Orexinergic system dysregulation, sleep impairment, and cognitive decline in Alzheimer disease

IMPORTANCE

Nocturnal sleep disruption develops in Alzheimer disease (AD) owing to the derangement of the sleep-wake cycle regulation pathways. Orexin contributes to the regulation of the sleep-wake cycle by increasing arousal levels and maintaining wakefulness.

OBJECTIVES

To study cerebrospinal fluid levels of orexin in patients with AD, to evaluate the relationship of orexin cerebrospinal fluid levels with the degree of dementia and the cerebrospinal fluid AD biomarkers (tau proteins and β-amyloid 1-42), and to analyze potentially related sleep architecture changes measured by polysomnography.

DESIGN, SETTING, AND PARTICIPANTS

We conducted a case-control study from August 1, 2012, through May 31, 2013. We included 48 drug-naive AD patients referred to the Neurological Clinic of the University Hospital of Rome Tor Vergata. Based on the Mini-Mental State Examination score, 21 patients were included in mild AD group (score, ≥21), whereas 27 were included in the moderate to severe AD group (score, <21). The control group consisted of 29 nondemented participants of similar age and sex.

EXPOSURE

Laboratory assessment of cerebrospinal fluid levels of orexin, tau proteins, and β-amyloid 1-42 and polysomnographic assessment of sleep variables.

MAIN OUTCOMES AND MEASURES

Levels of orexin, tau proteins, and β-amyloid 1-42; macrostructural variables of nocturnal sleep (total sleep time, sleep efficiency, sleep onset and rapid eye movement [REM] sleep latencies, non-REM and REM sleep stages, and wakefulness after sleep onset); and Mini-Mental State Examination scores.

RESULTS

Patients with moderate to severe AD presented with higher mean (SD) orexin levels compared with controls (154.36 [28.16] vs 131.03 [26.55]; P < .01) and with more impaired nocturnal sleep with respect to controls and patients with mild AD. On the other hand, in the global AD group, orexin levels were positively correlated with total tau protein levels (r = 0.32; P = .03) and strictly related to sleep impairment. Finally, cognitive impairment, as measured by the Mini-Mental State Examination, was correlated with sleep structure deterioration.

CONCLUSIONS AND RELEVANCE

Our results demonstrate that, in AD, increased cerebrospinal fluid orexin levels are related to a parallel sleep deterioration, which appears to be associated with cognitive decline. Therefore, the orexinergic system seems to be dysregulated in AD, and its output and function appear to be overexpressed along the progression of the neurodegenerative process. This overexpression may result from an imbalance of the neurotransmitter networks regulating the wake-sleep cycle toward the orexinergic system promoting wakefulness.

Electroencephalographic spiking activity, drug levels, and seizure occurrence in epileptic patients

We investigated the relationships among the electroencephalographic spiking rate, drug levels, and seizure occurrence in 44 patients with focal epilepsy. Seizure occurrence was continuously monitored by personnel or videorecording and spiking rate was quantified by an automatic detection method. Results indicate that drug levels do not influence spiking rate, and spiking rate does not change before seizures but increases markedly after them, particularly secondarily generalized seizures. This increase can last several days and is observed during wakefulness and sleep. High or low spiking rates do not influence the occurrence of seizures. We suggest that interictal spikes may passively reflect damage to the brain, a damage which is worsened by further seizures. Spikes may not be directly related to seizure generation.

