Mesenteric veins are more sensitive than arteries to the constrictor effects of sympathetic nerve stimulation and alpha-adrenoceptor agonists. We tested the hypothesis that alpha(1)- and alpha(2)-adrenoceptors interact to enhance adrenergic reactivity of mesenteric veins. We studied neurogenic and agonist-induced constrictions of mesenteric veins and arteries in vitro. Norepinephrine concentration-response curves were left-shifted in veins compared to arteries. UK 14,304 (0.01-1 microM, alpha(2)-adrenoceptor receptor agonist) did not constrict arteries or veins but enhanced constrictions and Ca(2+) signals mediated by alpha(1)-adrenoceptor stimulation in veins. Yohimbine (alpha(2)-adrenoceptor receptor antagonist) and MK912 (alpha(2C)-adrenoceptor receptor antagonist), but not alpha(2A)- or alpha(2B)-adrenoceptor antagonists, produced rightward shifts in norepinephrine concentration-response curves in veins. Pharmacological studies revealed that alpha(1D)-adrenoceptors mediate venous constrictions. Norepinephrine responses in veins from alpha(2C)-adrenoceptor knock-out (KO) mice were not different from wild type veins. Yohimbine inhibited norepinephrine constrictions in alpha(2C)-adrenoceptor KO veins suggesting that there is upregulation of other alpha(2)-adrenoceptors in alpha(2C)-KO mice. These data indicate that alpha(1D)- and alpha(2C)-adrenoceptors interact in veins but not in arteries. This interaction enhances venous adrenergic reactivity. Mesenteric vein-specific alpha(2)-adrenoceptor linked Ca(2+) and perhaps other signaling pathways account for enhanced venous adrenergic reactivity.

• MeSH
• alfa-1-adrenergní receptory - agonisté farmakologie   MeSH
• alfa-1-adrenergní receptory metabolismus   fyziologie   MeSH
• alfa-2-adrenergní receptory - agonisté farmakologie   MeSH
• alfa-2-adrenergní receptory - antagonisté farmakologie   MeSH
• alfa-2-adrenergní receptory genetika   metabolismus   fyziologie   MeSH
• arteriae mesentericae účinky léků   fyziologie   MeSH
• myši inbrední C57BL MeSH
• myši knockoutované MeSH
• myši MeSH
• noradrenalin fyziologie   MeSH
• protein - isoformy antagonisté a inhibitory   MeSH
• sympatický nervový systém účinky léků   MeSH
• techniky in vitro MeSH
• vápníková signalizace účinky léků   MeSH
• vazokonstrikce účinky léků   MeSH
• vena mesenterica účinky léků   fyziologie   MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• srovnávací studie MeSH
• Názvy látek
• Adra1d protein, mouse MeSH Prohlížeč
• Adra2c protein, mouse MeSH Prohlížeč
• alfa-1-adrenergní receptory - agonisté MeSH
• alfa-1-adrenergní receptory MeSH
• alfa-2-adrenergní receptory - agonisté MeSH
• alfa-2-adrenergní receptory - antagonisté MeSH
• alfa-2-adrenergní receptory MeSH
• noradrenalin MeSH
• protein - isoformy MeSH

Oscillatory network activity arises from interactions between synaptic and intrinsic membrane properties of neurons. In this review, we summarize general mechanisms of synchronous neuronal oscillations. In addition, we focus on recent experimental and computational studies which suggest that activity-dependent changes of ionic environment can affect both the synaptic and intrinsic neuronal properties and influence the network behavior. GABA(A) receptor (GABA(A)R)-mediated signaling, that is based on Cl(-) and HCO(3)(-) permeability, is thought to be important for the oscillogenesis and synchronization in cortical networks. A remarkable feature of GABAergic synapses is that prolonged GABA(A)R activation may lead to switching from a hyperpolarizing to a depolarizing response. This is partly due to a positive shift of the GABA(A) R reversal potential (E(GABA)) that is generated by GABA-induced Cl(-) accumulation in neurons. Recent studies suggest that activity-dependent E(GABA) changes may have important implications for the mechanisms of gamma oscillations and seizure-like discharges. Thus, a better understanding of the impact of intracellular Cl(-) dynamics on network behavior may provide insights into the mechanisms of physiological and pathological brain rhythms. Combination of experiments and simulations is a promising approach for elucidating which properties of the time-varying ionic environment can shape the dynamics of a given circuit.

