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https://www.readbyqxmd.com/read/26654376/mind-and-brain-consciousness-in-unresponsive-subjects
#1
COMMENT
M Bruce MacIver
A new study shows that subjects rendered unresponsive with sedatives do not exhibit a stereotypic 'unconscious' response to direct cortical stimulation; instead, agent-specific effects are seen that can distinguish between unresponsiveness with and without consciousness.
December 7, 2015: Current Biology: CB
https://www.readbyqxmd.com/read/26314691/median-raphe-stimulation-induced-motor-inhibition-concurrent-with-suppression-of-type-1-and-type-2-hippocampal-theta
#2
Brian H Bland, Cheryl E Bland, M Bruce MacIver
This study investigated behavioral, anatomical and electrophysiological effects produced by electrical stimulation of posterior hypothalamic (PH) or median raphe (MR) nuclei, independently and during combined stimulation of both PH and MR. These three stimulation conditions were applied during spontaneous behavior in an open field and during PH stimulation-induced wheel running, while simultaneously recording hippocampal (HPC) field activity. An additional objective was to determine the effects of MR stimulation on Type 1 movement related theta and Type 2 sensory processing related theta...
March 2016: Hippocampus
https://www.readbyqxmd.com/read/24977633/anesthetic-agent-specific-effects-on-synaptic-inhibition
#3
M Bruce MacIver
BACKGROUND: Anesthetics enhance γ-aminobutyric acid (GABA)-mediated inhibition in the central nervous system. Different agents have been shown to act on tonic versus synaptic GABA receptors to different degrees, but it remains unknown whether different forms of synaptic inhibition are also differentially engaged. With this in mind, we tested the hypothesis that different types of GABA-mediated synapses exhibit different anesthetic sensitivities. The present study compared effects produced by isoflurane, halothane, pentobarbital, thiopental, and propofol on paired-pulse GABAA receptor-mediated synaptic inhibition...
September 2014: Anesthesia and Analgesia
https://www.readbyqxmd.com/read/22344244/teaching-an-old-gaba-receptor-new-tricks
#4
REVIEW
James R Trudell, Edward Bertaccini, M Bruce Maciver
The accompanying articles in this issue of the journal's special collection describe attempts to improve on the dynamics of distribution and reduce side effects of analogs of etomidate and benzodiazepines. Both classes of drugs have their principal sites of action on γ-aminobutyric acid type A receptors, although at very different binding sites and by different mechanisms of action. Herein, we review the structure of γ-aminobutyric acid type A receptors and describe the location of the 2 likely binding sites...
August 2012: Anesthesia and Analgesia
https://www.readbyqxmd.com/read/22323512/a-novel-aquaporin-3-in-killifish-fundulus-heteroclitus-is-not-an-arsenic-channel
#5
Dawoon Jung, Bryce MacIver, Brian P Jackson, Roxanna Barnaby, J Denry Sato, Mark L Zeidel, Joseph R Shaw, Bruce A Stanton
The Atlantic killifish (Fundulus heteroclitus) is a model environmental organism that has an extremely low assimilation rate of environmental arsenic. As a first step in elucidating the mechanism behind this phenomenon, we used quantitative real-time PCR to identify aquaglyceroporins (AQPs), which are arsenite transporters, in the killifish gill. A novel homolog killifish AQP3 (kfAQP3a) was cloned from the killifish gill, and a second homolog was identified as the consensus from a transcriptome database (kfAQP3b)...
May 2012: Toxicological Sciences: An Official Journal of the Society of Toxicology
https://www.readbyqxmd.com/read/21701380/human-subthalamic-neuron-spiking-exhibits-subtle-responses-to-sedatives
#6
M Bruce Maciver, Helen M Bronte-Stewart, Jamie M Henderson, Richard A Jaffe, John G Brock-Utne
BACKGROUND: During deep brain stimulation implant surgery, microelectrode recordings are used to map the location of targeted neurons. The effects produced by propofol or remifentanil on discharge activity of subthalamic neurons were studied intraoperatively to determine whether they alter neuronal activity. METHODS: Microelectrode recordings from 11 neurons, each from individual patients, were discriminated and analyzed before and after administration of either propofol or remifentanil...
August 2011: Anesthesiology
https://www.readbyqxmd.com/read/21471535/meat-lipid-profiles-a-comparison-of-meat-from-domesticated-and-wild-southern-african-animals
#7
COMPARATIVE STUDY
Bruce Davidson, James Maciver, Eric Lessard, Kelly Connors
BACKGROUND: The link between meat and various chronic diseases has been qualified recently, and is now accepted as being related to the amount of saturated fat present. Other work has shown differences in total lipid profiles between meat from 'wild' and 'domesticated' animals, with the 'wild' reflecting higher levels of polyunsaturated and lower saturated fat. This study assessed both meat types from South African sources. MATERIALS AND METHODS: All 'wild' meat samples were obtained fresh from a specialist restaurant...
March 2011: In Vivo
https://www.readbyqxmd.com/read/19494804/abused-inhalants-enhance-gaba-mediated-synaptic-inhibition
#8
M Bruce MacIver
Abused inhalants are widely used, especially among school-age children and teenagers, and are 'gateway' drugs leading to the abuse of alcohol and other addictive substances. In spite of this widespread use, little is known about the effects produced by inhalants on the central nervous system. The similarity in behavioral effects produced by inhalants and inhaled anesthetics, together with their common chemical features, prompted this study of inhalant actions on a well-characterized anesthetic target, GABA synapses...