Tracking the time-varying cortical connectivity patterns by adaptive multivariate estimators

The directed transfer function (DTF) and the partial directed coherence (PDC) are frequency-domain estimators that are able to describe interactions between cortical areas in terms of the concept of Granger causality. However, the classical estimation of these methods is based on the multivariate autoregressive modelling (MVAR) of time series, which requires the stationarity of the signals. In this way, transient pathways of information transfer remains hidden. The objective of this study is to test a time-varying multivariate method for the estimation of rapidly changing connectivity relationships between cortical areas of the human brain, based on DTF/PDC and on the use of adaptive MVAR modelling (AMVAR) and to apply it to a set of real high resolution EEG data. This approach will allow the observation of rapidly changing influences between the cortical areas during the execution of a task. The simulation results indicated that time-varying DTF and PDC are able to estimate correctly the imposed connectivity patterns under reasonable operative conditions of signal-to-noise ratio (SNR) ad number of trials. An SNR of five and a number of trials of at least 20 provide a good accuracy in the estimation. After testing the method by the simulation study, we provide an application to the cortical estimations obtained from high resolution EEG data recorded from a group of healthy subject during a combined foot-lips movement and present the time-varying connectivity patterns resulting from the application of both DTF and PDC. Two different cortical networks were detected with the proposed methods, one constant across the task and the other evolving during the preparation of the joint movement.

Responses of intracellularly recorded cortical neurons to the iontophoretic application of dopamine

Considering that a well-defined dopaminergic projection from the mesencephalic structures to the rat frontal cortex has been demonstrated, the purpose of this research was to study the action of iontophoretically applied dopamine (DA) on intracellularly recorded rat frontal neurons. The stimulation of the substantia nigra (SN) and the ventral tegmental area (VTA) evoked EPSP-IPSP sequences in these cells. About 50% of the tested neurons, widely distributed in all the frontal cortex, responded to DA application and no difference in the response to DA was observed between neurons with monosynaptic inputs and neurons with polysynaptic inputs. The catecholamine depolarized the cell membrane and decreased the firing rate, generally without significant changes in membrane resistance, as already observed in rat and cat striatal cells. In some neurons the decrease of the spikes preceded the membrane depolarization. Considering the complex effect of DA on the electrical properties of these neurons, these results seem to be indicative of a mechanism of action dependent on metabolic changes.

CSF lactate levels, τ proteins, cognitive decline: a dynamic relationship in Alzheimer's disease

OBJECTIVES

To investigate, in patients with Alzheimer's Disease (AD), the possible interplay linking alteration of neuronal energy metabolism, as measured via cerebrospinal fluid (CSF) lactate concentration, to severity of AD neurodegenerative processes and impairment of cognitive abilities.

METHODS

In this study we measured and correlated CSF lactate concentrations, AD biomarker levels (τ-proteins and β-amyloid) and Mini-Mental State Examination (MMSE) score in a population of drug-naïve patients with AD ranging from mild (MMSE≥21/30) to moderate-severe (MMSE<21/30) cognitive decline. They were compared to healthy controls and patients with vascular dementia (VaD).

RESULTS

Patients with AD (n=145) showed a significant increase of CSF lactate concentration compared to controls (n=80) and patients with VaD (n=44), which was higher in mild (n=67) than in patients with moderate-severe AD (n=78). Moreover, we found, in either the whole AD population or both subgroups, a CSF profile in which higher CSF levels of t-τ and p-τ proteins corresponded to lower concentrations of lactate.

CONCLUSIONS

We verified the occurrence of high CSF lactate levels in patients with AD, which may be ascribed to mitochondria impairment. Hypothesising that τ proteins may exert a detrimental effect on the entire cellular energy metabolism, the negative correlation found between lactate and τ-protein levels may allow speculation that τ toxicity, already demonstrated to have affected mitochondria, could also impair glycolytic metabolism with a less evident increase of lactate levels in more severe AD. Thus, we suggest a dynamic relationship between neuronal energy metabolism, τ proteins and cognitive decline in AD and propose the clinical potential of assessing CSF lactate levels in patients with AD to better define the neuronal brain metabolism damage.

Repetitive transcranial magnetic stimulation of the motor cortex ameliorates spasticity in multiple sclerosis

OBJECTIVE

To investigate whether repetitive transcranial magnetic stimulation (rTMS) can modify spasticity.

