Natural Phytochemicals as SIRT Activators-Focus on Potential Biochemical Mechanisms

Sirtuins are a family of proteins with enzymatic activity. There are seven mammalian sirtuins (SIRT1-SIRT7) that are found in different cellular compartments. They are a part of crucial cellular pathways and are regulated by many factors, such as chemicals, environmental stress, and phytochemicals. Several in vitro and in vivo studies have presented their involvement in anti-inflammatory, antioxidant, and antiapoptotic processes. Recent findings imply that phytochemicals such as resveratrol, curcumin, quercetin, fisetin, berberine, and kaempferol may regulate the activity of sirtuins. Resveratrol mainly activates SIRT1 and indirectly activates AMPK. Curcumin influences mainly SIRT1 and SIRT3, but its activity is broad, and many pathways in different cells are affected. Quercetin mainly modulates SIRT1, which triggers antioxidant and antiapoptotic responses. Fisetin, through SIRT1 regulation, modifies lipid metabolism and anti-inflammatory processes. Berberine has a wide spectrum of effects and a significant impact on SIRT1 signaling pathways. Finally, kaempferol triggers anti-inflammatory and antioxidant effects through SIRT1 induction. This review aims to summarize recent findings on the properties of phytochemicals in the modulation of sirtuin activity, with a particular focus on biochemical aspects.

Current Treatment of Melanoma Brain Metastases

Melanoma is a type of skin cancer in which there is a strong correlation between its occurrence and exposure to ultraviolet radiation. Although it is not the most common skin cancer, it has the highest mortality rate of all skin cancers. The prognosis of patients is significantly worsened by melanoma metastasis to the brain, which often occurs in patients with advanced disease. The formation and development of melanoma metastases to the brain involve a very complex process, and their mechanisms are not fully understood. One of the ways for metastatic melanoma cells to survive and develop cancer in the brain environment is the presence of oncogenic BRAF mutation, which occurs in up to 50% of metastatic melanoma cases. Before discovering new methods of treating metastases, the overall survival of patients with this disease was 6 months. Currently, research is being conducted on new drugs using immunotherapy (immune checkpoint inhibitors: anti-PD-1, anti-CTLA-4) and targeted therapy (BRAF and MEK inhibitors) to improve the prognosis of patients. In this article, we summarize the current state of knowledge about the results of treating brain metastases with new systemic therapies.

The prevalence of negative attitudes towards nurses and depressive symptoms in nurses working in cardiology departments in Malopolska region, preliminary results

Funding Acknowledgements

Type of funding sources: None.

Introduction

A significant increase in negative attitudes towards nurses accompanied by exacerbation of depressive symptoms in nurses working in cardiology departments have been observed.

Objective

The assessment of the intensity of negative attitudes towards nurses and depressive symptoms experienced by nurses working in cardiology departments in Malopolska region.

Methods

A cross-sectional study was conducted between 2020 and 2022. It was carried out in a group of 130 nurses working in conservative cardiology departments and 72 nurses working in interventional cardiology departments. The nurses were randomly selected from the register of hospital employed nurses of Malopolska Regional Chamber of Nurses and Midwives. The incidence and intensity of negative experiences at work were determined based on NAQ (The Negative Acts Questionnaire) and the incidence and intensity of depressive symptoms were measured by means of Beck’s depression scale.

Results

Among all the nurses surveyed 58% of them experienced some negative attitudes and the exacerbation of mild, moderate and severe depressive symptoms was observed in 37.1%, 18.3% and 4.5% of respondents respectively; no significant differences were found between conservative cardiology departments and interventional cardiology departments. A positive correlation was observed between the exacerbation of depressive symptoms and negative attitudes towards nurses r=0.335, p<0.001, and this correlation was stronger in interventional cardiology departments r=0.397, p<0.001. The risk of developing depressive symptoms was 3.4 times higher in nurses exposed to negative attitudes than in those who did not experience such behaviours (95% CI: 1.61-7.62).

Conclusions

The results of this study show that nurses working in cardiology departments in Malopolska region are exposed to negative attitudes and suffer from exacerbated depressive symptoms, which might affect the quality of the patient care they provide.

