecture were evaluated at 1, 2, 4, 6, 9, and 12 months of abstinence. We report the results of the seven patients who completed 1 year of evaluations and of those patients who achieved only partial abstinence. Polysomnographic recordings were taken, level of depression was measured with the HAM-D, and urinary cotinine levels also were evaluated. HAM-D scores were analyzed with and without sleep items. Nicotine abstinence reduced latency to rapid eye movement (REM) sleep and increased HAM-D scores, suggesting that chronic smokers have depressive symptoms that may be controlled by nicotine administration.

[Neurogenesis in the adult brain]

INTRODUCTION

The discovery that new neurons continue to be generated in the adult brain has modified the concept of brain plasticity and has brought to light new mechanisms that ensure the homeostasis of the nervous system.

DEVELOPMENT

Neurogenesis, that is to say, the process involving the generation of new neurons, has been shown to occur in the hippocampus and in the olfactory bulb in adult mammals, which suggests that neuronal stem cells persist throughout the entire lifespan. The primary precursors have been identified in specialised regions called neurogenic niches. Interestingly, the cells that give rise to the new neurons in the adult brain express markers for glial cells, a cell lineage that is a long way from that of neurons. Studies conducted during the development of the brain have shown that radial glial cells not only give rise to astrocytes but also neurons, oligodendrocytes and ependymal cells. In addition, it is known that radial glial cells are also the precursors of neuronal stem cells in the adult brain.

CONCLUSIONS

Overall, these data support the idea that stem cells develop from a neuroepithelial-glial radial-astrocytic lineage. Thus, identifying the primary precursors, both in the developing brain and in the adult brain, is essential to understand the functioning of the nervous system and, from there, to develop strategies for neuronal replacement in the adult brain when needed.

Prism adaptation in spinocerebellar ataxia type 2

Patients with spinocerebellar ataxia type 2 (SCA2), develop severe pontine nuclei, inferior olives, and Purkinje cell degeneration. This form of autosomal dominant cerebellar ataxia is accompanied by progressive ataxia and dysarthria. Although the motor dysfunction is well characterized in these patients, nothing is known about their motor learning capabilities. Here we tested 43 SCA2 patients and their matched controls in prism adaptation, a kind of visuomotor learning task. Our results show that their pattern of brain damage does not entirely disrupt motor learning. Rather, patients had impaired adaptation decrement, but surprisingly a normal aftereffect. Moreover, the mutation degree could discriminate the degree of adaptation. This pattern could reflect the net contribution of two adaptive mechanisms: strategic control and spatial realignment. Accordingly, SCA2 patients show an impaired strategic control that affects the adaptation rate, but a normal spatial realignment measured through the aftereffect. Our results suggest that the neural areas subserving spatial realignment are spared in this form of spinocerebellar ataxia.

Modafinil enhances extracellular levels of dopamine in the nucleus accumbens and increases wakefulness in rats

Modafinil (MOD) is a wakefulness-promoting drug that improves the alertness levels in narcolepsy; however, the molecular mechanism of action remains to be elucidated. We found that after a single icv injection of MOD (10 microg/5 microl) the extracellular levels of dopamine (DA) and l-DOPA collected from the nucleus accumbens were increased and decreased, respectively. Separately, the icv administration of MOD (10 microg/5 microl) to rats enhanced wakefulness (W) whereas diminished sleep during 4h. Lastly, the alertness induced by MOD was partially antagonized by the sleep-inducing endocannabinoid anandamide (ANA). We conclude that MOD enhances the extracellular levels of DA, promotes W and its effects on sleep are partially blocked by ANA.

Effect of transcranial magnetic stimulation on oxidative stress induced by 3-nitropropionic acid in cortical synaptosomes

This study evaluates the effect of transcranial magnetic stimulation (TMS; 60 Hz and 0.7 mT) treatment on 3-nitropropionic acid (20 mg/kg i.p./day for 4 days)-induced oxidative stress in cortical synaptosomes of Wistar rats. The oxidative derangement was confirmed by a high level of lipid peroxidation products and protein carbonyls, together with a decreased in reduced glutathione (GSH) content, catalase and GSH-peroxidase (GSH-Px) activities. Additionally, it was observed a reduction in succinate dehydrogenase (SDH) activity. All changes were partially prevented or reversed by administration of TMS. These results show that TMS reduces oxidative stress in cortical synaptosomes, and suggest that TMS may protect neuronal and maintain synaptic integrity.