METHODS

We used high-frequency (5 Hz) and low-frequency (1 Hz) rTMS protocols in 19 remitting patients with relapsing-remitting multiple sclerosis and lower limb spasticity.

RESULTS

A single session of 1 Hz rTMS over the leg primary motor cortex increased H/M amplitude ratio of the soleus H reflex, a reliable neurophysiologic measure of stretch reflex. Five hertz rTMS decreased H/M amplitude ratio of the soleus H reflex and increased corticospinal excitability. Single sessions did not induce any effect on spasticity. A significant improvement of lower limb spasticity was observed when rTMS applications were repeated during a 2-week period. Clinical improvement was long-lasting (at least 7 days after the end of treatment) when the patients underwent 5 Hz rTMS treatment during a 2-week protocol. No effect was obtained after a 2-week sham stimulation.

CONCLUSIONS

Repetitive transcranial magnetic stimulation may improve spasticity in multiple sclerosis.

Assessing cortical functional connectivity by partial directed coherence: simulations and application to real data

The aim of this paper is to test a technique called partial directed coherence (PDC) and its modification (squared PDC; sPDC) for the estimation of human cortical connectivity by means of simulation study, in which both PDC and sPDC were studied by analysis of variance. The statistical analysis performed returned that both PDC and sPDC are able to estimate correctly the imposed connectivity patterns when data exhibit a signal-to-noise ratio of at least 3 and a length of at least 27 s of nonconsecutive recordings at 250 Hz of sampling rate, equivalent, more generally, to 6750 data samples.

Non-invasive evaluation of input-output characteristics of sensorimotor cerebral areas in healthy humans

The topography of scalp SEPs to mixed and sensory median nerve (MN) and to musculocutaneous nerve stimulation was examined in 20 healthy subjects through multichannel (12-36) recording in a 50 msec post-stimulus epoch. MN-SEPs in both frontal leads were characterized by an N18, P20, N24, P28 complex showing maximal amplitude at contralateral parasagittal sites. This was sometimes partly obscured by a wide wave N30 having a fixed latency, but a steep amplitude gradient moving toward the scalp vertex. A P40 component followed, having longer peak latencies, moving the recording sites from contralateral medial parietal toward the vertex and frontal ipsilateral positions. MN-SEPs in contralateral parietal leads contained a widespread N20 with a maximum source posterior to the Cz-ear line. The following P25 enveloped two subcomponents - early and late P25 - having different distributions. The late P25 showed a maximum - coincident with that of wave N20 - which was localized more posteriorly than that of the early P25. An inconstant wave N33 with progressively longer peak latencies from sagittal toward lateral positions was then recorded. MN-SEPs in contralateral central positions showed a well-localized P22 wave in which both the parietal early P25 and the frontal P20 were vanishing. Common or separate generators for frontal, central and parietal SEPs were discriminated by evaluating the influence of stimulus rate and intensity, as well as of general anesthesia and transient CBF deficits, investigated in 7 patients undergoing carotid endarterectomy. Unifocal anodal threshold shocks were separately delivered to each of the scalp electrodes and motor action potentials were recorded from the target muscle in order to delineate the scalp representation of the motor strip for the upper limb and, consequently, to monitor, through SEP tracings, the short-latency sensory input to the motor cortex for hand and shoulder muscles. This was characterized by a boundary zone separating the parietal N20-early P25 complex, from the fronto-central N18-P22 one. This zone had an oblique direction strongly resembling that of the central sulcus.