• MeSH
• biologické hodiny fyziologie   MeSH
• buněčná membrána metabolismus   MeSH
• iontový transport fyziologie   MeSH
• korová synchronizace MeSH
• nervový přenos fyziologie   MeSH
• nervový útlum fyziologie   MeSH
• neurony metabolismus   fyziologie   MeSH
• receptory GABA-A fyziologie   MeSH
• synapse metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• receptory GABA-A MeSH

This study extends our previous work by examining the effects of alpha2-adrenoceptors under cold stimulation involving the increase of myogenic vascular oscillations as increases of very-low-frequency and low-frequency of the blood pressure variability. Forty-eight adult male Sprague-Dawley rats were randomly divided into four groups: vehicle; yohimbine; hexamethonium+yohimbine; guanethidine+yohimbine. Systolic blood pressure, heart rate, power spectral analysis of spontaneous blood pressure and heart rate variability and spectral coherence at very-low-frequency (0.02 to 0.2 Hz), low-frequency (0.2 to 0.6 Hz), and high-frequency (0.6 to 3.0 Hz) regions were monitored using telemetry. Key findings are as follows: 1) Cooling-induced pressor response was attenuated by yohimbine and further attenuated by hexamethonium+yohimbine and guanethidine+yohimbine, 2) Cooling-induced tachycardia response of yohimbine was attenuated by hexamethonium+yohimbine and guanethidine+yohimbine, 3) Different patterns of power spectrum reaction and coherence value compared hexamethonium+yohimbine and guanethidine+yohimbine to yohimbine alone under cold stimulation. The results suggest that sympathetic activation of the postsynaptic alpha2-adrenoceptors causes vasoconstriction and heightening myogenic vascular oscillations, in turn, may increase blood flow to prevent tissue damage under stressful cooling challenge.

• MeSH
• alfa-2-adrenergní receptory - antagonisté farmakologie   MeSH
• alfa-2-adrenergní receptory fyziologie   MeSH
• hemodynamika účinky léků   fyziologie   MeSH
• krevní tlak účinky léků   fyziologie   MeSH
• krysa rodu Rattus MeSH
• náhodné rozdělení MeSH
• nízká teplota škodlivé účinky   MeSH
• potkani Sprague-Dawley MeSH
• srdeční frekvence účinky léků   fyziologie   MeSH
• telemetrie metody   MeSH
• vazokonstrikce účinky léků   fyziologie   MeSH
• yohimbin farmakologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• alfa-2-adrenergní receptory - antagonisté MeSH
• alfa-2-adrenergní receptory MeSH
• yohimbin MeSH

Cognitive flexibility is a major requirement for successful behavior. nNeural oscillations in the alpha frequency band were repeatedly associated with cognitive flexibility in task-switching paradigms. Alpha frequencies are modulated by working memory load and are used to process information during task switching, however we do not know how this oscillatory network communication is modulated. In order to understand the mechanisms that drive cognitive flexibility, ERPs, oscillatory power and how the communication within these networks is organized are of importance. The EEG data show that during phases reflecting preparatory processes to pre-activate task sets, alpha oscillatory power but not the small world properties of the alpha network architecture was modulated. During the switching only the N2 ERP component showed clear modulations. After the response, alpha oscillatory power reinstates and therefore seems to be important to deactivate or maintain the previous task set. For these reactive control processes the network architecture in terms of small-world properties is modulated. Effects of memory load on small-world aspects were seen in repetition trials, where small-world properties were higher when memory processes were relevant. These results suggest that the alpha oscillatory network becomes more small-world-like when reactive control processes during task switching are less complex.