Cannabidiol, a constituent ofCannabis sativa, modulates sleep in rats

Delta(9)-tetrahydrocannabinol (Delta(9)-THC) and cannabidiol (CBD) are two major constituents of Cannabis sativa. Delta(9)-THC modulates sleep, but no clear evidence on the role of CBD is available. In order to determine the effects of CBD on sleep, it was administered intracerebroventricular (icv) in a dose of 10 microg/5 microl at the beginning of either the lights-on or the lights-off period. We found that CBD administered during the lights-on period increased wakefulness (W) and decreased rapid eye movement sleep (REMS). No changes on sleep were observed during the dark phase. Icv injections of CBD (10 microg/5microl) induced an enhancement of c-Fos expression in waking-related brain areas such as hypothalamus and dorsal raphe nucleus (DRD). Microdialysis in unanesthetized rats was carried out to characterize the effects of icv administration of CBD (10 microg/5 microl) on extracellular levels of dopamine (DA) within the nucleus accumbens. CBD induced an increase in DA release. Finally, in order to test if the waking properties of CBD could be blocked by the sleep-inducing endocannabinoid anandamide (ANA), animals received ANA (10 microg/2.5 microl, icv) followed 15 min later by CBD (10 microg/2.5 microl). Results showed that the waking properties of CBD were not blocked by ANA. In conclusion, we found that CBD modulates waking via activation of neurons in the hypothalamus and DRD. Both regions are apparently involved in the generation of alertness. Also, CBD increases DA levels as measured by microdialysis and HPLC procedures. Since CBD induces alertness, it might be of therapeutic value in sleep disorders such as excessive somnolence.

Survival rates through time of hypocretin grafted neurons within their projection site

Narcolepsy is a sleep disorder characterized by excessive daytime sleepiness, inadvertent transitions from wakefulness to rapid eye movement sleep (so called "sleep-onset REMS period") and cataplexy (sudden bilateral skeletal muscle weakness during waking without impairment of consciousness). This disorder has been recently linked to a loss of hypocretin (HCRT) neurons making narcolepsy a neurodegenerative disease. Neuronal replacement could be used to reverse the symptoms of narcolepsy. Towards this end, we have recently reported that HCRT neurons from rat pups can survive when grafted into the pons of adult rats. Here, we investigate the time-course of survival of grafted HCRT neurons into the pons of adult rats. The HCRT neurons are present only in the lateral hypothalamus, and therefore suspension of cells from this region was derived from 8- to 10-day-old rat pups (donor), and grafted into the pons of adult (60 days old) host rats. Control rats received a transplant that consisted of cells from the cerebellum where no HCRT neurons are present. All adult host rats were sacrificed 1, 3, 6, 9, 12, 24, or 36 days after grafting. Immunohistochemistry was used to identify and count the presence of the HCRT grafted neurons in the target area. The tally of HCRT neurons present in the graft zone 1 day post-grafting was considered to be the baseline. From day 3 to 36 post-transplant there was a steady decline in the number of HCRT neurons. We also noted that on day 36, the HCRT neurons that survived in the pons had morphological features that were similar to mature HCRT neurons in the adult lateral hypothalamus, suggesting that these neurons might be functionally active. Control rats that received grafts of cerebellar tissue did not show HCRT neurons in the target area. These results demonstrate that there is a progressive decline in the number of transplanted neurons, but a significant percentage of HCRT neurons do survive until day 36. This study highlights the potential use of transplants as a therapeutical tool in order to treat narcolepsy.

Transcranial magnetic stimulation attenuates cell loss and oxidative damage in the striatum induced in the 3-nitropropionic model of Huntington's disease

An investigation was conducted on the effect of transcranial magnetic field stimulation (TMS) on the free radical production and neuronal cell loss produced by 3-nitropropionic acid in rats. The effects of 3-nitropropionic acid were evaluated by examining the following changes in: the quantity of hydroperoxides and total radical-trapping antioxidant potential (TRAP), lipid peroxidation products, protein carbonyl groups, reduced glutathione (GSH) content, glutathione peroxidase (GSH-Px), catalase and succinate dehydrogenase (SDH) activities; total nitrite and cell death [morphological changes, quantification of neuronal loss and lactate dehydrogenase (LDH) levels]. Our results reveal that 3-nitropropionic acid induces oxidative and nitrosative stress in the striatum, prompts cell loss and also shows that TMS prevents the harmful effects induced by the acid. In conclusion, the results show the ability of TMS to modify neuronal response to 3-nitropropionic acid.