Sleep microstructure and EEG epileptiform activity in patients with juvenile myoclonic epilepsy

Clinical and EEG manifestations of juvenile myoclonic epilepsy (JME) occur in a strict relationship to the sleep-wake cycle, particularly to transition phases (awakening, falling asleep, afternoon relaxation after work). JME manifestations are deactivated during sleep. Because arousal fluctuations during NREM sleep may be controlled by the same neurophysiologic mechanisms regulating awakening, we studied the relationship between the cyclic alternating pattern (CAP) and JME manifestations. All-night polysomnographic recordings of 10 JME patients were analyzed for variations of epileptiform EEG abnormalities in relation to sleep stages and to different microstructural variables (NCAP, CAP, phases A and B). CAP rates (ratio between total CAP duration and total NREM sleep duration) were also calculated. Average CAP rate was 46.70%, significantly higher than that (23%) of an age-matched control group. Macrostructural analysis showed only a trend toward a slight predominance of EEG epileptiform activity during slow wave sleep but no significant correlation between spiking rates and sleep stages. Microstructural analysis confirmed the CAP modulation of EEG epileptiform activity, with maximum appearance of epileptiform abnormalities during phase A CAP (normalized spiking rate = 4.00 +/- 0.98) and strong inhibition during phase B (0.06 +/- 00.6). Intermediate values were noted during NCAP (0.54 +/- 0.27). No correlation was noted between spiking rates during NREM sleep and CAP rates, possibly indicating that in JME patients the increased CAP rate may be partially independent of epileptiform EEG activity. Our data suggest that in JME patients CAP may be a neurophysiologic oscillator organizing expression of the epileptiform discharges independent of the tendency of the individual patient to produce epileptiform EEG discharges.

Nocturnal sleep and daytime somnolence in untreated patients with temporal lobe epilepsy: changes after treatment with controlled-release carbamazepine

PURPOSE

To define sleep disturbances in patients with temporal lobe epilepsy (TLE) and explore the association between carbamazepine (CBZ) therapy, sleep, and daytime somnolence.

METHODS

We recorded nocturnal polysomnography and measured subjective and objective daytime somnolence in a group of newly diagnosed TLE patients, who had no evidence of anatomic brain lesion on neuroimaging and had never been treated before. Recordings were performed at baseline, after the initial administration of 400 mg CBZ-controlled release (CR) and after 1 month of treatment (400 mg twice daily b.i.d.). The findings were compared with those of a group of young healthy volunteers, both at baseline and after the first administration of CBZ. The chronic effect of CBZ-CR treatment was evaluated only in TLE patients.

RESULTS

At baseline, nocturnal sleep patterns of TLE patients did not show marked alterations when the influence of seizures, cerebral lesions, and drugs had been ruled out. In both the TLE and the control groups, initiation of CBZ therapy provoked a reduction and a fragmentation of rapid eye movement (REM) sleep and an increase in the number of sleep stage shifts. In the TLE group, these effects were almost completely reversed after 1 month of treatment, and no significant difference was noted between baseline condition and long-term follow-up. With regard to daytime sleepiness, initial administration of the drug caused an increase in objective sleepiness only in the control group. Subjective sleepiness was higher in the control group than in the TLE group but was not modified by the drug.

CONCLUSIONS

We conclude that CBZ-CR has negative effects on REM sleep during initial administration but chronic treatment does not significantly modify nocturnal sleep or daytime somnolence.

Action of GP 47779, the active metabolite of oxcarbazepine, on the corticostriatal system. II. Modulation of high-voltage-activated calcium currents

GP 47779, the active metabolite of oxcarbazepine (OCBZ) inhibits glutamatergic excitatory postsynaptic potentials (EPSPs) in rat striatum (described in the accompanying article). This effect was presumed to involve the modulation of the calcium (Ca2+) signals at either pre- or postsynaptic level. Therefore, we directly tested whether GP 47779 could modulate Ca2+ conductances in cortical as well as in striatal neurons. GP 47779 produced a reversible dose-dependent decrease in high-voltage-activated (HVA) Ca2+ currents evoked by membrane depolarization in isolated cortical pyramidal cells. GP 47779-mediated reduction in HVA Ca2+ currents, if occurring also at corticostriatal axon terminals, might explain the reduction of glutamate release in the striatum. An inhibitory action of GP 47779 on HVA Ca2+ currents was also observed in isolated striatal neurons. The effect of HVA Ca2+ currents in cortical and striatal neurons persisted in the presence of nifedipine, suggesting that dihydropyridine-sensitive channels were not involved in the GP 47779-mediated responses. We propose that the modulation of HVA Ca2+ channels by this carbamazepine (CBZ) analogue may account for its inhibitory action on transmitter release.