The Trend of Authentic Leadership Skills in Nursing Education: The Key Role of Perfectionism and Self-Efficacy

(1) Background: Shaping leadership skills is a complex process, which may be modified by psychological factors such as self-efficacy and perfectionism. The aim of the study was to determine whether perfectionism can be a mediator between self-efficacy, and authentic leadership skills in nursing students; (2) Methods: The cross-sectional study included 615 Polish nursing students (women = 96.3%) was carried out at Medical University of Warsaw in 2019. The following research tools were used: Authentic Leadership Questionnaire, Almost Perfect Scale-Revised (APS-R), and General Self-Efficacy Scale (GSES); (3) Results: The level of perfectionism is a significant mediator of relations between self-efficacy as measured by the GSES and the level of authentic leadership (Sobel test: t = 6.958; p < 0.000). The relation, without a mediating factor, is positive, and the standardized beta coefficient for the feeling of self-efficacy totals beta = 0.470 (p < 0.000), while in the presence of a mediator the strength of the correlation is smaller and amounts to beta = 0.366 (p < 0.000); (4) Conclusions: Personality factors such as self-efficacy and perfectionism play an important role in shaping AL skills of nursing students. Therefore, academic teachers should pay special attention to strengthening students’ self-efficacy and adaptive perfectionism. In this context, adequate feedback and reflection may be important.

Willingness to Oppose Smoking among Pregnant Women

Even though smoking causes numerous threats to the developing foetus, it is the most common addiction in Polish women of reproductive age. Most studies undertake to examine the subject of opposing second-hand smoking or creating tools to reprimand pregnant women more effectively using a qualitative methodology. The study aimed to determine the profile of a pregnant woman who is willing to oppose the smoking of another pregnant woman. The research was conducted using an original multiple-choice questionnaire. The survey was shared on websites for expecting parents. Completed questionnaires were collected from 11,448 pregnant women. The Wald test for logistic regression was used for statistical analysis. Predictors of whether someone would draw another pregnant women's attention to the fact that smoking is harmful were: intellectual work (OR 1.136; p-value 0.020) and currently being a student (OR 1.363; p-value 0.004), involvement of the child's father (OR 1.377; p-value < 0.001), contact with social campaigns (OR 1.150; p-value 0.005) and knowledge about the consequences of smoking, as well as talking to the midwife about the harmfulness of cigarettes during pregnancy (OR 1.655; p-value < 0.001). Interpersonal relationships leave scope for public health interventions. It is worth enhancing criticism against smoking by specialists through information and education campaigns.

Analysis of the polymeric abrasive paste regeneration for abrasive flow machining

The influence of conditions and the sifting process efficiency of the worn-out polymeric abrasive paste containing silica (SiO2) and polymer chips remaining after the surface treatment were investigated. The abrasive paste regeneration process consisted of sifting the used paste through sievesof a vibrating screen, on which abrasive grains and polymer chips were recovered. The diameter of the sieve holes determined the size of the recovered abrasive grains and polymer chips, on the size of which the efficiency of the process depended. The lowest efficiency of the sifting process was obtained using a sieve with the holes diameter equal to the diameter of the grain and the polymer chips of thegiven fraction. The highest efficiency of the sifting process was obtained for a sieve with a diameter of 0.032 mm. The regenerated polymeric abrasive paste can be reused in the process of abrasive flow machining.

Intracranial complications after surgical removal of nasal polyps

Acute otitis media can be caused by viruses (nonsuppurative inflammation) and bacteria (suppurative inflammation). The suppurative inflammation is a risk factor for endocranial complications, including subdural empyema burdened with a high mortality. The authors present a clinical case of a 67-year-old man treated by surgery for a subdural empyema in the course of the acute suppurative otitis media.

Iatrogenic pneumothorax in a 4-week-old girl: new diagnosis of congenital lobar emphysema

A 4-week-old female patient presented with severe respiratory distress, hypoxia and apnoeic episodes on a background of a few-day history of coryza and cough. There was significantly reduced air entry on the left side and a displacement of the apex beat to the right of the chest. The examination findings with oxygen desaturations and a right-sided mediastinal shift on chest X-ray led to a diagnosis of tension pneumothorax following which a needle thoracentesis was undertaken. This appeared to worsen the patient's clinical condition; hence, a chest drain was inserted with unsatisfactory clinical improvement. In view of the presentation and lack of clinical improvement after chest drain insertion, the case was transferred to the paediatric respiratory team in a tertiary centre where the diagnosis was revised to congenital lobar emphysema based on chest computer tomography findings. She subsequently benefited from a left upper lobectomy and lingulectomy and was discharged home 4 days after surgery.