• MeSH
• dospělí MeSH
• elektroencefalografie * MeSH
• evokované potenciály MeSH
• kognice fyziologie   MeSH
• lidé středního věku MeSH
• lidé MeSH
• mapování mozku MeSH
• mladiství MeSH
• mladý dospělý MeSH
• paměť fyziologie   MeSH
• reakční čas MeSH
• zdraví dobrovolníci pro lékařské studie MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladiství MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The psychomotor tempo (tapping) and its relation to alpha frequency was investigated in 100 7- to 15-year-old children. The frequency of alpha rhythm increased in proportion to age, and the maximum and preferential tapping frequencies revealed an increasing tendency, too. Mainly the preferential tapping frequency correlated with the age-dependent increment of EEG alpha frequency. Simultaneously, the variability of the tapping frequency decreased. During a phase of relatively stable tapping performance regular fluctuations in the tapping frequency occurred with a period duration between 0.67 and 13.3 s. These oscillations of the motor activity developed during ontogenesis: The slow fluctuations were found in all groups, whereas those with shorter periods were best pronounced in the older children. The development of EEG and psychomotor indices are assumed to be based on the morphological and functional maturation of the developing brain. Therefore, they may be used as a tool to assess the normal and disturbed brain development.

• MeSH
• alfa rytmus EEG * MeSH
• dítě MeSH
• lidé MeSH
• mladiství MeSH
• periodicita MeSH
• psychomotorický výkon fyziologie   MeSH
• věkové faktory MeSH
• vývoj dítěte * MeSH
• Check Tag
• dítě MeSH
• lidé MeSH
• mladiství MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH

BACKGROUND: The cognitive role of the subthalamic nucleus (STN) remains largely unknown. METHODS/RESULTS: A modified protocol with a dual task elicited local field event-related potentials (ERPs) within the STN. No generators of ERPs were elicited by the standard oddball protocol in the STN (at variance with recordings from the putamen, caudate and pallidum). Repetitive transcranial magnetic stimulation (rTMS) over the right inferior frontal cortex caused a shortening of latencies of ERPs in standard and dual protocols. No changes were observable after the rTMS over the dorsolateral prefrontal cortex and sham stimulation. In the STN, only the tasks with an increased demand on executive functions produced the alpha-/beta-event-related desynchronization/synchronization in visuomotor tasks with single letters writing. CONCLUSION: Our results indicate a specific, task-related involvement of the STN in the cognitive activities. Cognitive processing in the STN is possibly processed via hyperdirect cortico-STN pathway. Certain effects of deep brain stimulation surgery on cognitive performance could be explained by a direct effect on 'cognitive' parts of the STN.

• MeSH
• akustická stimulace metody   MeSH
• biofyzika MeSH
• elektroencefalografie metody   MeSH
• elektromyografie metody   MeSH
• evokované potenciály fyziologie   MeSH
• funkční lateralita MeSH
• kognice fyziologie   MeSH
• lidé MeSH
• neuropsychologické testy MeSH
• nucleus subthalamicus patofyziologie   MeSH
• Parkinsonova nemoc komplikace   patologie   terapie   MeSH
• periodicita * MeSH
• psychoakustika MeSH
• transkraniální magnetická stimulace metody   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• klinické zkoušky MeSH
• práce podpořená grantem MeSH

Performing hypoxia-reoxygenation cycles in cell culture with a cycle duration accurately reflecting what occurs in obstructive sleep apnea (OSA) patients is a difficult but crucial technical challenge. Our goal was to develop a novel device to expose multiple cell culture dishes to intermittent hypoxia (IH) cycles relevant to OSA with limited gas consumption. With gas flows as low as 200 ml/min, our combination of plate holders with gas-permeable cultureware generates rapid normoxia-hypoxia cycles. Cycles alternating 1 min at 20% O2 followed by 1 min at 2% O2 resulted in Po2 values ranging from 124 to 44 mmHg. Extending hypoxic and normoxic phases to 10 min allowed Po2 variations from 120 to 25 mmHg. The volume of culture medium or the presence of cells only modestly affected the Po2 variations. In contrast, the nadir of the hypoxia phase increased when measured at different heights above the membrane. We validated the physiological relevance of this model by showing that hypoxia inducible factor-1α expression was significantly increased by IH exposure in human aortic endothelial cells, murine breast carcinoma (4T1) cells as well as in a blood-brain barrier model (2.5-, 1.5-, and 6-fold increases, respectively). In conclusion, we have established a new device to perform rapid intermittent hypoxia cycles in cell cultures, with minimal gas consumption and the possibility to expose several culture dishes simultaneously. This device will allow functional studies of the consequences of IH and deciphering of the molecular biology of IH at the cellular level using oxygen cycles that are clinically relevant to OSA.