Effect of apomorphine on cortical inhibition in Parkinson's disease patients: a transcranial magnetic stimulation study

In this study, transcranial magnetic stimulation (TMS) of the primary motor hand area was used to test cortical excitability in Parkinson's disease (PD) patients. Motor evoked potentials (MEPs) to TMS were studied at rest by utilising distinct paired-pulse TMS protocols. Out of 29 untreated PD patients and 29 healthy subjects, early cortical inhibition (1-6 ms) was studied in a first subgroup of 17 PD patients and 15 healthy subjects, whereas late cortical inhibition (20-200 ms) was studied in a second subgroup of 21 PD patients and 19 healthy subjects. In all PD patients the same TMS protocols were performed before and after 3 h of apomorphine infusion. In comparison to healthy subjects, untreated PD patients showed a significant reduction of both early and late cortical inhibition, which was maximal at 2-3 ms, and at 80-100 ms, respectively. Apomorphine administration consistently reversed all the MEP abnormalities found in PD patients. The lack of TMS effects on the Hoffman's reflex (HR), at those intervals revealing the reduced inhibition in PD patients, is compatible with a supraspinal origin of the observed MEP abnormalities. Our data suggest that the cortical and/or subcortical loss of dopaminergic transmission in PD patients is associated with impaired motor cortical inhibitory mechanisms, as tested by a decreased early and late MEP inhibition.

Different TMS patterns of intracortical inhibition in early onset Alzheimer dementia and frontotemporal dementia

OBJECTIVE

To investigate putative changes in cortical excitability of patients affected by early-onset mild dementia by means of transcranial magnetic stimulation (TMS) and to verify whether a peculiar neurophysiological profile may contribute to characterise Alzheimer's disease (AD) vs frontotemporal dementia (FTD).

METHODS

Motor threshold and intracortical inhibition (ICI) and facilitation (ICF) after paired-pulse TMS (inter-stimulus intervals from 1 to 20 ms) were studied in two groups of early-onset demented patients with a neuropsychological profile suggestive of AD (n = 12) and FTD (n = 8). Twelve age-matched healthy subjects were considered as control group. In both patient groups, recordings were performed before and after a single oral dose of 4 mg galantamine.

RESULTS

No significant difference in motor threshold was observed among the three studied groups. On the contrary, early-onset AD showed a significant reduction of ICI compared to control group, no changes were detected in FTD patients. No significant changes in ICF were found between both patient groups and healthy subjects. The acute administration of galantamine reversed the modified ICI in AD group.

CONCLUSIONS

The differential pattern of ICI exhibited by early-onset AD vs FTD in the early stage of disease may represent a non-invasive, reproducible electrophysiological tool, which may contribute to early differential diagnosis and, possibly, to monitor therapeutic effectiveness.

SIGNIFICANCE

The present results support the possibility that subtle, early modifications in intracortical circuitry features AD, but not FTD patients.

Hyperhomocysteinemia in epileptic patients on new antiepileptic drugs

PURPOSE

Older enzyme-inducing antiepileptic drugs (AEDs) may induce supraphysiologic plasma concentrations of total (t) homocysteine (Hcy). The aim of the present study was to investigate the effect of new AEDs on plasma tHcy levels.

METHODS

Patients 18-50 years of age, on AEDs monotherapy, with no other known cause of hyper-tHcy were enrolled. Plasma tHcy, folate, vitamin B(12), and AEDs levels were determined by standard high-performance liquid chromatography (HPLC) methods. Methylenetetrahydrofolate-reductase (MTHFR) polymorphisms were checked using Puregene genomic DNA purification system (Gentra, Celbio, Italy). A group of healthy volunteers matched for age and sex was taken as control.