September 2009: Neuropsychopharmacology: Official Publication of the American College of Neuropsychopharmacology
https://www.readbyqxmd.com/read/19151276/anesthetics-discriminate-between-tonic-and-phasic-gamma-aminobutyric-acid-receptors-on-hippocampal-ca1-neurons
#9
Mark C Bieda, Henry Su, M Bruce Maciver
BACKGROUND: Anesthesia is produced by a depression of neuronal signaling in the central nervous system (CNS); however, the mechanism(s) of action underlying this depression remain unclear. Recent studies have indicated that anesthetics can enhance inhibition of CNS neurons by increasing current flow through tonic gamma-aminobutyric acid (GABA(A)) receptor gated chloride channels in their membranes. Enhanced tonic inhibition would contribute to CNS depression produced by anesthetics, but it remains to be determined to what extent anesthetic actions at these receptors contribute to CNS depression...
February 2009: Anesthesia and Analgesia
https://www.readbyqxmd.com/read/18199338/slow-gaba-a-mediated-synaptic-transmission-in-rat-visual-cortex
#10
Michael P Sceniak, M Bruce Maciver
BACKGROUND: Previous reports of inhibition in the neocortex suggest that inhibition is mediated predominantly through GABA(A) receptors exhibiting fast kinetics. Within the hippocampus, it has been shown that GABA(A) responses can take the form of either fast or slow response kinetics. Our findings indicate, for the first time, that the neocortex displays synaptic responses with slow GABA(A) receptor mediated inhibitory postsynaptic currents (IPSCs). These IPSCs are kinetically and pharmacologically similar to responses found in the hippocampus, although the anatomical specificity of evoked responses is unique from hippocampus...
2008: BMC Neuroscience
https://www.readbyqxmd.com/read/16510775/cellular-actions-of-urethane-on-rat-visual-cortical-neurons-in-vitro
#11
Michael P Sceniak, M Bruce Maciver
Urethane is widely used in neurophysiological experiments to anesthetize animals, yet little is known about its actions at the cellular and synaptic levels. This limits our ability to model systems-level cortical function using results from urethane-anesthetized preparations. The present study found that action potential discharge of cortical neurons in vitro, in response to depolarizing current, was strongly depressed by urethane and this was accompanied by a significant decrease in membrane resistance. Voltage-clamp experiments suggest that the mechanism of this depression involves selective activation of a Ba2+-sensitive K+ leak conductance...
June 2006: Journal of Neurophysiology
https://www.readbyqxmd.com/read/16508384/anesthesia-in-silico
#12
EDITORIAL
Michael P Sceniak, M Bruce MacIver
No abstract text is available yet for this article.
March 2006: Anesthesiology
https://www.readbyqxmd.com/read/16409641/isoflurane-depresses-hippocampal-ca1-glutamate-nerve-terminals-without-inhibiting-fiber-volleys
#13
Bruce D Winegar, M Bruce MacIver
BACKGROUND: Anesthetic-induced CNS depression is thought to involve reduction of glutamate release from nerve terminals. Recent studies suggest that isoflurane reduces glutamate release by block of Na channels. To further investigate this question we examined the actions of isoflurane, TTX, extracellular Ca2+, CNQX and stimulus voltage (stim) on glutamate-mediated transmission at hippocampal excitatory synapses. EPSPs were recorded from CA1 neurons in rat hippocampal brain slices in response to Schaffer-collateral fiber stimulation...
2006: BMC Neuroscience
https://www.readbyqxmd.com/read/15647528/anesthetic-induced-burst-suppression-eeg-activity-requires-glutamate-mediated-excitatory-synaptic-transmission
#14
Heath S Lukatch, Cynthia E Kiddoo, M Bruce Maciver
Many anesthetics evoke electroencephalogram (EEG) burst suppression activity in humans and animals during anesthesia, and the mechanisms underlying this activity remain unclear. The present study used a rat neocortical brain slice EEG preparation to investigate excitatory synaptic mechanisms underlying anesthetic-induced burst suppression activity. Excitatory synaptic mechanisms associated with burst suppression activity were probed using glutamate receptor antagonists (CNQX and APV), GABA receptor antagonists, and simultaneous whole cell patch clamp and microelectrode EEG recordings...
September 2005: Cerebral Cortex
https://www.readbyqxmd.com/read/15579203/multiple-synaptic-and-membrane-sites-of-anesthetic-action-in-the-ca1-region-of-rat-hippocampal-slices
#15
Sky Pittson, Allison M Himmel, M Bruce MacIver
BACKGROUND: Anesthesia is produced by a depression of central nervous system function, however, the sites and mechanisms of action underlying this depression remain poorly defined. The present study compared and contrasted effects produced by five general anesthetics on synaptic circuitry in the CA1 region of hippocampal slices. RESULTS: At clinically relevant and equi-effective concentrations, presynaptic and postsynaptic anesthetic actions were evident at glutamate-mediated excitatory synapses and at GABA-mediated inhibitory synapses...
December 3, 2004: BMC Neuroscience
https://www.readbyqxmd.com/read/15140905/major-role-for-tonic-gabaa-conductances-in-anesthetic-suppression-of-intrinsic-neuronal-excitability
#16
Mark C Bieda, M Bruce MacIver
Anesthetics appear to produce neurodepression by altering synaptic transmission and/or intrinsic neuronal excitability. Propofol, a widely used anesthetic, has proposed effects on many targets, ranging from sodium channels to GABA(A) inhibition. We examined effects of propofol on the intrinsic excitability of hippocampal CA1 neurons (primarily interneurons) recorded from adult rat brain slices. Propofol strongly depressed action potential production induced by DC injection, synaptic stimulation, or high-potassium solutions...
September 2004: Journal of Neurophysiology
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