Serum VEGF-A concentrations in patients with central nervous system (CNS) tumors

Angiogenesis plays an essential role in tumors development. In case of central nervous system tumors, the most important role in this process plays VEGF-A. The purpose of this study was to determine the plasma concentration of this agent in patients treated surgically because of intracranial tumors. The study involved 48 adult patients, both sexes, treated surgically because of a brain tumor. The control group consisted of 50 adult volunteers of both sexes, without cancer diagnosis. Based on the studies, it was found that serum VEGF-A levels before surgery are higher in patients with central nervous system tumors (10.39–150.57 pg/ml, median 41.70 pg/ml) than in non-cancer patients (0.00–130.77 pg/ml, median 22.56 pg/ml). The association between serum VEGF-A level and malignancy and histological type of intracranial tumor has not beed confirmed. The highest average preoperative serum VEGF-A level was found in patients with low grade gliomas, slightly lower (close to each other) in those with high grade gliomas and meningiomas, while the lowest level was characteristic for metastatic tumors. High variation in results was observed in patients with low grade gliomas (52.56 pg/ml)—higher than those reported in patients with high grade gliomas (32.38 pg/ml). In the rest types of tumors the differentiation was similar and oscillated within 23.08–27.50 pg/ml.

Stratum corneum molecular mobility in the presence of natural moisturizers

The outermost layer of the skin, the stratum corneum (SC), is a lipid-protein membrane that experiences considerable osmotic stress from a dry and cold climate. The natural moisturizing factor (NMF) comprises small and polar substances, which like osmolytes can protect living systems from osmotic stress. NMF is commonly claimed to increase the water content in the SC and thereby protect the skin from dryness. In this work we challenge this proposed mechanism, and explore the influence of NMF on the lipid and protein components in the SC. We employ natural-abundance (13)C solid-state NMR methods to investigate how the SC molecular components are influenced by urea, glycerol, pyrrolidone carboxylic acid (PCA), and urocanic acid (UCA), all of which are naturally present in the SC as NMF compounds. Experiments are performed with intact SC, isolated corneocytes and model lipids. The combination of NMR experiments provides molecularly resolved qualitative information on the dynamics of different SC lipid and protein components. We obtain completely novel molecular information on the interaction of these NMF compounds with the SC lipids and proteins. We show that urea and glycerol, which are also common ingredients in skin care products, increase the molecular mobility of both SC lipids and proteins at moderate relative humidity where the SC components are considerably more rigid in the absence of these compounds. This effect cannot be attributed to increased SC water content. PCA has no detectable effect on SC molecular mobility under the conditions investigated. It is finally shown that the more apolar compound, UCA, specifically influences the mobility of the SC lipid regions. The present results show that the NMF components act to retain the fluidity of the SC molecular components under dehydrating conditions in such a way that the SC properties remain largely unchanged as compared to more hydrated SC. These findings provide a new molecular insight into how small polar molecules in NMF and skin care products act to protect the human skin from drying.

Skin membrane electrical impedance properties under the influence of a varying water gradient

The stratum corneum (SC) is an effective permeability barrier. One strategy to increase drug delivery across skin is to increase the hydration. A detailed description of how hydration affects skin permeability requires characterization of both macroscopic and molecular properties and how they respond to hydration. We explore this issue by performing impedance experiments on excised skin membranes in the frequency range 1 Hz to 0.2 MHz under the influence of a varying gradient in water activity (aw). Hydration/dehydration induces reversible changes of membrane resistance and effective capacitance. On average, the membrane resistance is 14 times lower and the effective capacitance is 1.5 times higher when the outermost SC membrane is exposed to hydrating conditions (aw = 0.992), as compared to the case of more dehydrating conditions (aw = 0.826). Molecular insight into the hydration effects on the SC components is provided by natural-abundance (13)C polarization transfer solid-state NMR and x-ray diffraction under similar hydration conditions. Hydration has a significant effect on the dynamics of the keratin filament terminals and increases the interchain spacing of the filaments. The SC lipids are organized into lamellar structures with ∼ 12.6 nm spacing and hexagonal hydrocarbon chain packing with mainly all-trans configuration of the acyl chains, irrespective of hydration state. Subtle changes in the dynamics of the lipids due to mobilization and incorporation of cholesterol and long-chain lipid species into the fluid lipid fraction is suggested to occur upon hydration, which can explain the changes of the impedance response. The results presented here provide information that is useful in explaining the effect of hydration on skin permeability.