• Klíčová slova
• cell hypertrophy, diabetic nephropathy, fibrosis, mTOR complex 1, microRNAs,
• MeSH
• buněčné kultury * přístrojové vybavení   MeSH
• časové faktory MeSH
• design vybavení MeSH
• endoteliální buňky metabolismus   MeSH
• faktor 1 indukovatelný hypoxií - podjednotka alfa metabolismus   MeSH
• hematoencefalická bariéra metabolismus   MeSH
• hypoxie buňky MeSH
• hypoxie metabolismus   MeSH
• kultivační média metabolismus   MeSH
• kyslík metabolismus   MeSH
• lidé MeSH
• nádorová hypoxie MeSH
• nádorové buněčné linie MeSH
• nádory prsu metabolismus   MeSH
• obstrukční spánková apnoe metabolismus   MeSH
• plyny MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• faktor 1 indukovatelný hypoxií - podjednotka alfa MeSH
• HIF1A protein, human MeSH Prohlížeč
• kultivační média MeSH
• kyslík MeSH
• plyny MeSH

The dorsal and ventral visual streams have been considered to play distinct roles in visual processing for action: the dorsal stream is assumed to support real-time actions, while the ventral stream facilitates memory-guided actions. However, recent evidence suggests a more integrated function of these streams. We investigated the neural dynamics and functional connectivity between them during memory-guided actions using intracranial EEG. We tracked neural activity in the inferior parietal lobule in the dorsal stream, and the ventral temporal cortex in the ventral stream as well as the hippocampus during a delayed action task involving object identity and location memory. We found increased alpha power in both streams during the delay, indicating their role in maintaining spatial visual information. In addition, we recorded increased alpha power in the hippocampus during the delay, but only when both object identity and location needed to be remembered. We also recorded an increase in theta band phase synchronization between the inferior parietal lobule and ventral temporal cortex and between the inferior parietal lobule and hippocampus during the encoding and delay. Granger causality analysis indicated dynamic and frequency-specific directional interactions among the inferior parietal lobule, ventral temporal cortex, and hippocampus that varied across task phases. Our study provides unique electrophysiological evidence for close interactions between dorsal and ventral streams, supporting an integrated processing model in which both streams contribute to memory-guided actions.

• Klíčová slova
• Alpha oscillations, Dorsal visual stream, Granger causality analysis, Intracranial EEG, Memory-guided actions, Phase-locking value, Theta oscillations, Ventral visual stream,
• Publikační typ
• časopisecké články MeSH