RESULTS

Two hundred fifty-nine patients (151 on newer and 108 on older AEDs) and 231 controls were enrolled. Plasma tHcy levels were significantly higher [mean values, standard error (SE) 16.8, 0.4 vs. 9.1, 0.2 microm; physiologic range 5-13 microm] and folate lower (6.3, 0.1 vs. 9.3, 0.1 nm; normal > 6.8 nm) in patients compared to controls. Patients treated with oxcarbazepine, topiramate, carbamazepine, and phenobarbital exhibited mean plasma tHcy levels above the physiologic range [mean values (SE) 16 (0.8), 19.1 (0.8), 20.5 (1.0), and 18.5 (1.5) microm, respectively]. Conversely, normal tHcy concentrations were observed in the lamotrigine and levetiracetam groups [both 11.1 (0.5) microm].

DISCUSSION

Oxcarbazepine and topiramate might cause hyper-tHcy, most likely because of the capacity of these agents to induce the hepatic enzymes. Because literature data suggest that hyper-tHcy may contribute to the development of cerebrovascular diseases and brain atrophy, a supplement of folate can be considered in these patients to normalize plasma tHcy.

Imaging functional brain connectivity patterns from high-resolution EEG and fMRI via graph theory

We describe a set of computational tools able to estimate cortical activity and connectivity from high-resolution EEG and fMRI recordings in humans. These methods comprise the estimation of cortical activity using realistic geometry head volume conductor models and distributed cortical source models, followed by the evaluation of cortical connectivity between regions of interest coincident with the Brodmann areas via the use of Partial Directed Coherence. Connectivity patterns estimated on the cortical surface in different frequency bands are then imaged and interpreted with measures based on graph theory. These computational tools were applied on a set of EEG and fMRI data from a Stroop task to demonstrate the potential of the proposed approach. The present findings suggest that the methodology is able to identify differences in functional connectivity patterns elicited by different experimental tasks or conditions.

Linear classification of low-resolution EEG patterns produced by imagined hand movements

Electroencephalograph (EEG)-based brain-computer interfaces (BCI's) require on-line detection of mental states from spontaneous EEG signals. In this framework, surface Laplacian (SL) transformation of EEG signals has proved to improve the recognition scores of imagined motor activity. The results we obtained in the first year of an European project named adaptive brain interfaces (ABI) suggest that: 1) the detection of mental imagined activity can be obtained by using the signal space projection (SSP) method as a classifier and 2) a particular type of electrodes can be used in such a BCI device, reconciling the benefits of SL waveforms and the need for the use of few electrodes. Recognition of mental activity was attempted on both raw and SL-transformed EEG data from five healthy people performing two mental tasks, namely imagined right and left hand movements.

Effect of antiepileptic drugs on sleep

The interactions between sleep and epilepsy are well known. A nodal point of the relationship between sleep and epilepsy is represented by pharmacological treatment. Sleep disturbances such as drowsiness are among the most frequent side effects of treatment with antiepileptic drugs, since they can deeply modify both sleep architecture and the sleep-wake cycle. Severe daytime somnolence affects patients' activities and it may facilitate the occurrence of seizures. These considerations underline the importance of antiepileptic drugs having anticonvulsant properties that do not negatively influence sleep and daytime somnolence. In this paper we review some relevant aspects of the effects of antiepileptic drugs on sleep.

Patterns of seizure activation after withdrawal of antiepileptic medication

Effects of withdrawal of anticonvulsant drugs on the temporal profile of occurrence and the type of seizures were investigated in 40 intractable epileptic patients who were candidates for surgical treatment. EEG and behavior were monitored while drugs were reduced to allow localization of the epileptogenic region. The rapid withdrawal of drugs caused a rebound effect, triggering either generalized seizures during a brief period or a longer-lasting increase in partial seizures. These increases in seizure frequency appeared related to change in dosage rather than to dosage itself, since they remained largely confined to the early period following reduction of an anticonvulsant.