Membrane lipid co-aggregation with α-synuclein fibrils

Amyloid deposits from several human diseases have been found to contain membrane lipids. Co-aggregation of lipids and amyloid proteins in amyloid aggregates, and the related extraction of lipids from cellular membranes, can influence structure and function in both the membrane and the formed amyloid deposit. Co-aggregation can therefore have important implications for the pathological consequences of amyloid formation. Still, very little is known about the mechanism behind co-aggregation and molecular structure in the formed aggregates. To address this, we study in vitro co-aggregation by incubating phospholipid model membranes with the Parkinson's disease-associated protein, α-synuclein, in monomeric form. After aggregation, we find spontaneous uptake of phospholipids from anionic model membranes into the amyloid fibrils. Phospholipid quantification, polarization transfer solid-state NMR and cryo-TEM together reveal co-aggregation of phospholipids and α-synuclein in a saturable manner with a strong dependence on lipid composition. At low lipid to protein ratios, there is a close association of phospholipids to the fibril structure, which is apparent from reduced phospholipid mobility and morphological changes in fibril bundling. At higher lipid to protein ratios, additional vesicles adsorb along the fibrils. While interactions between lipids and amyloid-protein are generally discussed within the perspective of different protein species adsorbing to and perturbing the lipid membrane, the current work reveals amyloid formation in the presence of lipids as a co-aggregation process. The interaction leads to the formation of lipid-protein co-aggregates with distinct structure, dynamics and morphology compared to assemblies formed by either lipid or protein alone.

Signal intensities in ¹H-¹³C CP and INEPT MAS NMR of liquid crystals

Spectral editing with CP and INEPT in (13)C MAS NMR enables identification of rigid and mobile molecular segments in concentrated assemblies of surfactants, lipids, and/or proteins. In order to get stricter definitions of the terms "rigid" and "mobile", as well as resolving some ambiguities in the interpretation of CP and INEPT data, we have developed a theoretical model for calculating the CP and INEPT intensities as a function of rotational correlation time τc and C-H bond order parameter SCH, taking the effects of MAS into account. According to the model, the range of τc can at typical experimental settings (5kHz MAS, 1ms ramped CP at 80-100kHz B1 fields) be divided into four regimes: fast (τc<1ns), fast-intermediate (τc≈0.1μs), intermediate (τc≈1μs), and slow (τc>0.1ms). In the fast regime, the CP and INEPT intensities are independent of τc, but strongly dependent on |SCH|, with a cross-over from dominating INEPT to dominating CP at |SCH|>0.1. In the intermediate regime, neither CP nor INEPT yield signal on account of fast T1ρ and T2 relaxation. In both the fast-intermediate and slow regimes, there is exclusively CP signal. The theoretical predictions are tested by experiments on the glass-forming surfactant n-octyl-β-d-maltoside, for which τc can be varied continuously in the nano- to millisecond range by changing the temperature and the hydration level. The atomistic details of the surfactant dynamics are investigated with MD simulations. Based on the theoretical model, we propose a procedure for calculating CP and INEPT intensities directly from MD simulation trajectories. While MD shows that there is a continuous gradient of τc from the surfactant polar headgroup towards the methyl group at the end of the hydrocarbon chain, analysis of the experimental CP and INEPT data indicates that this gradient gets steeper with decreasing temperature and hydration level, eventually spanning four orders of magnitude at completely dry conditions.

Characterization of stratum corneum molecular dynamics by natural-abundance ¹³C solid-state NMR

Despite the enormous potential for pharmaceutical applications, there is still a lack of understanding of the molecular details that can contribute to increased permeability of the stratum corneum (SC). To investigate the influence of hydration and heating on the SC, we record the natural-abundance (13)C signal of SC using polarization transfer solid-state NMR methods. Resonance lines from all major SC components are assigned. Comparison of the signal intensities obtained with the INEPT and CP pulse sequences gives information on the molecular dynamics of SC components. The majority of the lipids are rigid at 32°C, and those lipids co-exist with a small pool of mobile lipids. The ratio between mobile and rigid lipids increases with hydration. An abrupt change of keratin filament dynamics occurs at RH = 80-85%, from completely rigid to a structure with rigid backbone and mobile protruding terminals. Heating has a strong effect on the lipid mobility, but only a weak influence on the keratin filaments. The results provide novel molecular insight into how the SC constituents are affected by hydration and heating, and improve the understanding of enhanced SC permeability, which is associated with elevated temperatures and SC hydration.