Two pairs of wire electrodes were used to record afferent and efferent single fibre extracellular action potentials (APs) from human nerve root filaments. The nerve fibres were identified according to the group to which they belong by comparing the afferent and efferent conduction velocity distribution histograms and identifying peaks and ranges of nerve fibre groups. Secondary muscle spindle afferents and alpha 2-motoneurones (FR) were identified by having the same peak group conduction velocity (calibration relation), which is 50 m/s at 36 degrees C. On the basis of AP wave form comparisons, the natural impulse patterns of five secondary muscle spindle afferents, two fusimotor motoneurones and two oscillatory firing alpha 2-motoneurones could be identified in the dorsal S4 root. The patterns of single endings of secondary spindle afferent fibres could be identified. The shortest interspike intervals of single endings of all secondary muscle spindle afferents had the same duration as the shortest interspike intervals of the two fusimotor fibres (80 ms) and equalled a half of the oscillation period of one repetitively firing alpha 2-motoneurone (6 Hz) probably innervating the external anal sphincter (three AP impulse train firing). In another more rostral dorsal root filament (probably S3 or S2) of the same human, the interspike intervals of six secondary spindle afferents were more variable. The values of peaks in the interspike interval distributions ranged from 60 to 102 ms. In the coccygeal root, the interspike interval duration ranged from 160 to 185 ms, directly contributing to the drive of the oscillatory firing alpha 2-motoneurone. The different agreement between the oscillation period and the interspike intervals of the spindle afferents in different segments indicate that the oscillatory firing CNS circuitry was localized within S3 to S5 segments of the conus medullaris for the drive of the anal sphincter. An alpha 2-motoneurone firing repeatedly with 1 to 2 AP impulse trains, innervating most likely the external urethral sphincter, fired at a frequency of 9.1 to 6.7 Hz, a similar frequency of the oscillation as the interspike intervals from two activated stretch receptors of the urinary bladder wall. The measurements of this brain-dead human indicates that in this case the neuronal circuitry driving the external anal sphincter was mainly confined to the sacral micturition and defecation centre, mainly located in the S3 to S5 segments.

• MeSH
• akční potenciály fyziologie   MeSH
• axony fyziologie   MeSH
• elektrická stimulace MeSH
• lidé MeSH
• mícha cytologie   fyziologie   MeSH
• močový měchýř inervace   fyziologie   MeSH
• motorické neurony fyziologie   MeSH
• nervosvalová vřeténka fyziologie   MeSH
• nervové vedení fyziologie   MeSH
• neurony aferentní fyziologie   ultrastruktura   MeSH
• neurony eferentní fyziologie   ultrastruktura   MeSH
• uretra inervace   fyziologie   MeSH
• urodynamika fyziologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

The molecular mechanisms involved in GPCR-initiated signaling cascades where the two receptors share the same signaling cascade, such as thyrotropin-releasing hormone (TRH) and angiotensin II (ANG II), are still far from being understood. Here, we analyzed hormone-induced Ca(2+) responses and the process of desensitization in HEK-293 cells, which express endogenous ANG II receptors. These cells were transfected to express exogenously high levels of TRH receptors (clone E2) or both TRH receptors and G(11)alpha protein (clone E2M11). We observed that the characteristics of the Ca(2+) response, as well as the process of desensitization, were both strongly dependent on receptor number and G(11)alpha protein level. Whereas treatment of E2 cells with TRH or ANG II led to significant desensitization of the Ca(2+) response to subsequent addition of either hormone, the response was not desensitized in E2M11 cells expressing high levels of G(11)alpha. In addition, stimulation of both cell lines with THR elicited a clear heterologous desensitization to subsequent stimulation with ANG II. On the other hand, ANG II did not affect a subsequent response to TRH. ANG II-mediated signal transduction was strongly dependent on plasma membrane integrity modified by cholesterol depletion, but signaling through TRH receptors was altered only slightly under these conditions. It may be concluded that the level of expression of G-protein-coupled receptors and their cognate G-proteins strongly influences not only the magnitude of the Ca(2+) response but also the process of desensitization and resistance to subsequent hormone addition.

• MeSH
• angiotensin II farmakologie   MeSH
• buněčná membrána účinky léků   metabolismus   MeSH
• časové faktory MeSH
• cholesterol analýza   metabolismus   MeSH
• hormon uvolňující thyreotropin farmakologie   MeSH
• kultivované buňky MeSH
• lidé MeSH
• proteiny vázající GTP - alfa-podjednotky Gq-G11 biosyntéza   účinky léků   genetika   MeSH
• receptory thyroliberinu biosyntéza   účinky léků   MeSH
• teplota MeSH
• transfekce MeSH
• vápník metabolismus   farmakologie   MeSH
• vápníková signalizace účinky léků   fyziologie   MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• angiotensin II MeSH
• cholesterol MeSH
• hormon uvolňující thyreotropin MeSH
• proteiny vázající GTP - alfa-podjednotky Gq-G11 MeSH
• receptory thyroliberinu MeSH
• vápník MeSH