Sleep disorders in adult-onset myotonic dystrophy type 1: a controlled polysomnographic study

BACKGROUND

  Sleep disturbances and excessive daytime somnolence are common and disabling features in adult-onset myotonic dystrophy type 1 (DM1).

METHODS

  Our study used questionnaires, ambulatory polysomnography and the multiple sleep latency test to evaluate sleep-wake cycle and daytime sleepiness in unselected adult-onset DM1 patients. We recruited 18 patients affected by adult-onset DM1 and 18 matched controls.

RESULTS

  Sleep efficiency was <90% in 16/18 patients, and it was significantly reduced when compared with controls. Reduced sleep efficiency was associated with abnormal respiratory events (5/18 patients) and/or periodic limb movements (11/18 patients). The Periodic Limb Movement Index was significantly increased in DM1 versus controls. A significantly lower mean MSLT sleep latency was detected in DM1 versus controls, but it did not reach pathological levels.

CONCLUSIONS

  Our controlled study demonstrated sleep alterations in unselected consecutive DM1 patients. Periodic limb movements in sleep are commonly associated with sleep disturbance in adult-onset DM1, and it may represent a marker of CNS neurodegenerative processes in DM1.

Sleep-related changes in baroreflex sensitivity and cardiovascular autonomic modulation

OBJECTIVE

We examined the effects of the various sleep stages on baroreflex sensitivity (BRS), and heart rate and blood pressure (BP) variability, and tested the hypothesis that there is a different behavior of the baroreflex control of the sinus node in response to hypertensive and hypotensive stimuli and in relation to different cycles of the overnight sleep.

DESIGN

Polygraphic sleep recordings were performed in 10 healthy males. The BP and the RR interval were continuously recorded during sleep.

METHODS

BRS was calculated by the sequences method. Autoregressive power spectral analysis was used to investigate the RR-interval and BP variabilities.

RESULTS

During rapid eye movement (REM) sleep BRS significantly increased in response to hypertensive stimuli in comparison with non-rapid eye movement (NREM) sleep and the awake state, whereas it did not change in response to hypotensive stimuli. In the first sleep cycle, BRS significantly increased during NREM in comparison with wakefulness, whereas during REM BRS in response to hypertensive stimuli did not show significant changes as compared with the awake state and/or with NREM. During REM occurring in the sleep cycle before morning awakening, BRS showed a significant increase in response to hypertensive stimuli in comparison with both NREM and the awake state.

CONCLUSIONS

During sleep, arterial baroreflex modulation of the sinus node is different in response to hypotensive and hypertensive stimuli particularly during REM. Furthermore, baroreflex control of the sinus node shows a non-uniform behavior during REM occurring in different nocturnal sleep cycles. These findings suggest that the arterial baroreflex is more effective in buffering the increased sympathetic activation associated with REM at the end of sleep than in the early night.

Effects of lamotrigine on nocturnal sleep, daytime somnolence and cognitive functions in focal epilepsy

OBJECTIVES

The aim of our study was to evaluate possible changes in nocturnal sleep, daytime somnolence and cognitive functions induced by add-on therapy with lamotrigine (LTG).

MATERIAL AND METHODS

Thirteen patients affected by seizures resistant to common antiepileptic drugs (AEDs) underwent nocturnal polysomnographic monitorings, daytime somnolence evaluations and a neuropsychological battery before and after 3 months of treatment with LTG.

RESULTS

With LTG therapy we observed a significant increase in REM sleep and a significant reduction in the number of entries into REM and stage shifts. No significant correlation was observed between the decrease in nocturnal epileptiform activity and the increase in REM sleep. Other sleep parameters were unmodified. No significant changes were observed in daytime somnolence and in cognitive performances.