Polarization transfer solid-state NMR for studying surfactant phase behavior

The phase behavior of amphiphiles, e.g., lipids and surfactants, at low water content is of great interest for many technical and pharmaceutical applications. When put in contact with air having a moderate relative humidity, amphiphiles often exhibit coexistence between solid and liquid crystalline phases, making their complete characterization difficult. This study describes a (13)C solid-state NMR technique for the investigation of amphiphile phase behavior in the water-poor regime. While the (13)C chemical shift is an indicator of molecular conformation, the (13)C signal intensities obtained with the CP and INEPT polarization transfer schemes yield information on molecular dynamics. A theoretical analysis incorporating the effect of molecular segment reorientation, with the correlation time τ(c) and order parameter S, shows that INEPT is most efficient for mobile segments with τ(c) < 0.01 μs and S < 0.05, while CP yields maximal signal for rigid segments with τ(c) > 10 μs and/or S > 0.5 under typical solid-state NMR experimental conditions. For liquid crystalline phases, where τ(c) < 0.01 μs and 0 < S < 0.3, the observed CP and INEPT intensities serve as a gauge of S. The combination of information on molecular conformation and dynamics permits facile phase diagram determination for systems with solid crystalline, solid amorphous, anisotropic liquid crystalline, and isotropic liquid (crystalline) phases as demonstrated by experiments on a series of reference systems with known phase structure. Three solid phases (anhydrous crystal, dihydrate, gel), two anisotropic liquid crystalline phases (normal hexagonal, lamellar), and two isotropic liquid crystalline phases (micellar cubic, bicontinuous cubic) are identified in the temperature-composition phase diagram of the cetyltrimethylammonium succinate/water system. Replacing the succinate counterion with DNA prevents the formation of phases other than hexagonal and leads to a general increase of τ(c).

Filter-exchange PGSE NMR determination of cell membrane permeability

A new PGSE NMR sequence is introduced for measuring diffusive transport across the plasma membrane of living cells. A "diffusion filter" and a variable mixing time precedes a standard PGSE block for diffusion encoding of the NMR signal. The filter is a PGSE block optimized for selectively removing the magnetization of the extracellular water. With increasing mixing time the intra- and extracellular components approach their equilibrium fractional populations. The rate of exchange can be measured using only a few minutes of instrument time. Water exchange over the plasma membrane of starved yeast cells is studied in the temperature range +5 to +32 degrees C.

A journey into the past--the history of thyroid surgery

We present a short sketch of how the knowledge of thyroid surgery has evolved throughout decades with pointing out to prominent surgeons who achieved great deeds in the history of thyroidectomy. The progress of thyroid surgery is believed to be of utmost importance because it reflects evolution of surgery itself. Although surgeons of our days can rely on wide range of examinations, modern equipment and endocrinological support, they should remember the rules in medicine, that are obligatory nowadays, have been created throughout decades. The abridged sketch of the history of thyroidectomy reflects how long, difficult and--many a time--dramatic way was surmounted by notable and brave pioneers of endocrinological surgery and how they advanced the surgical treatment of the thyroid from the dark ages into the modern era.

Variability of thyroid blood flow Doppler parameters in healthy women

The purpose of this study was to estimate variability of flow Doppler parameters in the superior thyroid artery (STHA) during the menstrual cycle in young women and to explore the influence of endogenous 17-b-estradiol (E2) and progesterone (PRG) on the velocity waveform. The plasma concentration of these hormones was correlated with flow velocities, pulsatility index (PUI), resistance index (RI) and acceleration index (accI) and time (accT), which were measured with color-coded duplex sonography 8 times during the cycle in 14 healthy women (age range: 23 to 25 years). Coefficient of variation (CV), interclass correlation (ICC), repeatability (repC) and pooled Pearson correlation (r) coefficients were used to estimate the variability of the parameters. The highest variability was found for accI and accT: CV = 48% and 31%; ICC = 0.51 and 0.45; repC = 2.8 and 95; r = 0.37 and 0.4, respectively. The CV for flow velocities varied from 25% to 26%, ICC from 0.53 to 0.56, repC from 8 to 17 and r has a value of 0.46. The respective values for RI and PUI were: 11%, 18%; 0.48, 0.55; 0.15, 0.48; and 0.46, 0.48. The diastolic blood pressure decreased significantly by 7 mmHg (p < 0.01) in the luteal phase, whereas other physiological variables were stable during the cycle. Although the fluctuations of the flow parameters during the cycle were not statistically significant, a weak linear correlation between flow velocities and concentration of E2 was found; for mean velocity r = 0.16, p < 0.05. Impedance indices showed an increasing trend in the luteal phase, along with increase of the pulse pressure index (PPI). The results showed that variability of the flow parameters in the STHA is substantial and that higher flow velocities are associated with increase of plasma concentration of 17-b-estradiol during the menstrual cycle in young women.

Influence of 17-beta-estradiol on cerebrovascular impedance during menstrual cycle in women

Numerous experimental studies showed that estrogen alters diameters of cerebral arteries by modifying production of vasoactive substances. In this study, we address a question whether increased concentration of 17-beta-estradiol (E2) during a typical menstrual cycle of young, healthy women influences cerebrovascular impedance, as measured with Doppler pulsatility index (PI) in the common (CCA), internal (ICA), and external (ECA) carotid arteries using duplex Doppler sonography. PI was determined and correlated with plasma E2 concentration in 14 women (ages 23-25) throughout their menstrual cycle. The concentration of E2 increased in the follicular phase of the cycle and reached a peak of 140-300 pg/ml on days 13 and 14, whereas concentration of progesterone remained low (<1 ng/ml). Along with an increase in E2 concentration, the ICA PI decreased from its initial level on average by 11% on day 13 and by 7% on day 14 (r=-0.41, P<0.05). In contrast, the value of the ECA PI showed an increasing trend during the peak of E2 concentration. There were no significant changes in the CCA PI as well as in the systolic blood pressure, heart rate, hematocrit, and hemoglobin concentration during the menstrual cycle. Cerebral vascular impedance in young women is modulated by concentration of E2 throughout the menstrual cycle. The decrease in the ICA PI during the late follicular phase seems to be attributed to a decrease in cerebrovascular resistance.

Microinjection of procaine into the pedunculopontine tegmental nucleus suppresses hippocampal theta rhythm in urethane-anesthetized rats

It was found that the cholinergic component of the pedunculopontine tegmental nucleus (PPN) is involved in the generation of theta rhythm in the hippocampus. However, it is still not known how important PPN is in the brainstem theta-generating system, where the nucleus reticularis pontis oralis is regarded as a primary generator. In the present experiment, performed on urethane-anesthetized rats, we studied the effect on the tail pinch-elicited hippocampal theta of unilateral inactivation of PPN by means of direct procaine microinjection. Procaine induced ipsilateral suppression of theta rhythm, manifested as desynchronization of hippocampal EEG, a shift of the fast Fourier transformation (FFT) power peak toward lower frequencies, and a reduction of FFT peak magnitude at theta band. Hippocampal field activity returned to normal (both its FFT peak frequency and magnitude) within 30 min after the injection. The results obtained indicate that PPN is critical for hippocampal theta generation but it may not be involved in encoding theta frequency.

Anatomical correlates of the lateral hypothalamic influence on waking-sleep relationship in the rat

Restricted electrolytic lesions of the lateral hypothalamus (LH) evoke sleeplessness in the rat. The present study was aimed to analyze a possible anatomical substrate of the LH hyposomnia within the hypothalamus. In a group of electrolytically lesioned LH rats the intensity of sleep disturbances, assessed on the basis of EEG records from the neocortex and the hippocampus, was confronted with the localization and the extent of destruction of the LH area and with the topography of known fiber systems of the medical forebrain bundle (MFB). In separate experiments the effects of the destruction of LH cell bodies by means of bilateral ibotenic acid (IBO) injections and inhibition of LH neuronal elements by bilateral muscimol (MUSC) administration were also tested. It was found that pronounced hyposomnia follows electrolytic but not IBO lesions of the LH/MFB area. The effective LH damage might have been localized at every level of its antero-posterior axis, from the preoptic area up to the posterior hypothalamus, suggesting involvement of fiber system(s) rather than a localized group of neuronal pericaria. The most effective lesions transsected projections descending from the preoptic/anterior hypothalamic area, olfactory structures, ventral striatum and the central amygdaloid nucleus as well as fibers connecting LH with the brainstem reticular formation, many of them using GABA as a neurotransmitter. Bilateral MUSC injections caused a dose-dependent, bicuculline-reversible, increase in waking time, most pronounced at a dose of 50 ng, which ressembled the effect of the electrolytic lesion. These results indicate that LH hyposomnia is not attributable to the damage to the intrahypothalamic neurons and suggest the participation of GABA-ergic transmission in LH in waking-sleep regulation.