CONCLUSION

LTG may produce positive effects on epileptic seizures and interictal abnormalities without interfering negatively on REM sleep, with improvement of sleep stability and without changes in daytime somnolence and neuropsychological performances. For these reasons it could be an important drug for improving epileptic patients' quality of life.

Reduced L-dopa absorption and increased clinical fluctuations in Helicobacter pylori-infected Parkinson's disease patients

We report that the area under the curve of L-dopa plasma concentration, following the administration of a single 250 mg L-dopa dose, is augmented after Helicobacter pylori (HP) eradication in six Parkinson's disease (PD) patients showing high IgG antibody titer against HP. A prolongation of L-dopa clinical benefit was also observed. We suggest that HP infection-activated gastric alterations may be responsible, at least in part, for the reported erratic efficacy of oral L-dopa therapy in some advanced PD patients. Given the high percentage of HP-positivity in the age cohorts including the largest prevalence of PD patients, we propose that HP eradication be recommended in all PD patients under L-dopa therapy.

Evidence in favor of a neurotransmitter role of glycine in the rat cerebral cortex

In the present study we analyze whether glycine satisfies some electrophysiological and biochemical criteria to consider it as a putative transmitter in the rat cerebral cortex. Intracellular recordings from rat sensory-motor cortex showed that in 15-20% of the tested neurons glycine hyperpolarized the cell membrane, decreased the firing rate and flattened the evoked EPSP-IPSP sequence by increasing the membrane conductance. The iontophoretic application of strychnine antagonized the block of 'spontaneous' firing and the membrane hyperpolarization induced by glycine. Moreover, in a group of neurons, strychnine decreased the amplitude and duration of the IPSP and brought back the membrane potential to resting values. Previously accumulated [3H]glycine and endogenous glycine were released from cortical synaptosomal preparations by depolarizing stimuli in a Ca2+-dependent way. The release pattern of glycine was qualitatively similar in cortical and in spinal synaptosomes. [14C]Glycine was rapidly synthetized from [14C]serine in cortical synaptosomal preparations, and the newly formed [14C]glycine was released by depolarizing stimuli in a Ca2+-dependent way. It is concluded that glycine, which is generally considered as an inhibitory neurotransmitter in the spinal cord, medulla and pons, may also have a transmitter role in a discrete number of cortical neurons of some mammalian species.U

Deep brain stimulation of both subthalamic nucleus and internal globus pallidus restores intracortical inhibition in Parkinson's disease paralleling apomorphine effects: a paired magnetic stimulation study

OBJECTIVE

We investigated the effect of bilateral subthalamic nucleus (STN) and internal globus pallidus (GPi) deep brain stimulation (DBS) on intracortical inhibition (ICI) in patients with advanced Parkinson's disease (PD).

METHODS

The activity of intracortical inhibitory circuits was studied in 4 PD patients implanted with stimulating electrodes both in STN and GPi by means of paired-pulse transcranial magnetic stimulation, delivered in a conditioning-test design at short (1-6 ms) interstimulus intervals (ISI). The effect of apomorphine on the same PD patients was also investigated.

RESULTS

We observed that implanted PD patients showed a significant increase in ICI during either bilateral STN or GPi DBS at 3 ms ISI, and during bilateral STN DBS at 2 ms ISI in comparison to their off DBS condition. The same statistical improvement was observed during apomorphine infusion at 3 and 2 ms ISI. In each condition, the electrophysiological changes were associated with a significant clinical improvement as measured by the Unified Parkinson's Disease Rating Scale motor examination.

CONCLUSIONS

These results are consistent with the hypothesis that basal ganglia DBS can mimic the effects of pharmacological dopaminergic therapy on PD patients cortical activity. We propose that in PD patients, the basal ganglia DBS-induced improvement of ICI may be related to a recovery in modulation of thalamo-cortical motor pathway.